Nanocrystal Heterostructures\nBased on Halide Perovskites\nand Metal Sulfides

We report the synthesis\nof nanocrystal heterostructures\ncomposed\nof CsPbCl<sub>3</sub> and PbS domains sharing an epitaxial interface.\nWe were able to promote the growth of a PbS domain (in competition\nwith the more commonly observed Pb<sub>4</sub>S<sub>3</sub>Cl<sub>2</sub> one) on top of the CsPbCl<sub>3</sub> domain by employing\nMn<sup>2+</sup> ions, the latter most likely acting as scavengers\nof Cl<sup>–</sup> ions. Complete suppression of the Pb<sub>4</sub>S<sub>3</sub>Cl<sub>2</sub> domain growth was then achieved\nby additionally selecting an appropriate sulfur source (bis(trimethylsilyl)sulfide,\nwhich also acted as a scavenger of Cl<sup>–</sup> ions) and\nreaction temperature. In the heterostructures, emission from the perovskite\ndomain was quenched, while emission from the PbS domain was observed,\npointing to a type-I band alignment, as confirmed by calculations.\nThese heterostructures, in turn, could be exploited to prepare second-generation\nheterostructures through selective ion exchange on the individual\ndomains (halide ion exchange on CsPbCl<sub>3</sub> and cation exchange\non PbS). We demonstrate the cases of Cl<sup>–</sup> →\nBr<sup>–</sup> and Pb<sup>2+</sup> → Cu<sup>+</sup> exchanges,\nwhich deliver CsPbBr<sub>3</sub>–PbS and CsPbCl<sub>3</sub>–Cu<sub>2‑<i>x</i></sub>S epitaxial heterostructures,\nrespectively.