A Strategy for Designing Multifunctional TADF Materials for High-Performance Non-doped OLEDs by Intramolecular Halogen Bonding

The development of multifunctional thermally activated delayed fluorescence (TADF) material with high efficiency is indeed a formidable challenge. The difficulty arises from the need to achieve multiple desirable radiation pathways simultaneously during the emission process. In this context, a novel strategy to construct multifunctional emitters with high emission efficiency by modulating intramolecular halogen bonding through structural isomerism is proposed. The designed molecule DMAC-2FDPS exhibits multifunctional features, including aggregation-induced emission, mechanochromic luminescence, room temperature phosphorescence, mechanoluminescence, and TADF. Notably, in neat film, DMAC-2FDPS demonstrates an exceptionally high photoluminescence quantum efficiency of up to 93%. Through single-crystal analysis and theoretical calculations, it is revealed that the intramolecular halogen bonding in this molecule plays a crucial role in achieving both multifunctional emission and high PLQY. Furthermore, when utilized in non-doped organic light-emitting diodes (OLEDs), DMAC-2FDPS achieves a maximum external quantum efficiency of up to 21.2%. To the best acknowledge, it is almost the highest efficiency for non-doped OLEDs based on multifunctional materials with five characteristics. These results certify a new strategy for the development of high-efficiency multifunctional TADF materials and devices. Highly-efficient multifunctional thermally activated delayed fluorescence (TADF) material is obtained through an intramolecular halogen bonding strategy, with five distinct characteristics including aggregation-induced emission, mechanochromic luminescence, room temperature phosphorescence, mechanoluminescence, and TADF.image