Gradient Luminescence\nEnhancement in Organic Metal\nHalide Perovskites via the Suppression of [SbCl<sub><i>n</i></sub>]<sup>3–<i>n</i></sup> Unit Distortion

Intrinsic stereochemical activity of the 5s<sup>2</sup> electron\nconfiguration in Sb<sup>3+</sup> leads to structural distortion within\n[SbCl<sub><i>n</i></sub>]<sup>3–<i>n</i></sup> units, which, while stabilizing the material, paradoxically\ndiminishes luminescence intensity due to induced asymmetry. To address\nthis issue, a strategy, which encompasses increasing the structural\ndimensions and introducing In<sup>3+</sup> doping, was developed to\nmitigate the geometrical distortion in the [SbCl<sub><i>n</i></sub>]<sup>3–<i>n</i></sup> units within the metal–organic\nperovskite (DABCO)<sub>2</sub>Sb<sub>2</sub>Cl<sub>10</sub>·H<sub>2</sub>O and (DABCO)<sub>2</sub>SbCdCl<sub>9</sub>·2H<sub>2</sub>O (DABCO = triethylenediamine). This dimensional augmentation confines\nlattice distortion effectively, and the In<sup>3+</sup> doping modifies\nthe 5s<sup>2</sup> electron configuration of Sb<sup>3+</sup>, thereby\nreducing the distortion at its origin. The unique suitability of indium-based\nhalides as a matrix for Sb<sup>3+</sup> doping is underscored by our\napproach, which capitalizes on their ability to regulate the electron\nconfiguration of Sb<sup>3+</sup>. This strategy has been validated\nthrough crystallographic data from single-crystal X-ray diffraction.\nBy effectively reducing the adverse effects of geometric distortion,\nseveral hundred-fold enhancements in the luminescent intensity of\nthe material have been achieved by our methodology, leading to potential\napplications in white-light LEDs. This advancement not only highlights\nthe pivotal role of structural symmetry in the optical properties\nof materials but also exemplifies the power of material engineering\nto optimize the optical performance.