Electrolyte pH dependent controlled growth of co-electrodeposited CZT films for application in CZTS based thin film solar cells

Understanding Cu–Zn–Sn co-electrodeposition is important from the view point of developing high quality CZTS (Cu₂ZnSnS₄) absorber layer for thin film solar cells. One of the major issue during electrodeposition is hydrogen evolution which can severely affect the growth of the depositing film. In the present study, the hydrogen evolution is controlled by systematically varying electrolyte pH during co-electrodeposition of Cu–Zn–Sn films. Cu–Zn–Sn metal precursor films were co-electrodeposited using electrolytic baths with pH varying from 4 to 8 and conditions for obtaining dense and stoichiometric Cu–Zn–Sn films were evaluated. Films electrodeposited with electrolyte pH of 6, 7 and 8 produced dense and continuous electrodeposited films in contrast to those deposited using electrolyte pH of 4 and 5. Films deposited with different electrolyte pH were sulphurized in Argon atmosphere and their physical characterization was carried out in order to find out conditions to obtain a dense and compact CZTS film having phase purity with appropriate stoichiometry resulting in a band gap of 1.45 eV.