Abstarct: This thesis has investigated the synthesis and characterization of lead-free organic-inorganic hybrids perovskite thin films (CH3NH3SnI3 and (CH3NH3)3Bi2I9). Since the optical properties of these laxyers significantly depend on the synthesis method, various methods such as the One-step spin-coated and thermal evaporation method and vapor assistant solution process for the synthesis of these thin films were used. The one-step spin coating method is the simplest and least expensive method of deposition of perovskite thin films, but due to the high reaction rate between the precursors and the rapid evaporation of the solvent and formed non-uniform laxyers, used the vapor assistant solution process and thermally evaporated method. Investigation of diffraction patterns in the synthesized laxyers showed CH3NH3SnI3 perovskite thin films with a tetragonal structure. Examination of the optical properties of the laxyers showed an improvement in the amount of absorption in the energy region used for perovskite solar cells. Solar cells, including the perovskite laxyer prepared by the vapor assistant solution process, have higher PCE. Then, to optimize the perovskite laxyer's electrical and optical properties, the substitution of Formamidinium cation was used instead of part of methylammonium ions. Study of the structural properties of the laxyers showed that with the entry of the Formamidinium into the MASnI3 compound, the crystal structure of the laxyer changes from the tetragonal to the orthorhombic. This substitution increased the optical absorption of the perovskite laxyer. In this study, to prevent rapid oxidation of SnI2, SnCl2 precursor was used to synthesizing perovskite laxyers. The use of SnCl2 precursor probably results in forming an intermediate phase that decomposes with increasing annealing time and eventually forms a perovskite phase. The formation of this intermediate phase slowed down, forming the perovskite laxyer and improving the crystallinity. The effect of hydroiodic acid additive on chlorinated laxyers was also investigated. The results show that adding hydroiodic acid at a rate of 1%V improves the amount of absorption in the study region. In the continuation of this study, perovskite thin laxyers baxsed on Bismuth were synthesized by two methods of spin coating and vapor assistant solution process, and then Methylammonium cation was replaced with Formamidinium cation. The study of the structural properties of these samples confirmed the formation of the perovskite structure of hexagonal. Examination of the optical properties of the samples showed that the perovskite laxyers have a high absorption coefficient (of the order 104 cm-1). Then the photovoltaic properties of solar cells made with these absorbent laxyers were also investigated.