Room-Temperature Phosphorescence and Tunable Persistent Luminescence in Purely Organic Doping Systems: Heavy-Atom Engineering, Insights, and Applications

Organic room-temperature phosphorescent (RTP) materials have attracted considerable attention due to their potential applications in optoelectronics, information encryption, and bioimaging. However, achieving efficient, long-lasting, and tunable persistent afterglow under ambient conditions remains a significant challenge. In this work, two 7H-benzo[c]carbazole (BCz) derivatives, BPBCz and BPBrBCz, were designed and synthesized to elucidate the effect of heavy-atom substitution on the RTP mechanism. The roles of guest heavy-atom engineering, host matrix rigidification, and host–guest triplet energy transfer in regulating RTP properties were systematically investigated. In the host–guest doping systems, bromine substitution on the guest molecules significantly accelerates the T 1 → S 0 transition process, enabling the simultaneous modulation of phosphorescence lifetime and quantum yield. Meanwhile, the benzophenone unit in the guest promotes efficient host–to–guest triplet–triplet energy transfer without perturbing the intrinsic triplet energy level of the BCz chromophore. As a result, the doping materials exhibit long-lasting afterglow, which is successfully applied in multilevel information encryption and sequential visual displays. This work provides a simple and effective strategy for constructing efficient and tunable pure organic RTP materials, offering promising potential for advanced anticounterfeiting and information security applications.