Non-vacuum thin-film CIGS modules

Non-vacuum techniques have been used to deposit coatings of copper indium gallium selenide (CIGS) and metal oxide transparent conductors useful for fabricating thin-film photovoltaic modules. Coatings are formed from nanoparticulate precursor materials using spraying, printing and spin-coating methods. Sprayed layers exhibit non-planar morphologies and low particle packing, and CIGS films made from sprayed precursor layers exhibit related non-planar morphologies and residual void space. The surface roughness of spray-derived CIGS films reduces the sheet conductance of overlying coatings; thin coatings of transparent conductors deposited on rough CIGS films exhibit sheet resistances up to two orders of magnitude higher than equivalent coatings on planar surfaces. Slurry additives can improve layer morphology and sintered film properties, but organic additives can leave carbon contamination of the sintered CIGS films. The fabrication of multi-cell modules imposes additional constraints on transparent conductor sheet conductance.