Exploring the properties of lead-free hybrid double perovskites using a combined computational-experimental approach

Density functional theory screening of the hybrid double perovskites (MA)(2)(BBiX6)-Bi-I (B-I = K, Cu, Ag, Tl; X = Cl, Br, I) shows that systems with band gaps similar to those of the MAPbX(3) lead compounds can be expected for B-I = Cu, Ag, Tl. Motivated by these findings, (MA)(2)TlBiBr6, isoelectronic with MAPbBr(3), was synthesised and found to have a band gap of similar to 2.0 eV.