Boron-Containing Molecules with Fluorescence-Phosphorescence Dual-Emission for Mechanochromism and Single Molecular White Light-Emitting Diodes

Organic molecules with fluorescence-phosphorescence dual-emission have attracted significant attention for their potential applications in white organic light-emitting diodes (WOLEDs). Herein, donor-accepter molecules, Mes*BA-Cz and (F)XylBA-Cz, are designed and synthesized, and the photoluminescence of these two compounds in solid state exhibits fluorescence-phosphorescence dual-emission. Through the single crystal study, the phosphorescent emission is mainly caused by the molecular stacking in the crystalline state, which is beneficial for aggregation-induced intersystem crossing. Dual emission behavior further caused the mechanochromism of the two compounds, with emission color changed between amorphous and crystalline state. White light photoluminescence with CIE coordinates of (0.33, 0.34) is achieved by doping (F)XylBA-Cz in the poly (methyl methacrylate) film. Furthermore, a WOLED based on (F)XylBA-Cz is manufactured with CIE coordinates of (0.31, 0.33), and the external quantum efficiency (EQE) reached 0.49%.