Effect of starting-solution pH on the growth of Cu2ZnSnS4 thin films deposited by spray pyrolysis

Cu2ZnSnS4 (CZTS) thin films, a potential solar-cell absorber material, have been successfully deposited onto soda lime glass held at a substrate temperature of 643 K. The effect of starting-solution pH on the properties of deposited films is investigated. The solution pH was varied in the range 3.0 to 5.5. The films were characterized by studying their composition, structural, optical and electrical properties. X-ray diffraction studies revealed that polycrystalline CZTS films with kesterite structure could be obtained from a solution with pH = 3.0. However, the films are nonstoichiometric and may contain binary phases in the amorphous form. Films deposited from a solution with pH = 4.5 contain binary phases in addition to CZTS. The lattice parameters of CZTS films are found to be a = 0.542 nm and c = 1.085 nm. The optical bandgap of these films is 1.45 eV and the optical absorption coefficient is > 10(4) cm(-1). (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim