Perovskite Quantum Heterostructure Constructed by Halide Mixing between a Single CsPbI 3 Nanocrystal and an Individual CsPbBr 3 Microplate.

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 CsPbI 3 nanocrystal (NC) on top of an individual CsPbBr 3 microplate to create a mixed-halide CsPbBr x I 3- x (0 < x < 3) NC by means of the anion exchange process. The formation of a CsPbBr x I 3- x /CsPbBr 3 heterostructure is confirmed by the much-enlarged geometric volume of the CsPbBr x I 3- x NC as compared to the original CsPbI 3 one, as well as by its capability of receiving photogenerated excitons from the CsPbBr 3 microplate with a larger bandgap energy. The quantum nature of this heterostructure is reflected from single-photon emission of the composing CsPbBr x I 3- x 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.