Cs(3)Cu(4)In(2)Cl(13) Nanocrystals: A Perovskite-Related Structure with Inorganic Clusters at A Sites

[Image: see text] An effort to synthesize the Cu(I) variant of a lead-free double perovskite isostructural with Cs(2)AgInCl(6) resulted in the formation of Cs(3)Cu(4)In(2)Cl(13) nanocrystals with an unusual structure, as revealed by single-nanocrystal three-dimensional electron diffraction. These nanocrystals adopt a A(2)BX(6) structure (K(2)PtCl(6) type, termed vacancy ordered perovskite) with tetrahedrally coordinated Cu(I) ions. In the structure, 25% of the A sites are occupied by [Cu(4)Cl](3+) clusters (75% by Cs(+)), and the B sites are occupied by In(3+). Such a Cs(3)Cu(4)In(2)Cl(13) compound prepared at the nanoscale is not known in the bulk and is an example of a multinary metal halide with inorganic cluster cations residing in A sites. The stability of the compound was supported by density functional theory calculations that also revealed that its bandgap is direct but parity forbidden. The existence of the Cs(3)Cu(4)In(2)Cl(13) structure demonstrates that small inorganic cluster cations can occupy A sites in multinary metal halides.