Realization of switching between TADF and HLCT emissions through modulation of the intramolecular charge transfer character

Abstract

A facile molecular design strategy for switching between thermally activated delayed fluorescence (TADF) and hybridized local and charge transfer (HLCT) emissions has been proposed on the basis of the DFT calculations. Donor–acceptor (D–A) type molecular assemblies with suitable electron acceptor units (4-phenylbenzo[c][1,2,5]thiadiazole (BZP) or 9-borafluorene (BF)) and donor fragments with different electron-donating abilities could effectively tune the proportion of intramolecular charge transfer character in the excited state, thus realizing both HLCT and TADF emissions by utilizing hot and cold excitons through reverse intersystem crossing (RISC) channels. The excited-state properties are analyzed in the theoretical framework of the state hybridization to reveal the intrinsic structure–property relationships between HLCT and TADF molecules. This work provides an in-depth understanding of the excited-state properties of TADF/HLCT molecules and offers an easy way to design both HLCT and TADF molecules together.