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THEORETICAL, EXPERIMENTAL, DEVICE FABRICATION, AND DEGRADATION STUDIES OF MATERIALS FOR OPTOELECTRONIC DEVICES
by
Azad M. Hassan
________________________________________________________________________
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)
December 2007
Copyright 2007 Azad M. Hassan
Object Description
| Title | Theoretical, experimental, device fabrication, and degradation studies of materials for optoelectronic devices |
| Author | Hassan, Azad M. |
| Author email | mhassan@usc.edu |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Chemistry |
| School | College of Letters, Arts and Sciences |
| Date defended/completed | 2007-07-31 |
| Date submitted | 2007 |
| Restricted until | Unrestricted |
| Date published | 2007-10-10 |
| Advisor (committee chair) | Thompson, Mark E. |
| Advisor (committee member) |
Bau, Robert Mansfeld, Florian |
| Abstract | The work presented in this thesis has two distinct objectives. The first objective is to design, synthesize, and study new materials for OLEDs and OPV cells and in the process make more efficient devices. The second objective is to study the extrinsic degradation mechanism of OLED and find a way to stop or slow down the degradation, so in the future more air stable devices can be produced.; Development of high triplet energy materials is important for both OLEDs and OPV cells. In OLEDs these materials can be effectively used either as hosts or as hole blocking materials and in OPV cells the materials can be used as exciton blocking layers (Buffer layers). The second chapter of this thesis describes the design, synthesis, and characterization studies of new phthalimide based high triplet energy materials for OLEDs and OPV cells. The chapter gives a detailed narrative of the electrochemical, photophysical, and density functional theory analysis (Ground and excited states) of all the materials.; The third chapter deals with thermochemistry, thin-film photophysics, and OLED fabrication studies of the phthalimide materials. The chapter delves into the OLED fabrication studies and investigates the behaviors of the devices fabricated with the phthalimides as hosts and as hole blocking layers (HBL) with red and green dopants. Very efficient green and red devices were obtained with the phthalimide HBL compared to the conventional BCP hole blocking layer.; Theoretical studies of platinum based broadband emitter, (dmappy)Pt(acac) are described in chapter four. In room temperature fluid solution, the (dmappy)Pt(acac) has been shown to emit in two different wavelengths, which shifts from blue to red depending on solvent polarity. Rotation of the dimethyl amino moiety on the phenyl ring causes the molecule to emit in different wavelengths. In the planar geometry, increased conjugation between the p orbital of the nitrogen atom and the pi orbitals of the phenyl ring causes the triplet energy of the system to decrease. When the dimethyl amino group rotates perpendicular to the plane of the molecule, the geometry of the dimethyl amino moiety becomes trigonal-by-pyramidal giving rise to two structural isomers: One with the nitrogen lone pairs facing up and the other with the lone pairs facing down. As a consequence, the conjugation between the p-pi orbitals decreases and the emission shifts to higher energy. In chapter four we investigate the spectroscopic behavior of this molecule by comparing the photophysical data with DFT and TDDFT calculations.; Theoretical investigation of (5NO2ppy)Pt(acac) is covered in chapter five. This molecules is important for both OLEDs and OPV cells. At 77K glass in 2me-THF and at room temperature in hexanes and polystyrene matrix emission from this molecule is observed around 550nm. In acetonitrile, toluene, and 2me-THF at 298 K no emission is observed. We believe that the emission of (5NO2ppy)Pt(acac) is controlled by the rotating NO2 group on the pyridine ring. Rotation of the NO2 group to the plane or perpendicular to the plane of the molecule may alter the emission properties of the molecule. Chapter five uses theoretical methods (DFT and TDDFT) to investigate the spectroscopic properties of (5NO2ppy)Pt(acac). |
| Keyword | OLEDs; OPV cells; solar cells; DFT; TDDFT; photophysics; optical spectroscopy; excited state; dark spots; computational studies; device |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Type | texts |
| Legacy record ID | usctheses-m859 |
| Rights | Hassan, Azad M. |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | http://www.usc.edu/isd/libraries/services/ask_a_librarian/email/ |
| Filename | etd-Hassan-20071010 |
| Archival file | uscthesesreloadpub_Volume29/etd-Hassan-20071010.pdf |
Description
| Title | Page 1 |
| Full text | THEORETICAL, EXPERIMENTAL, DEVICE FABRICATION, AND DEGRADATION STUDIES OF MATERIALS FOR OPTOELECTRONIC DEVICES by Azad M. Hassan ________________________________________________________________________ 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) December 2007 Copyright 2007 Azad M. Hassan |
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