Highly-Efficient Doped and Nondoped Organic Light-Emitting Diodes with External Quantum Efficiencies over 20% from a Multifunctional Green Thermally Activated Delayed Fluorescence Emitter

Thermally activated delayed fluorescence (TADF) emitters integrated with aggregation-induced emission (ME) property are expected to enable nondoped organic light-emitting diodes (OLEDs) with merits of high efficiency and simple fabrication process. We previously proposed a novel design strategy of combining ME and TADF features to develop AIE-TADF emitters with asymmetric structure, leading to an AIE-TADF emitter 4,4-CzSPz exhibiting mechanoluminescence. Herein, photophysical, thermal, and electro-luminescence properties of neat 4,4-CzSPz films have been systematically investigated. It was found that 4,4-CzSPz film exhibits a high photoluminescence quantum efficiency of 97.3% and excellent thermal properties. Significantly, 4,4-CzSPz afforded its doped and nondoped OLEDs with very high external quantum efficiencies of 26.2% and 20.7%, respectively, which are rarely reported among TADF-based OLEDs. The results demonstrate universal applications of 4,4-CzSPz in OLEDs with different device configurations for achieving high efficiency.