Nanocrystal Heterostructures Based on Halide Perovskites and Metal Sulfides.

We report the synthesis of nanocrystal heterostructures composed of CsPbCl and PbS domains sharing an epitaxial interface. We were able to promote the growth of a PbS domain (in competition with the more commonly observed PbSCl one) on top of the CsPbCl domain by employing Mn ions, the latter most likely acting as scavengers of Cl ions. Complete suppression of the PbSCl domain growth was then achieved by additionally selecting an appropriate sulfur source (bis(trimethylsilyl)sulfide, which also acted as a scavenger of Cl ions) and reaction temperature. In the heterostructures, emission from the perovskite domain was quenched, while emission from the PbS domain was observed, pointing to a type-I band alignment, as confirmed by calculations. These heterostructures, in turn, could be exploited to prepare second-generation heterostructures through selective ion exchange on the individual domains (halide ion exchange on CsPbCl and cation exchange on PbS). We demonstrate the cases of Cl → Br and Pb → Cu exchanges, which deliver CsPbBr-PbS and CsPbCl-CuS epitaxial heterostructures, respectively.