Enhancing Luminescence in Hue-Tunable White-Light Emitting K₄CdCl₆:Sb³⁺,Mn²⁺ All-Inorganic Halide Perovskites: Insights from Defect Engineering and Energy Transfer

All-inorganic halide perovskites (AIHPs) have emerged as highly promising optoelectronic materials owing to their remarkable properties, such as high-optical absorption coefficients, photoluminescence efficiencies, and dopant tolerance. Here, we investigate the AIHPs K 4 CdCl 6:Sb 3+,Mn 2+ that demonstrate hue-tunable white-light emission with an exceptional photoluminescence quantum yield of up to 97%. Through a detailed investigation, we reveal that efficient energy transfer from Sb 3+ to Mn 2+ plays a dominant role in the photoluminescence of Mn 2+, instead of the conventional 4 T 1g → 6 A 1g transition of Mn 2+ . Thermodynamic analysis highlights the crucial role of a Cl-rich environment in obtaining the K 4 CdCl 6 phase, while transformation from K 4 CdCl 6 to KCdCl 3 can be achieved under Cl-poor and K-poor conditions. The theoretical analysis reveals that defect Cl i is more readily formed compared to defect V K, corroborating experimental findings that the K 4 CdCl 6:Sb 3+ phase is exclusively obtained when the solution contains HCl concentrations higher than 4 mol L –1 . Our work provides valuable insights into the photoluminescence mechanism of Sb 3+, defect engineering through heterovalent doping, and efficient energy transfer between Sb 3+ and Mn 2+ in K–Cd–Cl-based perovskites, which offers a new perspective for the design and development of novel AIHPs with superior optoelectronic performance.