Enhancing Thermally Activated Delayed Fluorescence Through Structural And Energetic Flexibility: Theoretical Studies

Alhmoud, Dieaa H.

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https://hdl.handle.net/2142/116493 Copy

Description

Title

Enhancing Thermally Activated Delayed Fluorescence Through Structural And Energetic Flexibility: Theoretical Studies

Author(s)

Alhmoud, Dieaa H.

Contributor(s)

Lin, Zhou

Issue Date

2022-06-21

Keyword(s)

Theory and Computation

Abstract

\begin{wrapfigure}{r}{0pt} \includegraphics[scale=0.20]{Abstract.eps} \end{wrapfigure} Thermally activated delayed fluorescence (TADF) is one of the most promising routes to enhance the luminescent efficiency of an organic light-emitting diode (OLED) device by converting a non-emissive triplet exciton (T$_1$) back to an emissive singlet configuration (S$_1$) through reverse intersystem crossing (RISC) before it fluoresces back to the ground state (S$_0$). However, the TADF rate is generally restricted if only the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) are involved. This is due to the conflict between a fast RISC rate between S$_1$ and T$_1$ (which requires a small HOMO--LUMO overlap), and a large transition dipole moment ($\mu_\text{T}$) between S$_1$ and S$_0$ (which requires a large HOMO--LUMO overlap).\footnote{A. Endo et al., {\it Appl. Phys. Lett.} {\bf 2011}, 98, 083302.} In the present study, we proposed two solutions to enhance the overall fluorescent rate: an inclusion of higher-lying singlet and triplet states (S$_{n\ge2}$ and T$_{n\ge2}$) in ISC--RISC routes to avoid the trade-off, and a fluxional molecular conformation to sample a broad range of HOMO--LUMO overlap. We provided a proof-of-concept for our solutions based on computational modeling of sample di-tert-butyl carbazole derivatives with the pyrazine or dipyrazine substituents (DTCz-Pz or DTCz-Pz), using a combination of density functional theory (DFT) and molecular dynamics (MD). Our study will provide a computational and quantitative strategy for the design of new TADF emitters with maximum luminescent efficiency.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Handle URL

https://hdl.handle.net/2142/116493

DOI

https://doi.org/10.15278/isms.2022.TL04

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Copyright 2022 held by the authors

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