The Role of Goldschmidt's Tolerance Factor in the Formation of A2BX6 Double Halide Perovskites and its Optimal Range

Vacancy-ordered double perovskites is a new branch of lead-free halide perovskites with properties promising for photovoltaic application. In this study, data about the crystal structure of 170 known A(2)BX(6) (X = I, Br, Cl, F) are collected and analyzed to solve a question of applicability of the Goldschmidt's tolerance factor and octahedral factor to double perovskites. It is found that Goldschmidt's tolerance factor is applicable for double perovskites in analog with ABX(3) perovskites. Suggested optimal ranges of Goldschmidt's factor expand the geometrical approach from ABX(3) perovskites to A(2)BX(6) double perovskites. The result is useful for up to 796 new full inorganic compounds having double-perovskite structure and designing new hybrid organic-inorganic double perovskites.