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Environmental friendly metal hybrid halides show great promise for white light emitting diode (WLED) applications due to their unique optical properties. Herein, a lead-free blue-light excited red-emitting Mn2+-based hybrid halide...

Lead halide perovskites have demonstrated promising emission tunability achieved by composition engineering, which makes them viable in several potential applications. Determining how to effectively control the crystalline structural transformation and composition in lead‐free halide perovskites is of great importance. Herein, a controllable synthetic method is reported to obtain the 0D metal halide perovskite derivatives (Cs1−xRbx)2InCl5∙H2O and (Cs1−xRbx)3InCl6, through synergistic regulation of the Cs/Rb feed ratios and the reaction solvent. When hydrochloric acid (HCl) is used as the reaction solvent, (Cs1−xRbx)2InCl5∙H2O is obtained at a high Cs/Rb feed ratio greater than 2:1, while (Cs1−xRbx)3InCl6 is obtained at a low Cs/Rb feed ratio of less than 2:5. However, when anhydrous methanol (MeOH) is used as the reaction solvent, only the (Cs1−xRbx)3InCl6 structure is obtained at all Cs/Rb feed ratios. In addition, a reversible crystalline structural transformation is demonstrated between (Cs0.67Rb0.33)2InCl5∙H2O and (Cs0.67Rb0.33)3InCl6 by immersing the as‐prepared products into MeOH and HCl sequentially, which generates a novel green/yellow reversible emission switch. The Sb3+ ion self‐trapped exciton emission and stability of the synthesized (Cs1−xRbx)2InCl5∙H2O and (Cs1−xRbx)3InCl6 are systematically investigated. The results are helpful for promoting the diverse photonics and optoelectronics applications of these environmentally stable perovskite derivatives.