Controlling ISC/RISC Competition Through Triplet State Characteristics Modulation in Pure Organic RTP Emission

ABSTRACT To achieve purely organic room‐temperature phosphorescence, one common strategy involves introducing n→π* transitions into the molecule to enhance spin‐orbit coupling. However, molecules designed with such structures typically require special conditions, such as low temperatures or a rigid environment, to exhibit room‐temperature phosphorescent emission. Building on this, further introducing heavy atoms into the molecule can enhance room‐temperature phosphorescence performance but often comes with strong fluorescence emission, leading to reduced phosphorescence efficiency. While adopting a donor–acceptor configuration can achieve relatively pure room‐temperature phosphorescence emission, the system inherently involves competing processes of inter‐system crossing and reverse inter‐system crossing, and clear strategies for effectively suppressing reverse inter‐system crossing remain elusive. To address this issue, this study systematically investigates the properties of triplet excitons by modulating molecular configurations and reveals a significant correlation between the proportion of triplet localized states and the resulting luminescence characteristics.