Facile Synthesis and Structural, Linear and Nonlinear Optical Investigation of p-type Cu2ZnGeS4 Thin Films as a Potential Absorber Layer for Solar Cells

The fabrication of new kesterite absorber layers has drawn tremendous attention among a number of researchers. This article reports the preparation of good-quality copper zinc germanium sulfide Cu 2 ZnGeS 4 (CZGS 4 ) thin films via a convenient spray pyrolysis method. The fabrication of an Al/ n -Si/Cu 2 ZnGeS 4 /Au heterojunction is also presented. X-ray diffraction results confirmed the tetragonal structure in the CZGS 4 samples. Additionally, energy-dispersive x-ray examination illustrated that the Cu 2 ZnGeS 4 samples possess a nearly stoichiometric composition. From the transmittance and reflectance data, the energy gap ( E g ), refractive index ( n ) and absorption coefficient ( α ) were assessed. According to the Tauc relation, the Cu 2 ZnGeS 4 thin samples exhibit a direct optical transition. The energy gap values were found to be in the range of 1.52–1.27 eV. The dispersion and nonlinear optical parameters of the Cu 2 ZnGeS 4 samples were also investigated. Electrical studies showed that the Al/ n -Si/Cu 2 ZnGeS 4 /Au heterojunction has good rectifying properties, with efficiency of 3.3%.