High‐Performance Ultraviolet Organic Light‐Emitting Diode Enabled by High‐Lying Reverse Intersystem Crossing

Abstract Ultraviolet (UV) organic emitters that can open up applications for future organic light‐emitting diodes (OLEDs) are of great value but rarely developed. Here, we report a high‐quality UV emitter with hybridized local and charge‐transfer (HLCT) excited state and its application in UV OLEDs. The UV emitter, 2BuCz‐CNCz, shows the features of low‐lying locally excited (LE) emissive state and high‐lying reverse intersystem crossing (hRISC) process, which helps to balance the color purity and exciton utilization of UV OLED. Consequently, the OLED based on 2BuCz‐CNCz exhibits not only a desired narrowband UV electroluminescent (EL) at 396 nm with satisfactory color purity (CIE x , y =0.161, 0.031), but also a record‐high maximum external quantum efficiency (EQE) of 10.79 % with small efficiency roll‐off. The state‐of‐the‐art device performance can inspire the design of UV emitters, and pave a way for the further development of high‐performance UV OLEDs.