A meta-linked benzoxazole-based wide-bandgap material for deep-blue electroluminescence and high-brightness,...

The development of efficient host materials is critical for achieving high-performance organic light-emitting diodes (OLEDs), particularly under high-brightness operation. Herein, we report a benzoxazole-based wide-bandgap material (m-PCzPBO) featuring a meta-linked donor-acceptor (D-A) structure. The introduction of meta-linkage and a twisted molecular conformation effectively suppresses π-conjugation, leading to a high triplet energy level (2.90 eV) and enlarged spatial occupation, which jointly mitigate triplet exciton annihilation. Single-crystal analysis reveals ordered intermolecular interactions that facilitate the formation of distinct hole- and electron-transport channels. As a non-doped emitter, m-PCzPBO enables deep-blue electroluminescence at 388 nm with negligible efficiency roll-off. More importantly, when employed as a universal phosphorescent host, it delivers high external quantum efficiencies of 24.43%, 26.23%, and 17.55% for green, yellow, and red devices, respectively, accompanied by ultrahigh luminance (>200 000 cd m^-2) and significantly suppressed roll-offs. These performances surpass those of conventional hosts such as CBP and mCP. The superior device characteristics originate from efficient Förster/Dexter energy transfer, suppressed triplet exciton annihilation, and inhibited back energy transfer enabled by the high triplet energy. This work provides an effective molecular design strategy toward high-efficiency, low-roll-off, and full-color OLEDs.