A Novel Strategy toward Thermally Activated Delayed Fluorescence from a Locally Excited State

Jingyao Chen; Xiaoxiao Xiao; Shuai Li; Yuai Duan; Guo Wang; Yi Liao; Qian Peng; Hongbing Fu; Hua Geng; Zhigang Shuai

doi:10.1021/acs.jpclett.2c00224

A Novel Strategy toward Thermally Activated Delayed Fluorescence from a Locally Excited State

J Phys Chem Lett. 2022 Mar 24;13(11):2653-2660. doi: 10.1021/acs.jpclett.2c00224. Epub 2022 Mar 17.

Authors

Jingyao Chen¹, Xiaoxiao Xiao¹, Shuai Li¹, Yuai Duan¹, Guo Wang¹, Yi Liao¹, Qian Peng², Hongbing Fu¹, Hua Geng¹, Zhigang Shuai³

Affiliations

¹ Department of Chemistry, Beijing Advanced Innovation Center for Imaging Theory and Technology, Capital Normal University, Beijing 100048, China.
² School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.
³ Department of Chemistry, Tsinghua University, Beijing 100083, China.

PMID: 35297633
DOI: 10.1021/acs.jpclett.2c00224

Abstract

It is well-known that thermally activated delayed fluorescence (TADF) is always generated from charge-transfer (CT) excited states in donor-acceptor (D-A) systems, which limits its application owing to a slow radiative process and a small stimulated emission cross section. Herein, a design strategy is proposed for realizing TADF from a locally excited (LE) state without a typical donor-acceptor type structure through controlling the intersystem crossing (ISC) and reverse intersystem crossing (RISC) processes between the lowest excited singlet with LE character and higher triplet states. Using this strategy, a boron difluoride derivative is theoretically predicted and experimentally synthesized to exhibit locally excited TADF (LE-TADF) with a fairly large radiative rate of 1.12 × 10⁸ s^-1, extremely fast RISC rate of 5.09 × 10¹⁰ s^-1, and a large stimulated emission cross section of 4.35 × 10^-17 cm², making this a promising organic amplified spontaneous emission (ASE) material. This work might open a new avenue to extend TADF materials, especially TADF laser emitters.