The present document reports on further experimental activities performed and results obtained at RSE’ labs regarding the validation of two new chalcogenides, Cu2MnSnS4 (CMTS) and Cu2FeSnS4 (CFTS), as alternative materials to the better known Cu2ZnSnS4 (CZTS) as active materials based on elements with high natural abundance for thin film (TF) photovoltaic (PV) cells.

During this task of the project, a detailed characterization of CMTS TF samples have been carried out at the level both of the final PV device (by admittance spectroscopy (AS)) and of the active material only (by XPS analysis), with the aim to understand the origin of the gap between the apparent good quality of the FS, deposited at RSE with a two-step process, and the limited performance of the respective PV cells. A new set of CMTS samples has been also deposited to study the reciprocal correlation among the TF chemical composition, the presence of compositional gradients (in particular for Sn) along the thickness of the TF and secondary phase formation.

The AS measurements highlighted the presence of different defects between CZTS and CMTS TFs and confirmed how the post deposition treatments (PDT), optimized to improve the performance of CZTS-based cells, are also positive for CMTS-based PV devices. The presence of oxygen, detected in the CMTS TFs by XPS analysis, seems to be the most critical aspect that justify the very low PV performance detected for all the CMTS samples deposited up to now.

As far as CFTS is concerned, having abandoned the possibility to deposit TF of this chalcogenide by the two-phase process commonly used in RSE, we proceeded to the synthesis of this material by a new process in order to obtain mono-crystalline grains (monograin). The aims is to use this grains to develop TF solar cells based an innovative approach known like “monograin-layer technology (MGL)”.

The synthesis of CFTS mono-grains has been studied and optimized to obtain particles that show: small granulometric dispersion, conformational homogeneity and high crystallographic purity. Exploring new applications of this chalcogenide in the electro-energetic field, CFTS has also been preliminarily tested as an anode material for sodium ion batteries .

The Report is available on the Italian site