Theoretical verification of intermolecular hydrogen bond induced thermally activated delayed fluorescence in SOBF-OMe* *Project supported by the National Natural Science Foundation of China (Grant Nos. 11974216, 11874242, 21933002, and 11904210), the Natural Science Foundation of Shandong Province, China (Grant No. ZR2019MA056), the Taishan Scholar Project of Shandong Province, China, and the Project funded by China Postdoctoral Science Foundation (Grant No.

Abstract

Thermally activated delayed fluorescence (TADF) molecules have attracted great attention as high efficient luminescent materials. Most of TADF molecules possess small energy gap between the first singlet excited state (S1) and the first triplet excited state (T1) to favor the up-conversion from T1 to S1. In this paper, a new TADF generation mechanism is revealed based on theoretical simulation. By systematic study of the light-emitting properties of SOBF-OMe in both toluene and in aggregation state, we find that the single SOBF-OMe could not realize TADF emission due to large energy gap as well as small up-conversion rates between S1 and T1. Through analysis of dimers, we find that dimers with intermolecular hydrogen bond (H-bond) are responsible for the generation of TADF, since smaller energy gap between S1 and T1 is found and the emission wavelength is in good agreement with experimental counterpart. The emission properties of SOBF-H are also studied for comparison, which reflect the important role of H-bond. Our theoretical results agree ith experimental results well and confirm the mechanism of H-bond induced TADF.