High‐Efficiency Luminescence and Robust Thermal Quenching Resistance in Organic–Inorganic Hybrid Indium‐Based Metal Halides

Low-dimensional lead-free metal halide perovskites have attracted considerable attention for the development of multifunctional optoelectronic materials owing to their extensive structural diversity and adjustable optical properties. However, organic cation-based low-dimensional metal halides often exhibit limited thermal stability, while inorganic cations-based ones have a poor solution processability. To address these challenges, this study proposes a hybrid organic–inorganic cation approach by utilizing both 4,4-difluoropiperidine (DFPD) and cesium (Cs+) to prepare low-dimensional metal halides: (DFPD)2CsInCl6. Two isostructural metal halides are developed: α-(DFPD)2CsInCl6 and β-(DFPD)2CsInCl6, which exhibit different space group symmetries. This strategy ensures both thermal stability and introduces structural diversity. Doping (DFPD)2CsInCl6 with antimony (Sb3+) enhances its PLQY from 0% to 100%. The emission centers of both materials exhibit temperature-insensitive behavior and maintain efficient and stable PL emission even at high temperatures (up to 400 K), making them excellent candidates as thermally stable phosphor materials for solid-state lighting applications. This work thus expands the scope of developing multifunctional low-dimensional metal halides.