Doping Induces Structural Phase Transitions in All-Inorganic Lead Halide Perovskite Nanocrystals

Doping engineering has emerged as one of the most powerful approaches to impart new optical and electronic properties to halide perovskite nanocrystals (NCs). However, the impact of dopants on the structure of perovskite NCs remains poorly understood. Here, we report on the finding of doping-induced structural phase transitions occurring in all-inorganic perovskite NCs. Using Ni2+-doped CsPbCl3 NCs as a model system, we show that Ni2+ doping causes the coexistence of dual subdomains of cubic and orthorhombic phases and inhibits the phase transition from cubic to orthorhombic in NCs with negligible atomic vacancies as the temperature decreases. Car-Parrinello molecular dynamics simulations reveal that the doping-induced structural phase transition results from the dopant-enabled release of lattice strain and a temperature-insensitive local structural change in the doped region of NCs. Since size mismatch between dopants and replaced ions widely exists in doped functional materials, our finding may not be limited to halide perovskite NCs, but could have implications even for other classes of doped NCs and bulk materials.