Dynamic Organic Radical Complex Emission from a Room-Temperature Phosphorescent Host–Guest System

Open-shell organic radical emitters hold promise for improving exciton utilization efficiency; however, triggering stable organic radical emission is rarely documented due to its high chemical reactivity. Herein, we present a universal design strategy for organic radical emitters by using an excited triplet state as an intermediate. The system features a long-lived room-temperature phosphorescence (RTP) guest embedded within a host matrix. Systematic investigations reveal a dynamic conversion from orange RTP to red radical complex emission under continuous photoexcitation. This phenomenon arises from long-lived triplet excitons, which facilitate photoinduced charge transfer (PICT) from the host to the guest, thereby triggering efficient radical emission with long-term chemical stability. We further demonstrate the excellent reversibility between guest RTP and host radical emission through alternating heat/recrystallization and photoexcitation processes. This triplet-mediated PICT strategy provides a promising pathway for the development of radical emitters with high efficiency towards advanced electroluminescent devices.