자료유형  

 학위논문

Control Number  

0016935395

International Standard Book Number  

9798380723862

Dewey Decimal Classification Number  

600

Main Entry-Personal Name  

Swartzfager, John R.

Publication, Distribution, etc. (Imprint  

[S.l.] : The Pennsylvania State University., 2023

Publication, Distribution, etc. (Imprint  

Ann Arbor : ProQuest Dissertations & Theses, 2023

Physical Description  

1 online resource(179 p.)

General Note  

Source: Dissertations Abstracts International, Volume: 85-05, Section: B.

General Note  

Advisor: Asbury, John B.

Dissertation Note  

Thesis (Ph.D.)--The Pennsylvania State University, 2023.

Restrictions on Access Note  

This item must not be sold to any third party vendors.

Summary, Etc.  

요약The first practical organic light emitting diode (OLED) was created by Kodak in 1987 and set off a new area of research for the organic optoelectronics community. Now, over 30 years later, OLEDs are used in a significant number of devices, from TV displays to smartphone screens. The current generation of OLEDs used in commercial displays are comprised of organometallic complexes which utilize heavy metals in order to allow for efficient spin-orbit coupling. The high spin-orbit coupling these molecules possess allows them to achieve internal quantum efficiencies (IQEs), for emission, of 100%. However, while these complexes do boast high IQEs, the use of expensive and toxic heavy metals do make them somewhat unattractive. The new generation of OLEDs being studied looks to retain the high IQEs of the last generation, while using purely organic molecules. In order to achieve this high efficiency with purely organic molecules researchers are looking to exploit thermally activated delayed fluorescence to allow for efficient use of both singlet and triplet excitons. Thermally activated delayed fluorescence (TADF) allows for triplet excitons, which in purely organic molecules are unable to emit, to be promoted to emissive singlet excitons by utilizing the thermal energy available to them. For TADF to work the singlet and triplet level must be within a few KT (~100 meV) of each other, to accomplish this electron donating and accepting moieties are connected together via a single bond. This allows for the HOMO and LUMO of the molecule to lie on the donor and acceptor respectively, doing so intimately couples the singlet-triplet energy gap with the conformational state of the molecule, especially the dihedral angle between the donor and acceptor unit. While this helps bring the singlet and triplet closer in energy it makes the photophysics of the molecule rather complicated and easily influenced by the local environment. While many studies have looked at the influence of molecular structure on the TADF efficiency, there hasn't been as much work on how the dynamic conformational motion of the molecule influences emission properties of the system.This dissertation focuses on utilizing time-resolved photoluminescence spectroscopy to study how the molecular dynamics of a TADF emitter, NAI-DMAC, influence its radiative rate. What was found is that reaching an emissive state following photoexcitation is an activated process, with the emission intensity closely following the change in the diffusion dynamics of the solvent with temperature. Based on this we believe that the TADF molecules may transiently access a distribution of conformational states, which avoids the need for a single conformation to be favored that is able to balance intersystem crossing and emission oscillator strength. This observation brings up questions about how TADF molecules are able to function efficiently in the solid state, where the conformational degrees of freedom are significantly reduced relative to solution phase.

Subject Added Entry-Topical Term  

Polymers.

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Fourier transforms.

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Carbon.

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Magnetic fields.

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Symmetry.

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Light emitting diodes.

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Hybridization.

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Mercury cadmium telluride.

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Aluminum.

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Chemistry.

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Chemical bonds.

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Anisotropy.

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Fluorides.

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Energy.

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Morphology.

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Physical chemistry.

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Molecular chemistry.

Index Term-Uncontrolled  

Organic light emitting diode

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Organic optoelectronics

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Internal quantum efficiencies

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Photophysics

Index Term-Uncontrolled  

Photoexcitation

Added Entry-Corporate Name  

The Pennsylvania State University.

Host Item Entry  

Dissertations Abstracts International. 85-05B.

Host Item Entry  

Dissertation Abstract International

Electronic Location and Access  

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Control Number  

joongbu:640494