Dual-site mixed layer-structured FA <sub/>x</sub> Cs <sub/>3a??x</sub> Sb <sub/>2</sub> I <sub/>6</sub> Cl <sub/>3</sub> Pb-free metal halide perovskite solar cells

摘要： Structure engineering of trivalent metal halide perovskites (MHPs) such as A3Sb2X9 (A ? a monovalent cation such as methyl ammonium (MA), cesium (Cs), and formamidinium (FA) and X ? a halogen such as I, Br, and Cl) is of great interest because a two dimensional (2D) layer structure with direct bandgap has narrower bandgap energy than a zero dimensional (0D) dimer structure with indirect bandgap. Here, we demonstrated 2D layer structured FACs2Sb2I6Cl3 MHP by dual-site (A and X site) mixing. Thanks to the lattice-symmetry change by I–Cl mixed halide, the shortest ionic radius of Cs, and the lower solution energy due to dual-site mixing, the FACs2Sb2I6Cl3 MHP had 2D layer structure and thereby the MHP solar cells exhibited improved short-circuit current density.