Life cycle environmental impacts from CZTS (copper zinc tin sulfide) and Zn3P2 (zinc phosphide) thin film PV (photovoltaic) cells

Abstract

While solar PV (photovoltaic) cells are promising for clean energy production, their mass deployment is hindered by production costs, material availability, and toxicity. Two materials that can overcome these challenges and replace today's CdTe (cadmium telluride) and CIGS (copper indium gallium diselenide) based PV cells are Zn3P2 (zinc phosphide) and CZTS (copper zinc tin sulfide). A cradle to gate life cycle assessment was conducted to understand the environmental impacts from these technologies. The impacts from Zn3P2 and CdTe were similar and lower than the impacts from CZTS and CIGS. While CdTe has the toxic Cd element, the ecotoxicity impact from material acquisition and processing was higher for Zn and P than for CdTe. In CIGS, the ecotoxicity impact came mainly from Ga and would be significantly reduced if CZTS were to replace CIGS in the commercial market. For all four thin films studied, the contribution of raw materials to total impact was much lower than the impact coming from electricity consumption during the manufacturing stage. Therefore, to reduce environmental impact, future PV technology development should focus more on the process improvement. The manufacturing stages that contributed most to the impact were the absorber layer for CIGS and CZTS and the substrate cleaning for CdTe and Zn3P2.