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Effects of cationic species on the structure and properties of hybrid organic-inorganic materials

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Effects of cationic species on the structure and properties of hybrid organic-inorganic materials

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Content Effects of Cationic Species on the Structure and Properties of Hybrid
Organic-Inorganic Materials
by
Megan Cassingham
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(Chemistry)
August 2024
Copyright 2024 Megan Cassingham

Acknowledgments
Pursuing a PhD has shown me the value of having a strong support network. While the
journey has been academically rigorous, I have learned that a PhD is as much about mental
fortitude and stamina as it is about intelligence. I am eternally grateful to my family
and friends who have supported me through this process from pandemic care packages to
listening to my woes to celebrating the wins along the way. I am proud to be able to share
this accomplishment with everyone who encouraged and supported me on this journey.

Table of Contents
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v
List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
Chapter 1:
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1.1 Looking to Perovskites for Inspiration . . . . . . . . . . . . . . . . . . 2
1.1.2 Harnessing the Power of the Cation . . . . . . . . . . . . . . . . . . . 5
1.2 Diverse Structures of the Hybrid Perovskite . . . . . . . . . . . . . . . . . . 6
1.3 Exploring Diverse Functionality of Hybrid Materials . . . . . . . . . . . . . . 8
1.3.1 Second Harmonic Generation . . . . . . . . . . . . . . . . . . . . . . 8
1.3.2 Emission Properties of 1D Materials . . . . . . . . . . . . . . . . . . 10
1.3.3 Excited State Charge Transfer . . . . . . . . . . . . . . . . . . . . . . 12
1.4 Thesis Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Chapter 2:
Polarizable anionic sublattices screen molecular dipoles in non-centrosymmetric
inorganic-organic hybrids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2 Experimental Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.3 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.5 Supplemental Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.5.1 Expanded Photophysics and Optical Measurements . . . . . . . . . . 26
2.5.2 Material Characterization . . . . . . . . . . . . . . . . . . . . . . . . 29
Chapter 3:
Computational analyses of diverse 2-aminoethylpyridine-based lead iodide hybrids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
3.2 Experimental Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

3.3 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
3.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
3.5 Supplemental Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.5.1 Dielectric Measurements . . . . . . . . . . . . . . . . . . . . . . . . . 39
Chapter 4:
Probing 1-methylquinoline and 1-naphthyl-amine based lead iodide hybrid materials for donor–acceptor charge transfer properties . . . . . . . . 41
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
4.2 Experimental Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
4.3 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
4.3.1 Structural Characterization and Packing Description . . . . . . . . . 47
4.3.2 Optical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
4.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
4.5 Supplemental Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
4.5.1 Solid State NMR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
4.5.2 VASP Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
4.5.3 Dielectric Measurements . . . . . . . . . . . . . . . . . . . . . . . . . 68
4.5.4 Material Characterization . . . . . . . . . . . . . . . . . . . . . . . . 69
Chapter 5:
Understanding the role of the organic dipole in templating the packing
of the extended solid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
5.2 Experimental Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
5.3 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
5.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
5.5 Supplemental Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

List of Tables
2.1 Integrated Intensities of (MDA)Pb2Br6 Emission Spectra . . . . . . . . . . . 27
2.2 Rietveld Refinement Results for (MDA)Pb2I6 and (MDA)Pb2Br6 . . . . . . . 29
2.3 Crystallographic Data for (MDA)Pb2Br6 . . . . . . . . . . . . . . . . . . . . 30
3.1 Comparison of Structural Details between (PEA)2PbI4, (2-AEP)2PbI4, and
(2-AEPH)PbI4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
3.2 Effective and Reduced Masses of Charge Carriers using SOC-DFT . . . . . . 36
4.1 Methyl Hydrogen and Ammonium Hydrogen Distances in (1-MQ)(1-NA)Pb2I6 65
4.2 Experimental Solid-State NMR Parameters . . . . . . . . . . . . . . . . . . . 66
4.3 Crystallographic Data for (1-MQ)PbI3 . . . . . . . . . . . . . . . . . . . . . 70
4.4 Crystallographic Data for (1-MQ)(1-NA)Pb2I6 . . . . . . . . . . . . . . . . . 71
5.1 Crystallographic Data for (ODA)PbI4 . . . . . . . . . . . . . . . . . . . . . . 87
5.2 Crystallographic Data for (MDA)PbCl4 . . . . . . . . . . . . . . . . . . . . . 88
5.3 Crystallographic Data for (DBP)PbCl3 . . . . . . . . . . . . . . . . . . . . . 89
5.4 Crystallographic Data for (4-MQ)PbI3 . . . . . . . . . . . . . . . . . . . . . 92
5.5 Crystallographic Data for (5-MQ)PbI3 . . . . . . . . . . . . . . . . . . . . . 93
5.6 Crystallographic Data for (1-MQ)PbBr3 . . . . . . . . . . . . . . . . . . . . 94

List of Figures
1.1 General Project Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 Perovskite Alignment Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 NREL Solar Cell Efficiency Chart . . . . . . . . . . . . . . . . . . . . . . . . 4
1.4 MAPI Electronic Strucutre . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.5 Charge Density of (MDA)Pb2I6 . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.6 Perovskite Structure Based on Dimensionality . . . . . . . . . . . . . . . . . 7
1.7 Second Harmonic Generation Diagram . . . . . . . . . . . . . . . . . . . . . 9
1.8 Exciton Emission Pathways . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.9 Schematic of 2D Mixed Hybrid System . . . . . . . . . . . . . . . . . . . . . 13
2.1 Rietveld Refinements of (MDA)Pb2I6 and (MDA)Pb2Br6 . . . . . . . . . . . 19
2.2 (MDA)Pb2I6 and (MDA)Pb2Br6, DOS and Band Diagrams . . . . . . . . . . 20
2.3 (MDA)Pb2I6 and (MDA)Pb2Br6 Kubelka-Munk Transform . . . . . . . . . . 21
2.4 (MDA)Pb2I6 and (MDA)Pb2Br6 TD Emission . . . . . . . . . . . . . . . . . 22
2.5 (MDA)Pb2I6 and (MDA)Pb2Br6 SHG . . . . . . . . . . . . . . . . . . . . . . 23
2.6 (MDA)Pb2I6 and (MDA)Pb2Br6 Capacitance and Loss . . . . . . . . . . . . 24
2.7 Kubelka-Munk Transforms of MDA and Pb Salts . . . . . . . . . . . . . . . 26
2.8 (MDA)Pb2Br6 Full TD Emission Data Set . . . . . . . . . . . . . . . . . . . 28

3.1 Crystal Structures of (PEA)2PbI4, (2-AEP)2PbI4, and (2-AEPH)PbI4 . . . . 34
3.2 Band Structures and Densities of State for (PEA)2PbI4, (2-AEP)2PbI4, and
(2-AEPH)PbI4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.3 Zoomed Band Structures and Densities of State for (PEA)2PbI4, (2-AEP)2PbI4,
and (2-AEPH)PbI4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
3.4 Dielectric Measurements of (2-AEP)2PbI4 and (2-AEPH)PbI4 on Warming . 39
3.5 Dielectric Measurements of (2-AEP)2PbI4 and (2-AEPH)PbI4 on Cooling . . 39
3.6 Dielectric Measurements of (PEA)2PbI4 . . . . . . . . . . . . . . . . . . . . . 40
4.1 (1-NA)PbI3 and (1-MQ)PbI3 Structures . . . . . . . . . . . . . . . . . . . . 48
4.2 (1-MQ)(1-NA)Pb2I6 Hybrid Structure . . . . . . . . . . . . . . . . . . . . . . 49
4.3 Cationic Dipoles of the Mixed Hybrid and Its End Members . . . . . . . . . 50
4.4 1H14N ssNMR Spectra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
4.5 1H14N D-HMQC ssNMR Spectra for (1-NA)PbI3, (1-MQ)PbI3, and (1-MQ)(1-
NA)Pb2I6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
4.6 207Pb Spin Echo ssNMR Spectra . . . . . . . . . . . . . . . . . . . . . . . . . 52
4.7 1H207Pb TONE D-HMQC ssNMR Spectra for (1-NA)PbI3, (1-MQ)PbI3, and
(1-MQ)(1-NA)Pb2I6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
4.8 1H→13C CP ssNMR Spectra for (1-NA)PbI3, (1-MQ)PbI3, and (1-MQ)(1-
NA)Pb2I6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
4.9 2H Spin Echo ssNMR Spectrum and 1H2H DE-RESPDOR Spectra . . . . . . 55
4.10 RMSD Curve Regarding the Distance Measurements . . . . . . . . . . . . . 56
4.11 DE-RESPDOR Dephasing Curves and Molecular Distance Visualization . . . 57
4.12 Density of States and Band Diagrams of a) (1-MQ)PbI3 b) (1-NA)PbI3 and
c) (1-MQ)(1-NA)Pb2I6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
4.13 Charge Density at the CBM and VBM of (1-MQ)PbI3 and (1-NA)PbI3 . . . 59

4.14 Normalized Kubelka-Munk Transform of (1-MQ)PbI3, (1-NA)PbI3, and (1-
MQ)(1-NA)Pb2I6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
4.15 Temperature Dependent Emission Spectra of a) (1-MQ)PbI3 b) (1-NA)PbI3
and c) (1-MQ)(1-NA)Pb2I6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
4.16 (1-NA)PbI3 Dielectric Measurements . . . . . . . . . . . . . . . . . . . . . . 62
4.17 Temperature Dependent Lifetime of a) (1-NA)PbI3 and b) (1-MQ)PbI3 . . . 63
4.18 Emission and Excitation Spectra of (1-NA)I and (1-MQ)I at 77 K . . . . . . 64
4.19 1H13C HETCOR ssNMR Spectra for (1-NA)PbI3, (1-MQ)PbI3, and (1-MQ)(1-
NA)Pb2I6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
4.20 Charge Density of (1-MQ)(1-NA)Pb2I6 at the VBM and CBM . . . . . . . . 67
4.21 (1-MQ)PbI3 Dielectric Measurements . . . . . . . . . . . . . . . . . . . . . . 68
4.22 (1-MQ)(1-NA)Pb2I6 Dielectric Measurements . . . . . . . . . . . . . . . . . 68
5.1 (ODA)PbI4 and (MDA)PbCl4 Structures . . . . . . . . . . . . . . . . . . . . 79
5.2 (MDA)PbCl4 Kubelka-Munk Transform and Temperature Dependent Emission 80
5.3 Density of States and Band Diagrams for (ODA)PbI4 and (MDA)PbCl4 . . . 80
5.4 (DBP)PbCl3 Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
5.5 Structures of (4-MQ)PbI3, (1-MQ)PbBr3, and (5-MQ)PbI3 . . . . . . . . . . 82
5.6 (1-MQ)PbBr3 Kubelka Munk Transform and Temperature Dependent Emission 83
5.7 (4-MQ)PbI3 Kubelka Munk Transform and Temperature Dependent Emission 84
5.8 (5-MQ)PbI3 Kubelka Munk Transform and Temperature Dependent Emission 85

Abstract
With the emergence of hybrid perovskites as promising solar harvesting materials just under two decades ago, the field has been inundated with studies about how to improve their
device performance. While their use in solar cells is a highly active area of research, there
is still much to be learned about the fundamentals of the interplay between the organic and
inorganic components. This body of work represents a contribution to the understanding of
structure property relationships in the field of hybrid organic-inorganic materials development. Chapter 2 explores the concept of incorporating polar organic cations into the solid
state with (MDA)Pb2Br6 and (MDA)Pb2I6; Chapters 3 and 4 discuss the methodology and
synthetic techniques used to create systems with mixed cations in the solid state. The final
Chapter explores materials which are analogous to those in Chapters 2, 3, and 4, but display
differences in structure or properties.
We sought to better understand how polar organic cations could lend themselves to a
solid state dipole in the first project by looking at materials based on 4,4’-methylenedianiline.
Initial probing showed that the lead iodide analog crystallized in a non-centrosymmetric or
polar space group. Exploring the bromide and chloride analogs indicated that the halide has
a strong impact on both the structure and second harmonic properties which result in the
chloride analog displaying centrosymmetry.
With the next two projects, we wanted to explore the possibility of incorporating more
than one cation in the solid state with ordered packing. This began with the phenethylamine (PEA) and 2-aminoethyl pyridine (2-AEP) systems which are well studied in the
layered material space. Despite similar structures between PEA and 2-AEP, the differences
in electronic properties prohibited them from crystallizing in the same solid. Stumbling upon
the 1-naphthylammonium (1-NA) lead iodide hybrid led us to explore that organic structure
as a candidate for solid phase, ordered mixing. Discovering that the 1-methylquinolinium

(1-MQ) lead iodide hybrid crystallized with nearly identitcal organic packing indicated that
(1-NA) and (1-MQ) might be able to pack together in a system. The discovery of (1-MQ)(1-
NA)Pb2I6 represents the first 1-D material that displays ordered cation packing in the solid
state. Both of these projects sought to create materials that might display interesting charge
transfer properties, which was not achieved. Although this goal was not met, much was
learned about how to better select cation pairs and leaves the door open to further research
to create materials that have both mixed, ordered cationic packing and interesting charge
transfer properties.

Chapter 1
Introduction
While this work highlights a wide variety of materials, three core Objectives were kept
in mind during these investigations as shown in Figure 1.1. The first Objective was to
explore hybrid materials which incorporate organic cations known to be optically active.
The second Objective focused on the ability of the cation to provide more tunability to the
properties of the extended solids. The third and final Objective aimed to create materials
with both donating and accepting cations alternating in the solid state in order to explore
charge transfer properties. The materials highlighted herein primarily fall initially into the
second Objective and shift to the study of materials that fit under Objective three. The first
Objective is a through line that is touched on throughout this body of work.
The major focus of Objective two is the synthesis and characterization of hybrids with
polar organic moieties. Based on preliminary investigations done by Taylor Hodgkins, a
hybrid inorganic-organic lead iodide material was identified as having a permanent dipole
in the solid state due to the organic packing. The material highlighted for Objective three
incorporates two distinct organic cations in the solid state. While the material discussed
in this body of work does not display charge transfer characteristics between the cations,
the ordered packing seen in the hybrid is the first of its kind and points towards new and
interesting avenues to explore in the realm of charge transfer materials.
This introduction will lay the motivational groundwork and provide a general view of
perovskites and more specifically hybrid lead halide materials as a wider class. Brief discus-

Figure 1.1: The three main objectives of this body of work
sions of second harmonic generation, excited state charge transfer, and are also included to
orient the reader around the types of characterization techniques to be discussed.
1.1 Motivation
The hunt for renewable energy sources has resulted in a wide variety of chemically interesting
materials. Over the past fifteen years, research into solar cells with hybrid perovksites as the
active solar absorbing component have exceeded 25% efficiency.[1] In addition to being more
efficient than silicon based cells, these devices are generally easier and cheaper to manufacture
as perovskites are highly solution processable.[2, 1] While there are clear advantages to
these materials, there is still room to improve them and tune them for a wider variety of
applications.[1]
1.1.1 Looking to Perovskites for Inspiration
At their most pure, perovskites are materials with the formula ABX3 with A and B always
being metals. While perovskites are a very large structure class in crystallography, perovskite

in the more recent lexicon largely refers to hybrid materials used for solar cells, light emitting
devices, and photodetectors among other uses. The work highlighted in this thesis is inspired
by this type of perovskite or more specifically, hybrid lead halide perovskites, which differ
from a pure perovskite in their composition. The primary target of more recent perovskite
studies is methylammonium lead iodide ((CH3NH3)PbI3, MAPI) seen in the bottom left
corner of Figure 1.2. This material contains corner sharing lead iodide octahedra with the
A site within the inorganic lattice containing the freely rotating methylammonium cation.
Figure 1.2: Depiction of the variety of materials given the moniker perovskite[3]
The past decade has been inundated with studies of hybrid metal-halide perovskites due
to their high tolerance to defects, solution processability, and optoelectronic properties, [4,
5, 6, 2] with the vast majority of attention focused on three dimensional structures, like
MAPI. [7] Figure 1.3 shows a vast array of solar cell devices and how their efficiencies have
improved over time. While these phases exhibit exceptional photovoltaic performance, their
functionality can be largely attributed to the inorganic portion of the hybrid,[8, 9, 10] with
the organic molecules serving primarily as structural building blocks. A major through line
across this body of work is carefully selecting cations, particularly those with unique optical

Figure 1.3: Experimental solar cell efficiencies from 1974 to now[11]
properties, to better hone the optoelectronic properties of the resulting extended solids.
Figure 1.4 shows the structure of MAPI with the organic cation shown in the A-site.
Looking at the PDOS and the band structure reveals that the methylammonium cation
does not contribute to the electronic strucutre in a meaningful way.[12] Both the conduction
band minimum and the valence band maximum only show contributions from the inorganic
portion of the material, depicted in green. The PDOS also shows only the I 5p and Pb
6p orbitals at the band edges. Changes to the cation in this corner sharing structure do
lead to minor changes in the packing, but the optoelectronic properties are still completely
dominated by the inorganic portion of the material. The systems highlighted in this body
of work aim to put the cation in a more active role in relation to the electronic properties
of the hybrids as well as other physical and optical properties. The next section will get
deeper into the discussion of choosing and tuning the cation to have more of an impact on
the properties of the material as a whole.

