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Proceedings Paper

The role of charge-transfer (CT) electronic states in photo-physical processes in organic electroluminescent materials (Conference Presentation)
Author(s): Xiankai Chen

Paper Abstract

Intra-molecular CT states play an important role in the photo-physical processes and eventual device performances of organic electroluminescent materials such as organic thermally activated delayed florescence (TADF) and radical emitters. For organic TADF emitters, we have shed light on how the energy levels and excitation characters of intra-molecular CT states impact electronic-structure parameters such as singlet-triplet energy gap, spin-orbit coupling, transition dipole moment, and thus reverse intersystem crossing and radiative decay processes. For organic radical emitters, we have designed donor-acceptor neutral radicals based on the electron-poor perchlorotriphenylmethyl (PTM) or tris(2,4,6-trichlorophenyl)methyl (TTM) radical moiety combined with different electron-rich groups. Experimental and quantum-chemical studies demonstrate that the molecules do not follow the Aufbau principle: The Singly Occupied Molecular Orbital (SOMO), mainly localized on the PTM [TTM] segment, is found to lie below the Highest (doubly) Occupied Molecular Orbital (HOMO), mainly localized on the donor segment. Such the non-Aufbau behavior in the organic radical emitters is resulted from a high-energy CT state. These donor-acceptor radicals provide a remarkable combination of strong D1-to-D0 emission yield (up to 54%) and high photo-stability (e.g., the half-lives reach up to several months under pulsed UV laser irradiation). Organic light-emitting diodes (OLEDs) based on a radical emitter show near-infrared (NIR) emission with a high maximal external quantum efficiency of 4.0 %.

Paper Details

Date Published: 10 September 2019
Proc. SPIE 11093, Organic and Hybrid Light Emitting Materials and Devices XXIII, 110930C (10 September 2019); doi: 10.1117/12.2530368
Show Author Affiliations
Xiankai Chen, Georgia Institute of Technology (United States)

Published in SPIE Proceedings Vol. 11093:
Organic and Hybrid Light Emitting Materials and Devices XXIII
Chihaya Adachi; Jang-Joo Kim; Franky So, Editor(s)

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