Experimental and numerical simulation of deposition time effect on ZnS thin films for CZTS-based solar cells

High-quality ZnS thin films as buffer layer have been successfully synthesized and simulated using the low-cost Mist CVD technique and the SCAPS-1D software for different deposition times (30, 40, 50, and 60 min). The structural, morphological, and optical properties of the prepared ZnS films have been investigated using X-ray diffraction (XRD), scanning electronic microscopy (SEM), atomic force microscopy (AFM), and UV–Vis spectrophotometer. The time deposition effect on ZnS films’ efficiency as a buffer layer has been evaluated. XRD pattern confirms the hexagonal/cubic structure of the prepared samples, with (111) as preferred orientation. Raman spectra confirm XRD findings by the two peaks located at 348 cm⁻¹ and 697 cm⁻¹ which correspond to ZnS samples' cubic and hexagonal structures. Scanning electronic microscopy (SEM) and atomic force microscopy (AFM) images show densely uniform grains with precise shapes and boundaries covering the entire sample's surface with a relative roughness for all deposition times. The optical transmittance shows an average of 78% in the visual field of light with an optical band gap varying between 3.69 and 3.80 eV. Numerical simulation of ZnO:Al/ZnS/CZTS/Mo cell using SCAPS-1D software shows that the sample deposited for 30 min presents the best performance with an efficiency of up to 8.9%.