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 6 octahedra ranging from 0D to 3D, exhibit a variety of photoluminescent properties. Single-band emission is observed in Sb-doped Rb 4 CdCl 6 (0D) and Cs 2 CdCl 4 (2D), while dual-band emission is seen in Sb-doped RbCdCl 3 (1D) and CsCdCl 3 (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 3 , the local cation vacancy V Cd ″ for Sb 3+ at the Cd 2+ site ([Sb□Cl 9 ] 6- ) significantly modifies the photoluminescence property, accounting for the observed dual-band emission alongside the nonlocal compensation case. This effect is insignificant in Sb-doped Rb 4 CdCl 6 , RbCdCl 3 , and Cs 2 CdCl 4 , due to the large distances or high formation energies of Cd vacancies in these hosts. However, in Sb-doped RbCdCl 3 , 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 n s 2 dopants but also provide valuable guidance for the design and optimization of luminescent materials.