Perovskite Quantum Heterostructure Constructed by Halide Mixing between a Single CsPbI₃ Nanocrystal and an Individual...

Ion migration is significantly enhanced in lead-halide perovskites with a soft crystal lattice, which can promote the formation of a heterogeneous interface between two such materials with different halide-anion compositions. Here we have deposited a single CsPbI₃ nanocrystal (NC) on top of an individual CsPbBr₃ microplate to create a mixed-halide CsPbBrI_3- (0 < x < 3) NC by means of the anion exchange process. The formation of a CsPbBrI_3-/CsPbBr₃ heterostructure is confirmed by the much-enlarged geometric volume of the CsPbBrI_3- NC as compared to the original CsPbI₃ one, as well as by its capability of receiving photogenerated excitons from the CsPbBr₃ microplate with a larger bandgap energy. The quantum nature of this heterostructure is reflected from single-photon emission of the composing CsPbBrI_3- NC, which can also be bulk-like during phase segregation to demonstrate a red shift in the photoluminescence peak that is opposite to the common trend observed in smaller-sized mixed-halide NCs.