Herein, we examine the impact of cations on the structural, morphological, optical properties and degradation of lead perovskite APbI₃ (where A = MA, FA, Cs). Its structure, surface morphology and optical properties have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-Visible spectrometer. The structure of perovskite thin films was found to be in the direction of (110) plane. It is seen from the XRD results that this kind of cation assumes a significant part in stabilising and improving the performance of APbI3 based solar cells. Here, the cesium lead iodide thin films show a smooth and homogenous surface and enormous grain size without pinhole perovskite film. An optical investigation uncovered that the band gap is in a range from 1.4 to 1.8 eV for the different cations. Additionally, in ~60% humidity under dark conditions for two weeks, the structural and optical properties of CsPbI3 films remained good. Furthermore, the efficiency of FTO/TIO2/CSPbI3/Spiro-Ometad/Au solar cells was calculated to be 21.48%.