Symmetry Disruption and Charge Localization: Unraveling Roles of Sb3+ in Enhancing Luminescence of Rare Earth Double Perovskites

Co-doping of rare earth (RE) and ns² metal ions with in double perovskites shows great promise for applications in anti-counterfeiting, display, and radiation detection. However, the intrinsic physical nature for the enhanced photoluminescence remains unclear. Herein, we use gadolinium-based double perovskite as the model and propose an effective strategy for co-doping RE3+ with Sb3+ ions (5s²) to modulate the photoluminescence and energy transfer. The incorporation of Sb³⁺ increases the absorption cross section, thereby overcoming the limitation of 4f–4f narrowband absorption transitions. Furthermore, Sb³⁺ acts as a bridge for energy transfer, significantly facilitating this process. Density functional theory calculations reveal that the introduction of Sb³⁺ disrupts the symmetry of the [RECl₆]^3– octahedra, leading to increased distortion. Additionally, the electrons in the [RECl₆]^3– octahedra exhibit stronger localization in the Sb³⁺/RE³⁺ co-doped system, which enhances the Cl^––RE³⁺ charge transfer process, thereby increasing the radiative transition rates and resulting in a high photoluminescence quantum yield. Our research elucidates the physical essence of Sb³⁺ enhanced luminescence in RE-based perovskites from both experimental and theoretical perspectives, providing valuable insights into modulation of luminescent properties and understanding of underlying physical mechanisms in RE³⁺ doped luminescent materials.