Realizing Highly Efficient Electro-Fluorescence with Co-axial Hybrid Local and Charge-transfer (HLCT) Excited State

Abstract

In this work, we report two high-performance donor-acceptor (D-A) electro-fluorescent materials DPXZ-PI and DPXZ-PICN with novel co-axial hybrid local and charge-transfer (HLCT) excited state design method. Featuring the direct bonding of strong electron donor diphenoxazine (DPXZ) and weak electron acceptor phenanthroimidazole (PI), the co-axial HLCT state is initially constructed in DPXZ-PI with high photoluminescence quantum yield (PLQY) of 81.74% and a high maximum external quantum efficiency (EQE) of 14.83% in doped organic light-emitting diode (OLED), which is among the best results of the HLCT emitter-based OLEDs. Notably, the co-axial HLCT state is robust upon the introduction of strong electron acceptor cyano-benzene, which allows the increasing of electron mobility in OLED and high EQE of 11.60% in non-doped OLED of DPXZ-PICN. Overall, the co-axial HLCT realizes the increasing of PLQY with maintained exciton utilizing efficiency (EUE) in OLED, which is an effective method for highly-efficient electro-fluorescent materials and devices.Key words: OLED; HLCT; spin-statistics; excited state; EQE.