Figure 1.4: Visualization of MAPI and its DOS and Band Structure[12]
1.1.2 Harnessing the Power of the Cation
Attempts to introduce organic moieties with more optical properties in the more desirable
visible range have demonstrated that the increased size that is typically required to achieve
larger molecules results in crystal structures with reduced dimensionality in the inorganic
connectivity through sheet and chain-like topologies.[13, 7, 14, 15, 16] While the reduced
connectivity between the metals and ligands in these phases makes them less attractive
for photovoltaic applications, where high charge-carrier mobility is required, the ability to
precisely control the separation between the HOMO and LUMO levels as well as the geometric shape of the molecules offers a promising avenue for tailoring the functionality of these
materials. [17, 10, 18, 19, 20, 16]
Research focusing on organic solar cells has resulted in devices with up to 11% efficiency.[21] Although the devices are not the most efficient, the benefits of these materials
include ease of manufacturing and abundant feed stocks. Additionally, organic chromophores
are highly tunable by nitrogen substitution.[22, 21, 23] Nitrogen substitution for carbon has
been shown to stabilize both the HOMO and LUMO energies. Specifically choosing and
tuning cations with high electron and hole mobilities and with fronteir orbitals near the
band edges of the inorganic lattice creates the possibility of avoiding many of the issues seen

in lower dimensional materials.
Incorporating chromophore cations with high optical tunability into inorganic frameworks
presents a way to avoid some of the pitfalls of either type of material alone. Combining
these moieties can create systems where the organic cation could inject a hole or an electron
onto the inorganic framework. Figure 1.5 shows the charge density of (MDA)Pb2I6 at the
VBM and CBM. Given the localization of the charge either around only the organic or only
the inorganic, this material shows the clear possibility for charge transfer between these
moieties. This concept is not extensively explored in this work but instead establishes the
idea of including optically active organic cations into inorganic lattices.
1.2 Diverse Structures of the Hybrid Perovskite
As stated earlier in this introduction, perovskite in the broader world of crystallography
is a particular crystal type with corner sharing octahedra and an ABX3 stoichiometry.[24]
The dimensionality of a perovskite always refers to how the inorganic lattice packs in the
solid state. In 3D hybrid perovskites, the A site is occupied by a small organic cation that
must fit the Goldschmidt tolerance factor.[25, 24] Figure 1.6 shows a generalized view of a 3D
perovskite with corner sharing octahedra. All octahedra in these systems are fully connected
with every halogen anion bridging two octahedra. As the cation grows and becomes too big
for the A site in a 3D system, the octahedra must pack in either a 2D or a 1D morphology
Figure 1.5: Charge density of (MDA)Pb2I6 on the valence band maximum (right) and
conduction band minimum (left)

to accommodate the larger organic molecule.
2D perovskites consist of sheets of corner sharing metal halide octahedra which usually
have either one or two cation thick layers between each sheet as seen in Figure 1.6. The
corner sharing connectivity is only seen in the plane of the sheets with the halides pointing
along the opposing axis towards the organic cations. The positively charged ammonium
portion of the organic cation packs in towards the negatively charged sheets. Some of
the materials discussed in this body of work are purely 2D, but a class called quasi 2D
perovskites also exists. Within the class of quasi 2D systems materials typically crystallize
as either Ruddlesden-Popper or Dion-Jacobsen phases.[24, 26] These materials incorporate
a larger and a smaller cation in a 3D and 2D style packing arrangement, respectively. In
this way, the structural aspects of 2D and 3D perovskites are combined in one system.
The majority of the materials discussed in this work are 1D perovskites. In this type of
system, edge sharing metal halide octahedra form chains which traverse along one axis of the
material, generalized in Figure 1.6. These materials can accommodate much larger cations
like dyes or chromophores. These materials typically have larger band gaps compared to
3D or 2D counterparts which makes them stronger candidates for incorporation of cationic
optoelectronic properties. As with any perovskite, the positively charged portion of the
cation packs toward the negatively charged inorganic chain. Unlike 2D or 3D systems, it is
much harder to predict the final strucutre of the material as many more structural knobs
are tunable when dimensionality is lowered. While not discussed in this work, there is one
Figure 1.6: Generalized Perovskite Structures Based on Dimensionality

final type of hybrid, 0D. These systems do not display any type of connectivity between the
metal halide octahedra in the system.
1.3 Exploring Diverse Functionality of Hybrid Materials
As stated earlier in this chapter, hybrid organic-inorganic systems are a desirable class of
materials due in part to their diverse applications.[4, 5, 2] The subsequent sections of this
chapter will cover in more detail the specific properties that will be discussed throughout
the thesis. Optical properties are the major focus with second harmonic generation of light
and emission properties of 1D materials getting specific focus, and the interplay of cationic
structure and extended solid properties is of particular interest to this work.
1.3.1 Second Harmonic Generation
The first set of materials discussed in Chapter 2 are of interest for their non-centrosymmetric
space group and therefore possible second harmonic generation (SHG) properties.[27] SHG
or frequency doubling is the process through which two photons are excited to a virtual
state and when they relax, one photon of half the wavelength and at exactly double the
frequency is emitted.[28, 29] This is an optical process but differs greatly from something like
fluorescence where excited photons relax and light is always emitted at less than double the
frequency of the incident radiation. Additionally, SHG is a very fast process happening within
femtoseconds of radiation whereas fluorescence typically occurs on the nanosecond time
scale.[29] Figure 1.7 shows simplified Jablonski diagrams comparing these two processes.[30]
The most notable application of SHG materials is in lasers.[27] SHG active crystals,
such as potassium dihydrogen phosphate, are used to convert 1064 nm red light into 532 nm
green light. While KDP is a very common SHG material, dozens of materials exist which also

Figure 1.7: Diagram highlighting the differences between fluorescence and second harmonic
generation[30]
exhibit non-linear optical properties. The criteria generally accepted as the most important
for SHG materials are acentricity, an absorption edge <200 nm, a large SHG coefficient
d
ij , a birefringence value that allows for phase matching between UV and DUV, chemical
stability and resistivity to laser damage, and the ability to grow large, high quality single
crystals.[31, 32, 33] While these guidelines are helpful when looking into well known material
classes, there is still much to learn in terms of material design for new SHG materials and
specifically looking at SHG properties in hybrid inorganic-organic materials.[29, 34]
Hybrid organic-inorganic systems are of particular interest as non-linear optic materials
because many have shown the ability to switch on and off in the presence of external stimuli,
such as temperature.[35, 36, 37] Altering the cation is the main way the structure is tuned
to achieve a non-centrosymmetric lattice. While some of these systems have shown much
better SHG intensity compared to potassium dihydrogen phosphate (KDP), a common SHG
standard,[34] other issues related to air and water stability as well as radiation stability are
not up to par. Even though materials such as KDP are not likely to be replaced by hybrid
materials, the design concepts around manipulating the cationic component demonstrate the
importance of the organic moiety of hybrid lead halides.

1.3.2 Emission Properties of 1D Materials
Studies have spanned from 3D perovskites[38, 39, 40] to quasi-2D systems and devices[41,
42, 43] to 2D perovskites[44, 45], but no 1D materials with ordered cations in a 1:1 mole ratio
have been reported. These diverse materials have shown the utility of combining cations, but
the nature of the packing does not often allow for direct interactions between the differing
species.[44, 45] 1D systems offer the ability for multi-plane interactions between cations in
the solid state. Judiciously choosing organic cations with unique properties in tandem opens
up the possibility of further enhancing optoelectronic properties of hybrid materials.
Low dimensional hybrid organic-inorganic materials offer the ability to more thoughtfully incorporate the optoelectronic properties of the cations into the overall material.[7, 46]
Because of the ability to more easily create self-trapped excitons, 1D materials have largely
been studied for their emission and other photophysical properties rather than solar harvesting device applications.[47, 48, 49] While the effects of changing the halide, the metal, or the
cationic species have been explored, there have not been investigations into mixing cations
in the solid state.
Excitons are simply free charge carriers generated when a system is stimulated to an
excited state.[50] These carriers relax into states with lower energy than the band gap and
cause lattice distortions, which is more easily achieved in lower dimensional systems.[50, 51,
52] In order to understand the mechanisms for emission in extended hybrid solids, intrinsic and extrinsic, radiative and nonradiative exciton recombination pathways must all be
considered.[53, 52] Lattice interactions or exciton-phonon coupling generally constitutes an
intrinsic pathway called intrinsic self trapping.[50, 53] When the binding energy of excitonphonon coupling exceeds a critical value, charge carriers become immobilized. Extrinsic
trapping can also occur when excitons are immobilized due to a defect rather than phonon
coupling. Once an exciton has relaxed slightly from the conduction band minimum energy
into a trap state, it then relaxes further through either radiative or nonradiative pathways

Figure 1.8: Exciton a) radiative and b) nonradiative decay pathways
to the ground state.[52, 53] Figure 1.8 shows how different traps can result in different decay
pathways from an excited state. Figure 1.8a & b depict radiative and nonradiative decay
pathways, respecitvely. Excitons can fall into different depth traps within the same system
leading to different emission pathways existing in one material.[51, 50, 53, 52]
Hybrid organic-inorganic systems clearly show unique emission character, but many materials still do not optoelectronically incorporate the organic cation.[54] The HOMO-LUMO
gap of organic cations largely used in hybrid materials is larger than the band gap of the
inorganic lattice.[50, 54] In systems with a lower dimensionality, the organic cation can have
a larger effect on the overall structure of the extended solid, but careful selection is still
necessary to have the cation play a more meaningful role in the optoelectronic properties.
Incorporating dye molecules or other optoelectronically interesting cations is a promising
direction to take these materials in.[54, 52]
While not completely achieved in this work, the possibility of combining cations in the
solid state in systems which allow them to interact creates a new and unique way to tune
optoelectronic properties of hybrid materials. Creating a network of donor and acceptor
cations could allow free excitons to move and recombine in new and interesting ways.

1.3.3 Excited State Charge Transfer
A significant part of the objective to explore cationic charge transfer within extended solids
was inspired by the work of Professor Mark Thompson. The idea of combining donor and
acceptor molecules in the same system has been extensively explored in the realm of organic
LEDs, and has created materials which are much more efficient at emitting light.[55, 56, 57]
These systems pair functionality within one material, or molecule, rather than needing to
rely on two unique materials.
As explored in the previous section, the emission properties of hybrid materials are
unique. Excitons are often subjected to trap states, but those that are not may be able to
act more as charge carriers in the excited state. While this process has been well explained
in molecular systems,[55, 34, 56] its origins are less evident in hybrid extended solids.[58, 59]
Additionally, the concept of transferring energy from 3D perovskites to molecular systems
has been explored,[60] but this still creates the issue of needing to tune two separate systems
to work together.
Recent research has explored combining donor and acceptor regions into one large molecule,[61]
but there have been no reports of extended solids exploiting these relationships. In single
molecule systems, charge transfer between two ligands is often facilitated by a metal bridge.
In solid systems, the charge transfer phenomenon has to happen across space rather than
through bonds. Charge transfer transitions in solid systems would come at lower energy
compared to absorption transitions for either cation which would also work to expand the
hybrid’s absorption spectrum. Ideally, the donor-acceptor charge transfer should lead to
charge injection into the inorganic chains or sheets. While this work only explores one
mixed cation hybrid, the proof of concept opens the door to more selectively choose donoracceptor pairs to explore how the cationic charge transfer interactions affect charge and
energy transfer to the inorganic moiety. Additionally, the more forgiving structure of 2D
perovskites may allow for more cationic structural diversity within the donor-acceptor pairs.

Figure 1.9: Left - possible structure of layered mixed hybrid. Right - examples of donor
and acceptor cations
Figure 1.9 shows a schematic of a hypothetical mixed layered perovskite and possible donor
and acceptor cations.
1.4 Thesis Overview
Chapters 2 discusses published work on non-centrosymmetric hybrid lead halide systems.[62]
Chapter 3 covers contributions to Gemma (Yang) Goh’s thesis work focusing on 2-AEP
and PEA lead halide hybrid systems. Chapters 4 explores mixing naphthylammonium and
quinolinium cations in the solid state to investigate the possibility of charge transfer between
cations suspended in an inorganic lattice. Chapter 5 details other materials related to those
discussed in Chapters 2 & 4 and goes into why structural differences in the extended solids
are seen with similar cationic species.
Chapter 2 explores how cations with strong dipoles can translate their properties to

extended solid systems. Two non-centrosymmetric, isostructural systems, (MDA)Pb2I6 and
(MDA)Pb2Br6, are investigated with a primary focus on second harmonic generation (SHG)
due to the permanent dipole in the structures.
Chapter 3 highlights computational contributions to the work of Goh et.al. on layered
phenethylammonium and 2-aminoethyl pyridinium lead iodide systems. Density functional
theory (DFT) was employed using the VASP program to gain a better understanding of the
electronic properties of the systems through band diagrams and density of state diagrams.
This chapter also includes work performed by Goh to give a holistic view of the project with
a particular focus on the dielectric measurements and correlations to the DFT calculations.
Chapter 4 transitions into the third Objective mentioned at the beginning of the chapter
and looks at systems with paired cations. The synthesis and characterization of the novel
system (1-MQ)(1-NA)Pb2I6 as well as the pure materials (1-MQ)PbI3 and (1-NA)PbI3 is
discussed in detail. Several ssNMR techniques are explored to determine the structure of the
mixed hybrid as X-ray techniques cannot distinguish between the two cations. This chapter
also discusses the optical properties of the three materials including temperature dependent
emission and lifetime.
Chapter 5 discusses further investigations into systems with analogous cations to 4,4’-
methylenedianilinium cations and methylquinolinium cations. Despite the cations being
isostructural to those in Chapters 2 & 4, the extended solid systems to not crystallize in the
same space groups. Possible explanations for this phenomenon will be discussed as well as
an analysis of each structure and select optical properties of the various systems.

Chapter 2
Polarizable anionic sublattices screen
molecular dipoles in non-centrosymmetric
inorganic-organic hybrids
2.1 Introduction
This chapter reports on a pair of hybrids based on 4,4’-methylenedianiline (C13H14N2; MDA),
chosen for its strong intrinsic dipole, in which the organic cations crystallize in a chevronlike pattern to create a strongly coherent dipole that breaks the inversion symmetry of
the structure to produce a polar material. X-ray diffraction, second harmonic generation
(SHG) studies, emission studies, and density functional theory (DFT) calculations were all
implemented to gain a better understanding of the role the cations play in these systems.
Despite isostructural systems, studies of the second harmonic generation (SHG) properties
of the iodide and bromide materials, (MDA)Pb2I6 and (MDA)Pb2Br6, reveal very different
results. The contrasting optical properties are attributed to differences in the character of
the halide sublattice and postulate that the increased polarizability of the iodide ions acts
to screen the local dipole moment, effectively reducing the local electric field in the crystals.

2.2 Experimental Details
The organic precursors, MDA·2HI and MDA·2HBr, were first prepared by dissolving 0.1 g
(0.50 mmol) of MDA in 5 mL of acetone. 0.5 mL of 57wt% (7.57 M) HI or 48wt% (8.89 M)
HBr was then added and stirred to combine. This solution was then transferred to a glass
Petri dish and placed on a warm hot plate to evaporate the solvent.
Crystals of (MDA)Pb2I6 were grown following the procedure reported by Lemmerer and
Billings. [13] 0.1 g (0.22 mmol) of lead (II) iodide (PbI2, 99.9985% (metals basis), Alfa
Aesar) and 0.055 g (0.28 mmol) 4,4’methylenedianiline (MDA, 97%, Sigma Aldrich) were
dissolved separately in 3 mL and 5 mL of hydroiodic acid (HI, 57 wt% (stabilized), Sigma
Alrdich) in 2 dram and 8 dram scintillation vials, respectively. Each solution was stirred
continuously while heating to 110 °C in an aluminum bead bath placed atop a hot plate.
Once the solids were fully dissolved, the solution of lead iodide was added to that of the
MDA and stirred while continuing to heat. The solution was allowed to cool naturally to
room temperature within the bead bath to encourage crystallization. The resulting crystals
were subsequently collected via vacuum filtration and rinsed thoroughly with diethyl ether
(≥98% (stabilized), VWR). To prevent any degradation due to exposure to the atmosphere,
samples were either stored in a dessicator or Ar-filled glove box to minimize degradation due
to atmospheric exposure.
The synthesis of (MDA)Pb2Br6 was adapted from the iodide with substituion of lead (II)
bromide (PbBr2, 99.998% (metals basis), Alfa Aesar) and hydrobromic acid (HBr, 48 wt%,
VWR). In contrast to the iodide, cooling to room temperature did not result in crystallization, so diethyl ether was layered on top at room temperature and allowed to sit for at least
24 hours. Attempts to make the chloride analog did not yield an isostructural product and
instead resulted in a slightly different polymorph that is discussed in the next chapter.
X-ray powder diffraction (XRD) was used to confirm the purity and composition of the
(MDA)Pb2I6 and (MDA)Pb2Br6. Samples were ground using an agate mortar and pestle

and characterized with a Bruker D8 Advance powder diffractometer equipped with a Cu-Kα
source and LynxEye XE–T detector. Data was collected from 5 to 70° 2θ angles with 0.02°
step size and 1 s per step. High resolution synchrotron XRD data was collected using the
mail-in program at the 11-BM beamline at the Advanced Photon Source (APS), Argonne
National Lab. Discrete detectors covering an angular range from -6 to 16◦ 2θ were scanned
over a 34◦ 2θ range, with data points collected every 0.001◦ 2θ and scan speed of 0.01◦
per s. The resulting patterns were evaluated using the method of Rietveld refinement as
implemented in the TOPAS-Academic (v6)[63] and GSAS-II software packages.[64] Figure
2.1 shows the results of the refinements as well as the Rwp values. Single crystal data for
(MDA)Pb2Br6 was collected using a Bruker APEX diffractometer with a CCD area detector.
Diffuse reflectance data was collected from 800–250 nm using a PerkinElmer Lambda 950
UV-Vis-NIR spectrophotometer equipped with a 150 mm integrating sphere to determine
the onset of absorption in powders diluted to 3 wt% in MgO and to approximate the optical
band gap using the Kubelka-Munk transform.[65]
Parallel plate capacitor method was used to measure the dielectric properties of (MDA)Pb2I6
and (MDA)Pb2Br6. Each material was ground using an agate mortar and pestle and pressed
into a 10 mm diameter, 2.02 mm thickness pellet. To adhere electrical contacts on either
faces of the pellets, conductive silver epoxy was used. The silver epoxy also acts as the
electrodes of the parallel plate capacitor. Dielectric measurements were taken from 2 to
400 K at frequencies of 1, 2, 5, 10, and 20 kHz. The sample temperature was achieved by
using a Quantum Design Physical Properties Measurement System (PPMS) Dynacool. The
dielectric measurements were taken using a Andeen-Hagerling 50 Hz - 20 kHz Ultra-precision
Capacitance Bridge (AH2700A).
Approximately 2 g of both (MDA)Pb2I6 and (MDA)Pb2Br6 were ground and sieved into
distinct particle size ranges (<20, 20–45, 45–63, 63–75, 75–90, 90–125 µm) for the phase
matching experiment. The respective powders were transferred to individual quartz tubes
and sealed for measurement. Relevant comparisons with known SHG-active materials were

made by grinding and sieving crystalline α-SiO2 and potassium dihydrogenphosphate (KDP)
into the same particle size ranges. The samples were excited using a Nd-YAG laser source
with 1064 nm output. Any light emitted at 532 nm was amplified via a photomultiplier tube
and collected at a detector. No index matching fluid was used in the experiment.
Photoluminesence spectra of (MDA)Pb2Br6 and (MDA)Pb2I6 were collected using neat
solid samples in a cryostat system as described below. Each sample was sandwiched between
two 1 mm thick sapphire disks and excited at 365 nm LED source. Steady state emission
spectra were collected from 4–290 K using a Photon Technology International QuantaMaster
model C-60SE spectrofluorimeter in tandem with a Janis model SHI-4-2 optical He cryostat
equipped with a Lakeshore model 335 temperature controller. Excited state lifetimes were
evaluated from 4–150 K and were determined by the time-correlated single-photon counting
method (TCSPC) using an IBH Fluorocube instrument using a 372 nm pulsed diode for
the (MDA)Pb2Br6 sample; whereas, the (MDA)Pb2I6 was not bright enough to evaluate the
lifetime at any temperature.
Periodic DFT calculations were performed using the Vienna Ab Initio Simulation Package
(VASP),[66, 67, 68, 69] using the projector augmented wave method to describe the interaction between core and valence electrons.[70] Density of states and band diagram plots were
visualized using sumo.[71] Pb 5d electrons were included in the valence, and all pseudopotentials were scalar-relativistic. Due to the size of the unit cells, the functional of Perdew, Burke
and Ernzerhof adapted for solids (PBEsol) [72] was used for geometrical relaxation, while
the Heyd, Scuseria and Ernzerhof (HSE06)[73, 74] functional, with the explicit inclusion of
spin-orbit coupling (HSE06+SOC), was used for electronic structure calculations, including
density of states and electronic band structure, performed using the PBEsol-relaxed structures. PBEsol and HSE06+SOC have been previously demonstrated to be highly accurate in
the prediction of structural and electronic properties respectively of hybrid inorganic-organic
materials.[6, 75, 76] The total energy of both bromide and iodide compounds was found to
be converged to within 1 meV per atom using a plane wave energy cutoff of 400 eV, and a

