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

Abstract 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 10 7 s −1 remains a challenge. In this work, a blue TADF sensitizer with k RISC of 9.71 × 10 6 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.