A Gold(I) Oxide Double Perovskite: Ba₂AuIO₆

Oxide perovskites offer improved stability compared to halide perovskite compounds for optoelectronic applications. Here, we report the first gold-containing double perovskite, Ba₂AuIO₆, and compare it to Ba₂AgIO₆ and Ba₂NaIO₆. Ba₂AuIO₆ and Ba₂AgIO₆ exhibit a monoclinic distortion from the cubic perovskite structure possessed by Ba₂NaIO₆ and have similar lattice constants despite the nominally larger size of Au⁺ compared to Ag⁺. Ba₂AgIO₆ shows photoluminescence (PL) at 2.10 eV, and Ba₂AuIO₆ exhibits PL at 1.30 and 1.47 eV. As prepared, both compounds appear stable under visible light at room temperature but decompose when subjected to gentle heating followed by illumination. Our data suggest that this behavior is due to the presence of -OH defects in the crystal structures. This discovery provides a new route to semiconductors with a near-IR band gap and identifies engineering challenges that must be addressed to use oxide perovskites for optoelectronic devices.