Γ-centred k-point mesh of 4×4×4. Geometry optimization was considered converged when
the forces on each atom fell below 0.01 eV Å
−1
, and the planewave cutoff was increased to
560 eV during relaxation to avoid Pulay stresses.
2.3 Results and Discussion
The preparation described above yielded small, yellow (iodide) or white (bromide) needle-like
crystals, which differs slightly from the report of Lemmerer and Billing for (MDA)Pb2I6 who
note their crystals adopted a plate-like habit.[13] Rietveld refinement [77] against synchrotron
XRD scattering from ground crystals, shown in Figure 2.1 (a) and (b), shows the bulk of the
product is a highly pure single phase with tables of the refined parameters given in Table
2.2 and 5.2.
The structure of the hybrid crystallizes in the non-centrosymmetric space group F dd2
(#43) and is illustrated from two different perspectives in the insets of Figure 2.1 (a) and
(b). The fully inorganic regions consists of edge-sharing chains of lead-centered octahedra
running along the c-axis with the MDA cations positioned in between and held in place
Figure 2.1: Results of the Rietveld refinement of the (a) (MDA)Pb2I6 and (b)
(MDA)Pb2Br6 structures against synchrotron X-ray diffraction data collected on the 11-
BM beamline at Argonne National Lab

through hydrogen bonding between the amine group and iodide ions. Interestingly, the
molecules adopt a chevron-like configuration with the methylene bridge of each pointing
in a coherent fashion along the c-axis, parallel to the inorganic chains, which creates an
obvious macroscopic dipole running throughout the material. Such an ordered dipole within
a polar space group should be expected to give rise to non-linear optical signals, which will
be revisited in detail later.
Figure 2.2: Density of states and band diagrams for (a) (MDA)Pb2I6 and (b) (MDA)Pb2Br6
The calculated densities of state (DOS) for (MDA)Pb2Br6 and (MDA)Pb2I6, shown in
Fig 2.2, reveals a contribution from the lead halide octahedra to both the conduction and
valence band edges. The MDA cations have a greater energy contribution to the valence
band maximum in (MDA)Pb2Br6 compared to (MDA)Pb2I6. As would be expected, the
band gap energy for the bromide hybrid increases relative to the iodide hybrid with a direct
band gap of 3.54 eV in (MDA)Pb2Br6 and a direct band gap of 2.69 eV in (MDA)Pb2I6.
The lead 6s and the bromine 4p/ iodine 5p orbitals in both materials are at the top of the

Figure 2.3: Kubelka–Munk transform of (a) (MDA)Pb2I6 and (b) (MDA)Pb2Br6 with
photos of powder inset.
valence band, but the carbon 2p orbital is much closer to the band edge in (MDA)Pb2Br6.
The lead 6p orbital sits at the conduction band minimum with the carbon 2p orbital very
close to the band edge in both hybrids. The experimental and computational band gap
values are quite close for (MDA)Pb2I6, but the computation overestimated the band gap for
(MDA)Pb2Br6 compared to experiment
Diffuse reflectance spectra in the UV-visible range were collected from powders of (MDA)Pb2I6,
(MDA)Pb2Br6, PbI2, PbBr2, MDA·2HI, and MDA·2HBr to examine the optical properties.
A Kubelka–Munk transformation was applied to each data set to estimate the optical band
gap of each sample. Transforms for PbI2, PbBr2, MDA·2HI, and MDA·2HBr can be found in
the Supplemental Information Figure 2.7. Figure 2.3 shows the Kubelka—Munk transform
for (MDA)Pb2I6 and (MDA)Pb2Br6 along with insets of the bulk powder for each sample.
The band gaps for (MDA)Pb2I6 and (MDA)Pb2Br6 are 2.65 eV and 2.90 eV, respectively, as
determined by a linear fit to the onset of absorption. The absorption onsets for both PbI2
and MDA·2HI were red shifted compared to (MDA)Pb2I6. Whereas, the absorption onset
forPbBr2 and MDA·2HBr were blue shifted compared to (MDA)Pb2Br6.
(MDA)Pb2Br6 emits weakly at 595 nm at 290 K and strongly at 630 nm when cooled
to 4 K (Figure 2.4)b while (MDA)Pb2I6 emits only very weakly at temperatures below
80 K in Figure 2.4a. In addition to the overall peak shapes, the temperature dependence

Figure 2.4: Emission of a) (MDA)Pb2I6 and b) (MDA)Pb2Br6 from 4 K to 290 K (λex
= 365 nm)Inset shows (MDA)Pb2Br6 lifetime curve and fit from 10–90K. Data fit using a
two-level model
of the principal emission band for bromide and iodide compounds show similar behavior.
(MDA)Pb2I6 has an emission maximum of 620 nm at 4 K with a red shift to 628 nm at
75 K. . At temperatures up to 40 K, there is a clear peak at 450 nm that can be attributed
to free exciton emission in (MDA)Pb2Br6. The small feature at 690 nm corresponds to the
frequency doubling of the light source Figure 2.8 shows the complete emission profile that
includes spectra at more temperatures.
The lifetime data for (MDA)Pb2Br6 show that at low temperatures, the material is frozen
into a state with a markedly longer lifetime as seen in the inset of Figure 2.4b. The integrated
intensities of the emission bands (replotted onto a cm−1 axis) are constant in the 10–90 K
range (Table 2.1). It is unlikely that the radiative and nonradiative rates would have the
same temperature dependence, so the changes in lifetime in this temperature regime are
due to a drop in the radiative rate at lower temperatures. Fitting of the lifetime data to
an Arrhenius model (Figure 2.4b inset) gives an activation energy between the long and
short lived states of 23 meV. Unfortunately, luminescence from (MDA)Pb2I6 is too weak
to give accurate lifetime data, even at the lowest temperatures. Above 100 K nonradiative
decay process(es) begins to compete with the radiative decay of the excited state, and the
luminance efficiency drops continuously to a photoluminescence quantum yield < 1%. at

room temperature for both compounds.
The polar nature of the space group encouraged us to investigate the non-linear optical
properties, which revealed SHG activity for both halides. When compared with α-SiO2, the
SHG intensity of the (MDA)Pb2I6 is about 0.5 times as strong in the <20 µm range; whereas,
the response for (MDA)Pb2Br6 is very slightly larger in the 95–125 µm size range, with the
iodide showing non-phase-matching behavior whereas the bromide does phase-match as seen
in Figure 5. A comparison of the phase-matching performance of (MDA)Pb2Br6 with KDP is
also shown in Figure 2.5. It is curious, however, that despite what appears to be a substantial
well-aligned molecular dipole, neither (MDA)Pb2I6 nor (MDA)Pb2Br6 displays a strong SHG
intensity. To better understand the polar nature of the material, temperature-dependent
capacitance measurements were performed and are shown in Figure 2.6. The real part of the
capacitance for both samples follows the typical dependence expected for a simple thermal
contraction of the lattice on cooling, and it is notable that there are no peaks or significant
changes in slope, which rules out any ferroelectric transitions below room temperature. More
interestingly, there appears to be a strong correlation between the evolution of luminescence
in the two phases and features in the dielectric loss. We attribute this observation to a
freezing of the rotation degrees of freedom on the ammonium portion of the MDA cations as
Figure 2.5: SHG Phase matching curves of (a) (MDA)Pb2I6 and (b) (MDA)Pb2Br6 relative
to α-SiO2.

previously described by Fabini et al, [78, 79] which would suppress a source of non-radiative
quenching of the excited state and allow the observation of luminescence.
Aside from the weak SHG, there are no signatures in the dielectric properties to suggest
that the ordered dipole on the MDA molecules introduces any novel functionality, which is
somewhat surprising given the highly coherent alignment within the structure. We, therefore,
postulate that the polarizability of the halide sublattice acts to screen the internal electric
field created by these dipoles.[80] A recent report from Shen et al offers deeper insight on this.
Their report on a non-centrosymmetric morpholinium lead chloride and bromide systems
show phase-matching SHG effects of 0.70 and 0.81 times KDP, respectively, which would
seem to contradict what is seen in the MDA hybrids.[16] Yet, in contrast to the materials
we report, the dipole in their hybrids is primarily arises from the acentric coordination
environment of the metal halide octahedra. So while we believe the local electric field on the
MDA molecules serves to polarize the charge cloud of the inorganic sublattice to produce a
screening effect, the dipole of the morpholinium compounds is actually expected to increase
in more polarizable lattices as this allows for greater displacement of lead from the center of
its octahedra, in good agreement with their observations.
Figure 2.6: Capacitance and loss measurements on (a) (MDA)Pb2I6 and (b) (MDA)Pb2Br6
While the dielectric constant was difficult to evaluate at room temperature due to very
high dielectric loss resulting from non-negligible electrical conductivity through the pellet, data collected at 2 K and 20 kHz indicates a value of 11.0 and 8.3 respectively for

(MDA)Pb2Br6 and (MDA)Pb2I6. This supports the idea that the reduced polarizability of
the (MDA)Pb2Br6 inhibits its ability to screen the internal electric field and allows it to
exhibit a stronger SHG response.[81, 82] This finding provides a powerful materials design
principle to guide the development of hybrids with polar or non-linear optical properties and
points towards chloride and fluoride based hybrids to ensure low electrical conductivity and
small screening of any resulting electric fields.
2.4 Summary
In summary, we have demonstrated that (MDA)Pb2I6 and (MDA)Pb2Br6 both adopt noncentrosymmetric structures and consequently, exhibit weak SHG activity. Counterintuitively,
the iodide exhibits a weaker dielectric constant than the bromide and as a result shows a
similarly weaker SHG response. This behavior suggests that the increased polarizability of
the iodide screens the ordered dipole on the MDA molecules. While neither material exhibits
a ferroelectric transitions, this trend in SHG activity may suggest that the design of polar
hybrids should focus on chloride-based phases to maximize the attainable dipole moment.

2.5 Supplemental Information
2.5.1 Expanded Photophysics and Optical Measurements
Figure 2.7: Kubelka Munk transforms of (a) MDA·2HBr (b) MDA·2HI (c) PbBr2 (d) PbI2
from diffuse reflectance data; x-intercept of red fit lines corresponds to the band gap of each
material

Table 2.1: Integrated Intensities of (MDA)Pb2Br6 Emission Spectra from 10–90 K
Temperature (K) Area (x105
)
10 3.26
12 3.26
14 3.25
16 3.24
18 3.25
20 3.25
25 3.31
30 3.33
35 3.34
40 3.34
45 3.44
50 3.41
60 3.47
70 3.55
80 3.76
90 3.85

Figure 2.8: Emission of (MDA)Pb2Br6 from 4 K to 290 K (λex = 365 nm)

2.5.2 Material Characterization
Table 2.2: Results of the Rietveld refinement of (MDA)Pb2I6 and (MDA)Pb2Br6 against
the synchrotron powder diffraction data.
Parameter (MDA)Pb2I6 (MDA)Pb2Br6
Space Group F dd2 F dd2
a 25.35484 (11) 23.892617
b 43.13847 (21) 41.678311
c 4.537309 (21) 4.370651
C1 (0.7712, 0.17342, 0.9399) (0.5, 0.5, 1.411)
C2 (0.7208, 0.18129, 0.8439) (0.4903, 0.52876, 1.2094)
H2 (0.691, 0.1703, 0.9175)
C3 (0.71397, 0.20524, 0.6404) (0.4365, 0.53759, 1.116)
H3 (0.6795, 0.2106, 0.5748) (0.4051, 0.5266, 1.1983)
C4 (0.75756, 0.22134, 0.5328) (0.4278, 0.5621, 0.9061)
H4 (0.3911, 0.5672, 0.8389)
C5 (0.80796, 0.21347, 0.6288) (0.4737, 0.57884, 0.796)
H5 (0.8377, 0.2245, 0.5552)
C6 (0.81478, 0.18952, 0.8323) (0.5279, 0.57204, 0.8907)
H6 (0.8492, 0.1841, 0.8979) (0.5588, 0.5841, 0.8163)
C7 (0.75, 0.25, 0.344) (0.5356, 0.54676, 1.1004)
H7 (0.5723, 0.5418, 1.1693)
H7A (0.7812, 0.2529, 0.2152)
H7B (0.7188, 0.2471, 0.2152)
N1 (0.7793, 0.1495, 1.163) (0.4637, 0.60461, 0.571)
H1A (0.8144, 0.1476, 1.2025) (0.467, 0.4964, 1.5432)
H1B (0.7666, 0.131, 1.0957) (0.533, 0.5036, 1.5432)
H1C (0.7619, 0.1549, 1.3323)
H1N (0.433, 0.6189, 0.652)
H2N (0.447, 0.596, 0.376)
H3N (0.5, 0.6159, 0.53)
I1/ Br1 (0.671777, -0.01021, 0.6956) (0.42612, 0.73777, 0.5526)
I2/ Br2 (0.845551, 0.099621, 0.67675) (0.55268, 0.66626, -0.4321)
I3/ Br3 (0.693605, 0.082704, 0.17638) (0.40478, 0.65269, 0.066)
Pb1 (0.762971, 0.048165, 0.69027) (0.48763, 0.7013, 0.05691)
Rwp 8.447 2.908

Table 2.3: Crystallographic data for single crystal structure determination of (MDA)Pb2Br6
Parameter (MDA)Pb2Br6
Chemical formula C13H16N2Pb2Br6
Formula weight 1094.12
Temperature (K) 100
Crystal system orthorhombic
Space Group F dd2
a 23.895 (5)
b 41.682 (9)
c 4.3708 (10)
Volume 4353.3(17)
Z 8
C1 (0.50000, 0.50000, 1.41100)
H1A (0.46701, 0.49635, 1.54323)
H1B (0.53299, 0.50365, 1.54323)
C2 (0.49030, 0.52876, 1.20940)
C3 (0.43650, 0.53759, 1.11600)
H3 (0.40513, 0.52657, 1.19828)
C4 (0.42780, 0.56210, 0.90610)
H4 (0.39106, 0.56722, 0.83891)
C5 (0.47370, 0.57884, 0.79600)
C6 (0.52790, 0.57204, 0.89070)
H6 (0.55877, 0.58406, 0.81626)
C7 (0.53560, 0.54676, 1.10040)
H7 (0.57234, 0.54182, 1.16931)
N1 (0.46370, 0.60461, 0.57100)
H1N (0.43300, 0.61890, 0.65200)
H2N (0.44700, 0.59600, 0.37600)
H3N (0.50000, 0.61590, 0.53000)
Br1 (0.42612, 0.73777, 0.55260)
Br2 (0.55268, 0.66626, -0.43210)
Br3 (0.40478, 0.65269, 0.06600)
Pb1 (0.48763, 0.70130, 0.05691)
Rint 0.035

