A 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 a triphenylamine moiety manifesting tunable solid-state luminescence and thermally activated delayed fluorescence (TADF). The compound shows strong fluorescence in both organic solutions and solid states. It exhibits significantly different emission colours in different aggregation states: bright orange emission in its crystalline solid state and red emission in the amorphous state. The orange and red emissive states are able to be reversibly switched by repetitive grinding–fuming processes with little fatigue. More importantly, the aggregation state plays a key role in the TADF properties. Its solid exhibits TADF properties in the amorphous state but not in the crystalline solid state due to the different ΔEST values in the relative morphologies.