${Cu}_2\mathit{\text{ZnSn}}{S}_4(\mathit{\text{CZTS}})$ is a non-toxic earth abundant material and a promising quaternary semiconductor compound of groups $I-II-IV-VI$ having a kesterite symmetrical structure. Due to its optimum direct bandgap, it has been considered as a suitable material for absorber layers for photovoltaic cell applications. This paper presents the numerical simulation and modeling of $\mathit{\text{CZTS}}$ based thin film kesterite photovoltaic cells using SCAP-1D software. The influence of device parameters such as the carrier concentration, thickness, densities of absorber, buffer and window layers, defect densities and the temperature effect on the performance of the $ZnO/CdS/\mathit{\text{CZTS}}/Mo$ photovoltaic cell structure are analyzed. Defect densities are added to the absorber layer and the interface between the buffer layer and the absorber layer. This type of solar cell does not comprise any toxic material and can lead to non-toxic thin film photovoltaic cells with outstanding optical properties. In this work, promising optimized results had been achieved with a conversion efficiency of 23.72%, a fill factor of 82.54%, a short-circuit current ($J_{sc})$ of 44.87 ${\text{mA}/\text{cm}}^2$ , and an open circuit voltage ${(V}_{oc})$ of 0.64V.

Presently, we inquire about the organic/inorganic cation effect on different properties based on structure, morphology, and steadiness in preparing a one-step solution of APbI₃ thin films, where A = MA, FA, Cs, using spin coating. This study was conducted to understand those properties well by incorporating device modeling using SCAPS-1D software and to upgrade their chemical composition. X-ray diffraction (XRD) was used to analyze the crystal structures. Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) were conducted to characterize the surface morphology; photoluminescence, Transmission Electron Microscopy (TEM), and a UV–Visible spectrometer helped us to study the optical properties. The (110) plane is where we found the perovskite’s crystalline structure. According to the XRD results and by changing the type of cation, we influence stabilization and the growth of the $APb{I}_3$ absorber layer. Hither, a homogenous, smooth-surfaced, pinhole-free perovskite film and large grain size are results from the cesium cation. For the different cations, the band gap’s range, revealed by the optical analysis, is from 1.4 to 1.8 eV. Moreover, the stability of $CsPb{I}_3$ remains excellent for two weeks and in a ~60% humid environment. Based on the UV–Visible spectrometer and photoluminescence characterization, a numerical analysis for fabricated samples was also performed for stability analysis by modeling standard solar-cell structures $HTL/APb{I}_3/ETL$. Modeling findings are in good agreement with experimental results that $CsPb{I}_3$ is more stable, showing a loss % in PCE of 14.28%, which is smaller in comparison to $FAPb{I}_3$ (44.46%) and $MAPb{I}_3$ (20.24%).