Deposition and Characterization of Si Substituted Cu 2 ZnSnS 4 Thin Films

The influence of the Si substitution ratio on the structural, morphological, and optical properties of Cu 2 ZnSnS 4 (CZTS) thin films was examined. The Cu 2 Zn(Si x Sn 1–x )S 4 thin films (x = 0, 0.25, 0.50, 0.75, and 1) were deposited on soda–lime glasses by spin coating technique and annealed in a quartz tube at 550 °C under H 2 S:Ar (1:9) flows. The X-ray diffraction (XRD) patterns showed that the crystal sizes of CZTS thin film decreased rapidly from 30 nm to 19 nm after the substitution of 25% Si to the Sn sites (Cu 2 Zn(Si 0.25 Sn 0.75 )S 4 thin films) and increased to the same range after increasing the Si substitution ratio. It was attributed to the highest dislocation density and strain values of the film after partial Si substitution to the structure. It was also reported that the Si substitution for Cu 2 ZnSnS 4 (CZTS) structure shifted both main XRD (from 28.51 to 28.62°) and Raman peaks (from 332 to 334 cm −1 ). Furthermore, the strong influence of Si addition on the optical properties of the films was examined. It was seen that the optical band gap of CZTS increases from 1.51 to 3.22 eV with the increase in Si ratio.