High‐Efficiency Red Organic Light‐Emitting Diodes with External Quantum Efficiency Close to 30% Based on a Novel Thermally Activated Delayed Fluorescence Emitter

作者：Yuan‐Lan Zhang, Quan Ran, Qiang Wang, Yuan Liu, Christian Hänisch, Sebastian Reineke, Jian Fan, Liang‐Sheng Liao · 发表于：Advanced Materials · 年份：2019 · DOI：10.1002/adma.201902368 · 被引用次数：323 · 研究领域：Organic Light-Emitting Diodes Research、Organic Electronics and Photovoltaics、Luminescence and Fluorescent Materials

Abstract Researchers have spared no effort to design new thermally activated delayed fluorescence (TADF) emitters for high‐efficiency organic light‐emitting diodes (OLEDs). However, efficient long‐wavelength TADF emitters are rarely reported. Herein, a red TADF emitter, TPA–PZCN, is reported, which possesses a high photoluminescence quantum yield (ΦPL) of 97% and a small singlet–triplet splitting (ΔEST) of 0.13 eV. Based on the superior properties of TPA–PZCN, red, deep‐red, and near‐infrared (NIR) OLEDs are fabricated by utilizing different device structure strategies. The red devices obtain a remarkable maximum external quantum efficiency (EQE) of 27.4% and an electroluminescence (EL) peak at 628 nm with Commission Internationale de L'Eclairage (CIE) coordinates of (0.65, 0.35), which represents the best result with a peak wavelength longer than 600 nm among those of the reported red TADF devices. Furthermore, an exciplex‐forming cohost strategy is adopted. The devices achieve a record EQE of 28.1% and a deep‐red EL peak at 648 nm with the CIE coordinates of (0.66, 0.34). Last, nondoped devices exhibit 5.3% EQE and an NIR EL peak at 680 nm with the CIE coordinates of (0.69, 0.30).