Narrowband helical emitter with frontier orbital confinement for stable deep-blue hybrid-tandem organic light-emitting diodes.

Achieving efficient, stable deep-blue organic light-emitting diodes (OLEDs) with high colour purity remains challenging due to the scarcity of emitters combining narrowband emission and high stability. Here we present a multiple-resonance emitter featuring a highly twisted helical configuration with spatially confined frontier molecular orbitals. This emitter decouples radiative transitions from structural distortion while mitigating spectral broadening from carbon-hydrogen bond repulsion and aggregation, exhibiting sharp emission at 460 nm with a full-width at half-maximum of only 12 nm in solution and nearly identical spectra across varying-polarity systems. A unicolour-hybrid-tandem OLED design integrating complementary exciton-harvesting mechanisms to overcome the efficiency-lifetime trade-off is proposed, achieving an external quantum efficiency of 39.7% and a lifetime of 539 h to 90% of 1,000 cd m⁻2 at a chromaticity y coordinate of 0.10. A stacking sequence of emitting units induces a twofold lifetime variation arising from outcoupling efficiency and photoelectric co-ageing differences. This co-engineering strategy advances commercially viable ultrapure-blue OLED displays.