LAUSR

In this study, a multiple resonance (MR) type blue emitter is synthesized, characterized, and evaluated for highly efficient and stable blue fluorescent organic light‐emitting diodes (OLEDs). The MR blue fluorescent emitter has a di‐tert‐butyl benzene substituent in the MR core structure to minimize quenching mechanisms by intermolecular interaction. The emitter shows a high photoluminescence quantum yield and small full width at half maximum of 22 nm, which realize high external quantum efficiency (EQE) of 11.4% in the single unit OLED and device lifetime up to 95% of the initial luminance (LT95) of 208 h at 1000 cd m−2 and over 10 000 h at 100 cd m−2. The optimized tandem device of the new blue emitter achieves high EQE over 25% and extremely long LT95 of over 500 h at 1000 cd m−2 and 30 000 h at 100 cd m−2. The lifetime of this work is one of the best data of blue OLED lifetime reported in the literature.