Theoretical study on acridine-thioxanthene bridged TADF molecules presenting TSCT and TBCT features and the design...

We have theoretically studied a series of acridine-thioxanthene bridged thermally activated delayed fluorescence (TADF) molecules, 2PhCzSpiroS, 2PhCzSpiroS-2, SpiroS-2TRZ, TPA-SpiroS-TRZ, BOP-SpiroS-TRZ and QX-SpiroS-TRZ by using DFT/TD-DFT methods, and screened out a series of potential full-color TADF materials. Firstly, we preliminarily predicted the ease of reverse intersystem crossing (RISC) and through-space charge transfer (TSCT) processes for these molecules through singlet-triplet energy gap calculation and weak interaction analysis. Secondly, we detailedly compared the effects of different combinations of TADF functional groups on the intersystem crossing (ISC) channels and radiative/non-radiative processes. In particular, these molecules contain a pair of isomers, whose frontier orbital energy levels are very close, but the electronic structures of the ground state and the excited state are quite different such as frontier orbital distributions. The comparative study reveals the significant influence of the geometrical configuration on the electronic structure and the transition characteristics of TSCT, through-bond charge transfer (TBCT), and local excitation (LE). Finally, we evaluated the TADF properties of these molecules and screened out the target molecules by comprehensively considering the radiative rate, ISC/RISC rate, and the determining parameters of non-radiative process such as the reorganization energy between the excited state and the ground state.