Physical properties of the low-cost CZTS absorber layer deposited by spin-coating: effect of the copper concentration associated with SCAPS-1D simulation

Five samples of copper zinc tin sulfide (CZTS) thin films were deposited by a spin-coating technique at various copper concentrations ranging from 0.5 M to 2.5 M in steps of 0.5 M, in order to improve their stability, efficiency, performance, and reduce the production costs. The XRD patterns showed the existence of the three main characteristic peaks of CZTS (112), (220), and (312), which indicated the formation of the kesterite structure of CZTS. The gap energy of the thin films was calculated based on the derivation method using the absorbance data, and the values obtained varied from 1.46-1.58 eV for 0.5, 1, 1.5, 2, and 2.5 M copper molarity, respectively. Hall effect measurements were used to determine conductivity, which in turn increased with the concentration of copper in the films. The characterization results showed that the sample C3, which represents the 1.5 M copper concentration, exhibited higher crystallinity and better optical and electrical performance than the others. Finally, a theoretical efficiency of 11.6% was obtained when simulating the solar cell using the CZTS thin film (CZTS/ZnS/S:ZnO) in the SCAPS-1D simulation program using the parameters obtained in this study. Under the adopted synthesis conditions, the theoretical simulation corroborated the experimental findings, thus confirming that the synthesized material is a promising candidate for solar cell applications as an absorber layer. The results obtained in this study support the use of spin-coated CZTS films as absorber layers in thin film solar cells and the use of only 1.5 M copper concentration to achieve an efficient absorber layer.