Abstarct: In this dissertation, CH3NH3PbI3 perovskite thin films were synthesized by two-step and one- step methods. Then the structural and optical properties of the synthesized CH3NH3PbX3 (X = Cl, Br, I) perovskite thin films were investigated. The results showed that the surface uniformity and surface coverage are better in two-step (spin-dip and spin-spin) method. Comparison of the CH3NH3PbI3 thin films prepared by spin- dip method showed that the best dipping time for perovskite structure formation is 10 minutes. In order to increase the stability of the propskite laxyers, the CH3NH3PbI3 was doped with bromine (Br). Investigation of the structural and optical properties of the laxyers showed that with introducing the bromine to CH3NH3PbI3, the crystalline structure was changed from tetragonal to the cubic and the bandgap was increased from 1.57 eV (for CH3NH3PbI3) to 2.3 eV (for CH3NH3PbBr3). By changing the dipping time of the PbI2 laxyer in CH3NH3Br solution or PbI2: PbBr2 laxyer in CH3NH3I solution, the appropriate amount of bromine entering the perovskite laxyer for solar cell applications was controlled. Due to the high consumption of the materials in the spin-dipping method, the perovskite thin films were also prepared by economical spin-spin coating method. The effect of different spin parameters such as speed, spin time, MAI solution concentration (7, 10, 20 and 40 mg/ml), MAI loading time, annealing time and also bromine concentration on the CH3NH3PbI3 perovskite laxyer were investigated. The results showed that the optimum concentration and loading time of MAI solution were 7 mg/ml and 40 s, respectively. Then some solar cells were made by a group of absorber laxyers prepared by spin-spin method and photovoltaic parameters of the cells were measured. Electrical measurements showed that, the cell contains a perovskite laxyer prepared by MAI concentration of 7 mg/ml has a longer electron lifetime and higher energy conversion efficiency (PCE). Then, in order to improve absorption in these cells, the polymeric hole transport laxyer (P3HT) was combined with PCBM and a bulk heterojunction (BHJ) was formed. This BHJ laxyer was used in polymeric solar cells as an absorber laxyer. With this technique, the non-absorbed photons are absorbed by this laxyer and thus will improve photovoltaic parameters of the cells. The analysis of the parameters obtained from the impedance spectroscopy showed that with the presence of the PCBM in the hole transport laxyer, recombination resistance increases and carrier transfer resistance decreases. Moreover, the results showed that the cell contains an absorber laxyer with an loading time of 40 seconds has the highest electron lifetime and PCE. In order to investigate the stability of solar cells including the absorber laxyer of CH3NH3PbI(3-x)Brx, the photovoltaic parameters of the cells were measured continuously for 162 days. The results of this study showed that even though the bromide-free perovskite device has the highest PCE (11.65%), but it suffer from a significant drop in PCE (86%) during 162 days. Comparison of the results showed that the lowest rate of efficiency loss (1%) was obtained for the cell including of an absorber laxyer prepared with I:Br molar ratio of 1:1 with a ratio of 9%.