Transforming colloidal CsPbBr nanocrystals with poly(maleic anhydride--1-octadecene) into stable CsPbBr perovskite emitters through intermediate heterostructures.

The preparation of strongly emissive CsPbBr perovskite nanocrystals with robust surface passivation is a challenge in the field of lead halide perovskite nanomaterials. We report an approach to prepare polymer-capped CsPbBr perovskite nanocrystals by reacting oleylammonium/oleate-capped CsPbBr nanocrystals with poly(maleic anhydride--1-octadecene) (PMAO). PMAO contains succinic anhydride units that are reactive towards the oleylamine species present on the CsPbBr nanocrystals' surface and produces polysuccinamic acid, which, in turn, triggers the CsPbBr to CsPbBr conversion. The transformation occurs through the formation of CsPbBr-CsPbBr heterostructures as intermediates, which are captured because of the mild reactivity of PMAO and are investigated by high-resolution electron microscopy. The CsPbBr-CsPbBr heterostructures demonstrate a dual emission at cryogenic temperature with an indication of the energy transfer from CsPbBr to CsPbBr. The fully-transformed CsPbBr NCs have high photoluminescence quantum yield and enhanced colloidal stability, which we attribute to the adhesion of polysuccinamic acid to the NC surface through its multiple functional groups in place of oleate and alkylammonium ligands. The PMAO-induced transformation of CsPbBr NCs opens up a strategy for the chemical modification of metal halide NCs initially passivated with nucleophilic amines.