Multiple resonance type thermally activated delayed fluorescence by dibenzo [1,4] azaborine derivatives

Jaehyun Bae; Mika Sakai; Youichi Tsuchiya; Naoki Ando; Xian-Kai Chen; Thanh Ba Nguyen; Chin-Yiu Chan; Yi-Ting Lee; Morgan Auffray; Hajime Nakanotani; Shigehiro Yamaguchi; Chihaya Adachi

doi:10.3389/fchem.2022.990918

Multiple resonance type thermally activated delayed fluorescence by dibenzo [1,4] azaborine derivatives

Front Chem. 2022 Sep 19:10:990918. doi: 10.3389/fchem.2022.990918. eCollection 2022.

Authors

Jaehyun Bae^{1

2}, Mika Sakai³, Youichi Tsuchiya¹, Naoki Ando³, Xian-Kai Chen¹, Thanh Ba Nguyen^{1

2}, Chin-Yiu Chan¹, Yi-Ting Lee¹, Morgan Auffray¹, Hajime Nakanotani^{1

2}, Shigehiro Yamaguchi^{3

4

5}, Chihaya Adachi^{1

2

6}

Affiliations

¹ Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, Fukuoka, Japan.
² Department of Chemistry and Biochemistry, Kyushu University, Fukuoka, Japan.
³ Department of Chemistry, Graduate School of Science, Nagoya University, Nagoya, Japan.
⁴ Research Center for Materials Science (RCMS) and Integrated Research Consortium on Chemical Sciences (IRCCS), Nagoya University, Nagoya, Japan.
⁵ Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Nagoya, Japan.
⁶ International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, Fukuoka, Japan.

Abstract

We studied the photophysical and electroluminescent (EL) characteristics of a series of azaborine derivatives having a pair of boron and nitrogen aimed at the multi-resonance (MR) effect. The computational study with the STEOM-DLPNO-CCSD method clarified that the combination of a BN ring-fusion and a terminal carbazole enhanced the MR effect and spin-orbit coupling matrix element (SOCME), simultaneously. Also, we clarified that the second triplet excited state (T₂) plays an important role in efficient MR-based thermally activated delayed fluorescence (TADF). Furthermore, we obtained a blue-violet OLED with an external EL quantum efficiency (EQE) of 9.1%, implying the presence of a pronounced nonradiative decay path from the lowest triplet excited state (T₁).

Keywords: TADF; azaborine; blue–violet OLED; multi-resonance; thermally activated delayed fluorescence.