Effects of 350 degrees C preheating of electrochemically stacked Cu-Sn-Zn layers in an inert atmosphere on structural and morphological properties of quaternary kesterite Cu2ZnSnS4 (CZTS) films obtained by sulfurization of the metallic layers were investigated. When the CZTS film was fabricated without the 350 degrees C preheating, the film contained a secondary Cu2SnS3 phase and other impurities. The CZTS film also showed poor adhesion to the bottom molybdenum (Mo) substrate with many crevices and voids in the film; a very thick MoS2 layer was formed at the top part of the Mo layer. These structural failures of the CZTS film were significantly reduced when the metallic precursor was preheated at 350 degrees C before sulfurization for 20 min: the CZTS film thus-obtained exhibited no secondary phases, good adhesion to the bottom Mo layer, flat and densely packed surface morphology, no appreciable crevices or voids, and formation of a relatively thin MoS2 layer. Based on results of studies on structural transformations during 350 degrees C preheating and successive sulfurization, such differences in properties of resulting CZTS films are attributed to differences in formation pathways. Moreover, since 350 degrees C preheating for a longer duration was found to be detrimental for the properties of resulting CZTS films, there should be an optimum duration of preheating to achieve a good CZTS film for solar cell application. As expected from these properties, the solar cell with an Al:ZnO/CdS/CZTS/Mo structure derived from the metallic precursor preheated at 350 degrees C for 20 min showed the best conversion efficiency of 5.6%. (C) 2013 Elsevier B.V. All rights reserved.