Investigation of Cu2ZnSnS4 thin film with preannealing process and ZnS buffer layer prepared by magnetron sputtering deposition

Abstract

Unlike traditional methods for fabricating a CdS buffer layer through chemical bath deposition in thin-film solar cells, this study fabricated a ZnS thin film by sulfurizing the Zn film that was deposited using a magnetron sputtering system at varied temperatures from 500° to 560 °C in a sulfurization furnace. The ZnS thin film have been used as a buffer layer on the Cu2ZnSnS4 absorption layer. In this study, the Cu2ZnSnS4 absorber layer was prepared by first depositing a copper–zinc–tin (CZT) precursor film with a metal stack order of Zn–Sn–Cu–Zn through magnetron sputtering, followed by a preannealing process on the CZT precursor, to promote the interdiffusion of elements for the transfer of the metal phase into the alloy phase. Experimental results revealed the increased crystallite size in the SEM observation, an enhanced Raman intensity at 336 cm−1, and a reduced FWHM value in the XRD study for the Cu2ZnSnS4 thin film fabricated at a sulfurization temperature of 510 °C for 20 min with a preannealing treatment of the CZT precursor at a temperature of 420 °C for 30 min. In addition, the improved optical transmittance to 81.3% and an increased optical band gap value to 3.28 eV due to the reduced grain boundaries was obtained for the ZnS film with improved crystallinity quality fabricated at a sulfurization temperature of 560 °C.