Room‐Temperature One‐Step Fabrication of Single‐Halogen RGB Perovskite Films Based on In Situ Spatially Confined Microreactor

ABSTRACT Metal halide perovskite exhibits high quantum efficiency and tunable bandgaps, rendering them highly promising for application in high‐definition displays. Through mixing halogens or quantum confinement, perovskite can achieve standard red, green, and blue (RGB) emission. However, the halogen segregation and crystal defects induced by the environment often deteriorate the spectral stability and color purity. Here, a spatially confined microreactor was constructed based on the synergistic confinement effect arising from perovskite‐oriented growth by Ni(CH 3 COO) 2 and the blocking crystallization by PEA + , resulting in a dominated formation of n = 2 phase in the single halogen system. In these perovskite composite films, the maximum brightness can exceed 200 000 cd/m 2 , and the LT 50 under 1000 cd/m 2 is above 1000 h. The CIE coordinates of RGB films are (0.696, 0.303), (0.134, 0.773), (0.147, 0.041), respectively, which represents 91.3% of the Rec. 2020 standard. Under intense illumination and thermal of LED beads (3.7 V), the CIE coordinates error of the film is only (± 0.01, ± 0.01) compared to the initial (3.0 V), which is much smaller than that of the mixed‐halide perovskite (± 0.1, ± 0.2). The results confirm that the pure Br or I single‐n‐phase distributed perovskite film is an ideal material for future wide‐color‐gamut displays.