Difluoroboron β-Diketonate Based Luminescent Material with Tunable Solid-state Emission and Thermally Activated Delayed Fluorescence

We demonstrate a solid luminescent material based on difluoroboron β-diketonate containing triphenylamine moiety manifesting tunable solid-state luminescence and thermally activated delayed fluorescence (TADF). The compound shows strong fluorescence in both the organic solutions and solid state. It exhibits significant different emission colors in different aggregation states, bright orange emission in its crystalline solid state and red emission in amorphous state. The orange and red emissive states are able to be reversibly switched by the repetitive grinding-fuming processes with little fatigue. More importantly, the aggregation state plays a key role on the TADF properties. Its solid exhibits TADF properties in amorphous state but not crystalline solid state due to the different △EST in relative morphologies.