Fabricating CsPbX₃-Based Type I and Type II Heterostructures by Tuning the Halide Composition of Janus CsPbX₃/ZrO₂...

Fabricating CsPbX₃-based heterostructures has proven to be a feasible way to tune their photophysical properties. Here, we report the successful fabrication of Janus CsPbX₃/ZrO₂ heterostructure nanocrystals (NCs), in which each CsPbX₃ NC is partially covered by ZrO₂. According to the band alignment, CsPbBr₃/ZrO₂ and CsPbI₃/ZrO₂ can be indexed as type I and type II composites, respectively. The type I composites display great enhancement in photoluminescence quantum yield (from 63 to 90%) and photoluminescence lifetime (from 12.9 to 66.1 ns) because of the charge carrier confinement and passivation effect provided by ZrO₂. In contrast, the type II composites can be used in photocatalytic reduction of CO₂ because electrons and holes are effectively separated and accumulated in ZrO₂ and CsPbI₃, respectively, under irradiation. Janus CsPbBr₃/ZrO₂ NCs showed a stability much higher than that of pristine CsPbBr₃ against polar solvent treatment. A stable and highly efficient light-emitting device with luminous efficiency up to 55 lm W^-1 is fabricated by using CsPbBr₃/ZrO₂ NCs as the green light source. This work may not only enrich the family of surface-passivated perovskite materials but also provide a good example for the rational design of specific composites in the metal halide perovskite field.