Characterization of one-step deposited Cu₂ZnSnS₄ thin films derived from a single crystalline powder

In this paper, Cu-deficient and Zn-rich Cu₂ZnSnS₄ (CZTS) single crystals were successfully grown by Bridgman technique. Following the investigation of structural and photo-electrical properties of the grown CZTS crystal, the powder extracted from it was evaporated through electron-beam technique for the fabrication of CZTS thin films by one-step deposition. Compositional analysis revealed that CZTS thin films were obtained with a composition stoichiometry very close to that measured for the crystal powder. Detailed XRD and Raman analyses have shown that the as-grown CZTS films have an amorphous matrix and then transform into a polycrystalline form with a monophase kesterite phase having (112) oriented plane direction following the post-annealing process at 500 °C. The optical band gap was found to be 1.50 eV for the CZTS film annealed 500 °C. The conducted photo-electrical measurements revealed that CZTS thin films have good sensitivity to the visible light, which is essential for an absorber layer in the solar cell device structure. The room temperature values of conductivity, mobility and hole carrier concentration of the films annealed at 500 °C were determined as ∼5.1 × 10^-4 (Ω cm)^-1, 1.22 cm²/V s and 2.6 × 10¹⁵ cm^-3, respectively.