Hydrazide Molecular Configuration Induced Phase Regulation and Defect Passivation Enable Efficient Quasi‐2D Blue Perovskite Light‐Emitting Diodes

Abstract Perovskite light‐emitting diodes (PeLEDs) have demonstrated significant potential in the display sector, attributed to their wide color gamut, narrow emission spectra, and cost‐effectiveness. Despite the rapid advancements in red and green PeLEDs, the attainment of high brightness and high external quantum efficiency (EQE) for blue PeLEDs remains a considerable challenge, which substantially limits their practical applications in white lighting and optical communication. In this study, a method for the passivation of blue quasi‐2D perovskites using hydrazide derivatives with varying alkyl chain lengths is presented. Density functional theory analysis indicates that hydrazide derivatives can effectively adsorb onto halogen vacancies, thereby reducing charge trapping states associated with undercoordinated Pb 2+ . Experimental results demonstrate that the optimal hydrazide derivative can better eliminate non‐radiative recombination loss, suppress ions migration, and regulate phase distribution, facilitating smoother energy transfer. Through this approach, stable sky‐blue PeLEDs are achieved with an EQE of 14.5% and a maximum luminance of 2659 cd m −2 . This work offers a systematic understanding of hydrazide additive design, which will further enhance the performance and stability of blue quasi‐2D PeLEDs.