The larger A cation occupies a cubo-octahedral site shared with
twelve X anions while the smaller B cation is stabilized in an
octahedral site shared with six X anions. The most studied perovskites
are oxides due to their electrical properties of ferroelectricity or
superconductivity. Halide perovskites received little attention until
layered organometal halide perovskites were reported to exhibit a
semiconductor-to-metal transition with increasing dimensionality
[1].