Electrodeposition of germanium-containing precursors for Cu2(Sn,Ge)S3 thin film solar cells

•Electrodeposition-based method for the fabrication of Cu2(Sn,Ge)S3 absorber layers.•Electrodeposition of smooth and compact layers containing Cu, Sn and Ge was achieved.•Direct electrodeposition of Ge and Cu-Ge alloys from an organic solvent.•Electrodeposition of Cu-Ge thin films with stable [Cu]/[Ge] ratio around 3.•Functioning solar cell device obtained from electrodeposited and annealed absorber.