Multiplying Phosphine‐Oxide Orientation to Enable Ultralow‐Voltage‐Driving Simple White Thermally Activated Delayed Fluorescence Diodes with Power Efficiency over 100 lm W⁻¹

Abstract

Abstract Thermally activated delayed fluorescence (TADF) white organic light‐emitting diodes (WOLED) hold great potential for daily lightings, but should overcome the current limitation in power conservation. Despite amount of efforts on developing efficient TADF emitters, it is demonstrated here that the host matrix actually controls exciton formation and allocation, therefore strongly determines power efficiency. Through multiplying P≐O orientations, 248DBTTPO matrix establishes “diffusion predominance” mode to support multidirectional carrier/exciton migration, which combines the advantages of “recombination predominance” and “transport predominance” modes in alleviating dopant–dopant interactions and rationalizing carrier and energy transfer. 248DBTTPO matrix effectively balances carrier flux, singlet radiation, and triplet quenching suppression of TADF emitters, and exciton allocation in its complementary white TADF systems. As consequence, 248DBTTPO endows its trilayer single‐emissive‐layer WOLEDs with the state‐of‐the‐art external quantum efficiency up to 27%, ultralow driving voltages, and consequently the record‐high power efficiency of 108.6 lm W −1 , which breaks through key bottleneck of TADF lighting.