Optimization of sputtered ZnS buffer for Cu2ZnSnS4 thin film solar cells

• Fully Cd-free CZTS/ZnS-buffer thin film solar cells were fabricated.
• Structural properties and composition of ZnS buffer were tuned varying the sputtering power.
• Effect of ZnS buffer thickness on solar cell performance was investigated.
• The best solar cell conversion efficiency (η) obtained was 2.11%.

Cu2ZnSnS4 (CZTS) thin film solar cells with sputtered zinc sulfide (ZnS) buffer layers are fabricated. The effect of ZnS (buffer layer) film thicknesses along with a CZTS absorber layer prepared by sputtered metallic precursor film followed by sulfurization on the solar cell properties is investigated. The impact of the sputtering power on the structural, morphological, compositional and optical properties of the ZnS buffer layers is studied. The optimized ZnS buffer layer with a thickness of ~ 30 nm in CZTS based solar cell structure exhibits the best solar cell conversion efficiency of 2.11% with open-circuit voltage of 311 mV, short-circuit current density of 12.16 mA/cm2 and fill factor of 0.55.