Stable Sky-Blue Perovskite LEDs Achieved by Efficient Sub-Bandgap Emission With 24.5% PCE

As an emerging light-source technology, blue perovskite light-emitting diodes (PeLEDs) have demonstrated remarkable progress in external quantum efficiency. However, their poor operational stability remains a critical bottleneck hindering further commercialization. Simultaneously achieving high power conversion efficiency (PCE) and brightness in the ultralow-voltage regime represents a promising strategy for realizing long-lived PeLEDs. Here, efficient defect passivation in perovskite emissive layers is demonstrated through the incorporation of a 0D perovskite phase, while simultaneously modulating the semiconductor characteristics from n-type to p-type via strategic bulky cation engineering. The resulting PeLED operates below the bandgap voltage, achieving a high PCE of 24.5%. Notably, the drastically reduced driving voltage suppresses Joule heating and ion migration, extending the operational lifetime to a record T₅₀ of 318.8 min at 1000 cd m⁻². This work provides a strategic roadmap for developing blue PeLEDs that simultaneously achieve high efficiency, high brightness, and long operational lifetime.