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

Xiankai Chen

doi:10.1117/12.2530368

10 September 2019 The role of charge-transfer (CT) electronic states in photo-physical processes in organic electroluminescent materials (Conference Presentation)

Xiankai Chen

Author Affiliations +

Proceedings Volume 11093, Organic and Hybrid Light Emitting Materials and Devices XXIII; 110930C (2019) https://doi.org/10.1117/12.2530368
Event: SPIE Organic Photonics + Electronics, 2019, San Diego, California, United States

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 %.

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Xiankai Chen "The role of charge-transfer (CT) electronic states in photo-physical processes in organic electroluminescent materials (Conference Presentation)", Proc. SPIE 11093, Organic and Hybrid Light Emitting Materials and Devices XXIII, 110930C (10 September 2019); https://doi.org/10.1117/12.2530368

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KEYWORDS

Organic light emitting diodes

External quantum efficiency

Laser irradiation

Molecules

Near infrared

Ultraviolet radiation

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