Chapter 3
Computational analyses of diverse 2-
aminoethylpyridine-based lead iodide hybrids
3.1 Introduction
(PEA)2PbI4 and (2-AEPH)PbI4 are two very extensively studied 2D or layered hybrid
organic-inorganic materials.[83, 84] This project focused on Objective 3 outlined in the Introduction to incorporate both donor and acceptor moieties into the solid state to explore
excited state charge transfer properties. Along with (PEA)2PbI4 and (2-AEPH)PbI4, the
novel (2-AEP)2PbI4 is also discussed because its similar cationic structure was thought to
give rise to similar packing. While the three molecules explored were found to be incompatible for creating a mixed cation system, much was gained in understanding the packing
in each of these systems and how variable charge centers impacts these well-known layered
materials.
The VASP calculations to better understand the optoelectronic properties of these materials are of particular highlight in this chapter. Looking at the band diagrams and density
of state plots as well as the charge carrier masses provided insight into how the structural

changes impact charge carrier mobility. This work and subsequent publication were in large
part completed by Yang (Gemma Goh) and this chapter will focus on the computational
contributions I made as well as context around the project as a whole.
3.2 Experimental Details
DFT calculations were performed on each of the three systems using the Vienna Ab Initio
Simulation Package (VASP).[66, 67, 68, 69] The projector augmented wave method was used
to describe the interaction between core and valence electrons.[70] Density of states and band
diagram plots were visualized using sumo.[71] Sumo was also used to calculate the electron
and hole effective masses from the band structures.[71] The functional of Perdew, Burke,
and Ernzerhof adapted for solids (PBEsol) [72] was used for geometrical relaxation. Spin
orbit coupling (PBEsol+SOC) was included for electronic structure calculations, including
density of states and electronic band structure. The total energy for all three compounds
converged to within 10 µeV per atom using a plane wave energy cutoff of 600 eV and a Γcentered k-point mesh of 2×2×1. The plane wave energy cutoff was not altered for the
geometric relaxation step and the calculation was considered converged when the forces on
each atom fell below 0.01 eV Å
−1
.
These calculations were performed by first converting the structures from the cifs to
POSCAR files using VESTA. The POSCAR file was then used to determine the kpoints and
the primitive cell using the sumo-kgen function as part of the sumo suite. The workflow then
proceeds to structural relaxations using ASE scripts to automate the iterrative calculations.
The relaxed structures are then used to perform self consistent (SCF) calculations. The
resulting CHGCAR file generated by this process is used in the density of state and band
structure calculations. The SCF, DOS, and band steps were performed at PBEsol and
PBEsol+SOC levels simultaneously. Once the DOS and band steps were complete, the
sumo package was used for visualization and further data processing. Sumo-dosplot and

sumo-bandplot were used to visualize the DOS diagrams and band structures, respectively.
Sumo-bandstats was used to determine the effective charge carrier masses from the band
calculations.
The temperature dependent dielectric properties of (PEA)2PbI4, (2-AEP)2PbI4 and (2-
AEPH)PbI4 were measured in a parallel plate geometry. Each material was ground using
an agate mortar and pestle and pressed into 6 mm diameter pellets. (2-AEP)2PbI4 pellet
was vapor deposited with Au, while (PEA)2PbI4 and (2-AEPH)PbI4 pellets were vapor deposited with Al, on both faces of the pellets. Powder XRDs were taken before and after metal
deposition to ensure that the crystal structures of the pellets were retained. Dielectric measurements were taken from 10 to 300 K at frequencies of 1, 2, 5, 10, and 20 kHz. The sample
temperature was controlled using a Quantum Design Physical Property Measurement System (PPMS) Dynacool. The dielectric measurements were taken using an Andeen-Hagerling
2700A 50 Hz-20 kHz Ultra-Precision Capacitance Bridge.
Further experimental details can be found in the article published on this work or in the
dissertation of Yang (Gemma) Goh. The discussion of results in this chapter will focus on
the computational analysis of the 2-aminoethylpyridine-based hybrids as well as inclusion
of the dielectric data which has some correlation to the electronic properties determined by
DFT calculations.
3.3 Results and Discussion
The (2-AEP)+ cation has previously been used as a spacer cation in 3D FA0.92MA0.08PbI3
(MA = methylammonium; FA = formamidinium) perovskite to form 2D/3D perovskite solar
cells. [85] Li et al. noted the presence of a secondary phase of 2-AEP hybrid, depending on
the annealing temperature. It was found that the secondary phase is likely (2-AEP)2PbI4,
which crystallizes in the orthorhombic space group P bcn (#60). As shown in Figure 3.1(b),
the 2D inorganic sheet consists of corner-sharing [PbI6]
4− octahedra. (2-AEP)+ forms or-

Figure 3.1: Crystal structures of (a) (PEA)2PbI4,[83] (b) (2-AEP)2PbI4, and (c) (2-
AEPH)PbI4.[84] Different perspectives of the (2-AEP)+ packing in (2-AEP)2PbI4 are shown.
ganic cation bilayers that alternate with the inorganic layers. Dipole arrows depict the
cancellation of dipoles that drives the π-π interaction between adjacent (2-AEP)+ cations,
where the π-π distance is 3.44 Å. The N-N distance in (2-AEP)+ is 2.76 Å, showing presence
of intramolecular hydrogen-bonding. The crystal structures are depicted using VESTA.[86]
A brief comparison of the structural details between (PEA)2PbI4, (2-AEP)2PbI4, and
(2-AEPH)PbI4 hybrids is given in Table 3.1. The lead iodide octahedra in (PEA)2PbI4 is
mainly distorted in-plane, resulting in a Pb–I–Pb angle of 153.3°. Both (2-AEP)2PbI4 and
Table 3.1: Comparison of Structural Details between (PEA)2PbI4,[83] (2-
AEP)2PbI4, and (2-AEPH)PbI4[84]
Compound (PEA)2PbI4 (2-AEP)2PbI4 (2-AEPH)PbI4
average Pb–I–Pb (°) 153.3 167.9 164.5
Da 0.006 0.011 0.013
σ
2b 3.6 11.8 26.2
interlayer distance (Å)c 9.94 7.60 3.75
penetration depth of NH3 (Å)d 0.57 0.32 1.44
Values were quantified using VESTA.[86] a D is the distortion index based on
bond lengths[87]. b σ
2
is the bond angle variance.[88]
c The interlayer distance is defined by the interplanar distance between terminal
iodides.
d Penetration depth of NH3 is defined by the interplanar distance betweeen nitrogen in the ammonium group and the plane of terminal iodides.

Figure 3.2: Calculated band structures and densities of states (PBEsol+SOC) of (a)
(PEA)2PbI4, (b) (2-AEP)2PbI4, and (c) (2-AEPH)PbI4, visualized using sumo.[71]
(2-AEPH)PbI4 octahedra are mainly distorted out-of-plane, resulting in Pb–I–Pb angles of
167.9°and 164.5°, respectively. For both the distortion index, D[87] and bond angle variance,
σ
2
,[88] (PEA)2PbI4 has the lowest value and (2-AEPH)PbI4 has the highest value. The
penetration depth of the ammonium group, defined by the interplanar distance between
the nitrogen on the ammonium group and the plane of terminal iodides, is the smallest in
(2-AEP)2PbI4, followed by (PEA)2PbI4, then (2-AEPH)PbI4.
The calculated densities of state (DOS) for each hybrid, shown in Figure 3.2, indicate that
the contribution from the organic component moves closer to the minimum of the conduction
band going from PEA2PbI4 to (2-AEP)2PbI4 to (2-AEPH)PbI4. This tracks with the LUMO
energies expected for the organic cations, where (PEA)+ has the highest LUMO, followed by
(2-AEP)+, then (2-AEPH)2+, which are effectively the LUMO energies for phenyl, pyridyl,
and pyridinium, respectively. The band dispersion of (2-AEP)2PbI4 and (2-AEPH)PbI4
(Figure 3.2) suggests significant electron mobilities particularly in (2-AEP)2PbI4, as supported by the effective charge carrier masses shown in Table 3.2. The effective charge carrier

Table 3.2: Effective and Reduced Masses of Charge Carriers using SOC-DFT. Note that
(0.1, 0, 0.5) lies between Z and T for (2-AEP)2PbI4 and (0.43, 0, 0) lies between Y and for
(2-AEPH)PbI4.
Material holes electrons reduced mass
& Direction (mh) (me) (µ)
PEA2PbI4 0.263 0.197 0.113
Γ → Y
PEA2PbI4 0.258 0.197 0.112
Γ → X
(2-AEP)2PbI4 0.321 0.169 0.111
(-0.1, 0, 0.5) → T
(2-AEP)2PbI4 0.404 0.143 0.106
(-0.1, 0, 0.5) → Z
(2-AEPH)PbI4 3.330 0.407 0.363
(0.43, 0, 0) → Y
(2-AEPH)PbI4 2.44 0.377 0.327
(0.43, 0, 0) → Γ
masses of (2-AEP)2PbI4 are comparable to (PEA)2PbI4. Unfortunately, the directions of
the charge carrier masses are all within the 2D lead iodide octahedra sheet, and no through
layer charge transport is observed. Looking closely at the band dispersion in the stacking
direction (Γ to Z) in Figure 3.2, both (PEA)2PbI4 and (2-AEP)2PbI4 are flat, whereas it
is relatively disperse in (2-AEPH)PbI4 as seen in Figure 3.3. This is not surprising given
that the interplanar distance between terminal iodides decreases going from (PEA)2PbI4 to
(2-AEP)2PbI4 to (2-AEPH)PbI4.
The dielectric measurements of both (2-AEP)2PbI4 and (2-AEPH)PbI4 pellets (Figures
3.5 and 3.4) reveal a non-negligible degree of loss, which reflects the semiconducting character
and implies the polycrystalline pellets exhibit some degree of electrical conductivity. The
capacitance and dielectric loss of both forms of the 2-AEP hybrids exhibit a feature-less
frequency dependence of a dielectric material that can be attributed to thermal contraction
during cooling, with the loss decreasing significantly at low temperatures. Both the cooling
and warming traces are effectively identical with the random fluctuations between points

simply reflecting vibrations of the sample holder and wires, implying no significant structural
or electronic transitions at low temperatures. This is contrasted with the overall lower loss
observed in the dielectric measurement of (PEA)2PbI4 pellet (Figure 3.6), indicating it has
a more insulating behavior compared to the 2-AEP hybrids. However, there is a significant
feature centered around 250 °C in the capacitance and dielectric loss of (PEA)2PbI4, which
could be related to a structural transition near room temperature. The higher seen loss in
the 2-AEP hybrids is believed to be related to the lower LUMO levels of (2-AEP)+ and (2-
AEPH)2+ compared to (PEA)+, as well as the higher organic contribution in the conduction
band minimum, as shown in the DOS plots (Figure 3.2). The presence of π-π interactions
in (2-AEP)2PbI4 should improve through layer charge transport, but ultimately was not
achieved due to the insulating alkylammonium chain. Future improvement to this system
would be to incorporate a conjugated ammonium chain to establish a continuous charge
transport from the π-π interaction in the ring to the chain into the 2D inorganic sheet.
3.4 Summary
In summary, we have successfully prepared a new 2D hybrid, (2-AEP)2PbI4, that contains
a novel face-to-face packing in the organic bilayer. We have also demonstrated that incorporating through-layer π-π interactions between adjacent organic molecules is a promising
Figure 3.3: Calculated band structures and densities of states (PBEsol+SOC) of (a)
(PEA)2PbI4, (b) (2-AEP)2PbI4, and (c) (2-AEPH)PbI4, visualized using sumo.[71] Zoomed
in along y-axis to highlight (Γ to Z) bands

avenue for promoting 3D charge transport, but that ultimately controlling the charge carrier
concentration in these hybrids remains challenging. Hence doping strategies that allow these
promising charge mobilities to be fully exploited must be pursued. Perhaps more importantly, we have highlighted that the final structure of the (2-AEP) phases, and likely any
hybrid containing molecules with multiple acidic sites, rely heavily on the solution processing
conditions.

3.5 Supplemental Information
3.5.1 Dielectric Measurements
Figure 3.4: Dielectric measurements of (a) (2-AEP)2PbI4 and (b) (2-AEPH)PbI4 pellets
from 10 K to 300 K.
Figure 3.5: Dielectric measurements of (a) (2-AEP)2PbI4 and (b) (2-AEPH)PbI4 pellets
from 300 K to 10 K.

Figure 3.6: Dielectric measurements of (PEA)2PbI4 pellets from (a) 300 K to 10 K and
(b) 10 K to 300 K.

Chapter 4
Probing 1-methylquinoline and 1-naphthylamine based lead iodide hybrid materials for donor–acceptor charge transfer
properties
4.1 Introduction
This chapter discusses a novel 1-D perovskitoid material, (1-MQ)(1-NA)Pb2I6, which incorporates two different organic cations in a 1:1 mole ratio. The structural properties of this
mixed system were explored using both X-ray and solid state NMR techniques because of
the similarities between the cations. In addition to the (1-MQ)(1-NA)Pb2I6 system, the end
member hybrids, (1-NA)PbI3 and (1-MQ)PbI3, were also investigated and provide further
insight into the structural characteristics. We find that electronic differences between the
1-methylquinolinium and 1-naphthylammonium cations drive the minor variation between
structures and the differences seen between the octahedra in (1-MQ)(1-NA)Pb2I6. These
results show that it is possible to incorporate two different organic cations in the solid state
and encourage further studies to tailor structure to achieve charge transfer character between

donating and accepting cations.
The second part of this chapter discusses the optical properties of these materials. Trends
between the three hybrids are explored and discussed by looking at diffuse reflectance, absorbance, temperature dependent emission intensity and lifetime, and PLQY of powders and
films. Despite the similarities between all three materials, the cations have a strong impact
on the optical properties of these systems.
4.2 Experimental Details
The precursor salt, 1-methylquinolinium iodide (C10H10NI, (1-MQ)I), was synthesized by
mixing 2 parts quinoline (98%, Sigma Aldrich) with iodomethane (99%, stab. with Cu,
Fisher) in approximately 10 mL of acetonitrile (HPLC, EMD Millipore). The solution was
then heated to 85 °C and stirred for 2 hours. Once the solution cooled to room temperature,
it was transferred to a glass petri dish to allow the solvent to evaporate. The resulting yellow
solid was vacuum filtered and rinsed with diethyl ether (≥98% (stabilized), VWR). Proton
NMR spectra using d-DMSO (Cambridge Isotope Laboratories) were collected to confirm
the purity and structure of the product.
1-methylquinolinium lead iodide ((1-MQ)PbI3) was prepared by dissolving 0.2 g (0.43 mmol)
of lead (II) iodide (PbI2, 99.9985% (metals basis), Alfa Aesar) and 0.12 g (0.44 mmol) of the
prepared (1-MQ)I salt in 2 mL and 3 mL of hydroiodic acid (HI, 57 wt% (stabilized), Sigma
Alrdich) in 2 dram and 8 dram scintillation vials, respectively. The organic salt solution was
stirred continuously in an aluminum bead bath on a hot plate until reaching 100 °C. Once
all solids were dissolved in both solutions, the lead solution was decanted into the organic
solution and allowed to briefly mix before turning off the heat. The resulting yellow crystals
were collected via vacuum filtration and rinsed with acetone (≥99.5%, VWR).
1-naphthylammonium lead iodide ((1-NA)PbI3) was prepared following the same procedure using 0.2 g of PbI2 (0.43 mmol) and 0.078 g (0.54 mmol) of 1-naphthylamine (C10H9N,

1-NA, 99%, Sigma Aldrich). The resulting product was vacuum filtered and rinsed with
diethyl ether.
The mixed hybrid, (1-MQ)(1-NA)Pb2I6, was synthesized by combining 0.038 g (0.27 mmol)
(1-NA) with 0.056 g (0.21 mmol) (1-MQ)I in an 8 dram vial and adding 5 mL of HI; 0.2 g
(0.43 mmol) of PbI2 was added to a 2 dram vial with 2 mL HI. The resulting product was
vacuum filtered and rinsed with diethyl ether. (1-NA)PbI3 and (1-MQ)(1-NA)Pb2I6 were
both stored in an Ar glove box to avoid degradation due to atmospheric exposure.
1-naphthylamine-d3 chloride salt was synthesized to create a deuterated version of the
mixed hybrid for ssNMR experiments. 100 mg of 1-naphthylamine was heated and dissolved
in 10 mL of deuterium chloride (DCl, 20% w/w in D2O, 99.5% isotopic). The resulting
product was analyzed by NMR and used to synthesize the mixed hybrid. (1-MQ)(1-NAd3)Pb2I6 was synthesized using the same procedure outlined above with the expectation
that some back conversion of the deuterons to protons would occur. Any resulting back
conversion did not affect the ssNMR experiments significantly.
Single crystal data for (1-MQ)PbI3 and (1-MQ)(1-NA)Pb2I6 were collected at 100 K using
a Rigaku XTALab Synergy diffractometer with a CCD area detector. The data reduction was
performed using Crysalis Pro and refined using Olex2 with the ShelXL program installed.[89]
Single crystal data was also collected for (1-NA)PbI3 to confirm the structure first reported
by Lemmerer and Billing and later reported with minor lattice changes by Mitrofanov et
al.[90, 91]
Solid-state NMR spectroscopy experiments were performed on a 9.4 T Bruker wide-bore
magnet equipped with a Bruker AVANCE III HD console (1H spin echo, 207Pb spin echo,
1H14N D-HMQC, 2H spin echo, 1H2H DE-RESPDOR) and equipped with a Bruker 1.3 mm
HX probe with MAS frequency. All experiments utilized N2 gas for spinning. 1H chemical
shifts were referenced to neat tetramethylsilane using adamantane (δiso(
1H) = 1.72 ppm) as
a secondary chemical shift reference. 207Pb and 2H chemical shifts were indirectly referenced
to neat TMS using the IUPAC recommended relative NMR frequency.[92] NMR spectra were

