A complex has a structure of formula (1A): SnXn·(m)L, wherein X is at least one type of halogen atoms, L is a polar solvent molecule, n is a value from 1.5 to 2.5, and m is a value from 0.3 to 1.9. A perovskite compound has a structure of formula (2A): RSnXj, wherein Sn has an oxidation number from 1.5 to 2.5, R is at least one type of a monovalent cation, X is at least one type of halogen atoms, and j is a value from 2.5 to 3.5, and the perovskite compound is free of tin oxide; or a perovskite compound has a structure of formula (2B): R2M2BiX1, wherein R is at least one type of a monovalent cation, X is at least one type of halogen atoms; M2 is a monovalent metal, and i is a value from 5.0 to 7.0.