Fabricating thin-film optoelectronic devices with modified surface

A method of fabricating thin-film optoelectronic devices, the method comprising:

• providing a substrate;
• forming a back-contact layer;
• forming at least one absorber layer, which absorber layer is made of an ABC chalcogenide material, wherein A represents one or more elements selected from a group consisting of Cu and Ag, B represents one or more elements selected from a group consisting of In, Ga, and Al, and C represents one or more elements selected from a group consisting of S, Se, and Te;
• adding at least one alkali metal, wherein adding the at least one alkali metal causes at least one crystal aggregate comprising at least one alkali crystal to form on a surface of the absorber layer;
• forming at least one cavity at the surface of the absorber layer by dissolving away from said surface of the absorber layer the at least one alkali crystal, wherein the forming at least one cavity comprises:
• wetting at least the surface of the absorber layer with an aqueous solution comprising ammonia;
• and
• then forming a buffer layer over the surface of the absorber layer, wherein the buffer layer comprises an element selected from the group of cadmium, zinc, indium and gallium.