Prevention of ion migration in lead halide perovskites upon plugging the anion vacancies with PbSe islands.

To circumvent the issue of halide ion exchange in perovskites, we have decorated CsPbBr 3 and CsPbI 3 nanocrystals with different sized PbSe nanoparticles and demonstrated that it effectively prevents anion exchange reaction in CsPbBr 3 /CsPbI 3 nanoheterostructures (NHSs) as a consequence of halide vacancy passivation by the more covalent selenide anion.