Revealing the Emission Mechanism in Sb3+-Doped All-Inorganic Cadmium Chloride Perovskite

Sb3+ doping endows many metal halide perovskites with diverse and efficient self-trapped exciton (STE) emissions. However, whether the source of STEs is the Sb3+ doping center or the pristine host remains unclear. In this study, we investigated the aliovalent Sb3+-doped RbCdCl3. Spectroscopic analyses before and after annealing showed that the Sb3+ dopant exists as [SbCl5·H2O]2–, which has vastly different optical behavior compared with [SbCl6]3– in other Rb-rich systems. The desorption of the coordinated water molecule results in a significant blue shift of the photoluminescence spectrum from 590 to 515 nm, verifying that environmental polarity has a large effect on STE behavior. Additionally, significant changes were observed in the absorption and photoluminescence excitation spectra of the Sb3+ color centers, while no obvious changes in the host structure were observed. The precise control of the Sb3+ coordination environment provided direct evidence that the STE emission originates from the Sb3+ center. These results clarify the underlying source of STEs in vacancy-related aliovalent ion-doped systems and may guide the design of emerging metal halide perovskite luminescent materials.