processed and analyzed with Bruker TopSpin version 3.6.4 (AVANCE III HD data) software.
The following experimental details are with respect to data acquired at B0 = 9.4 T with
the 1.3 mm HX NMR probe. 1H spin echo solid-state NMR spectra of (1-NA)PbI3, (1-
MQ)PbI3, and (1-MQ)(1-NA)Pb2I6 were recorded with a 50 kHz MAS frequency, and the
1H longitudinal relaxation time constants (T1) were ca. 3.3 s, 19.3 s, and 6.9 s, respectively.
All experiments utilized a 1.3*T1 s recycle delay. 207Pb spin echo solid-state NMR spectra
of (1-NA)PbI3, (1-MQ)PbI3, and (1-MQ)(1-NA)Pb2I6 were recorded with a 50 kHz MAS
frequency, and all experiments utilized a 0.5 s optimized recycle delay. The 207Pb isotropic
chemical shift tensor parameter (δiso) was determined with the solid line shape analysis
(SOLA) module in the Bruker TopSpin 3.6.4 software.
For the 1H14N D-HMQC2
solid-state NMR experiment, the symmetry-based SR4
2
1 dipolar
recoupling sequence[93] was applied on the 1H channel at the 2nd order rotary resonance
recoupling condition.[94, 95, 96] The optimum total dipolar recoupling time used for the
(1-MQ)(1-NA)Pb2I6 was 1.28 ms, and the 14N excitation and reconversion pulse lengths had
a duration of one rotor period. The 14N RF field was 62.1 kHz. 2H spin echo solid-state
NMR spectra of (1-MQ)(1-NA-d3)Pb2I6 were recorded with a 20 kHz MAS frequency, and all
experiments utilized a 0.1 s recycle delay. 1H2H DE-RESPDOR9
experiments of (1-MQ)(1-
NA-d3)Pb2I6 were performed with 50 kHz MAS and 2H saturation pulses that were 30 µs
(1.5 × τ rot) in duration with 107.5 kHz RF field. The SR4
2
1 heteronuclear dipolar recoupling
sequence was applied to the 1H spins to reintroduce the 1H-2H dipolar interaction under
MAS.[93] A control (without a 2H saturation pulse) and dephased (with a 2H saturation
pulse) point were recorded at each recoupling time considered in this experiment. The 1H
T1 of (1-MQ)(1-NA-d3)Pb2I6 was ca. 6.8 s and 7.1 s for high-frequency (aromatic protons)
and low-frequency (-CH3) signals, respectively; all experiments utilized a 9.23 s recycle delay
and considered the low-frequency signal (-CH3) to construct the RESPDOR dephasing curve.
The 2H isotropic chemical shift (δiso), CQ, and η were determined by extracting side band
manifolds from the one-dimensional (1D) spin echo spectrum and fitting the manifold with

the SOLA module in the Bruker TopSpin 3.6.4 software. A summary of all experimental
data is shown in Table S1 in supplementary information.
SIMPSON v4.1.1 was used to run numerical solid-state NMR simulations.[97, 98, 99]
The archived data includes the SIMPSON input codes. Except for the 1H π/2 pulses, all
the pulses in the files were finite in duration. The 1H2H DE-RESPDOR dephasing curves
were simulated using rep678 crystal file, 13 γ-angles, 107.5 kHz 2H RF field. The 1H2H
DE-RESPDOR numerical simulations for the (1-MQ)(1-NA-d3)Pb2I6 were done considering
a multispin 1H-2Hn (n=3) system and corresponding Euler angles.
Powder X-ray data was collected to confirm the composition and purity of all three hybrids before performing optical measurements. Samples were first ground using an agate
mortar and pestle and the patterns were collected on a Bruker D8 Advance powder diffractometer equipped with a Cu-Kα source and LynxEye XE–T detector. Data was collected
every 0.02° from 5 to 70° 2θ angles with 1 s per step. The patterns for each of the hybrid
materials were evaluated using the method of Rietveld refinement as implemented in the
TOPAS-Academic (v6)[63].
Temperature dependent photoluminesence and lifetime data were collected from 3–290 K
using neat solid samples. Each sample was sandwiched between two 1 mm thick sapphire
discs before being placed into the cryostat system. Samples were excited at 365 nm and
data was collected from 400–800 nm for the steady state emission spectra using a Photon
Technology International QuantaMaster model C-60SE spectrofluorimeter in tandem with
a Janis model SHI-4-2 optical He cryostat equipped with a Lakeshore model 335 temperature controller. Select spectra for the organic salts in 2-methyltetrahydrofuran (2MeTHF,
stabilized, Fisher Scientific) were collected using the Photon Technology International QuantaMaster model C-60SE spectrofluorimeter at 77 K. Excited state lifetimes were evaluated
from starting at 3 K until signal was too weak to collect data and were determined by the
time-correlated single-photon counting method (TCSPC) using an IBH Fluorocube instrument using a 372 nm pulsed diode.

PLQY values were measured using a Hamamatsu Quantaurus-QY Plus UV-NIR absolute
PL quantum yield spectrometer with an excitation wavelength of 400nm. Microcrystalline
powders of (1-MQ)PbI3 and (1-NA)PbI3 were loaded into quartz tubes and the PLQY was
measured at RT. At 77K, the tubes were placed inside of a quartz liquid nitrogen finger
Dewar set inside the integrating sphere.
Diffuse reflectance data was collected from 800–250 nm using a PerkinElmer Lambda 950
UV-Vis-NIR spectrophotometer equipped with a 150 mm integrating sphere to determine the
onset of absorption in powders diluted to 3 wt% in magnesium (II) oxide (MgO, 98%, ACROS
Organics) and to approximate the optical band gap using the Kubelka-Munk transform.[65]
The temperature dependent dielectric properties of (1-NA)PbI3, (1-MQ)PbI3, and (1-
MQ)(1-NA)Pb2I6 were measured in a parallel plate geometry. Each material was ground
using an agate mortar and pestle and pressed into 6 mm diameter pellets. All pellets were
vapor deposited with Al on both faces of the pellets. Powder XRDs were taken before and
after metal deposition to ensure that the crystal structures of the pellets were retained.
Dielectric measurements were taken from 10 to 300 K at frequencies of 1, 2, 5, 10, and
20 kHz. The sample temperature was controlled using a Quantum Design Physical Property
Measurement System (PPMS) Dynacool. The dielectric measurements were taken using an
Andeen-Hagerling 2700A 50 Hz-20 kHz Ultra-Precision Capacitance Bridge.
Density functional theory (DFT) calculations were performed using the projector-augmented
wave method within the Vienna Ab Initio Simulation Package (VASP), [66, 67]. The density of states and band diagram plots were plotted using sumo [71]. Due to the size of the
unit cells, the functional of Perdew, Burke, and Ernzerhof [100] was used for geometrical
relaxation, while the functional of Heyd, Scuseria, and Ernzerhof (HSE06), [73, 101] with
the explicit inclusion of spin–orbit coupling (HSE06+SOC), was used for electronic structure
calculations, including density of states and electronic band structure, performed using the
PBEsol-relaxed structures. Geometry optimization was considered to have converged when
the forces on each atom fell below 0.01 eV Å˘1, and the plane wave cutoff was increased

to 600 eV during relaxation to avoid Pulay stress. Partial charge density information was
generated using pymatgen [102].
4.3 Results and Discussion
4.3.1 Structural Characterization and Packing Description
The synthesis of each material yielded similar small, tabular, yellow crystallites; though, the
crystallization process can be altered to produce larger single crystals. All three materials
crystallize in the Pbca space group as shown in Figures 4.1 and 4.2. The refinement data
for (1-MQ)PbI3 and (1-MQ)(1-NA)Pb2I6 can be found in Tables 5.6 and 4.4. The inorganic
portion of each 1-D material consists of similar face-sharing lead iodide octahedra. In the
(1-MQ)PbI3 and (1-NA)PbI3 materials, the inorganic chains are parallel to the b-axis while
in (1-MQ)(1-NA)Pb2I6 the chains are parallel to the a-axis. Each of the end member hybrids
has one unique lead site whereas the mixed hybrid crystallizes with three.
When comparing just (1-MQ)PbI3 and (1-NA)PbI3, there are very minor differences aside
from the different cations. A small distortion in the bond angles in (1-MQ)PbI3 is seen due
to the difference in location of the cationic charge center comparted to (1-NA)PbI3. In
(1-NA)PbI3, the inorganic octahedra have very symmetric bond lengths and angles. In (1-
MQ)PbI3, the angles in the octahedra are distorted further away from 90° and 180° to bring
the iodine atoms closer to the nitrogen atoms in the quinolinium rings. The distortion of the
octahedra means that the distance between the nitrogen atoms in the rings and the iodine
atoms on the octahedra changes from 4.225 Å to 4.090 Å when compared to the equivalent
carbon atom in 1-naphthylammonium. By comparing the interatomic distances between
the amine nitrogens and the nearest iodine atoms to the interatomic distances between the
methyl carbons and the nearest iodine atoms in (1-NA)PbI3 and (1-MQ)PbI3, respectively, it
was concluded that hydrogen bonding potentially plays a significant role in the (1-NA)PbI3
whereas other electrostatic interactions are the driving force in (1-MQ)PbI3. The shortest

Figure 4.1: View of (a) (1-NA)PbI3 and (b) (1-MQ)PbI3 down the b-axis.
ammonium nitrogen to iodine distance in (1-NA)PbI3 is 3.529 Å which is on the longer end
of the scale for hydrogen bonds. The shortest distance between a quinolinium nitrogen and
and iodine in (1-MQ)PbI3 is 3.912 Å which is on the scale of other electrostatic interactions.
While hydrogen bonding is not possible in (1-MQ)PbI3, hydrogen bonding does play a role
in the cationic packing of 1-naphthylammonium in (1-NA)PbI3.
Refinement of the single crystal data for the mixed hybrid revealed a doubling of the
c-axis resulting in an approximate unit cell volume doubling of the system. Since the carbon and nitrogen atoms in the 1-methylquinolinium and 1-naphthylammonium cations are
indistinguishable by X-ray methods, the atomic position of those atoms could not be differentiated during the refinement. Despite not being able to definitively assign the carbon and
nitrogen atom positions, the X-ray data indicate that the mixed hybrid does incorporate
both cations and is not a solid solution, as seen in Figure 4.2.
Additionally, the lead iodide octahedra are either canted or the lead-iodide bonds are
slightly distorted from fully symmetric depending on the lead site, indicating a mixing of the
organic cations. The octahedra tilt slightly in planes where the cations appear to be pointing
in opposite directions in relation to the methyl or amino groups. In the planes where the
cations are facing more in the same direction, the octahedra instead distort to bring the iodide
atoms closer to the nitrogen atoms. The cations pack in a more symmetrical way around the

canted octahedra leading to the whole unit shifting rather than distorting as it does at the
other lead site where the cations do not pack symmetrically around the octahedra. Looking
at the cationic packing around the octrahedral rods, the canted octahedra are surrounded
by four 1-naphtylammonium cations and two 1-methylquinolinium cations and vice versa
for the distorted cations. Given the 1-naphtylammonium cations exhibit hydrogen bonding
interactions with the iodine atoms, 1-methylquinolinium cations interact with the iodine
atoms more strongly with different electrostatic interactions, and 1-naphthylammonium is
more easily distorted than 1-methylquinolinium, it is understandable that the octahedra
surrounded by more 1-naphthylammonium cations would cant and the octahedra surrounded
by more 1-methylquinolinium cations would distort. Additionally, the dipole strengths of
1-napthylammonium and 1-methylquinolinium are 7.95 and 2.42 debye, respectively. Figure
4.3 shows the dipoles of the 1-napthylammonium and 1-methylquinolinium cations in red
and blue, respectively. The strong 1-NA dipoles are symmetrically packed around the tilted
octahedra leading to a symmetric change rather than an asymmetric distortion.
Figure 4.2: (1-MQ)(1-NA)Pb2I6 hybrid structure: 1-NA cations are shown in blue and
teal. 1-MQ cations are shown in red and pink

In order to confirm the ordering and arrangement of the 1-NA and 1-MQ cations in
the crystal structure of (1-MQ)(1-NA)Pb2I6, we performed a variety of solid-state NMR
experiments. Figures 4.4a-c show 1H spin echo solid-state NMR spectra of (1-NA)PbI3, (1-
MQ)PbI3, and (1-MQ)(1-NA)Pb2I6. 1H longitudinal relaxation time constants (T1) were
measured with saturation recovery experiments and gave values of ca. 3.3 s, 19.3 s, and 6.9 s
for (1-NA)PbI3, (1-MQ)PbI3, and (1-MQ)(1-NA)Pb2I6, respectively. The observation of an
intermediate 1H T1 for (1-MQ)(1-NA)Pb2I6 is consistent with mixing of cations in the same
Figure 4.3: Visualization of the 1-NA and 1-MQ dipoles in a) (1-NA)PbI3 b) (1-MQ)(1-
NA)Pb2I6 c) (1-MQ)PbI3
Figure 4.4: 1H spin echo solid-state NMR spectra of a) (1-NA)PbI3, b) (1-MQ)PbI3, and
c) (1-MQ)(1-NA)Pb2I6. d) 1H14N dipolar heteronuclear multiple quantum correlation (DHMQC)[103] solid-state NMR spectrum of (1-MQ)(1-NA)Pb2I6. All NMR spectra were
acquired with a 9.4 T magnetic field and a 50 kHz magic angle spinning (MAS) frequency.

crystalline lattice. The 1H solid-state NMR spectra of all compounds shows two main sets
of 1H NMR signals, with the lower-frequency signals having maximum intensity around 5.5
ppm, and the second higher-frequency signals having maximum intensity around 8.5 ppm.
For (1-MQ)PbI3, and (1-MQ)(1-NA)Pb2I6 the low-frequency 1H NMR signal is assigned to
methyl groups of 1-MQ. For all compounds, the high-frequency 1H NMR signals primarily
arise from aromatic hydrogen atoms.
1H14N dipolar heteronuclear multiple quantum correlation (D-HMQC)1
experiments were
performed on all three compounds. The 1H14N D-HMQC spectra show that the ammonium
hydrogen atoms of 1-NA resonate at ca. 9 ppm, while the methyl protons of 1-MQ (which
are adjacent to the quinoline nitrogen atom) resonate at 5.5 ppm (Figure 4.4d and Figure
4.5). As expected, the indirect 14N dimension clearly shows two distinct 14N NMR signals.
These NMR signals are centered at –280 ppm and –107 ppm and are assigned the ammonium
nitrogen of 1-NA and the quinolinium nitrogen of 1-MQ, respectively. These assignments are
obvious when comparing the 1H14N D-HMQC spectra of each compound and considering the
observed 1H correlations (Figure 4.5). Both 14N NMR signals have a single well-defined discontinuity, consistent with the presence of only one of each nitrogen atom in the asymmetric
unit of the crystal structure of (1-MQ)(1-NA)Pb2I6.
Figure 4.5: 1H14N D-HMQC[103] solid-state NMR spectra for a) (1-NA)PbI3, b) (1-
MQ)PbI3, and c) (1-MQ)(1-NA)Pb2I6. The spectra were acquired in a 9.4 T magnetic
field with a 50 kHz MAS frequency. The optimum total dipolar recoupling time used for all
experiments was 1.28 ms.

Figures 4.6a-c show 207Pb solid-state NMR spectra of (1-NA)PbI3, (1-MQ)PbI3, and (1-
MQ)(1-NA)Pb2I6, respectively. Peak fitting was used to determine the isotropic chemical
shifts (δiso) of each 207Pb solid-state NMR spectra shown in Figure 1. The δiso for 207Pb
solid-state NMR spectra of each (1-NA)PbI3 and (1-MQ)PbI3 hybrid systems are 952 ppm
and 891 ppm, respectively. The mixed cation (1-MQ)(1-NA)Pb2I6 shows a 207Pb spectrum
with a peak that is similar in breadth to that of (1-NA)PbI3, which is somewhat surprising
given that there are three distinct Pb atoms in the asymmetric unit of the crystal structure
of (1-MQ)(1-NA)Pb2I6. However, it is well known that lead and tin iodide perovskites often
give rise to homogeneously broadened 119Sn and 207Pb NMR signals.[104, 105, 106, 107, 108]
The homogeneous broadening arises from the strong scalar and dipolar couplings between
207Pb and 127I (a 100% abundant I = 5/2 nucleus) and dynamic exchange of iodide atoms
or fast 127I relaxation that is caused by sizeable quadrupolar interactions.[106, 107] Due to
the homogeneous broadening of the 207Pb solid-state NMR spectra, it is difficult to observe
distinct 207Pb NMR signals for (1-MQ)(1-NA)Pb2I6.
Figure 4.6: 207Pb spin echo solid-state NMR spectra of a) (1-NA)PbI3, b) (1-MQ)PbI3,
and c) (1-MQ)(1-NA)Pb2I6. All NMR spectra were acquired with a 9.4 T magnetic field and
a 50 kHz magic angle spinning (MAS) frequency.

