Influence of deposition time and annealing treatments on the properties of chemically deposited Sn2Sb2S5 thin films and photovoltaic behavior of Sn2Sb2S5-based solar cells

Abstract

Abstract Thin films of chemical bath deposited tin antimony sulphide (Sn2Sb2S5) were tuned by varying the deposition time between 1 and 3 h, and postdeposition heat treatments. The films were grown on soda lime glass (SLG) and on molybdenum glass (Mo-SLG) substrates, respectively. The film thickness increased with deposition time up to 2 h and decreased thereafter. Structural analysis from X-ray diffractometry showed that the films were single phase. This was corroborated by X-ray photoelectron spectroscopy (XPS) analysis. Energy-dispersive spectroscopy results give antimony/sulphur (Sb/S) ratio and antimony/tin (Sb/Sn) ratio that increased with deposition time in the SLG substrates only. Optical constants extracted from optical spectroscopy measurements give optical absorption coefficient (α) > 104 cm−1, and direct energy bandgap with values in the range 1.30 to 1.48 eV. The Hall effect measurements performed on films grown on the SLG substrates indicated that the films were p-type electrical conductivity with electrical resistivity in the range 103 to 104 Ωcm. The films grown on the Mo-SLG served as absorber layers to fabricate thin film heterojunction solar cell devices in the substrate configuration with a cadmium sulphide (CdS) window partner. The best device yielded a short-circuit current density of 20 mA/cm2, open-circuit voltage of 0.012 V and a solar conversion efficiency of 0.04%.