Enhanced solar cell performance by optimization of spray coated CZTS thin film using Taguchi and response surface method

The present study aims to investigate the optimum deposition conditions for preparation of CZTS thin films using the spray pyrolysis method. CZTS is a vital semiconducting material now days, as it requires the constituents, which are non-toxic and easily available as well. The Taguchi approach is implemented for optimization. Major quality control parameters considered are: copper to zinc plus tin (Cu/Zn + Sn) ratio; zinc to tin (Zn/Sn) ratio; substrate temperature; and spray time. Three levels of each parameter are selected. This attributes L9 (3(4)) orthogonal array according to Taguchi design. The signal to noise (S/N) ratio and an analysis of variance is carried out to achieve an optimum combination of quality control parameters. In the present study, thin films are optimized in terms of the band gap. The solar cell is fabricated for each experiment and for an optimum combination as well. A novel cell fabrication (inverted) is introduced which can cover full light spectra. The cell is fabricated as FTO/i-ZnO/Al:ZnO/CdS/CZTS/CuS/FTO. More than 17% improvement in efficiency is observed by the cell fabricated using optimum condition than the best efficiency achieved by orthogonal array 2, among all 9 arrays. Furthermore, to achieve specific optimum condition, response surface methodology (RSM) is implemented. The RSM is carried out for a multiple response (band gap and efficiency). The films are characterized by X-ray diffraction and field emission scanning electron microscopy. Optical properties are studied by UV-Visible spectroscopy. The elemental study is carried out using energy-dispersive X-ray spectroscopy.