Figure 4.7: 1H207Pb TONE D-HMQC[109] solid-state NMR spectra for a) (1-NA)PbI3, b)
(1-MQ)PbI3, and c) (1-MQ)(1-NA)Pb2I6. The spectra were acquired in a 9.4 T magnetic
field with a 50 kHz magic angle spinning (MAS) frequency. The optimum total dipolar
recoupling time used for all experiments was 1.2 ms. d) The comparison of 207Pb spin echo
solid-state NMR spectrum of (1-MQ)(1-NA)Pb2I6 with the extracted columns corresponding
to two different 1H chemical shifts in Figure c.
1H207Pb t1-noise eliminated (TONE) D-HMQC[109] were performed on all three compounds (Figure 4.7). These experiments show correlations between the 207Pb NMR signals
and 1H NMR signals of both cations, confirming that the cations are within a 5 Å of the Pb
atoms in all systems. Interestingly, extracting 207Pb NMR spectra at different 1H chemical
shifts (columns) from the 2D 1H207Pb TONE D-HMQC spectrum of (1-MQ)(1-NA)Pb2I6
results in partial resolution of distinct 207Pb NMR signals, consistent with the presence of
multiple Pb sites in the asymmetric unit of this compound (Figure 4.7).
We also performed plane wave density functional theory gauge-including projector augmented wave (GIPAW)[110] calculations on all compounds. These calculations predict 207Pb

Figure 4.8: 1H→13C CP solid-state NMR spectra for a) (1-NA)PbI3, b) (1-MQ)PbI3, and
c) (1-MQ)(1-NA)Pb2I6. The spectra were acquired in a 9.4 T magnetic field with a 50 kHz
MAS frequency.
isotropic chemical shielding (δiso) are 6906 ppm and 6860 ppm for (1-NA)PbI3 and (1-
MQ)PbI3 hybrid systems, respectively. In contrast, for the (1-MQ)(1-NA)Pb2I6 three different 207Pb sites were predicted with δiso = 6604 ppm, 6796 ppm, and 6898 ppm (Figure
4.6c).
The 1H→13C cross polarization (CP) solid-state NMR spectra of (1-MQ)(1-NA)Pb2I6
provide additional evidence for ordering of the cation positions in (1-MQ)(1-NA)Pb2I6. Similar full widths at half height (FWHH) of ca. 152 Hz and ca. 169 Hz are observed for the
methyl 13C NMR signals of (1-MQ)PbI3 and (1-MQ)(1-NA)Pb2I6, respectively (Figure 4.8).
Finally, we prepared a sample of (1-MQ)(1-NA)Pb2I6 where the ammonium hydrogen
atoms were replaced with deuteron atoms in order to enable 2H solid-state NMR experi-

Figure 4.9: a) 2H spin echo solid-state NMR spectrum (black) of (1-MQ)(1-NA)Pb2I6
mixed hybrid system in a 9.4 T magnetic field with a 20 kHz MAS frequency. The peak
fitting is shown in cyan solid line. b) 1H2H DE-RESPDOR spectra recorded (red) with or
(black) without 30 µs
2H saturation pulses. The difference spectrum (green) is shown below.
Both spectra were acquired in a 9.4 T magnetic field with a 50 kHz MAS frequency.
ments. As discussed below, the 2H-labelling enabled us to perform 1H-2H dipolar coupling
measurements that can probe the distance between methyl and ammonium protons of 1-MQ
and 1-NA.
Figure 4.9a shows the 2H spin echo solid-state NMR spectrum (black) acquired at B0
= 9.4 T magnetic field with 20 kHz MAS frequency, and the simulation is shown in cyan.
The 2H isotropic chemical shift (δiso), quadrupolar coupling constant (CQ), and asymmetry
parameter (η) were obtained by fitting the peak intensities of the side band manifold. The
simulation gives the 2H δiso, CQ, η which are 7.1 ppm, 164 kHz, and 0.12, respectively. The
measured CQ values suggest there is relatively slow reorientation of the ND3 groups on the
2H NMR time scale.
Figure 4.9b shows 1H2H DE-RESPDOR[111, 93] dephased spectrum (red, S) recorded
with 2H saturation pulses and the control spectrum (black, S0) recorded without saturation
pulses. The difference spectrum (S0-S, green) is illustrated below. A plot of 1– S/S0 yields
as a function of the recoupling duration yields the dephasing curve (Figure S6a). Here, all
experimental data points correspond to the dephasing observed at the methyl protons of the
1-MQ; although, due to the limited resolution of the 1H NMR spectra, the dephasing from
the aromatic 1H spins will also contribute. With knowledge of the 2H, CQ, and η, the 1H2H

Figure 4.10: Root Mean Square Deviation (RMSD) curve as a function of 1H-2H distances
DE-RESPDOR dephasing curve for the deuterated (1-MQ)(1-NA)Pb2I6 can be modeled.
Multispin 1H-2H (n = 3) numerical SIMPSON simulations were performed to model the
dephasing curve. In order to simplify the analysis, we assume that the dipolar couplings
are the same for all 1H-2H spin pairs. Although the crystal structure of (1-MQ)(1-NA)Pb2I6
suggests unique 1H-2H distances for each hydrogen and deuterium atom, it is important to
keep in mind that the methyl groups are likely rotating with frequencies on the order of
a MHz, which will result in averaging of the distances (and slight averaging of the dipolar
coupling constant). A root mean square deviation (RMSD) calculation was utilized to identify the best fit 1H-2H distance. This analysis suggested that the average 1H-2H distance
is 3.8 Å between the methyl protons of 1-MQ and the 2H of the 1-NA molecule (Figure
4.10). Figure 4.11 shows part of the crystal structure of (1-MQ)(1-NA)Pb2I6 illustrating the
distances between a methyl groups of 1-MQ and the nearest ammonium groups of 1-NA.
All DE-RESPDOR dephasing simulations were performed with a multispin 1H-2H3 system
to mimic coupling between a methyl hydrogen and three ammonium deuterons. Note, plane
wave DFT was used to optimize the H atom positions in this structure. The distances for
the methyl hydrogen (H atom q) to to the three nearest ammonium H atoms (H atoms a,b,
and c) is 3.95 Å. For all of the methyl protons the average distance to the nearest three
ammonium protons is 4.45 Å (Table S1). While our measured value of 3.8 Å is shorter than
this average value, it is important to keep in mind that there are additional nearby ammo-

nium groups in the lattice that will also contribute to the dephasing in the 1H2H RESPDOR
experiments, explaining why the measured distance is shorter than the average distance seen
in the DFT optimized crystal structure. In summary, the 1H2H RESPDOR experiments are
consistent with the proposed crystal structure of (1-MQ)(1-NA)Pb2I6 that shows ordering of
the 1-NA and 1-MQ positions in the lattice that results in the hydrogen atoms of the methyl
and ammonium groups separated by 4.45 Å on average.
4.3.2 Optical Properties
Based on the density of states and band diagram data, it is evident that (1-MQ)PbI3 and
(1-MQ)(1-NA)Pb2I6 have similar conduction band character as seen in Figure 4.12a & c.
Each material displays an isolated band with cationic character which contrasts the continuous nature seen in the bands of (1-NA)PbI3 in Figure 4.12b. These isolated bands
represent the lower LUMO energy of the 1-methylquinolinium cation in relation to the
1-naphthylammonium cation and are responsible for the similarity in emission character
between (1-MQ)PbI3 and (1-MQ)(1-NA)Pb2I6. In these two systems, it is likely that the
inorganic framework quenches the 1-methylquinolinium triplet emission at low temperatures.
(1-NA)PbI3 shows a steady increase in emission intensity and new features as the temperaFigure 4.11: a) 1H2H DE-RESPDOR dephasing curves for the (1-MQ)(1-NA-d3)Pb2I6: Red
circles correspond to the experimental data points. The solid lines correspond to numerical
SIMPSON simulation for 1H–2H distances of 3.70, 3.75, 3.80, 3.85, 3.90, 3.95, and 4.00
Å, respectively. b) Representation of orientation of molecules and the distance between
ammonium hydrogen atoms of 1-NA and methyl hydrogen atoms of 1-MQ in the plan wave
DFT optimized crystal structure.

Figure 4.12: Density of states and band diagrams of a) (1-MQ)PbI3 b) (1-NA)PbI3, and
c) (1-MQ)(1-NA)Pb2I6
ture is lowered indicating the material instead displays both triplet and self trapped exciton
emission at lower temperatures. Additionally, the bands in all three systems are quite flat
and do not display much dispersivity.
Charge density projections visualized using VESTA also reveal interesting differences between the the materials. Figure 4.13 shows the projected charge densities for (1-MQ)PbI3
and (1-NA)PbI3 at the conduction band minimum and valence band maximum of each system. In the case of (1-NA)PbI3, the charge density is localized around the inorganic portion
of the system at the band edges. Probing further into each band reveals some differences
in the charge density map, but the localization stays around the inorganic octahedra. In
(1-MQ)PbI3, the charge density shift from the inorganic octahedra at the valence band maximum to the pi-orbitals of the 1-MQ cations at the conduction band minimum. Looking
deeper into the bands, the charge density largely remains localized around the inorganic
octahedra and organic cations in the valence and conduction bands, respectively. (1-MQ)(1-
NA)Pb2I6 displays electronic properties very similar to (1-MQ)PbI3. Figure 4.20 shows the

Figure 4.13: Charge density at the conduction band minimum and valence band maximum
of (1-NA)PbI3 (left) and (1-MQ)PbI3 (right)
charge density at the VBM and CBM for (1-MQ)(1-NA)Pb2I6. The VBM displays inorganic
character around all octahedra and the CBM displays organic character localized around
the (1-MQ) cations. Going deeper into the conduction band reveals further organic character. Deeper in the valence band, differing charge density around the inorganic octahedra
is observed. While the charge density does not point to any interesting charge transfer
phenomenon, it does further show the connection between the (1-MQ)PbI3 and (1-MQ)(1-
NA)Pb2I6 systems.
When compared to the experimental data, the computational data shows similar trends in
band gap values. While the computational and experimental values do not match perfectly,
(1-MQ)(1-NA)Pb2I6 has the smallest band gap and (1-NA)PbI3 has the largest band gap
with the (1-MQ)PbI3 band gap falling between the two but closer to (1-MQ)(1-NA)Pb2I6.
The experimental diffuse reflectance data shown as normalized Kubelka-Munk transforms
can be seen in Figure 4.14
The similarities and differences seen in the computational data also translate to the
emission data. (1-MQ)PbI3 emits most strongly at 55 K at 620 nm. The emission intensity
initially increases upon warming from 3 K and decreases after peaking at 55 K with weak
emission at 605 nm occurring at room temperature as can be seen in Figure 4.15a. Minor

Figure 4.14: Normalized Kubelka-Munk Transform of (1-MQ)PbI3, (1-NA)PbI3, and (1-
MQ)(1-NA)Pb2I6
shifts from the 620 nm peak can be seen on both sides of the 55 K mark but no major red
or blue shift is observed or correlated to temperature. At 77 K, the measured PLQY of this
material is 34% which was used to determine that at 55 K the PLQY is slightly higher at
38.4%.
The peak profiles of (1-NA)PbI3 and (1-MQ)PbI3 are notably different, particularly at low
temperatures. Despite the structural similarities between the hybrids, (1-NA)PbI3 exhibits
clear triplet state emission below 45 K whereas no triplet emission is observed in (1-MQ)PbI3
or (1-MQ)(1-NA)Pb2I6. At temperatures below 45 K, (1-NA)PbI3 exhibits emission from
both a molecular triplet state and a broader emission from the system as a whole, shown
in Figure 4.15b. The triplet emission begins starting at 40 K and grows in intensity as the
system reaches 3 K. In addition to the triplet signal, there is also a large red shift from 582
nm to 656 nm as the signal appears and the system cools. As discussed above the, HOMOLUMO gaps of 1-MQ and 1-NA are different and the LUMO of 1-MQ falls at a lower energy
than the conduction band energy of the inorganic portion of the hybrid. This is the case for
both (1-MQ)PbI3 and (1-MQ)(1-NA)Pb2I6 which is why the emission profiles are so similar.
Since the LUMO in (1-NA) is higher than that of (1-MQ) and it falls above the conduction

Figure 4.15: Temperature dependent emission spectra of a) (1-MQ)PbI3 b) (1-NA)PbI3,
and c) (1-MQ)(1-NA)Pb2I6 (λex = 365 nm)
band minimum, there is a larger gap between the CBM and the triplet state. The triplet
state cannot be seen as a band, but it exists at an energy between the CBM and VBM.
In (1-NA)PbI3, this state is populated at lower temperatures and structured emission is
observed. At low temperatures, there is not enough energy to depopulate the triplet state
by intersystem crossing or another mechanism. In (1-MQ)PbI3 and (1-MQ)(1-NA)Pb2I6,
the triplet is quenched by the inorganic states which are closer in energy.
The temperature dependent emission profile of (1-MQ)(1-NA)Pb2I6 is very similar to the
trend seen in (1-MQ)PbI3. The emission intensity peaks at 80 K after a gradual increase
from 3 K seen in Figure 4.15c. Additionally, the λmax of both materials is around 620 nm.
There is also no triplet character in the emission as the LUMO of the (1-MQ) cations falls
at a lower energy and the inorganic states quench the triplet.

Figure 4.16: Dielectric measurements for (1-NA)PbI3 upon warming (left) and cooling
(right)
Dielectric measurements conducted by Yang (Gemma) Goh revealed correlated trends in
(1-NA)PbI3 but not (1-MQ)PbI3 or (1-MQ)(1-NA)Pb2I6. Figure 4.16 shows the dielectric
response in the capacitance and loss as a function of temperature upon warming and cooling.
A small feature in the loss seen at high frequency peaking at about 100 K roughly corresponds
to the initial onset of triplet emission in the hybrid. At 100 K in the emission profile, a small
peak begins to grow in almost as a shoulder at the high energy edge of the main feature.
As the temperature decreases, the main feature also begins to red shift. This correlated
feature in the dielectric loss could be indicative of freezing of the ammonium rotation as
cooling occurs. Dielectric measurements were also taken for (1-MQ)PbI3 (Figure 4.21) and
(1-MQ)(1-NA)Pb2I6 (Figure 4.22) but no features were observed which could correlate to
emission features.
The temperature dependent lifetime profiles of (1-NA)PbI3 and (1-MQ)PbI3 can also shed
light on the difference in emission mechanism. Fitting of the lifetime data to an Arrhenius
model in both systems (Figure 4.17) gives an activation energy much larger than the long
and short lived states of 86 meV in (1-NA)PbI3 and 404 meV in (1-MQ)PbI3. Neither system
shows large changes in the lifetime values as the temperature decreases with differences of
only about 10 µs. Because the lifetime mostly levels out below 60 K in (1-MQ)PbI3, the
radiative rate of emission must be declining at lower temperatures as the emission intensity

begins to decrease.
To better understand the differences in emission properties in the hybrids, the organic
salts were also investigated. Figure 4.18 shows the emission and excitation spectra of the
(1-NA)I and the (1-MQ)I salts in 2Me-THF. While no triplet emission character is seen in
(1-MQ)PbI3, there is clear triplet character in (1-MQ)I in solution. One possibility for this
discrepancy could be the dispersion of the ions in solution versus the solid state packing.
In the solid, the cations are much closer to the iodine anions which creates a possibility to
overpower the triplet state through charge transfer interactions.
Because the charge density is localized around the methylquinolinium cations in (1-
MQ)PbI3 and (1-MQ)(1-NA)Pb2I6 at the bottom of the conduction band, there is a higher
possibility of charge transfer occurring from the cations to the anion centers. This band is
lower in energy than the triplet state and is therefore a quenching feature. On the other
hand, charge density of (1-NA)PbI3 at the bottom of the conduction band is more spread
and is present on both the cation and anion centers. The conduction band minimum of
(1-NA)PbI3 is higher in energy than the midgap triplet state which does not appear as a
band and at low energy phonons are quenched and can no longer couple to the triplet. This
does not present the possibility for charge transfer in the excited state and the self trapped
Figure 4.17: Temperature dependent lifetime of a) (1-NA)PbI3 and b) (1-MQ)PbI3 fit with
a two level Arrhenius model

Figure 4.18: Emission and Excitation Spectra of a) (1-NA)I and b) (1-MQ)I in 2Me-THF
at 77 K
exciton state and the triplet excited state instead appear below 40 K in the emission profile.
4.4 Summary
In summary, we have decisively shown that the organic cations in (1-MQ)(1-NA)Pb2I6 pack
in an ordered fashion using both single crystal X-ray and solid state NMR techniques. The
large difference in the dipoles of the 1-NA and 1-MQ cations gives rise to minor differences
in the lead sites and may contribute to the ability to overcome entropy and avoid random
packing. This material is the first of its kind demonstrating the possibility to further explore
this space and target stronger donor-acceptor pairs to create more interesting charge transfer
characteristics.
Additionally, the optical properties of these materials display how powerful the cation can
be in contributing to the electronic structure. Despite 1-NA and 1-MQ being very similar
structurally, the differences in the dipole energies and the HOMO-LUMO gap energies in
these cations greatly impacts the emission profile of each material. Charge density at the
conduction band minimum dictates the emission state of the systems.

4.5 Supplemental Information
4.5.1 Solid State NMR
Figure 4.19: 1H13C HETCOR[112] solid-state NMR spectra for a) (1-NA)PbI3, b) (1-
MQ)PbI3, and c) (1-MQ)(1-NA)Pb2I6. The spectra were acquired in a 9.4 T magnetic field
with a 50 kHz MAS frequency.
Table 4.1: Information on the distance between methyl hydrogen and ammonium hydrogen
atoms in 1-NA and 1-MQ in the optimized crystal structure
Label Distance (Å) Label Distance (Å)
pa 5.27 pd 4.53
pb 3.93 pe 5.85
pc 4.78 pf 5.08
qa 4.38 qd 6.22
qb 3.51 qe 7.60
qc 3.96 qf 6.73
ra 5.05 rd 5.71
rb 4.08 re 7.05
rc 5.10 rf 6.58
Averages 4.45 6.15

Table 4.2: Experimental Solid-State NMR Parameters
Figure NMR B0(T) MAS τ rec.delay # of scans X. sat X RF Field Dip. Recoupling Expt.
Experiment (kHz) (s) scans pulse (µs) (kHz) time/ (ms) time (h)
Figure 1a 1H Spin echo 9.4 50 4.23 64 - - - 0.08
Figure 1b 1H Spin echo 9.4 50 25.1 64 - - - 0.45
Figure 1c 1H Spin echo 9.4 50 8.97 64 - - - 0.16
Figure 1d 207Pb Spin echo 9.4 50 0.5 20480 - - - 2.8
Figure 1e 207Pb Spin echo 9.4 50 0.5 20480 - - - 2.8
Figure 1f 207Pb Spin echo 9.4 50 0.5 61440 - - - 8.5
Figure 1g 1H14N DHMQC 9.4 50 9.23 - 20 62.1 1.28 5.3
Figure 2a 2H Spin echo 9.4 20 0.1 112640 - - - 3.1
Figure 2b 1H2H DE-RESPDOR 9.4 50 9.23 64 30 107.5 2.4 0.33
Figure 2c 1H2H DE-RESPDOR 9.4 50 9.23 64 30 107.5 variable 2.6

4.5.2 VASP Calculations
Figure 4.20: Charge density of (1-MQ)(1-NA)Pb2I6 at the VBM and CBM

4.5.3 Dielectric Measurements
Figure 4.21: Dielectric measurements for (1-MQ)PbI3 upon warming (left) and cooling
(right)
Figure 4.22: Dielectric measurements for (1-MQ)(1-NA)Pb2I6 upon warming (left) and
cooling (right)

4.5.4 Material Characterization
1H NMR of 1-methylquinolinium iodide (1-MQ)I salt
1H NMR (400 MHz, DMSO-d6) δ 9.49 (ddt, J = 5.8, 1.6, 0.8 Hz, 1H), 9.27 (m, 1H), 8.48
(m, 2H), 8.28 (ddd, J = 8.8, 7.0, 1.5 Hz, 1H), 8.16 (dd, J = 8.4, 5.8 Hz, 1H), 8.05 (ddd, J
= 8.1, 7.0 1.0 Hz, 1H), 4.63 (d, J = 0.6 Hz, 3H)

