Abstract
Energy-efficient lighting sources are desired to provide another solution of carbon emission reduction. White organic light-emitting diodes are promising, because of theoretical internal quantum efficiencies for 100% electric-to-light conversion. However, pure organic fluorescent materials still face a challenge in harvesting triplet excitons for radiation. Herein, we report a white fluorescent organic light-emitting diode having an external quantum efficiency of 30.7% and a power efficiency of 120.2 lm W(-1). In the single emissive layers, we use blue thermally activated delayed fluorescent emitters to sensitize a yellow fluorescent emitter. Transient photoluminescence and electroluminescence analyses suggest that a blue thermally activated delayed fluorescent molecule with ~100% reverse intersystem crossing efficiency and negligible triplet nonradiative rate constant completely converts triplet to singlet, suppressing triplet quenching by a yellow fluorescent emitter and ensuring 100% power conversion.