Method for post-treating an absorber layer

A method for post-treating an absorber layer for photoelectric conversion of incident light into electric current, comprising:

• providing a chalcogen-containing absorber layer on a carrier;
• applying a post-treatment layer on a surface of the absorber layer;
• thermally diffusing the at least one post-treatment material into the absorber layer, during thermal diffusion, selectively increasing a surface termination of the absorber layer by controlling surface termination by chalcogen independently of passivation of the absorber layer by an alkali metal;
• and
• measuring an increased surface S-correlated Raman signal of the absorber layer after the post-treatment to confirm a level of the surface S-correlated Raman signal of the absorber layer,
• wherein the at least one post-treatment material has a dual function as 1) a supplier of the alkali metal for alkali passivation of the absorber layer and also as 2) a supplier of a sulfide for surface termination of the absorber layer with the increased surface S-correlated Raman signal after the post-treatment without or with additional surface cleaning, wherein the post-treatment layer contains exactly one post-treatment material selected from the group consisting of exactly one oxygen compound of an alkali chalcogenide and exactly one hydrogen-oxygen compound of an alkali chalcogenide, wherein only one single alkali element is chemically bound in the post-treatment material.