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 2 H -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 (Δ E T ) between the host and guests, reaching 1530.32 ms with a large Δ E T (>0.8 eV) and 1292.82 ms with a small Δ E T (<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.