Tailor‐Made Multi‐Resonance Terminal Emitters toward Narrowband, High‐Efficiency, and Stable Hyperfluorescence Organic Light‐Emitting Diodes

Abstract Multi‐resonance emitters (MREs) are a promising candidate for fulfilling the harsh requirements of display applications due to their unique photophysical properties. Recently, MREs have been widely used as a terminal emitter in hyperfluorescence organic light‐emitting diodes (HF‐OLEDs); however, since MREs are always thermally activated delayed fluorescence (TADF)‐active, possessing long triplet lifetimes in millisecond order, they result in severe chemical degradation. Instead of shortening the delayed lifetime of MREs by molecular design, herein, a low‐triplet pyrene unit is introduced into an MRE scaffold to achieve narrowband emission and quick removal of triplets in MREs simultaneously. Blue HF‐OLED based on the non‐TADF MRE demonstrates a high external quantum efficiency of 20% and a tenfold improvement in stability, compared to those of the HF‐OLEDs with standard MREs. An opposite direction of molecular design of MREs for the sophisticated exciton generation and transfer system in HF‐OLEDs is proposed to enhance device lifetime without sacrificing color purity and efficiency.