High Triplet Energy Phosphine Sulfide Host Materials with Selectively Modulated Electrical Performance for Blue Electrophosphorescence

Bipolar host materials consisting of electron-donating (D) and -accepting (A) moieties are significant advances in broadening the recombination zone to suppress the quenching effects of emissive phosphors in the emission layer for achieving a high-efficiency blue electrophosphorescence device. However, it is still a daunting and challenging issue to design bipolar blue host molecules that have high triplet energy (ET) and balanced charge transportation simultaneously in the directly linked D–A molecules, owing to their high tendency in forming low-energy charge-transfer (CT) states. Herein, on account of the high-polarization, electron-withdrawing, and insulating features of the acceptor of aryl phosphine sulfide (APS), a series of blue host materials in D–A/D–A–D skeletons with high ET's are constructed and facilely prepared. Thus, designed host materials show high ET's up to 3.02 eV, suitable highest occupied molecular orbitals and lowest unoccupied molecular orbitals, and balanced hole/electron flux, which facilitate blue phosphorescent organic light-emitting diodes (PhOLEDs) with a maximum external quantum efficiency of 14.1%, power efficiency of 21.4 lm W–1, and current efficiency of 27.8 cd A–1. These findings demonstrate the important role of APS unit in designing and developing host materials with high ET's and balanced carrier flux for high-performance blue PhOLEDs.