Hot exciplexes in U-shaped TADF molecules with emission from locally excited states

A Lennart Schleper; Kenichi Goushi; Christoph Bannwarth; Bastian Haehnle; Philipp J Welscher; Chihaya Adachi; Alexander J C Kuehne

doi:10.1038/s41467-021-26439-w

Hot exciplexes in U-shaped TADF molecules with emission from locally excited states

Nat Commun. 2021 Oct 26;12(1):6179. doi: 10.1038/s41467-021-26439-w.

Authors

A Lennart Schleper¹, Kenichi Goushi^{2

3}, Christoph Bannwarth⁴, Bastian Haehnle¹, Philipp J Welscher¹, Chihaya Adachi^{5

6}, Alexander J C Kuehne^{7

8}

Affiliations

¹ Institute of Organic and Macromolecular Chemistry, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany.
² Department of Applied Chemistry and Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka, 819-0395, Japan. goushi@opera.kyushu-u.ac.jp.
³ International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishiku, Fukuoka, 819-0395, Japan. goushi@opera.kyushu-u.ac.jp.
⁴ Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074, Aachen, Germany. bannwarth@pc.rwth-aachen.de.
⁵ Department of Applied Chemistry and Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka, 819-0395, Japan. adachi@cstf.kyushu-u.ac.jp.
⁶ International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishiku, Fukuoka, 819-0395, Japan. adachi@cstf.kyushu-u.ac.jp.
⁷ Institute of Organic and Macromolecular Chemistry, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany. alexander.kuehne@uni-ulm.de.
⁸ DWI - Leibniz-Institute for Interactive Materials, Forckenbeckstraße 50, 52074, Aachen, Germany. alexander.kuehne@uni-ulm.de.

Abstract

Fast emission and high color purity are essential characteristics of modern opto-electronic devices, such as organic light emitting diodes (OLEDs). These properties are currently not met by the latest generation of thermally activated delayed fluorescence (TADF) emitters. Here, we present an approach, called "hot exciplexes" that enables access to both attributes at the same time. Hot exciplexes are produced by coupling facing donor and acceptor moieties to an anthracene bridge, yielding an exciplex with large T₁ to T₂ spacing. The hot exciplex model is investigated using optical spectroscopy and quantum chemical simulations. Reverse intersystem crossing is found to occur preferentially from the T₃ to the S₁ state within only a few nanoseconds. Application and practicality of the model are shown by fabrication of organic light-emitting diodes with up to 32 % hot exciplex contribution and low efficiency roll-off.

Abstract

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