Regulating the Order–Disorder Phase Controlling in K 2 RbInCl 6 Single Crystal Toward the Highly Efficient Luminescence

ABSTRACT Indium halide inorganic perovskite has attracted widespread attention due to its high photoluminescence efficiency and wide‐spectrum luminescence. The ordered arrangement characteristics of A‐site bimetallic ions, K + and Rb + , have a significant impact on 0D K 2 RbInCl 6 perovskite luminescence properties but have not been explored. Here, we report a crystallization‐kinetics‐modulated ordered structure of 0D K 2 RbInCl 6 perovskite. By regulating the crystallization rate and temperature, a series of single crystals with adjustable ordered arrangements were obtained, enabling high photoluminescence performance. The single‐crystal structure shows that the ordered arrangements of the A‐site cation are layered along the (100) direction. The ordered single crystal exhibits a significantly higher PLQY (∼100%) than the disordered counterpart. The electronic structure calculations were performed to elucidate the luminescence mechanism. These results demonstrate that the A‐site ordered property provides an effective structural handle for tuning excited‐state behavior in 0D halide perovskites and offers new guidance for the design of efficient luminescent halide materials.