Table 4.3: Crystallographic data for single crystal structure determination of (1-MQ)PbI3
Parameter (1-MQ)PbI3
Chemical formula C10H10NPbI3
Formula weight 732.08
Temperature (K) 100
Crystal system orthorhombic
Space Group P bca
a 14.7847 (2)
b 8.03690 (10)
c 25.4893 (4)
Volume 3028.72(7)
Z 8
CA (0.57490, 0.95400, 0.33850)
HA (0.55799, 1.01727, 0.36738)
CB (0.55740, 0.79600, 0.43750)
HB (0.59751, 0.88419, 0.44748)
HC (0.54993, 0.72062, 0.46649)
HD (0.49975, 0.84121, 0.42790)
CC (0.66150, 0.52200, 0.30690)
HE (0.68410, 0.46336, 0.27821)
C5 (0.62930, 0.69700, 0.29920)
N6 (0.59660, 0.70380, 0.39190)
C9 (0.62570, 0.55200, 0.39560)
H9 (0.62526, 0.50645, 0.42911)
C10 (0.65870, 0.44500, 0.35440)
H10 (0.67609, 0.33488, 0.35983)
C11 (0.63070, 0.76300, 0.24980)
H11 (0.65031, 0.70249, 0.22093)
C12 (0.60060, 0.93000, 0.24540)
H12 (0.59730, 0.98071, 0.21269)
C14 (0.57580, 1.01600, 0.29080)
H14 (0.55860, 1.12682, 0.28690)
C24 (0.60170, 0.78000, 0.34400)
I2 (0.31778, 0.80615, 0.51178)
I3 (0.42038, 0.31652, 0.41206)
I4 (0.34122, 0.80822, 0.33879)
Pb1 (0.24977, 0.56038, 0.4207)
Rint 0.064

Table 4.4: Crystallographic data for single crystal structure determination of (1-MQ)(1-
NA)Pb2I6
Parameter (1-MQ)(1-NA)Pb2I6
Chemical formula C20H18N2Pb2I6
Formula weight 732.08
Temperature (K) 100
Crystal system orthorhombic
Space Group P bca
a 7.87499(18)
b 24.7657(7)
c 31.1618(9)
Volume 6077.5(3)
Z 13
Pb1 (0.86504, 0.37992, 0.25032)
I2 (0.61947, 0.29268, 0.20825)
Pb3 (0.50000, 0.50000, 0.00000)
Pb4 (0.00000, 0.50000, 0.00000)
I5 (0.61385, 0.47081, 0.21116)
I6 (1.10809, 0.37399, 0.16862)
I7 (0.25089, 0.41721, 0.04706)
I8 (0.75227, 0.51410, 0.08092)
I9 (0.25052, 0.59232, 0.03370)
C15 (0.60810, 0.31040, 0.09250)
N10 (0.63530, 0.36650, 0.10310)
H15A (0.66455, 0.38657, 0.07703)
H15B (0.72831, 0.36941, 0.12385)
H15C (0.53137, 0.38152, 0.11562)

Table 4.4 – continued from previous page
Parameter (1-MQ)(1-NA)Pb2I6
C20 (0.46600, 0.28370, 0.10090)
H20 (0.37689, 0.30407, 0.11380)
C11 (1.01200, 0.27880, 0.04360)
H11 (1.11576, 0.29622, 0.03661)
C13 (0.85250, 0.19590, 0.04380)
H13 (0.84333, 0.15830, 0.03814)
C1 (0.89010, 0.30750, 0.06220)
H1 (0.90383, 0.34501, 0.06771)
C21 (0.73900, 0.28000, 0.07340)
C23 (0.56500, 0.20020, 0.07400)
H23 (0.55093, 0.16280, 0.06843)
C26 (0.71660, 0.22620, 0.06360)
C36 (0.43100, 0.23030, 0.09320)
H36 (0.32502, 0.21441, 0.10013)
C18 (0.99400, 0.22450, 0.03380)
H18 (1.08455, 0.20655, 0.01953)
N9 (0.19000, 0.55750, 0.16330)
C7 (0.26890, 0.51420, 0.13830)
H9A (0.31024, 0.52792, 0.11333)
H9B (0.19019, 0.48837, 0.13246)
H9C (0.35546, 0.49945, 0.15373)
C3 (0.28660, 0.60530, 0.16740)
C2 (0.45040, 0.61420, 0.15080)
H2 (0.50755, 0.58677, 0.13511)
C6 (0.03920, 0.54900, 0.17990)

Table 4.4 – continued from previous page
Parameter (1-MQ)(1-NA)Pb2I6
H6 (-0.01624, 0.51534, 0.17597)
C8 (0.52600, 0.66360, 0.15770)
H8 (0.63690, 0.67005, 0.14684)
C12 (0.28990, 0.69530, 0.19560)
H12 (0.23494, 0.72385, 0.21047)
C4 (0.44470, 0.70370, 0.18000)
H4 (0.49894, 0.73756, 0.18428)
C5 (-0.04100, 0.59110, 0.20410)
H5 (-0.14941, 0.58543, 0.21666)
C16 (0.03810, 0.63810, 0.20890)
H16 (-0.01625, 0.66642, 0.22421)
C17 (0.20570, 0.64670, 0.19110)
Rint 0.0495

Chapter 5
Understanding the role of the organic
dipole in templating the packing of the
extended solid
5.1 Introduction
This chapter focuses on work that exists as an extension of the ideas presented in Chapter
2 and Chapter 4. Although the materials disucssed in this chapter utilized very similar
organic cations to those in Chapter 2 and Chapter 4, the resulting structures presented
different packing. This chapter will explore the possible reasons for those differences and
how patterns and predictions could be made for similar materials in the future. Other
systems were also attempted including the other halide analogs and various organic cations,
but the work presented here discusses the hybrids with the most complete characterization.
In addition to (MDA)Pb2I6 and (MDA)Pb2Br6 discussed in Chapter 2, several other
hybrid materials with similar organic cations or different halides were explored. Despite
the seemingly small changes, (MDA)PbCl4, (ODA)PbI4, and (TDA)PbI4 all crystallize in a
similar layered morphology. This chapter details the structural differences in these materials
and the possible reasons why these materials do not crystallize in the F dd2 space group.

After the initial discovery of the similar structures of (1-NA)PbI3 and (1-MQ)PbI3
resulting in the synthesis of (1-MQ)(1-NA)Pb2I6 as detailed in Chapter 4, several other
methylquinolinium based hybrid systems were targeted. This chapter highlights 3 main materials, (4-MQ)PbI3, (1-MQ)PbBr3, and (5-MQ)PbI3, and discusses similarities and differences with (1-MQ)PbI3. Both structure and photophysical properties are discussed in detail.
Despite several attempts and several different crystallization methods, only the iodine based
naphthylammonium hybrid could be synthesized.
5.2 Experimental Details
0.1 g (0.22 mmol) of lead (II) bromide (PbBr2, 99.998% (metals basis) and 0.055 g (0.28 mmol)
4,4’methylenedianiline (MDA, 97%, Sigma Aldrich) were dissolved separately in 3 mL and
5 mL of hydrobromic acid (HBr, 48 wt%, VWR) in 2 dram and 8 dram scintillation vials,
respectively. Each solution was stirred continuously while heating to 110 °C in an aluminum
bead bath placed atop a hot plate.
Once the solids were fully dissolved, the solution of lead bromide was added to that of
the MDA and stirred while continuing to heat. The solution was allowed to cool naturally to
room temperature within the bead bath to encourage crystallization. The resulting crystals
were subsequently collected via vacuum filtration and rinsed thoroughly with diethyl ether
(≥98% (stabilized), VWR). The synthesis of (MDA)PbBr4 results in colorless white needlelike crystals which contrasts the tabular crystals of (MDA)Pb2Br6. In order to preferentially
grow (MDA)PbBr4 a higher concentration of starting materials in hydrobromic acid was
used.
A similar procedure was followed for the synthesis of (MDA)PbCl4 using 0.1 g (0.36 mmol)
of lead (II) chloride (PbCl2, 99.999% (metals basis),Sigma-Aldrich) and 0.035 g (0.18 mmol)
4,4’methylenedianiline (MDA, 97%, Sigma Aldrich). The precursors were dissolved separately in 2 mL and 8 mL of hydrochloric acid (HCl, 38 wt%, Sigma-Aldrich) in 2 dram and

8 dram scintillation vials, respectively. The resulting crystals were collected via vacuum
filtration and rinsed thoroughly with diethyl ether (≥98% (stabilized), VWR).
A similar procedure was followed for the synthesis of (ODA)PbI4 using 0.22 g (0.48 mmol)
of lead (II) iodide (PbI2, 99.9985% (metals basis), Alfa Aesar) and 0.036 g (0.18 mmol)
4,4’oxydianiline (ODA, 4-aminophenyl ether, 98%, Acros Organics). The precursors were
dissolved separately in 5 mL and 5 mL of hydroiodic acid (HI, 57 wt% (stabilized), Sigma
Alrdich) in 2 dram and 8 dram scintillation vials, respectively. The resulting crystals were
collected via vacuum filtration and rinsed thoroughly with ethanol (200 proof, Koptec) which
was determined to dissolve the co-crystallized organic iodide salt.
(DBP)PbCl3 was synthesized using 0.1 g (0.36 mmol) of lead (II) chloride (PbCl2,
99.999% (metals basis), Sigma-Aldrich) and 0.076 g (0.36 mmol) 4,4’-diaminobenzophenone
(DBP, Sigma Aldrich). The precursors were dissolved separately in 5 mL and 5 mL of hydroiodic acid (HI, 57 wt% (stabilized), Sigma Alrdich) in 2 dram and 8 dram scintillation
vials, respectively. Crystals grew upon cooling aand were rinsed with acetone (≥99.5%,
VWR).
The precursor salt, 1-methylquinolinium iodide (C10H10NI, (1-MQ)I), was synthesized
by mixing 2 parts quinoline (98%, Sigma Aldrich) with iodomethane (99%, stab. with Cu,
Fisher) in approximately 10 mL of acetonitrile (HPLC, EMD Millipore). The solution was
then heated to 85 °C and stirred for 2 hours. Once the solution cooled to room temperature,
it was transferred to a glass petri dish to allow the solvent to evaporate. The resulting yellow
solid was vacuum filtered and rinsed with diethyl ether (≥98% (stabilized), VWR). Proton
NMR spectra using DMSO-d6 (Cambridge Isotope Laboratories) were collected to confirm
the purity and structure of the product.
1-methylquinolinium lead bromide ((1-MQ)PbBr3) was prepared by dissolving 0.2 g
(0.43 mmol) of lead (II) bromide (PbBr2, 99.9985% (metals basis), Alfa Aesar) and 0.12 g
(0.44 mmol) of the prepared (1-MQ)I salt in 2 mL and 3 mL of hydroiodic acid (HI, 57 wt%
(stabilized), Sigma Alrdich) in 2 dram and 8 dram scintillation vials, respectively. The

organic salt solution was stirred continuously in an aluminum bead bath on a hot plate
until reaching 100 °C. Once all solids were dissolved in both solutions, the lead solution was
decanted into the organic solution and allowed to briefly mix before turning off the heat.
The resulting yellow crystals were collected via vacuum filtration and rinsed with acetone
(≥99.5%, VWR). The synthesis was directly adapted from the synthesis of (1-MQ)PbI3
discussed in the previous chapter.
X-ray characterization techniques were used to determine the structure of all hybrids.
Single crystal data were collected at 100 K using a Rigaku XTALab Synergy diffractometer
with a CCD area detector. The data reduction was performed using Crysalis Pro and refined
using Olex2 with the ShelXL program installed.[89] The crystallographic data for single
crystal structure determination for all materials can be found at the end of this chapter in
the supplemental information.
Diffuse reflectance data was collected from 800–250 nm using a PerkinElmer Lambda 950
UV-Vis-NIR spectrophotometer equipped with a 150 mm integrating sphere to determine
the onset of absorption in powders diluted to 3 wt% in MgO and to approximate the optical
band gap using the Kubelka-Munk transform.[65]
Photoluminesence spectra were collected using neat solid samples in a cryostat system as
described below. Each sample was sandwiched between two 1 mm thick sapphire disks and
excited at 365 nm LED source. Steady state emission spectra were collected from 4–290 K
using a Photon Technology International QuantaMaster model C-60SE spectrofluorimeter
in tandem with a Janis model SHI-4-2 optical He cryostat equipped with a Lakeshore model
335 temperature controller.
DFT calculations were performed on each of the three systems using the Vienna Ab Initio
Simulation Package (VASP).[66, 67, 68, 69] The projector augmented wave method was used
to describe the interaction between core and valence electrons.[70] Density of states and band
diagram plots were visualized using sumo.[71] Sumo was also used to calculate the electron
and hole effective masses from the band structures.[71] The functional of Perdew, Burke,

and Ernzerhof adapted for solids (PBEsol) [72] was used for geometrical relaxation. Spin
orbit coupling (PBEsol+SOC) was included for electronic structure calculations, including
density of states and electronic band structure. The total energy for all three compounds
converged to within 10 µeV per atom using a plane wave energy cutoff of 600 eV and a Γcentered k-point mesh of 2×2×1. The plane wave energy cutoff was not altered for the
geometric relaxation step and the calculation was considered converged when the forces on
each atom fell below 0.01 eV Å
−1
.
These calculations were performed by first converting the structures from the cifs to
POSCAR files using VESTA. The POSCAR file was then used to determine the kpoints and
the primitive cell using the sumo-kgen function as part of the sumo suite. The workflow then
proceeds to structural relaxations using ASE scripts to automate the iterrative calculations.
The relaxed structures are then used to perform self consistent (SCF) calculations. The
resulting CHGCAR file generated by this process is used in the density of state and band
structure calculations. The SCF, DOS, and band steps were performed at PBEsol and
PBEsol+SOC levels simultaneously.
5.3 Results and Discussion
Instead of crystallizing in a non-centrosymmetric space group like the MDA lead iodide and
bromide hybrids, other systems crystallize in a layered morphology as shown in Figure 5.1.
Both materials as well as (TDA)PbI4 and a different MDA polymorph, (MDA)PbBr4, instead
form layers of corner sharing lead halide octahedra with the organic cations sitting between
the layers. The positively charged ammonium portions of the cations pack in towards the
negatively charged octahedral layers. A trend can be seen relative to atomic electronegativity; as the halide or the cation becomes more electronegative, a layered structure is
preferred.
When compared to (MDA)Pb2I6 and (MDA)Pb2Br6, the MDA and ODA cations in

Figure 5.1: Structures of a) (ODA)PbI4 and b) (MDA)PbCl4
(ODA)PbI4 and (MDA)PbCl4 are highly distorted. In (MDA)Pb2I6 and (MDA)Pb2Br6, the
dihedral angle between the two aniline groups is about 90° whereas in both (ODA)PbI4
and (MDA)PbCl4 the angle is closer to 45°. More cationic twisting occurs in the layered
structure to place the ammonium groups close to the halide charge centers. Additionally,
when comparing (ODA)PbI4 and (MDA)PbCl4, a difference in the cation packing is observed.
In (ODA)PbI4, the cations pack in the same orientation layer to layer, but in (MDA)PbCl4,
the cations alternate between the layers. The differences in cations also results in tighter
packing between layers in (MDA)PbCl4 and shorter intermolecular distances; though, the
twisting of the cation means that no π-π interactions can occur.
When comparing the octahedral layers between (ODA)PbI4 and (MDA)PbCl4, a notable
difference can be observed. In (ODA)PbI4, Pb-I bond lengths are less distorted and the
octahedra do not heavily overlap going from one layer to the next. In (MDA)PbCl4, the
Pb-Cl bond lengths are distorted in the a-b plane of the layers and the octahedra overlap
much more significantly from layer to layer. This difference in octahedra is likely templated
by the differences in the organic packing between the layers.
(MDA)PbCl4 displays moderate emission intensity at low temperatures as seen in Figure
5.2b; note that the peak at 690 nm is the Raman signature from the excitation source. Near
room temperature a single peak at 505 nm is observed. As the material cools, a secondary
peak begins to emerge at 602 nm. This peak grows in tandem with the main feature and
briefly becomes more intense at 100 K. As would be expected, (MDA)PbCl4 has a larger

Figure 5.2: a) Kubelka-Munk transform (MDA)PbCl4 b) emission of (MDA)PbCl4 from
50 - 290 K (λex = 365 nm)
band gap than (MDA)Pb2I6 and (MDA)Pb2Br6 as shown in Figure 5.2a. Although the
structures differ, it is common for the band gap of a hybrid series to increase going from
iodide to bromide to chloride.[113]
Interesting trends can also be observed when comparing electronic properties of these
Figure 5.3: Density of states and band diagrams for a) (ODA)PbI4 and b) (MDA)PbCl4

Figure 5.4: (DBP)PbCl3 Structure viewed down the b-axis
hybrids. The bands in (ODA)PbI4 are very disperse and quite close, leading to a band gap of
about 1 eV. Additionally, there is not significant organic character at either the conduction
band minimum or valence band maximum as seen in Figure 5.3a. In (MDA)PbCl4 the
bands are not highly dispersive at the valence band edge, but do show some dispersivity
at the conduction band minimum as shown in Figure 5.3b. There is also good agreement
between the calculated band gap energy and the experimental band gap energy of 3.07
eV. While the structure of (MDA)PbCl4 is quite different to those of (MDA)Pb2Br6 and
(MDA)Pb2I6, the band gap is larger than both as would be expected when going from less
to more electronegative halides.
(DBP)PbCl3 is quite different compared to the other hybrid discussed. It also forms a
layered solid, but the PbCl octahedra are highly distorted as shown in Figure 5.4 Similar to
(ODA)PbI4 and (MDA)PbCl4, the organic cation is distorted with a dihedral angle of 28.9°
between the two aniline groups. The cations also display pseudo-n = 2 packing with free
chloride anions between the cationic species rather than another layer of octahedra. The
somewhat strange, densely packed lead-chloride octahedra layers require more cations in the
interlayer space to balance the negative charge in the layer.
It is not all together clear why small changes in the organic cations lead to such large
changes in the extended solid, but some trends do stand out. When looking at the structure
of (MDA)Pb2Br6 and (MDA)Pb2I6 in comparison with (ODA)PbI4 and (MDA)PbCl4, it
is clear that the centrosymmetric system is more favorable. Although (MDA)Pb2Br6 and

