Hydrogen Bond Density over Energy Level Matching─A New Paradigm for Room-Temperature Phosphorescence in Doped Systems

This research challenges the long-standing paradigm that energy level alignment is essential for achieving efficient phosphorescence in host–guest doped systems. We demonstrate that hydrogen bonding interactions can serve as a dominant factor for realizing ultralong organic room-temperature phosphorescence (UORTP), even in the absence of energy-level matching. Using 2H-1,2,3-triazole-4,5-dicarboxylic acid dimethyl ester (Trdae) as the host, the RTP lifetime of the doped materials is enhanced irrespective of the triplet energy gap (ΔET) between the host and guests, reaching 1530.32 ms with a large ΔET (>0.8 eV) and 1292.82 ms with a small ΔET (<0.25 eV), both far exceeding the pure Trdae (1060.80 ms). Comprehensive spectroscopic analyses confirm that hydrogen bonding interactions are crucial for facilitating triplet–triplet energy transfer (TTET). This work establishes a general design strategy based on hydrogen bond density-regulated exciton trapping, providing a new molecular-level perspective for engineering long-afterglow materials beyond conventional energy-level matching constraints.