Sulfone–Isoquinoline Dopants Activated Phosphorescence Beyond Room Temperature

ABSTRACT 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.