Photoelectrochemical Behavior of Bismuth-Containing Cu2ZnSnS4 (CZTS) Absorber Layers for Photovoltaic Applications

Abstract

Fast and straightforward characterization of semiconductors is crucial for the efficient progress of new generation light-harvesting materials. Photoelectrochemical characterization, in particular, is a powerful method to understand the relative quality of semiconductors. Cu2ZnSnS4 (CZTS) is a promising eco-friendly and earth-abundant absorber for photovoltaic applications. The efficiency of CZTS, however, can be improved by rational manipulation of crystal, morphology, and doping. In this work, we study the incorporation of bismuth into CZTS films in order to improve its crystal quality. Electrodeposited Cu-Zn-Sn-Bi (CZTB) metallic precursors were grown from a single deposition bath and were sulfurized, resulting in CZTS layers containing < 1 at% bismuth. Investigation of crystallographic features of resulting CZTS-Bi layers provided insight into the doping role of Bi. Composition was determined by EDS and structural properties, the degree of ordering was analyzed with XRD and Raman Spectroscopy. Finally, we investigated the correlation between phase purity and photoelectrochemical response of materials. Structural analyses suggest that the Zn-rich sample presents better phase purity and improved crystallinity compared to Sn-rich samples. The grain size of relatively phase pure samples is larger in Zn-rich CZTS than the plain CZTS layers. The highest photoresponse of 2.65 mA/cm2 is observed at a Zn-rich CZTS-Bi layer.