Harmonization of rapid triplet up-conversion and singlet radiation enables efficient and stable white OLEDs

White organic light-emitting diodes (WOLEDs) hold significant promise in illumination and displays, but achieving high efficiency while maintaining stability is an ongoing challenge. Here, we strategically combine a blue donor-acceptor thermally activated delayed fluorescence (TADF) emitter featuring rapid reverse intersystem crossing rate and a yellow multi-resonance TADF emitter renowned for the fast radiative transition process to achieve warm WOLEDs with exceptional power efficiency exceeding 190 lm W^-1 and external quantum efficiency (EQE) of 39%, setting records for WOLEDs. Meanwhile, these devices also exhibit an extended operational lifetime (LT₈₀) of 446 h at an initial luminance of 1000 cd m^-2. Another group of blue and yellow emitters based on our strategy achieves a standard white emission and a high EQE of 35.6%, confirming the universality of our strategy. This work presents a versatile strategy to harmonize singlet exciton radiation and triplet exciton up-conversion, thus achieving a win-win situation of efficiency and stability.