Matthew Sheldon1

1, Texas A&M University, College Station, Texas, United States

All-inorganic, CsPbX3 (X=Cl, Br, I) quantum dot nanocrystals have been shown to have great promise for optical and optoelectronic applications due to excellent stability, high fluorescent quantum yields, and optical tunability via a facile halide exchange reaction. This presentation will discuss our recent progress obtaining refined synthetic control over either cation exchange or, alternatively, metal deposition on CsPbX3 nanoparticles. The oleylamine ligand shell commonly used to stabilize all-inorganic perovskite nanocrystals may be used to reduce metal salts allowing for metal cations to either exchange with Pb2+ in the perovskite crystal lattice or deposit as elemental metal on the surface of the nanocrystals. Our central insight is that the reaction kinetics for exchange or deposition are driven by the excess metal cation in solution. For example, when gold salt alone is added to CsPbBr3 nanoparticles, cation exchange occurs, but if an excess of Pb2+ is added, Au metal only deposits on the perovskite surface with domain size determined by the gold solution concentration. The cation exchange reaction represents a new manner of post-synthetic tunability that may aid in the search for lead free all-inorganic perovskite, producing in this case, the near-IR emitting mixed valence semiconductor, CsAu2Br6, reported for the first time after our initial studies. We also note the high fluorescence quantum yield maintained in Au-CsPbBr3 heterostructures with efficiencies up to 75%. This surprising result could provide new insights into the optoelectronic properties of the all-inorganic perovskite nanocrystals, as well as the interactions between metal and semiconductors on the nanoscale, important for a variety of optoelectronic applications. We will discuss our recent progress expanding the range of all-inorganic Perovskite nanostructures obtainable via metal exchange and deposition reactions.