Constructing High‐Efficiency and Stable Hyperfluorescence Blue OLEDs via TADF Sensitizers with Very Short Delayed Lifetimes

Hyperfluorescence blue organic light-emitting diodes (OLEDs) are promising for fabricating pure organic blue devices with high efficiency and color purity by employing thermally activated delayed fluorescence (TADF) sensitizers and multiple-resonance TADF (MR-TADF) emitters. However, developing blue TADF sensitizers with the rate of reverse intersystem crossing (k_RISC) over 10⁷ s^-1 remains a challenge. In this work, a blue TADF sensitizer with k_RISC of 9.71 × 10⁶ s^-1 has been designed by regulating the energy levels of the excited states and enhancing the spin-orbit coupling (SOC) effect. v-DABNA is further doped to fabricate the hyperfluorescence device, which exhibits a high maximum external quantum efficiency of 31.0% and a long operational lifetime of 175.4 h. The results reveal the significance of k_RISC and pave the way for designing blue TADF sensitizers and hyperfluorescence devices.