Optimizing molecular aggregation-induced emission (AIE) behavior of phosphoryl center π-conjugated heterocycles by tuning chemical features of the tether groups

In this paper, we obtained phosphoryl center π-conjugated heterocycles TSP and TSOP by changing the bridging atoms of TOP from oxygen atoms to sulfur atoms and sulfone groups and found that TOP cannot emit light in both solution and solid states, TSP has an aggregation-induced emission (AIE) characteristic, and TSOP can emit light in both solution and solid states. To explain this phenomenon, the recombination energy based on the S₁ state has been calculated and found that their low-frequency vibration intensity is TOP > TSP > TSOP. In general, the higher of low-frequency vibrations ratio, the higher the proportion of non-radiative transitions of molecules. And the AIE characteristics of TSP has been characterized. The organic light-emitting diodes (OLED) based on TSP have been prepared. When the doping ratio is 8%, TSP obtains the best EL efficiency, with the maximum η_ext of 0.79%, η_L of 1.63 cd A⁻¹ and η_P of 1.03 lm W⁻¹ with maximum luminance (L_max) of 2293.1 cd m⁻² at 10.0 V.