Thermally Activated Delayed Fluorescence with Nanosecond Emission Lifetimes and Minor Concentration Quenching: Achieving High‐Performance Nondoped and Doped Blue OLEDs

Abstract

Simultaneously achieving a high photoluminescence quantum yield (PLQY), ultrashort exciton lifetime, and suppressed concentration quenching in thermally activated delayed fluorescence (TADF) materials is desirable yet challenging. Here, a novel acceptor–donor–acceptor type TADF emitter, namely, 2BO‐sQA, wherein two oxygen‐bridged triarylboron (BO) acceptors are arranged with cofacial alignment and positioned nearly orthogonal to the rigid dispirofluorene‐quinolinoacridine (sQA) donor is reported. This molecular design enables the compound to achieve highly efficient (PLQYs up to 99%) and short‐lived (nanosecond‐scale) blue TADF with effectively suppressed concentration quenching in films. Consequently, the doped organic light‐emitting diodes (OLEDs) base on 2BO‐sQA achieve exceptional electroluminescence performance across a broad range of doping concentrations, maintaining maximum external quantum efficiencies (EQEs) at over 30% for doping concentrations ranging from 10 to 70 wt%. Remarkably, the nondoped blue OLED achieves a record‐high maximum EQE of 26.6% with a small efficiency roll‐off of 14.0% at 1000 candelas per square meter. By using 2BO‐sQA as the sensitizer for the multiresonance TADF emitter ν‐DABNA, TADF‐sensitized fluorescence OLEDs achieve high‐efficiency deep‐blue emission. These results demonstrate the feasibility of this molecular design in developing TADF emitters with high efficiency, ultrashort exciton lifetime, and minimal concentration quenching.