Bridge-tuned through-space charge transfer for TADF and HLCT emissions

Abstract

Thermally activated delayed fluorescence (TADF) and hybridized local and charge transfer (HLCT) emitters represent two distinct yet highly efficient classes of electroluminescent materials. However, their designs are commonly independent due to their unique mechanisms for converting cold/hot triplet excitons into singlet excitons through the reverse intersystem crossing (RISC) process. In this study, we propose a novel design strategy to achieve TADF/HLCT emissions using structurally similar U-shaped donor–acceptor (D–A) type molecules. Specifically, we employ different π-conjugated molecules, 9,9-dimethylxanthene (XAN) and anthracene (AN), as bridges to connect the donor (diphenylamine and carbazole, DPA/Cz) and acceptor (diphenyltriazine, TRZ). This approach allows us to regulate the through-space charge transfer (TSCT) between donor and acceptor, as well as fine-tune the proportion of locally excited (LE) states in the singlet states, thereby facilitating TADF/HLCT emissions. This work provides an in-depth understanding of the intrinsic structure–property relationships of TSCT-based TADF/HLCT molecules, offering a novel methodology for concurrently designing both TADF and HLCT materials.