Designing thermally activated delayed fluorescence emitters with through-space charge transfer: a theoretical study.

Recently, thermally activated delayed fluorescence (TADF) molecules with through-space charge transfer (TSCT) features have been widely applied in developing organic light-emitting diodes with high luminescence efficiencies. The performance of TSCT-TADF molecules depends highly on their molecular structures. Therefore, theoretical investigation plays a significant role in designing novel highly efficient TSCT-TADF molecules. Herein, we theoretically investigate two recently reported TSCT-TADF molecules, 1'-(2,12-di--butyl[1,4]benzoxaborinino[2,3,4-]phenoxaborinin-7-yl)-10-phenyl-10-spiro[acridine-9,9'-fluorene] (AC-BO) and 1-(2,12-di--butyl[1,4]benzoxaborinino[2,3,4-]phenoxaborinin-7-yl)-9',9'-dimethyl-9'-spiro [fluorene-9,5'-quinolino[3,2,1-]acridine](QAC-BO). The calculated photophysical properties ( excited state energy levels and luminescence properties) for these two compounds are in good agreement with experimental data. Based on the systematic analysis of structure-performance relationships, we design three novel TSCT-TADF molecules with high molecular rigidity and evident TSCT features, , DQAC-DBO, DQAC-SBO, and DQAC-NBO. They exhibit deep-blue light emissions and fast reverse intersystem crossing rates (s). Our calculations demonstrate that the nearly coplanar orientation of the donor and acceptor is critical to achieve remarkable s and fluorescence efficiencies in TSCT-TADF molecules.