Oxygen-bridged triarylboron substituted anthracene emitters with high-lying triplet–singlet intersystem crossing for efficient deep-blue OLEDs

Abstract

Hot exciton emitters have been confirmed as promising materials for the construction of blue organic light-emitting diodes (OLEDs). Here, two new deep-blue hot exciton emitters, D–A type BOOAn and A–D–A type 2BOOAn, are designed and synthesized by using the rigid oxygen-bridged triarylboron structure as the acceptor (A) and anthracene as the donor (D). The 2BOOAn-based doped devices achieved efficient deep-blue emission with a maximum external quantum efficiency (EQE_max) of 10.1%, an electroluminescence (EL) emission peak at 440 nm, CIE coordinates of (0.151, 0.073), and a calculated exciton utilisation efficiency (EUE) of 46–68%. Finally, the presence of reverse intersystem crossing from high-lying triplet T₂ to S₁ (hRISC) was experimentally verified. In addition, the transient EL (Tr-EL) analysis and the magneto-electroluminescence (MEL) measurement showed that the TTA mechanism hardly contributes to the EL process, so the high EUE of the device can be mainly attributed to the hot exciton mechanism.