Improved Uniformity of Electrical Injection Enables Bright and Suppressed Efficiency Roll‐Off Inverted Light‐Emitting Diodes Based on FAPbBr 3

Abstract Perovskite light‐emitting diodes (PeLEDs) have been substantiated as promising candidates for high‐efficiency electroluminescence. However, the maximum external quantum efficiency (EQE) of state‐of‐the‐art PeLED is typically achieved at relatively low current densities and exhibits severe efficiency roll‐off under intense electrical excitation, thereby restricting their development in high‐power applications. Specifically, the uniformity of electrical injection has usually been neglected in optimization strategies, primarily due to inadequate comprehension of the microscale injection. In this study, a modified deposition method, marked static reaction deposition, is developed. The residence of precursor solution on the magnesium‐doped zinc oxide substrate enables the perovskite crystalline growth homogeneously, thereby enabling the construction of a perovskite polycrystalline emission film with an ultra‐low root mean square roughness of 0.72 nm. The resultant enhancement in electrical injection uniformity effectively suppresses localized carrier over‐injection and mitigates EQE roll‐off. The fabricated PeLED demonstrates a maximum luminance of 590,000 cd m −2 at a high current density of 964 mA cm −2 and maintains an EQE exceeding 10% at current densities up to 1000 mA cm −2 . These findings delineate a novel and broadly applicable optimization paradigm for realizing high‐luminance, low roll‐off, and efficient PeLEDs.