Exploring the Critical Factors Toward Spectrally Stable Mixed‐Halide Blue Perovskite LEDs

Abstract Metal mixed‐halide perovskite has demonstrated considerable potential in the development of solution‐treated blue light‐emitting diodes (LEDs) with high external quantum efficiency, excellent color purity, and tunable wavelength. However, the severe phase segregation of mixed‐halide perovskite under bias voltage would lead to the spectral instability of LEDs. Therefore, suppressing phase segregation of Br/Cl perovskite towards spectrally stable blue perovskite LEDs (PeLEDs) is a big challenge. In this work, we systematically explore the influence of perovskite component, preparation conditions, and device structures on the spectral stability of PeLEDs. We have observed that the stable spectra increased the proportion of Cs in the A‐site cations, passivator, and the annealing temperature of perovskite films. Finally, we achieve a spectra‐stable and high‐performance blue PeLED under optimized conditions. Our findings provide important guidance for preparing spectrally stable PeLEDs.