Enhancing the Efficiency of SnS Solar Cells bia Band-Offset Engineering with a Zinc Oxysulfide Buffer Layer

Abstract

SnS is a promising earth-abundant material for photovoltaic applications. Heterojuction solar cells were made by vapor deposition of p-type tin(II) sulfide, SnS, and n-type zinc oxysulfide, Zn(O,S), using a device structure of soda-lime glass/Mo/SnS/Zn(O,S)/ZnO/ITO. A record efficiency was achieved for SnS-based thin-film solar cells by varying the oxygen-to-sulfur ratio in Zn(O,S). Increasing the sulfur content in Zn(O,S) raises the conduction band offset between Zn(O,S) and SnS to an optimum slightly positive value. A record SnS/Zn(O,S) solar cell with a S/Zn ratio of 0.37 exhibits short circuit current density ((J_{sc})), open circuit voltage ((V_{oc})), and fill factor (FF) of (19.4 mA/cm^{2}), 0.244 V, and 42.97%, respectively, as well as an NREL-certified total-area power-conversion efficiency of 2.04% and an uncertified active-area efficiency of 2.46%.