Electrodeposition methods of gallium and gallium alloy films and related photovoltaic structures

A method of forming a p-type semiconductor layer for a photovoltaic device, comprising:

• electroplating a first layer onto a conductive surface of a substrate, wherein said first layer is selected from the group consisting of a copper layer and a copper-gallium layer;
• electroplating a second layer onto said first layer, wherein said second layer is selected from the group consisting of an indium layer, a gallium layer, an indium-gallium layer, a copper-indium diselenide layer, and a copper-gallium-diselenide layer;
• and optionally
• electroplating a third layer onto said second layer, wherein said third layer is selected from the group consisting of a gallium layer and an indium layer;
• and
• optionally electroplating a fourth layer onto said third layer, wherein said fourth is selected from the group consisting of selenium and sulfur;
• wherein said electroplating is carried out by a method comprising:
• contacting:
• (i) a substrate and (ii) a solution comprising:
• a precursor comprising an element selected from the group consisting of copper, gallium, indium, selenium, sulfur and a combination thereof;
• optionally a metalloid compound additive;
• further optionally an organic additive having at least a sulfur atom;
• and a solvent to dissolve said precursors;
• wherein the solution is free of complexing agents;
• adjusting a pH of said solution to a range selected from the group consisting of a pH of about zero to less than about 2.6 and a pH of about 12.6 to about 14, and applying a current to electroplate said substrate to produce said first, second, third or fourth layers;
• and
• annealing said first, said second and said third layers in the presence of a selenium source and/or sulfur source to form the p-type semiconductor layer.