Reducing series resistance in Cu₂ZnSn(S,Se)₄ nanoparticle ink solar cells on flexible molybdenum foil substrates

Earth abundant Cu₂ZnSnS₄ nanoparticle inks were deposited on molybdenum foil substrates and subsequently converted to high quality thin film Cu₂ZnSn(S,Se)₄ photovoltaic absorbers. Integration of these absorbers within a thin film solar cell device structure yields a solar energy conversion efficiency which is comparable to identical devices processed on rigid glass substrates. Importantly, this is only achieved when a thin layer of molybdenum is first applied directly to the foil. The layer limits the formation of a thick Mo(S,Se) layer resulting in a substantially reduced series resistance.