Synchronous Optimization of Light Outcoupling and Carrier Recombination for Efficient and Spectral Stable Blue Perovskite Light‐Emitting Diodes.

Despite the significant progress of blue perovskite light‐emitting diodes (PeLEDs) in recent years, huge challenges still remain in improving their efficiency and spectral stability. In this work, a new strategy is reported to realize efficient and spectral stable blue PeLEDs through synchronously optimizing light outcoupling and carrier recombination of perovskite films. By introducing additives in both precursor solution and antisolvent, the crystallization of the perovskite films is regulated, leading to a spontaneous formation of undulant morphology, which favorably enhances the light outcoupling efficiency. Meanwhile, the formation of low‐dimensional perovskite phases is suppressed, in accompany with a reduced defect density and accelerated energy transfer, leading to a rapid concentration of excitons in the target perovskite phases and a significant enhancement of radiative carrier recombination. Resultantly, the optimized blue perovskite films show a high photoluminescent quantum yield approaching 80%, and the corresponding optimized PeLEDs show a high external quantum efficiency (EQE) of 11.88%, which significantly outperforms the control device with only 1.96%. Importantly, the optimized perovskite films and PeLEDs also exhibit improved spectral stability. This work provides a new pathway toward realizing efficient and spectral‐stable PeLEDs via simultaneously tackling the issues of light outcoupling and carrier recombination in the devices. [ABSTRACT FROM AUTHOR]