Abstract
The present study intends to investigate the effect of film thickness on the novel kesterite Cu2CdGeS4 (CCGS4) thin films that are deposited by a chemical bath deposition procedure at room temperature. The XRD data demonstrates that the polycrystalline Cu2CdGeS4 structure was displayed in all the prepared samples with an orthorhombic single phase. Utilizing spectrophotometric measurements of transmittance and reflectance spectra throughout the spectral range of 300–2500 nm, the optical characteristics were investigated. The optical analysis of the Cu2CdGeS4 thin films indicated that the refractive index n-values of the chemically deposited Cu2CdGeS4 films rise from 2.47 to 3.44 by increasing the thickness, while the absorption coefficient values of the Cu2CdGeS4 films are in the range of 105 cm−1. On the other hand, as the film thickness rises, the dielectric constant and optical conductivity also rise. The electronic transitions of the chemically deposited Cu2CdGeS4 thin films were caused by allowed direct transitions, and the optical band gap was found to be reduced from 1.53 eV to 1.27 eV as the film thickness enlarged, while the Urbach energy improved from 0.19 eV to 0.25 eV. Also, the nonlinear optical parameters of the Cu2CdGeS4 thin films strongly depend on the film thickness, and these values were improved by increasing the film thickness. The hot-probe experiment yields a negative voltage for each sample, confirming our films' propensity for p-type semiconductor behavior.
•For the first time, P-type Cu2CdGeS4 thin films were synthesized by the chemical bath deposition technique.•FE-SEM and XRD techniques were used to study the structure of Cu2CdGeS4 thin films.•The optical and optoelectrical parameters of the Cu2CdGeS4 films were studied.•The nonlinear optical parameters of the Cu2CdGeS4 thin films were determined.