Preparation of (Cu,Ag)2SnS3 Thin Films by Sulfurization and Their Application to Solar Cells

Abstract

(Cu,Ag)2SnS3 (CATS) thin films and solar cells have been fabricated by sulfurization process for the first time and their properties have been investigated. In first experiment, the stacked NaF/(Ag+Cu)/Sn precursor deposited by sequential evaporation of Sn, Ag and Cu elements and NaF followed by crystallization in selenium/tin mixing atmosphere for 30 min at 570°C. The Ag/(Ag+Cu) mole ratio and the grain sizes in the thin films increased with increasing the Ag/(Ag+Cu) mole ratio in the evaporation materials. In second experiment, two kinds of precursors constructed by NaF/(Ag+Cu)/Sn (Precursor A) and NaF/Sn/(Ag+Cu) (Precursor B) were crystallized by annealing in selenium/tin mixing atmosphere for 30 min at the various temperature. The open circuit voltage Voc in the CATS solar cells prepared from precursor B were larger than those from precursor A. The grain growth in CATS thin films was observed with increasing the sulfurization temperature. The best performance of the CATS solar cell fabricated from precursor B at the sulfurization temperature of 530°C corresponded to an open circuit voltage of 257mV, a short circuit current density of 9.31 mA/cm2, a fill factor of 0.26, and an efficiency of 0.61%, which was the first report of the photovoltaic effect for CATS thin film.