ABSTRACT
The oxidation of Sn2+ to the chemically more stable Sn4+ analog impedes the charge neutrality of the perovskite and causes the degradation of the perovskite by formation of oxides/hydroxides of tin, and furthermore, Sn4+ leads to hole doping of the material. Even though encouraging stability data has already been reported, the main drawback of tin halide perovskites is the chemical instability of the divalent metal cation, which is due to the oxidation of Sn2+ to Sn4+ in ambient conditions. The family of pnictogen-noble metal halide double perovskites is especially interesting for photovoltaic applications because of the structural similarity, that is, three-dimensional structures, to lead-based perovskites despite the different valencies of the metal cations incorporated. In addition, a huge variety of material compositions is amenable due to the high number of possible element combinations of monovalentand trivalent metal cations together with organic and inorganic cations, and halide anions.
