Fig. 1: Molecular design of binary phosphine-carbazole systems for delayed room temperature phosphorescence (DRTP).
From: Delayed room temperature phosphorescence enabled by phosphines
a Illustrations of proposed energy transfer mechanisms for instant room temperature phosphorescence (IRTP) and delayed room temperature phosphorescence (DRTP). In contrast to rapid energy transfer in IRTP systems between excited states with constant π-π* characteristics, the incorporation of different n-π* featured intermediate energy levels increases transition probability, but elongates energy transfer routine and reduces transition rate, therefore postpones RTP emission. T1 and Tn* refer to the first single-molecular and π-π stacking-stabilized triplet states localized on π-π* featured units; TM is the intermediate triplet state contributed by n-π* units. b Chemical structures of IRTP molecules DCzSBr and DCzDBr based on brominated carbazoles, and DRTP molecules DCzSBrSP and DCzSBrSPO containing phosphine units with n-π* characteristics as mediate groups. c Photos of DCzSBr, DCzDBr, DCzSBrSP and DCzSBrSPO powders excited with UV light at 365 nm and after UV excitation for 1.6-4.0 s.
