Surfactant-induced anion exchange and morphological evolution for composition-controlled caesium lead halide perovskites with tunable optical properties

Abstract

Environmentally stable lead halide perovskite nanostructures with engineered composition and morphology are attractive because of their exotic optical properties. Here, we report the synthesis of monodispersed (∼20 nm) CsPbI3 cubic perovskite nanocrystals (NCs) using edible olive oil as a solvent as well as a chelating reagent. Thereafter, bromide anion exchange reaction using the cetyl trimethyl ammonium bromide surfactant in hexane is carried out at relatively lower temperatures to synthesize caesium lead halide perovskites with variable halide compositions and tunable band gaps. Interestingly, because of the formation of micelles, continuous morphology evolution varying from NCs of different sizes to nanowires (NWs) and nanosheets is observed. The anion exchange temperature has a distinct effect on the morphology of the CsPbBr3 nanostructure and the anion exchange reaction rate. Finally, an easy solution-processed photoconductive device is demonstrated using as-grown CsPbBr3 NWs, indicating its potential for optoelectronic applications.