Dimensionality-driven photoluminescence enhancement in Cl/Br mixed-halide organic–inorganic hybrid cadmium halides

In this study, we report the successful synthesis of four organic-inorganic hybrid materials by systematically varying the Cl/Br halide ratio in a system comprising 4-(2-ammonioethyl)pyridinium organic cations and cadmium halides. An increase in Cl content induces a structural transition from zero-dimensional to two-dimensional (2D) frameworks, with the 2D phase featuring a unique corrugated layered architecture composed of corner-, edge-, and face-sharing Cd-halide octahedra. All compounds exhibit broadband blue photoluminescence, and a clear correlation is observed between halide mixing, increased structural distortion, and enhanced photoluminescence quantum yield (PLQY). Notably, the PLQY increases significantly from 6% to 36% in the 2D mixed halide compound. These findings underscore the effectiveness of halide composition modulation in tuning both structural dimensionality and optical performance, providing valuable insights for the rational design of high-efficiency luminescence materials.