Environmental performance of Kesterite monograin module production in comparison to thin-film technology

Kesterite-based structures are being extensively studied for solar module productions due to their earth abundant and nontoxic nature, high absorption coefficient, and a wide variety of scalable deposition methods. Kesterites are mostly manufactured using thin-film technology. However, in the last decade, the monograin approach has gained further attention, providing a third alternative to mono-crystalline wafer and thin film methods. This is due to its high throughput, low-cost deposition techniques, flexibility, and light weight. Despite the technical advancements in the monograin technology, their environmental impacts have not been studied in the literature. This paper, for the first time, presents a cradle to gate environmental life cycle assessment of CZTS monograin module production. The analysis is designed to identify the environmental hotspots associated with materials, energy usage, and manufacturing processes. The results were compared to CZTS thin-film and the commercially available CIGS technologies. The analyses suggested that the front contact accounted for the majority of impact in all categories due to the use of silver. The normalisation results showed that the marine aquatic ecotoxicity impact category dominated the overall impact results. A comparison of CZTS monograin and thin film production demonstrated that monograin outperformed the thin film technology when silver was substituted with alternative materials and was proximate to CIGS even considering their higher achieved efficiency. The analysis presents considerable environmental benefits associated with the monograin technology. Further savings in emissions could be achieved with improved conversion efficiency and usage of renewable energy sources in the manufacturing stages.