Efficient and Stable Perovskite LED Prepared by the Regulation of Vertical Spatial Crystallization Dynamics

Abstract Quasi‐2D perovskite‐based light‐emitting diodes (Q‐2D PeLEDs) have recently gained attention as promising technology for future lighting and displays, due to their remarkable advancements in device efficiency. In order to make Q‐2D PeLEDs technology practical in display and lighting applications, it is essential to ensure a long lifespan, particularly at large area and high brightness levels. In this work, the top‐down crystallization mechanism of the Q‐2D perovskite films is explored through introducing alkali metal Na + to precisely control the phase distribution in the vertical space. Furthermore, the robust interactions between Na + and PbBr 6 4− octahedra increases the lifetime of the device by orders of magnitude via passivating the halogen vacancies on the perovskite surface as well as replacing insulating ligands, reducing Joule heat. Eventually, the operating half‐lifetime ( T 50 ) of small area device (0.04 cm 2 ) exceeds 612 h and even when the effective area is expanded ≈56 times (2.25 cm 2 ), the T 50 remains impressively high at 115 h. Additionally, these devices exhibit excellent external quantum efficiency (EQE) reaches 26.5% and 19.2%, respectively.