Cu2ZnSnS4 thin film solar cells by fast coevaporation



Solar cells based on kesterite-type Cu2ZnSnS4 (CZTS) were fabricated on molybdenum coated soda lime glass by evaporation using ZnS, Sn, Cu, and S sources. The coevaporation process was performed at a nominal substrate temperature of 550°C and at a sulfur partial pressure of 2–3 × 10−3 Pa leading to polycrystalline CZTS thin films with promising electronic properties. The CZTS absorber layers were grown copper-rich, requiring a KCN etch step to remove excess copper sulfide. The compositional ratios as determined by energy-dispersive X-ray spectroscopy (EDX) after the KCN etch are Cu/(Zn + Sn): 1.0 and Zn/Sn: 1.0. A solar cell with an efficiency of 4.1% and an open-circuit voltage of 541 mV was obtained. Copyright © 2010 John Wiley & Sons, Ltd.