Tunable Room‐Temperature Phosphorescence Property of Benzo[a]Phenothiazine Derivatives and the Selectivity to Host Matrixes

Abstract Research of purely organic room temperature phosphorescence (RTP) is a hot topic, and host‐guest doping method has been widely utilized in the construction of related materials. Until now, the fine regulation of phosphorescence property for host‐guest doping system is still difficult for the unclear structure‐property relationship. This work designs and synthesizes three benzo[a]phenothiazine derivatives with different oxidation degrees, then dopes them into different polymer and small molecule hosts. It is found that increasing the oxidation degree of sulfur atom in guest molecules could slow down the radiative and non‐radiative transition of triplet excitons, thus prolonging the RTP lifetime gradually in doping system. Furthermore, obvious selectivity of phosphorescence guest toward small molecule host is observed, in which the doping systems with similar molecular structures for host and guest showed much promoted RTP efficiency. With the careful match of host and guest, a balanced RTP property with phosphorescence efficiency and lifetime of 10.22% and 1.18 s is realized. Based on these excellent RTP materials, the applications of information encryption and 3D printing are demonstrated.