Sulfone–Isoquinoline Dopants Activated Phosphorescence Beyond Room Temperature

Purely organic room-temperature phosphorescence (RTP) materials are of growing interest for bioimaging, anti-counterfeiting, and optoelectronic applications. However, impurity-induced RTP has challenged the reliability of many reported single-component systems. Herein, we systematically investigated a series of sulfone-based RTP materials and observed that their phosphorescence vanished upon rigorous purification, highlighting the critical role of trace impurities. Notably, the introduction of only 0.01 wt% of a rationally designed sulfone-isoquinoline dopant (SO2PzQ7) into the pure SF2Pz system effectively activated intense yellow afterglow with a lifetime of 273 ms under ambient conditions. The doped system exhibited exceptional thermal stability, maintaining a visible afterglow up to 413 K. Notably, the phosphorescence signal almost completely recovered upon cooling after heating, and the on-off switching process was repeatable for more than six cycles, demonstrating excellent reversibility. This strategy was further extended to sulfone derivatives containing carbazole and phenothiazine units, which were RTP-inactive alone but became RTP-active upon doping with rationally designed sulfone-isoquinoline dopants. Theoretical calculations support a host-guest energy transfer mechanism that facilitates efficient intersystem crossing (ISC) and triplet-state stabilization. Our findings highlight the crucial role of impurity traps in RTP and propose a generalizable, scalable approach to construct reproducible and thermally stable organic RTP systems.