Unraveling the Photoluminescent Properties of Sb-Doped Cd-Based Inorganic Halides: A First-Principles Study.

Sb-doped Cd-based inorganic halides, with varying connections of CdCl octahedra ranging from 0D to 3D, exhibit a variety of photoluminescent properties. Single-band emission is observed in Sb-doped RbCdCl (0D) and CsCdCl (2D), while dual-band emission is seen in Sb-doped RbCdCl (1D) and CsCdCl (3D). Density-functional-based first-principles calculations were conducted. The results reveal that cation vacancies, acting as charge compensators, influence the luminescence properties of dopant centers. In CsCdCl, the local cation vacancy for Sb at the Cd site ([Sb□Cl]) significantly modifies the photoluminescence property, accounting for the observed dual-band emission alongside the nonlocal compensation case. This effect is insignificant in Sb-doped RbCdCl, RbCdCl, and CsCdCl, due to the large distances or high formation energies of Cd vacancies in these hosts. However, in Sb-doped RbCdCl, two different potential energy minima, one that involves typical structure relaxation and the other that is off-center, lead to the observed dual-band emission. Furthermore, the shift of the charge transition level illustrates the different temperature dependences of the dual-band emission caused by the charge-compensating point defects. These insights not only enhance our understanding of luminescent materials based on halides containing s dopants but also provide valuable guidance for the design and optimization of luminescent materials.