Manganese-substituted Kesterite thin films for Earth-abundant photovoltaic applications

Thin film low-cost and eco-friendly photovoltaic devices are based on Cu2ZnSn(S,Se)4. To reduce production costs and improve sustainability, manganese can substitute zinc since Mn is safe and Earth-abundant, and it can be used as a light absorber1) Here, we report on the growth and characterization of Cu2MnSnS4 thin films, produced both by a two-step deposition process and by a sol-gel-based method. The metallic precursors have been deposited by sputtering, and the stack annealed at high temperatures in sulphur atmosphere. The layers, obtained in a Cu-poor and Mn-poor compositional regime, have been tested in solar devices with a record efficiency of 1.13%, with an open-circuit voltage of about 445 mV, delivered after over one year from the first PV measurement. X-ray diffraction and photoelectron, Raman, photoluminescence, and admittance spectroscopies have been used to characterize Cu2MnSnS4, and a scenario of high defectivity has emerged.2) Therefore, we moved to a sol-gel-based method, to improve the quality of the material reducing defectivity. An ink, prepared by dissolving in dimethylsulfoxide metal salts and thiourea, used as the only source of sulphur, was deposited by blade coating to obtain thin films. Sol-gel transition took place in air and then samples were annealed at 550°C under argon atmosphere. The so obtained thin films were fully characterized showing promising preliminary results. References: 1)Le Donne A., Trifiletti V., Binetti S., Front. Chem, 2019, 7:297. 2)Trifiletti V., Frioni L., Tseberlidis G., Vitiello E., Danilson M., Grossberg M., Acciarri M., Binetti S., Marchionna S., Solar Energy Materials & Solar Cells, 2023, 254 112247