Intermolecular Interaction-Induced Thermally Activated Delayed Fluorescence Based on a Thiochromone Derivative

Exploration of new extrinsic ways to modulate thermally activated delayed fluorescence (TADF) to achieve high exciton utilization efficiency in organic light emitting diodes (OLEDs) is highly desirable. A new thiochromone derivative 2,3-bis(4-(9H-carbazol-9-yl)phenyl)-4H-thiochromen-4-1,1-dioxide (THI-PhCz) with tunable photophysical properties from crystals to amorphous states is reported. THI-PhCz shows molecular-packing-dependent TADF in different aggregation states based on the differences of intermolecular interactions. Furthermore, it is observed that THI-PhCz doped in amorphous films of different hosts also shows host-dependent TADF with a short delay lifetime (108 ns), which is interpreted as the effect of host-guest intermolecular interaction on the (CT)-C-3 state except for the effect on the (CT)-C-1 state in reported references. This work provides a new perspective for generation of TADF by tuning intermolecular interactions in crystals and amorphous films except for molecular design, which is expected to contribute in achieving low-efficiency roll-off OLEDs with effective exciton utilization efficiency.