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High‐Power‐Efficiency White Thermally Activated Delayed Fluorescence Diodes Based on Selectively Optimized Intermolecular Interactions

Besides low cost and environmental sustainability, high power efficiency is an essential condition for daily lighting applications, and one of main challenges for thermally activated delayed fluorescence (TADF) white organic light‐emitting diodes (WOLED). Here, it is demonstrated that power efficiency can be improved through accurately modulating intermolecular interactions. An asymmetrical phosphine oxide (PO) molecule named 246DBFTPO is constructed, in which the steric hindrance and inductive effect of PO groups restrain π–π stacking but form continuous intermolecular hydrogen bond networks. The steric anisotropy of PO groups leads to the heterogeneous molecular distribution in 246DBFTPO matrix, accompanied by the homogeneous intermolecular interactions. Compared to symmetrical and semi‐symmetrical PO congeners, 246DBFTPO provides balanced carrier transport, efficient host–dopant and dopant–dopant energy transfer, and effective quenching suppression. Based on its electron mobility of 10−5 cm2 V−1 s−1 and a 90% photoluminescence quantum yield of its dually doped white TADF film, 246DBFTPO is simultaneously competent as host and electron transporting material in a trilayer single‐EML full‐TADF WOLED, leading to a record power efficiency of 76.7 lm W−1.