Electroplating Solutions and Methods For Deposition of Group IIIA-VIA Films

A method of forming an absorber layer over a surface of a base, the method comprising:

• forming a metal layer over the surface of the base, wherein the metal layer comprises a Group IIIA material;
• co-depositing Group IIIIA and Group VA materials to form a Group IIIA-VIA layer on the metal layer using pulse electroplating that varies an electroplating pulse between a first higher value and a second lower value, wherein at the first higher value electroplating of at least one of Ga and In predominates, and wherein at the second lower value electroplating of one of Se, Te and S predominates, wherein the step of co-depositing the Group IIIA-VIA layer uses a roll-to-roll electroplating process wherein the base having the metal layer is continuously advanced within an electroplating solution held in a deposition chamber as at least one electric field is formed between at least one anode to deposit the Group IIIA-VIA layer onto the metal layer;
• and
• reacting the metal layer and the Group IIIA-VIA layer to form the absorber layer.