Control of Doping in Cu2SnS3 through Defects and Alloying

As the world’s demand for energy grows, the search for cost competitive and earth abundant thin film photovoltaic absorbers is becoming increasingly important. A promising approach to tackle this challenge is through thin film photovoltaics made of elements that are abundant in the Earth’s crust. In this work, we focus on Cu2SnS3, a promising earth abundant absorber material. Recent publications have presented 3% and 6% device efficiencies using Cu2SnS3-based absorber materials and alloys, respectively. However, little is understood about the fundamental defect and doping physics of this material, which is needed for further improvements in device performance. Here, we identify the origins of the changes in doping in sputtered cubic Cu2SnS3 thin films using combinatorial experiments and first-principles theory. Experimentally, we find that the cubic Cu2SnS3 has a large phase width and that the electrical conductivity increases with increasing Cu and S content in the films, which cannot be fully explained ...