Strategic improvement of Cu2MnSnS4 films by two distinct post-annealing processes for constructing thin film solar cells

Abstract The synthesis approach using a non-toxic solution-based method accompanied with special post-annealing processes demonstrates the great potential to realize industrial manufacture of earth-abundant materials for sustainable photovoltaics. Exploration of an appropriate post-annealing process is significant to gain insight into the crystallization of solar materials. The earth-abundant Cu 2 MnSnS 4 (CMTS) thin films were fabricated by post-sulfuring as-prepared precursors and the results have been compared with that of directed-annealed samples. It was found that the sulfurization procedure not only can support to enhance the crystallinity but also help to obtain a nearly stoichiometric CMTS thin film which also free of SnS secondary phase. This reaction also contributes to sustainable incorporation of S into CMTS to a considerable extent and formation of notable large grains; whereas, it leads to the formation of a typical bi-layer microstructure containing large grains (500–800 nm) on the top and fine grains at the bottom. Through the sulfurization approach, the device performance is improved with the power conversion efficiency shows a 170% increase which mainly via the boost of open circuit and fill factor compared with that of direct-annealed processed. These results offers a novel research direction for preparing pure-sulfide CMTS thin film for the potential application in low-cost solar cells.