Enhanced Photoluminescence and Imaging Applications of Sb-Doped Cs₂CdCl₄ and Cs₃Cd₂Cl₇ Driven by Structure–Property Relationships

Ruddlesden-Popper phases Cs2CdCl4 and Cs3Cd2Cl7 are widely used in experimental research of optoelectronics due to their excellent doping matrix properties, but their optoelectronic mechanisms have not been fully explored. This study uses first-principles calculations and experiments to analyze the differences in point defect crystal growth and optoelectronic properties caused by Sb doping of these two materials. Sb tends to replace the position of Cd in both structures. Additional doping energy levels are introduced in the Sb doping of Cs2CdCl4, and the flat band edge increases the local charge density and improves the electron-hole recombination efficiency. The photoluminescence quantum yield (PLQY) of 0.1% Sb:Cs2CdCl4 doping is as high as 79.09%. Molecular dynamics simulations show that the octahedral distortion of [SbCl6]3- in Cs2CdCl4 is highly sensitive to temperature, and the Jahn-Teller distortion causes the formation of self-trapped excitons, which is more conducive to the generation of exciton recombination luminescence. In contrast, Sb doping of Cs3Cd2Cl7 produces a lower PLQY, which can be explained by the more delocalized charge distribution at its band edges and the lower octahedral structural distortion. Sb:Cs2CdCl4 exhibits high-performance X-ray imaging capabilities. This work provides valuable insights and guidance for optimizing Sb-doped Cd-based optoelectronic materials.