Facile one‐step synthesis of efficient hybridized local and charge transfer emitter for ultraviolet electroluminescence with low roll‐off

Abstract

Abstract Ultraviolet organic light‐emitting diodes (UV‐OLEDs) have attracted increasing attention in the applications of phototherapy, high‐density information storage, sterilization, photocuring and so on, yet the development of efficient short‐wavelength emitters remains challenging due to the irreconcilable contradiction between fluorescence efficiency and short molecular conjugation length. Here, we design and synthesize a simple yet efficient donor–acceptor–donor (D–A–D) type UV emitter D3CZ4F featuring a hybridized local and charge transfer state, via a facile one‐step coupling reaction. The multiple intramolecular non‐covalent C–H⋯F locking interactions enhance molecular rigidity as well as promote the planarization of the excited state geometry, leading to a large oscillator strength of 1.3989 and a high solid‐state photoluminescence quantum yield of 86%. Consequently, the doped device with D3CZ4F as an emitter not only emits high color‐purity UV emission at 388 nm with color coordinates of (0.165, 0.025), but also furnishes a maximum external quantum efficiency (EQE) of up to 8.97% and a small roll‐off with the EQE of 8.15% at 500 cd m−2. Moreover, the non‐doped device achieved a surprised EQE of 7.33% with an emission peak at 390 nm and color coordinates of (0.164, 0.027), respectively.