(MDA)Pb2I6 were able to crystallize in a non-centrosymmetric space group, changing the
electronegativity of the halide or dipole of the cation has a systemic effect on packing.
Interesting packing trends can also be observed when looking beyond (1-NA)PbI3 and
(1-MQ)PbI3 discussed in Chapter 4. While the synthesis of each quinoline based material
resulted in similarly colored yellow crystals, the packing varies quite a bit between these three
materials. Figure 5.5 shows the crystal structure of each material that will be discussed. (4-
MQ)PbI3 and (1-MQ)PbBr3 have similar lead halide, face-sharing chains, and (5-MQ)PbI3
has dimer chains which are edge-sharing. When these three materials are compared to (1-
NA)PbI3 and (1-MQ)PbI3, it is clear that the electronic strucutre of the cation drives the
packing. (1-MQ)PbBr3 has the same structure as (1-MQ)PbI3 because the cations are the
same in both system. As the nitrogen is moved around the ring to get 4-MQ or 5-MQ, more
obvious changes occur.
In the (4-MQ)PbI3 system, the quinolinium cations rotate to put the nitrogen atoms
closer to the inorganic octahedra. This results in the methyl groups packing along the aaxis rather than the c-axis in (1-MQ)PbBr3. Additionally, the distortion of the octahedra
Figure 5.5: a) (4-MQ)PbI3 b) (1-MQ)PbBr3 c) (5-MQ)PbI3

Figure 5.6: (1-MQ)PbBr3 a) Kubelka Munk transform and b) temperature dependent
emission intensity (λex = 365 nm)
is significantly less severe that in (1-MQ)PbBr3 or (1-MQ)PbI3. Despite a similar structure,
the (5-MQ) cations pack very differently compared to the (4-MQ) or (1-MQ) cations.
Comparing the optical properties of these systems to each other and to (1-MQ)PbI3
also reveals interesting patterns. Sharing the same cation and general structure means that
(1-MQ)PbBr3 has very similar emission properties to (1-MQ)PbI3. Both materials display
emission maxima at temperatures warmer than the lowest measured, 3.5 K. In (1-MQ)PbBr3,
the emission intensity grows as the material is warmed from 3.5 K to 80 K when it then
begins to decrease towards room temperature as seen in Figure 5.6b. Swapping the halides
in the case of (1-MQ)PbBr3 and (1-MQ)PbI3 results in more intense emission in the bromide
analog which is common within these types of materials. Additionally, the band gap is blue
shifted in (1-MQ)PbBr3 compared to (1-MQ)PbI3 at 2.58 eV (Figure 5.6a). There is also a
charge transfer feature seen in the Kubelka Munk Transform at 4 eV corresponding to the
transfer between the organic cations and the bromide ions. A similar feature also appears
in the transform for (1-MQ)PbI3.
The trend in the lifetime values differ compared to those of (1-MQ)PbI3. In (1-MQ)PbI3,
the lifetime values which are able to be found by fitting the data to a monoexponential
equation begin relatively flat at lower temperatures and drop steeply before leveling out at

Figure 5.7: (4-MQ)PbI3 a) Kubelka Munk transform and b) temperature dependent emission intensity (λex = 365 nm)
higher temperatures. In (1-MQ)PbBr3, the lifetime values display a much more linear trend
with respect to temperature. The increase in lifetime values with the corresponding decrease
in emission intensity indicates that the non-radiative rate is increasing.
The trends in the optical properties of (4-MQ)PbI3 differ quite a bit from (1-MQ)PbI3
and (1-MQ)PbBr3. Clear triplet character can be seen at temperatures of 50 K and below
as shown in Figure 5.7b. Above 50 K, the triplet character begins to die out and broader red
shifted emission begins. The differences in structure are likely responsible for the disparate
emission profiles. The organic cations pack in a very different way compared to (1-MQ)PbI3.
Additionally, the octahedra are less distorted in the (4-MQ)PbI3 structure. While VASP
calculations were not performed for this system, it is likely that the triplet energy of (4-MQ)
is lower than the energy of the conduction band minimum and a trap state is created at
lower temperatures similar to (1-NA)PbI3. The absorption features observed in Figure 5.7a
are similar to those seen in (5-MQ)PbI3 with a distinct absorption signature at around 3.25
eV and around 4.25 eV.
The optical properties of (5-MQ)PbI3 were also explored. The Kubelka-Munk transform
and temperature dependent emission profiles are shown in Figure 5.8 The experimental band
gap of 2.49 eV is in the general range of other methylquinolinium hybrids but the emission
properties are quite different. At the lowest measured temperatures, the emission is much

Figure 5.8: (5-MQ)PbI3 a) Kubelka Munk transform and b) temperature dependent emission intensity (λex = 365 nm)
more structured and shows some triplet character. As the system is warmed, the major
peak red shifts and becomes significantly weaker. Although the emission profile is different
from other similar systems, the octahedral packing in this system is also different likely
contributing to the emission property variance.
5.4 Summary
While (MDA)Pb2I6 and (MDA)Pb2Br6 displayed interesting non-centrosymmetric structures
templated in part by the dipole of the cations, the study of further systems did not yield
analogous structures. The ability of the bromide analog to pack in either a 1D or a 2D
morphology indicates that the difference in energy between these two structures is very
small and changes to the cation can have a major impact. Despite minor cationic structural
changes, other factors such as electronegativity drove these materials to pack in a layered
fashion.
In the case of the quinoline-based materials, the position of the nitrogen in the ring
relative to the methyl group has a major impact on the solid state packing. When the
methyl group is on the same ring as the nitrogen, the structure looks more similar to that
of (1-MQ)PbI3. For (5-MQ)PbI3, the nitrogen atom and the methyl group are further apart

which leads to a very different inorganic packing arrangement. The results from both of
these groups of materials show how impactful the organic cation is on both the structure
and properties of the extended solid.

5.5 Supplemental Information
Table 5.1: Crystallographic data for single crystal structure determination of (ODA)PbI4
Parameter (ODA)PbI4
Chemical formula C12H14N2OPbI4
Formula weight 1094.12
Temperature (K) 100
Crystal system orthorhombic
Space Group P bcm
a 23.895 (5)
b 41.682 (9)
c 4.3708 (10)
Volume 4353.3(17)
Z 8
C1 (0.38911, 0.25730, 0.50460)
C2 (0.43941, 0.29950, 0.48750)
H2 (0.44795, 0.37843, 0.42052)
C3 (0.47675, 0.22430, 0.56970)
H3 (0.51145, 0.25054, 0.55884)
C4 (0.46354, 0.11150, 0.66740)
C5 (0.41343, 0.06900, 0.68320)
H5 (0.40486, -0.00978, 0.75035)
C6 (0.37596, 0.14310, 0.59970)
H6 (0.34135, 0.11503, 0.60831)
N1 (0.34968, 0.33820, 0.41840)
H1N (0.32020, 0.30700, 0.44100)
H2N (0.35010, 0.42740, 0.44400)
H3N (0.35010, 0.33400, 0.31880)
O1 (0.50000, 0.03020, 0.75000)
Pb1 (0.25000, 0.75000, 0.50000)
I1 (0.24592, 0.55954, 0.18616)
I2 (0.37007, 0.70600, 0.52051)
Rint 0.035

Table 5.2: Crystallographic data for single crystal structure determination of (MDA)PbCl4
Parameter (MDA)PbCl4
Chemical formula C13H16N2PbCl4
Formula weight 549.27
Temperature (K) 100
Crystal system orthorhombic
Space Group P bcm
a 8.5532(3)
b 8.0858(3)
c 24.8803(9)
Volume 1720.71(11)
Z 4
Pb1 (0.23854, -0.05179, 0.25000)
Cl1 (0.52881, 0.11716, 0.25000)
Cl2 (0.09463, 0.24790, 0.25000)
Cl3 (0.28134, -0.02024, 0.36254)
N1 (0.37590, 0.34830, 0.34857)
H1A (0.47846, 0.36361, 0.35216)
H1B (0.34674, 0.37679, 0.31550)
H1C (0.35319, 0.24233, 0.35421)
C1 (0.29270, 0.45080, 0.38779)
C6 (0.34160, 0.45300, 0.44001)
H6 (0.42626, 0.38919, 0.45092)
C2 (0.16730, 0.54330, 0.37063)
H2 (0.13509, 0.54033, 0.33494)
C5 (0.26260, 0.55210, 0.47649)
H5 (0.29486, 0.55489, 0.51217)
C4 (0.13640, 0.64680, 0.46042)
C3 (0.09060, 0.64050, 0.40771)
H3 (0.00542, 0.70339, 0.39666)
C7 (0.04340, 0.75000, 0.50000)
H7A -(0.02384, 0.82372, 0.47970)
H7B -(0.02383, 0.67627, 0.52030)
Rint 0.0262

Table 5.3: Crystallographic data for single crystal structure determination of (DBP)PbCl3
Parameter (DBP)PbCl3
Chemical formula C14H14N2OPbCl3
Formula weight 563.25
Temperature (K) 100
Crystal system monoclinic
Space Group P21/c
a 30.4525(9)
b 7.4174(2)
c 7.7408(2)
α 90°
β 93.254°
γ 90°
Volume 4353.3(17)
Z 4
Pb1 (0.53638, 0.46762, 0.22552)
Cl1 (0.53672, 0.69091, 0.51889)
Cl2 (0.56599, 0.15375, 0.38638)
Cl3 (0.62649, 0.53491, 0.25406)
Cl4 (0.97299, 0.23356, 0.99221)
O1 (0.82554, 1.19570, 0.43370)
C2 (0.81530, 1.05940, 0.35740)
C21 (0.84943, 0.92560, 0.31250)
C22 (0.84308, 0.73990, 0.31890)
H22 (0.81574, 0.69411, 0.34420)
C23 (0.87734, 0.62220, 0.28790)

Table 5.3 – continued from previous page
Parameter (DBP)PbCl3
H23 (0.87328, 0.49820, 0.29502)
C24 (0.91715, 0.69140, 0.24660)
C25 (0.92379, 0.87240, 0.23590)
H25 (0.95091, 0.91686, 0.20625)
C26 (0.89006, 0.99020, 0.26930)
H26 (0.89472, 1.11385, 0.26261)
N2 (0.95373, 0.56940, 0.21620)
H2A (0.96205, 0.51339, 0.31430)
H2B (0.97622, 0.63248, 0.17915)
H2C (0.94517, 0.48825, 0.13653)
C31 (0.76792, 1.02230, 0.30900)
C32 (0.75442, 0.91900, 0.16690)
H32 (0.77548, 0.86359, 0.10250)
C33 (0.71068, 0.89640, 0.11850)
H33 (0.70227, 0.82746, 0.02192)
C34 (0.67969, 0.97610, 0.21360)
C35 (0.69109, 1.07730, 0.35850)
H35 (0.66974, 1.12934, 0.42380)
C36 (0.73551, 1.09880, 0.40350)
H36 (0.74380, 1.16716, 0.50070)
N3 (0.63342, 0.94690, 0.16350)
H3A (0.62851, 0.97277, 0.05183)
H3B (0.61695, 1.01785, 0.22624)
H3C (0.62652, 0.83211, 0.18187)
Rint 0.0246

Table 5.3 – continued from previous page
Parameter (DBP)PbCl3

Table 5.4: Crystallographic data for single crystal structure determination of (4-MQ)PbI3
Parameter (4-MQ)PbI3
Chemical formula C10H10NPbI3
Formula weight 732.08
Temperature (K) 100
Crystal system orthorhombic
Space Group P bca
a 15.89840
b 7.86190
c 25.16880
Volume 3145.889
Z 8
Pb1 (0.25045, 0.09265, 0.42599)
I1 (0.32401, 0.34399, 0.33729)
I2 (0.08731, 0.32474, 0.42381)
I3 (0.33421, 0.34294, 0.51315)
C1 (0.68360, -0.01590, 0.34390)
H1A (0.67091, -0.11413, 0.36511)
H1B (0.74183, 0.01328, 0.34812)
H1C (0.67236, -0.04049, 0.30723)
C2 (0.62980, 0.13060, 0.36157)
C3 (0.59930, 0.13620, 0.41260)
H3 (0.61231, 0.04998, 0.43657)
C4 (0.54890, 0.27190, 0.42827)
H4 (0.52676, 0.27362, 0.46246)
N5 (0.53230, 0.39570, 0.39610)
H5 (0.50400, 0.48000, 0.40300)
C6 (0.56140, 0.40090, 0.34466)
C7 (0.53880, 0.53630, 0.31228)
H7 (0.50611, 0.62490, 0.32550)
C8 (0.56480, 0.53720, 0.26160)
H8 (0.54920, 0.62656, 0.23948)
C9 (0.61410, 0.40880, 0.24170)
H9 (0.63266, 0.41467, 0.20667)
C10 (0.63630, 0.27230, 0.27227)
H10 (0.66855, 0.18525, 0.25773)
C11 (0.61030, 0.26290, 0.32627)
Rint 0.0251

Table 5.5: Crystallographic data for single crystal structure determination of (5-MQ)PbI3
Parameter (5-MQ)PbI3
Chemical formula C10H10NPbI3
Formula weight 731.07
Temperature (K) 100
Crystal system monoclinic
Space Group P21/c
a 4.5122
b 23.1429
c 14.3266
α 90°
β 96.648°
γ 90°
Volume 1486.002
Z 6
Pb1 (0.15911, 0.55563, 0.88517)
I2 (0.27967, 0.41663, 0.95528)
I3 (0.59818, 0.52774, 0.73310)
I4 (0.09187, 0.68218, 0.82119)
C2 (0.35370, 0.83420, 0.94090)
C3 (0.21500, 0.86470, 0.86090)
C5 (0.56230, 0.78810, 0.93860)
H5 (0.62260, 0.77659, 0.88004)
C10 (0.29200, 0.84840, 0.76440)
H10A (0.50710, 0.85296, 0.76238)
H10B (0.18343, 0.87361, 0.71721)
H10C (0.23532, 0.80812, 0.75108)
N8 (0.41000, 0.82090, 1.10640)
H8 (0.36678, 0.83180, 1.16210)
C4 (-0.05200, 0.92310, 0.96260)
H4 (-0.18887, 0.95383, 0.96837)
C11 (0.67680, 0.76030, 1.01780)
H11 (0.81270, 0.72932, 1.01393)
C6 (0.07390, 0.89590, 1.04110)
H6 (0.02558, 0.90688, 1.10144)
C1 (0.01490, 0.90670, 0.87180)
H1 (-0.08270, 0.92563, 0.81790)
C9 (0.59740, 0.77680, 1.10410)
H9 (0.67415, 0.75720, 1.16003)
C7 (0.27900, 0.85070, 1.03130)
Rint 0.0334

Table 5.6: Crystallographic data for single crystal structure determination of (1-MQ)PbBr3
Parameter (1-MQ)PbBr3
Chemical formula C10H10NPbBr3
Formula weight 591.11
Temperature (K) 100
Crystal system orthorhombic
Space Group P bca
a 14.4076
b 7.7746
c 24.61650
Volume 2757.376
Z 8
Pb1 (0.24958, 0.56867, 0.42265)
Br2 (0.31393, 0.81103, 0.51211)
Br3 (0.41707, 0.32805, 0.41346)
Br4 (0.33766, 0.81440, 0.34337)
N5 (0.59370, 0.70450, 0.39170)
C14 (0.59730, 0.78510, 0.34310)
C6 (0.62250, 0.54800, 0.39860)
H6 (0.61941, 0.49828, 0.43385)
C15 (0.55230, 0.80100, 0.43890)
H15A (0.59181, 0.90003, 0.44782)
H15B (0.54810, 0.72494, 0.47049)
H15C (0.49013, 0.84200, 0.42916)
C13 (0.56980, 0.95900, 0.33700)
H13 (0.54865, 1.02565, 0.36698)
C9 (0.63090, 0.69300, 0.29870)
C7 (0.65800, 0.44900, 0.35580)
H7 (0.67963, 0.33545, 0.36214)
C12 (0.57540, 1.02900, 0.28470)
H12 (0.55824, 1.14522, 0.27868)
C8 (0.66110, 0.51500, 0.30760)
H8 (0.68282, 0.44772, 0.27793)
C11 (0.60600, 0.92800, 0.24130)
H11 (0.60652, 0.97776, 0.20605)
C10 (0.63420, 0.76800, 0.24690)
H10 (0.65623, 0.70424, 0.21652)
Rint 0.0707

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Abstract (if available)

Abstract With the emergence of hybrid perovskites as promising solar harvesting materials just under two decades ago, the field has been inundated with studies about how to improve their device performance. While their use in solar cells is a highly active area of research, there is still much to be learned about the fundamentals of the interplay between the organic and inorganic components. This body of work represents a contribution to the understanding of structure property relationships in the field of hybrid organic-inorganic materials development. We sought to better understand how polar organic cations could lend themselves to a solid state dipole in the first project by looking at materials based on 4,4’-methylenedianiline. Initial probing showed that the lead iodide and bromide analogs crystallized in a non-centrosymmetric or polar space group.We also wanted to explore the possibility of incorporating more than one cation in the solid state with ordered packing. This began with the phenethylamine (PEA) and 2-aminoethyl pyridine (2-AEP) systems which are well studied in the layered material space. Stumbling upon the 1 naphthylammonium (1-NA) lead iodide hybrid led us to the discovery of (1-MQ)(1-NA)Pb2I6 which represents the first 1-D material that displays ordered cation packing. Although the goal of creating materials with interesting charge transfer was not met, much was learned about how to better select cation pairs and leaves a path for further research to be conducted on these systems.

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Creator Cassingham, Megan (author)

Core Title Effects of cationic species on the structure and properties of hybrid organic-inorganic materials

School College of Letters, Arts and Sciences

Degree Doctor of Philosophy

Degree Program Chemistry

Degree Conferral Date 2024-08

Publication Date 07/17/2024

Defense Date 05/13/2024

Publisher Los Angeles, California (original), University of Southern California (original), University of Southern California. Libraries (digital)

Tag inorganic chemistry,materials development,OAI-PMH Harvest,perovskite

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Advisor Melot, Brent (committee chair), Malmstadt, Noah (committee member), Thompson, Mark (committee member)

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