Blue Thermally Activated Delayed Fluorescence-Emitting Phosphine Oxide Hosts for Ultrasimple and Highly Efficient White Organic Light-Emitting Diodes

摘要

Among a series of carbazole–diphenylphosphine oxide hybrids x2ArPO,rnblue thermally activated delayed fluorescence (TADF)-emitting host m2tBCzPOrnwith optimal electron-withdrawing and steric effects is successfullyrnconstructed to demonstrate the superiority of blue TADF-emitting host inrnadaptable exciton allocation for white light-emitting diodes (WOLEDs), whichrnrealizes the negligible singlet–triplet splitting (ΔEST) of 0.02 eV, the photoluminescencernquantum yield beyond 75% and the top-rank external quantumrnefficiency (EQE) with the maxima of 13.8% and 22.2% from its blue andrnyellow devices. Its high-efficiency blue TADF emission and excellent hostrncharacteristics are perfectly harmonized in its ultrasimple four-layer WOLEDrnwith monodoping single-emissive layer to support the state-of-the-art performance,rnincluding EQE up to 21.3%, roll-off within 10% at 1000 cd m−2, andrnexcellent spectral stability.