Intermolecular interaction approach for TADF
(Conference Presentation)

Ken-Tsung Wong

doi:10.1117/12.2236457

4 November 2016 Intermolecular interaction approach for TADF (Conference Presentation)

Ken-Tsung Wong

Proceedings Volume 9941, Organic Light Emitting Materials and Devices XX; 99410B (2016) https://doi.org/10.1117/12.2236457
Event: SPIE Organic Photonics + Electronics, 2016, San Diego, California, United States

Abstract

Materials with thermally activated delayed fluorescence (TADF) have recently emerged as new fluorescent emitters for highly efficient organic light-emitting diodes (OLEDs). Molecule with TADF behavior needs to have a small singlet–triplet energy difference (ΔES-T) that allows the up-conversion from nonradiative triplet state (T1) to radiative singlet state (S1) via reverse intersystem crossing (RISC) process. Generally, molecules with small ΔES-T can be obtained via carefully manipulate the degree of “intramolecular” charge transfer (ICT) between electron-donating and -accepting components, such that the electron exchange energy that contributes to ΔES-T, can be minimized. Alternatively, excited state with small ΔES-T can be feasibly realized via “intermolecular” charge transfer occurring at the interface between spatially separating donor (D) and acceptor (A) molecules. Because the exchange energy decreases as the HOMO-LUMO separation distance increases, theoretically, the intermolecular D/A charge transfer state (or exciplex) should have rather small ΔES-T, leading to efficient TADF. However, it is still a challenge to access highly efficient exciplex systems. This is mainly because exciplex formation is commonly accompanied with a large red shift of emission spectra and long radiative lifetime, which tend to diminish photoluminescence quantum yield (PLQY) as well as electroluminescence (EL) performance. Until now, exciplex-based OLEDs with external quantum efficiency (EQE) above 10% are still limited. By judicious selection of donor and acceptor, the formation of efficient exciplex can be feasibly achieved. In this conference, our recent efforts on highly efficient exciplexes using C3-symmetry triazine acceptors and various donors, and their device characteristics will be presented.

Conference Presentation

Citation Download Citation

Ken-Tsung Wong "Intermolecular interaction approach for TADF (Conference Presentation)", Proc. SPIE 9941, Organic Light Emitting Materials and Devices XX, 99410B (4 November 2016); https://doi.org/10.1117/12.2236457

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KEYWORDS

Molecules

Organic light emitting diodes

Electroluminescence

External quantum efficiency

Luminescence

Interfaces

Printed circuit board testing

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