Influence of ZnS Sputtering Power on Film Adhesion and Cu2ZnSnS4 Solar Cells

The stacking precursors Mo/ZnS/SnS/Cu were sputtered on soda-lime glass (SLG) substrates using different sputtering power of ZnS changing from 50 W to 140 W. Cu2ZnSnS4 (CZTS) thin films were obtained by annealing the precursors. The effects of ZnS sputtering powers on the morphology, microstructure and adhesion in ZnS and followed CZTS thin films were investigated. ZnS thin films with different power were hexagonal wurtzite with (008) preferred orientation. The compressive stress in ZnS thin film increased by an order of magnitude with sputtering power from 50 W to 140 W. When sputtering power of ZnS was lower than 80 W or higher than 110 W, the crack and even falling off phenomenon were observed in the annealed CZTS thin films. From 80 W to 110 W, the surface of CZTS thin film was even but more holes and secondary phases appeared at higher power of 110 W. The CZTS solar cell was fabricated with ZnS thin films sputtered at 80 W, which showed the open circuit voltage of 572 mV, the short circuit current density of 14.23 mA/cm2 and the conversion efficiency of 3.34 %.