Ink for producing compound semiconductor thin film, compound semiconductor thin film produced using the ink, solar cell having compound semiconductor the thin film, and process for producing solar cell

An ink for forming a compound semiconductor thin film comprising:

• an organic solvent;
• a binder comprising a compound comprising an S atom or an Se atom, the binder being dispersed in the organic solvent;
• and
• metallic compound particles dispersed in the organic solvent, the metallic compound particles being a compound semiconductor comprising Cu, Zn, Sn and at least one of S and Se, wherein
• the compound comprising an S atom or an Se atom is represented by the following chemical formula:
• X represents an S atom or an Se atom, and R1, R2, R3, and R4 independently represent a hydrogen atom or an alkyl group or an aryl group having 1 to 10 carbon atoms,
• the metallic compound particles and the binder are such that
• the metallic compound particles contain an Se atom and the binder contains an S atom and optionally an Se atom,
• the metallic compound particles contain an S atom and the binder contains an Se atom and optionally an S atom, or
• the metallic compound particles contain an S atom and an Se atom and the binder contains at least one of an S atom and an Se atom, and
• an S/(S+Se) molar ratio of a mixture of the binder contained in the ink and the metallic compound particles is from 0.05 to 0.9.