Earth-Abundant Thin Film Solar Cells Based on Cu2MnSnS4

An attractive solution for the preparation of In and Ga free chalcogenides which may allow terawatt range photovoltaic (PV) applications relies on I2-II-IV-VI4 species, such as copper zinc tin sulfide/selenide. A further alternative belonging to this class of materials is Cu2MnSnS4 (CMTS), which consists of abundant and non-toxic elements and shows high absorption coefficient and direct band gap suitable for PV applications. In this work, CMTS thin films were grown on Mo-coated soda lime glasses by a two-step process (evaporation in vacuum of the metal precursors followed by annealing in sulfur vapors). SLG/Mo/Sn/Cu/Mn stack structures were sulfurized at 585°C with an initial step at 115°C to enhance the metal intermixing, paying particular attention to the control of Mn/Sn ratio and to the effect of different annealing ramping rate. Some proof of concept PV device based on Cu-poor/Mn-rich CMTS samples were prepared and tested (efficiency 0.6%, open-circuit voltage 303 mV, short-circuit current density 5.1 mA/cm2, fill factor 38.5%). The beneficial effects of low temperature post-deposition annealing were also investigated, which provided literature record performance (efficiency 0.83%, open-circuit voltage 354 mV, short-circuit current density 5.8 mA/cm2, fill factor 40%)