This study represents the investigation of In2S3 thin films, which have been deposited with different Indium salts (Chloride, Acetate, and Nitrate) using the Chemical Spray Pyrolysis (CSP) method. The Mott-Schottky analysis has been used in case of studying the electrical properties of films such as conduction and valence band, carrier densities, Fermi level (E-fn), flat band potential, and semiconductor type. In the next step, the Rb(1)MAFA perovskite solar cell has been simulated, and the results have been validated by the experimental data (with the least parameters for fitting). Finally, In2S3 layers have been inserted on the SnO2 layer to decrease the recombination rate and enhance the efficiency of the solar cell. The results represent that the In2S3 layers with acetate source improve the band bending at the perovskite/ETL interface, the electron transfer will increase, and the result would be an increment in the open-circuit voltage (V-OC), as well as the cell PCE. The efficiency of 23.47% is the recorded PCE, which is approximately 3% more than the reference case.