Figure 4.

The four polymorphs of CsSnI₃. On the top row, the three black perovskite structures are shown: a) cubic B‐α, b) tetragonal B‐β, and c) orthorhombic B‐γ. d) The bottom row shows the yellow crystal where the tin halide octahedral networks are fragmented into 1D chains. In all four images, the green spheres represent the Cs atom, whereas the purple polyhedra represent the octahedral perovskite cage formed by the bonding of the Sn (steel blue) and I (dark purple) atoms. a–d) Reproduced with permission.^{[ 59 ]} Copyright 2015, The American Physical Society.