Boosting Luminescence in Cs3Sb2Cl9-Derived Cs4MnSb2Cl12 through Cd2+ Dopant Incorporation

Low-dimensional halide perovskites, as distinguished members of the perovskite family, have garnered significant attention due to their exceptional optical properties. However, strategies for dimensional phase-structure transition using low-dimensional precursors remain underexplored. Herein, a room-temperature two-step supersaturation recrystallization (SR) method was developed. The precursor perovskite Cs 3 Sb 2 Cl 9 was first synthesized, followed by the modulation of its luminescence properties. Subsequently, it was found that the addition of 1 mol CsCl and 1 mol MnCl 2 ·4H 2 O successfully yielded the two-dimensional (2D) metal halide perovskite Cs 4 MnSb 2 Cl 12 . Specifically, Mn 2+ ions were incorporated as luminescent centers, where equimolar CsCl and MnCl 2 ·4H 2 O (1 mmol each) induced a 2D phase-structure transition, enabling effective emission control. To address the weak orange-red emission of Cs 4 MnSb 2 Cl 12 , Cd 2+ was strategically doped to form Cs 4 Cd x Mn 1- x Sb 2 Cl 12 series. With increasing Cd 2+ content, non-monotonic luminescence enhancement was observed, reaching maximum intensity at x = 0.8. This is attributed to the Cd 2+ doping, which weakens the Mn–Mn coupling and breaks the symmetry of the [MnCl 6 ] 4− octahedra, thereby converting the parity-forbidden d–d transition of Mn 2+ into a partially spin-allowed transition and enhancing the Mn 2+ emission. Simultaneously, the improved crystallinity reduces the defect density, thus diminishing non-radiative decay via defect sites and ultimately leading to enhanced luminescence efficiency. This work enriches synthesis strategies for 2D metal halide layered perovskites and provides a novel approach for luminescence control of Sb-based systems.