This report describes the optimization activity on the growth processes of Cu2MnSnS4 (CMTS) thin films (TFs), in order to validate this chalcogenide (obtainable from elements highly available in nature) as a new active material for solar cells, alternative to the most known Cu2ZnSnS4 (CZTS). The CZTS deposition for photovoltaic (PV) applications has already been optimized at RSE via a two-phase process involving the deposition of metal precursors by sputtering in the form of a multilayer, to be later treated in an oven together with sulfur. Starting from the protocols already used for CZTS, a comparative study was conducted in this activity to evaluate the versatility of the RSE process for depositing chalcogenide TFs also with other formulations. Through an appropriate selection of targets in the sputtering sources, some series of CMTS samples were deposited to study how the main process parameters influence the chemical-physical characteristics of the TFs, proceeding in a similar way to what has already been done with the CZTS. This approach fosters a better understanding of how the CMTS lends itself to the deposition of TFs for PV, also highlighting the main differences compared to the better known CZTS.
Said work of deposition and characterization of the CMTS TFs was supported by an update and in-depth study of the specific literature on this material; from this it emerged that i) the Mn-based compound includes at least three compounds as possible stable secondary phases quaternaries belonging to the thio-spinel family; and ii) the PV efficiency record is still particularly low (< 1%).
CMTS TFs were extensively characterized at morphological, compositional, and electrical levels in order to identify the best parameters to produce TFs with optimal features for PV applications (e.g., purity, homogeneity, and adhesion). By appropriately selecting some of the features of the CMTS TFs (e.g., purity, thickness) and implementing in the finalization phase the same innovative processes already studied for improving the performance of CZTS-based cells, a record cell with efficiency ≈0.9 % with voltage of ≈430mV (+100mV compared to the literature) could be obtained which proves to be an excellent support for a finer study of correlation between deposition parameters and PV performance.