Investigation of potassium doping and defect healing mechanism in core-shell CsPbBr₃/SiO₂ quantum dots

In this work, we firstly succeed in revealing the exact K⁺ doping and defect healing mechanism in core-shell CsPbBr₃/SiO₂ QDs. The K⁺ doping mechanism depended on the K⁺ doping concentration. The K ions were doped into interstitial sites at low K⁺ doping concentrations (1 and 2%); however, the K ions were substituted into Cs⁺ sites at high K⁺ doping concentration (3%). K ions were doped into core-shell CsPbBr₃/SiO₂ QDs, which induced the lattice strains in the crystal structure, leading to structural distortions. These lattice strains were simultaneously relaxed by external stimuli and underwent crystal reconstruction, resulting in the diffusion of K ions within the lattice. This sequence of processes converted the disordered structures into ordered structures. The multi-passivation process of introducing K⁺ into the core-shell CsPbBr₃/SiO₂ QDs not only enhanced the photoluminescence quantum yields (PLQYs) but also improved the environmental stabilities by reducing the trap density and preventing the penetration of polar molecules by the SiO₂ shell.