Solvent effect on the photophysical properties of thermally activated delayed fluorescence molecules

Xiaotong Zhang; Yurong Shi; Lei Cai; Yong Zhou; Chuan-Kui Wang; Lili Lin

doi:10.1016/j.saa.2019.117473

Solvent effect on the photophysical properties of thermally activated delayed fluorescence molecules

Spectrochim Acta A Mol Biomol Spectrosc. 2020 Jan 15:225:117473. doi: 10.1016/j.saa.2019.117473. Epub 2019 Aug 21.

Authors

Xiaotong Zhang¹, Yurong Shi¹, Lei Cai¹, Yong Zhou¹, Chuan-Kui Wang², Lili Lin³

Affiliations

¹ Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, School of Physics and Electronics, Shandong Normal University, 250014 Jinan, China.
² Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, School of Physics and Electronics, Shandong Normal University, 250014 Jinan, China. Electronic address: ckwang@sdnu.edu.cn.
³ Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, School of Physics and Electronics, Shandong Normal University, 250014 Jinan, China. Electronic address: linll@sdnu.edu.cn.

PMID: 31470345
DOI: 10.1016/j.saa.2019.117473

Abstract

As the third-generation organic electroluminescent materials, thermally activated delayed fluorescence (TADF) molecules have become the research focus recently. Significant solvent effect on TADF molecules were found experimentally, while theoretical investigations are quite limited. In this work, the solvent effect on photophysical properties of DCBPy and DTCBPy are investigated with first-principles calculations. The solvent polarity has slight influence on the molecular geometries and orbitals, while it can decrease the energy gap between the first singlet excited state (S1) and first triplet excited state (T1) significantly. Both the oscillator strength and the radiation rates of S1 increase with larger solvent polarity. The large energy gap between S1 and T1 induce negligible intersystem crossing (ISC) and reverse ISC rates between them, which also indicates higher triplet excited states are involved in the up-conversion process. Our results provide valuable information about solvent influence on the light-emitting properties of TADF molecules, which could help one better understand the light-emitting mechanism of them and favor the design of TADF molecules.

Keywords: Excited state; First-principles; Solvent effect; Thermally activated delayed fluorescence.