Deposition of Cu2ZnSnS4 thin films by magnetron sputtering and subsequent sulphurization

Top-down magnetron sputtering with subsequent, separate sulphurization was used to deposit Cu2ZnSnS4 (CZTS) absorber layers for solar cells. Cu, ZnS and SnS targets were used to deposit the absorber layers onto soda lime glass substrates. The sputtering system was first calibrated for individual Cu, ZnS and SnS deposition. CZTS thin film was then deposited by co-sputtering followed by annealing at 530°C in sulphurous conditions at atmospheric pressure for 30 minutes. Scanning electron microscopy, x-ray diffraction, Raman and UV-visible absorption spectroscopy were used to characterize the absorber film. It was found to have properties potentially suitable for use in high-efficiency solar cells. These include phonon peaks corresponding to quaternary CZTS, a high absorption coefficient of 1.1 × 105 cm−1, a direct optical band gap of 1.5 eV, a kesterite CZTS phase and stoichiometric ratios of Cu/[Zn+Sn] = 0.82 and Zn/Sn = 1.19.