Cu2ZnSnS4 Thin Film Solar Cells Produced by Thiourea Complexes Suspension

Cu2ZnSnS4 (CZTS) thin films are grown by a two step process aimed for low toxicity requirements and relatively low temperature annealing in S2 atmosphere. The chemical process developed is based on the metal complexation plus the thermolysis of thiourea to form a highly condensed precursor film. The reagents used are copper acetate, zinc acetate and thiourea dissolved in methanol. Ethylene glycol and polyvinyl alcohol are employed as additives to improve filmation. The suspension obtained is deposited by drop-casting on soda-lime glasses with a layer of sputtered molybdenum and annealed at 450 °C in sulfur vapors obtaining a good quality microcrystalline CZTS phases. Preliminary solar cells fabricated using a CdS buffer layer show an efficiency of about 1%.