Persistent Link:
http://hdl.handle.net/10150/289012
Title:
Device physics of organic light-emitting diodes
Author:
Shaheen, Sean E.
Issue Date:
1999
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
This work investigated several aspects of OLED device physics. The mechanisms responsible for the efficiency enhancement typically seen when a dye molecule is doped into the emission layer were examined. By comparing the spectra and efficiencies of single-layer devices for varying dopant concentrations, it was found that both charge transfer and energy transfer from the host molecule to the dye dopant are important processes. The measured efficiencies for photoluminescence and electroluminescence were found to be consistent with a simple model developed to explain the functional dependence on the dopant concentration. Work was also done on the enhancement of electron injection from an aluminum cathode using a thin layer of LiF. A double-layer device with the blue emitter DPVBi showed a factor of 50 enhancement in quantum efficiency upon insertion of a LiF layer. This technique has important practical application since it allows for the use of an environmentally-stable aluminum cathode while retaining high device efficiency. The effect of the ionization potential of the hole transport layer on the efficiency of a double-layer device was also investigated. TPD side-group polymers were used as the hole transport layer. The device efficiency was shown to increase as the ionization potential of the hole transport layer was pushed further from the work-function of ITO. This trend was attributed to an improved balance between the injection rates of holes and electrons. A Monte Carlo simulation of a single-layer device was developed which demonstrated the importance of balanced injection to obtain high efficiency. Drawing upon these results, an optimized OLED was fabricated which exhibited a luminous efficiency of 20 lm/W for green emission. This is one of the highest OLED efficiencies reported as of the date of this writing.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Chemistry, Physical.; Physics, Condensed Matter.; Engineering, Materials Science.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Physics
Degree Grantor:
University of Arizona
Advisor:
Peyghambarian, Nasser

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleDevice physics of organic light-emitting diodesen_US
dc.creatorShaheen, Sean E.en_US
dc.contributor.authorShaheen, Sean E.en_US
dc.date.issued1999en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThis work investigated several aspects of OLED device physics. The mechanisms responsible for the efficiency enhancement typically seen when a dye molecule is doped into the emission layer were examined. By comparing the spectra and efficiencies of single-layer devices for varying dopant concentrations, it was found that both charge transfer and energy transfer from the host molecule to the dye dopant are important processes. The measured efficiencies for photoluminescence and electroluminescence were found to be consistent with a simple model developed to explain the functional dependence on the dopant concentration. Work was also done on the enhancement of electron injection from an aluminum cathode using a thin layer of LiF. A double-layer device with the blue emitter DPVBi showed a factor of 50 enhancement in quantum efficiency upon insertion of a LiF layer. This technique has important practical application since it allows for the use of an environmentally-stable aluminum cathode while retaining high device efficiency. The effect of the ionization potential of the hole transport layer on the efficiency of a double-layer device was also investigated. TPD side-group polymers were used as the hole transport layer. The device efficiency was shown to increase as the ionization potential of the hole transport layer was pushed further from the work-function of ITO. This trend was attributed to an improved balance between the injection rates of holes and electrons. A Monte Carlo simulation of a single-layer device was developed which demonstrated the importance of balanced injection to obtain high efficiency. Drawing upon these results, an optimized OLED was fabricated which exhibited a luminous efficiency of 20 lm/W for green emission. This is one of the highest OLED efficiencies reported as of the date of this writing.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectChemistry, Physical.en_US
dc.subjectPhysics, Condensed Matter.en_US
dc.subjectEngineering, Materials Science.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplinePhysicsen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorPeyghambarian, Nasseren_US
dc.identifier.proquest9946796en_US
dc.identifier.bibrecord.b39904817en_US
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