Chem. J. Chinese Universities ›› 2024, Vol. 45 ›› Issue (10): 20240282.doi: 10.7503/cjcu20240282

• Physical Chemistry • Previous Articles     Next Articles

Heavy Atom Effect’s Influence on the Triplet State and Upconversion Efficiency in MR-TADF Systems

WEI Yaxiong(), YI Kai, DUAN Doudou, XU Xinsheng()   

  1. Anhui Province Key Laboratory for Control and Applications of Optoelectronic Information Materials,School of Physics and Electronic Information,Anhui Normal University,Wuhu 241002,China
  • Received:2024-06-11 Online:2024-10-10 Published:2024-08-21
  • Contact: WEI Yaxiong, XU Xinsheng E-mail:yaxiongwei@ahnu.edu.cn;xxsheng@mail.ahnu.edu.cn
  • Supported by:
    the Applied Basic Research Project of Wuhu City, China(2022jc13);the National Natural Science Foundation of China(22203004);the Anhui Normal University 2023 Year Scholarship and Supplementary Discipline Construction Project, China(2023GFXK160)

Abstract:

Multi-resonance thermally activated delayed fluorescence(MR-TADF) containing heavy atoms exhibits low energy loss, intense absorption, high intersystem crossing(ISC) efficiency, and long triplet state lifetime. In this work, three heavy metal-free MR-TADF molecules combined oxygen, sulfur, and selenium atoms were chosen, designated as BN-2O, BN-2S, and BN-2Se. The heavy atom effect of these compounds was studied using theoretical calculations and nanosecond transient absorption spectra. The ISC efficiencies of BN-2O, BN-2S, and BN-2Se are determined to be 39.4%, 74.7%, and 95.0%, respectively, while the triplet state lifetimes are found to exceed 10 μs. The upconversion system comprising BN-2Se/1,4-bis(triisopropylsilethynyl) naphthalene(1,4-DTNA) demonstrates a high upconversion quantum yield(ΦUC, the maximum value of 50%) of up to 8.7% in solution, with a threshold excitation intensity as low as 1.7 mW/cm2, which is lower than the solar irradiance of 2.7 mW/cm2. Additionally, the economically viable BN-2S and BN-2O show satisfactory ΦUC values of 5.9% and 3.9%, with low Ith values of 6.2 and 15 mW/cm2.

Key words: Multi-resonance thermally activated delayed fluorescence, Triplet-triplet annihilation upconversion, Heavy atom effect

CLC Number: 

TrendMD: