Direct-coated Cu2SnS3 films from molecular solution inks for solar photovoltaics

Cu-based solution/ink coated sulphides have gained tremendous interest in last few years for low-cost solar cells. In this paper, pure copper tin sulphide films have been directly-coated from two different types of molecular solution inks developed with ethylene glycol and ethylene glycol - isopropyl alcohol mixture. Structural, compositional and microstructural properties of direct-coated films were studied and compared. The formation of pure tetragonal copper tin sulphide is confirmed by X-ray diffraction and Raman spectroscopy analysis. Overall it is found that films deposited from ethylene glycol - isopropyl alcohol mixture (glycoholic ink) are comparatively smoother and denser. An X-ray photoelectron study confirms the presence of Cu+ state in the films. The films are photoconducting and show p-type conduction. In general, microstructure of the films was found to depend upon type of solvents.