The role of gold oxidation state in the synthesis of Au-CsPbX3 heterostructure or lead-free Cs2AuIAuIIIX6 perovskite nanoparticles

Abstract

Here, we report that the oxidation state of gold plays a dominant role in determining the reaction products when gold halide salts are mixed with all-inorganic lead halide perovskite nanocrystals. When CsPbX₃ nanocrystals react with Au(I) halide salts, Au nanoparticles are deposited on the surface of the perovskites through the reduction of Au¹⁺ ions by the surfactant ligand shell, to produce Au-CsPbX₃ heterostructures. These heterostructures preserve comparably high photoluminescence quantum yield (PLQY) and show identical XRD diffractograms as the parent CsPbX₃ nanocrystals. In contrast, the reaction of CsPbX₃ nanocrystals with Au(III) halide salts promotes complete cation exchange of Pb ions by Au ions in the nanocrystal perovskite lattice. The cation exchange products, Cs₂Au^IAu^IIIBr₆ or Cs₂Au^IAu^IIICl₆, show XRD patterns corresponding to a tetragonal mixed halide perovskite crystal structure and show no visible photoluminescence. This crucial dependence on the oxidation state of the Au ion informs synthetic strategies for producing and optimizing metal-perovskite heterostructures and lead-free perovskite nanoparticles.