Efficient Self-Trapped Exciton Emission in Ruddlesden–Popper Sb-Doped Cs3Cd2Cl7 Perovskites

Metal halide perovskites (MHPs) have attracted extensive attention due to their excellent optoelectronic properties. Among them, layered two-dimensional (2D) metal halide materials with special structures have attracted extensive attention due to their superior stability and optoelectronic properties. Here, we report the 2D Ruddlesden–Popper (RP) phase Cs3Cd2Cl7 synthesized by a solvothermal method, and the photoluminescence quantum yields (PLQYs) of the pristine Cs3Cd2Cl7 sample (PLQY ∼ 10%) can be increased to 68 ± 5% through appropriate Sb3+ doping. This should be the highest PLQY of all reported all-inorganic RP-phase Cd-based perovskites so far. Our results indicate that the highly efficient cyan emission can be attributed to the common self-trapped exciton (STE) emission of the triplet states of Cd2+ and Sb3+ induced by strong electron–phonon coupling, and Sb3+:Cs3Cd2Cl7 has excellent structural and spectral stability. This new material should be a promising candidate for optoelectronic applications in the future.