New routes to sustainable photovoltaics: evaluation of Cu2ZnSnS4 as an alternative absorber material



Thin film heterojunction solar cells based on chalcopyrites such as Cu(In,Ga)Se2 have achieved impressive efficiencies. However concern about the long term sustainability of photovoltaics based on scarce or expensive raw materials has prompted the search for alternative absorber materials. In this work, films of the p-type absorber Cu2ZnSnS4 (CZTS) were prepared by electroplating metallic precursors sequentially onto a molybdenum-coated glass substrate followed by an nealing in a sulfur atmosphere. The polycrystalline CZTS films were characterized by photoelectrochemical methods, which showed films were p-type with doping densities of the order of 1016 cm–3 and a band gap of 1.49 eV, close to the optimum value for terrestrial solar energy conversion. Preliminary results obtained for solar cells fabricated with this material are promising. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)