Different Routes of Fixed pH to Electrodeposit Cu2ZnSnS4 for Photovoltaic Devices

Abstract

Cu2ZnSnS4 films have been prepared by sulfurizing ternary and quaternary precursors electrodeposited on conducting glass. Citrate and hydroxyl concentrations were used to adjust the pH value in 5.9 and they produce deposits with different properties. The deposits were characterized by X-ray diffraction, multi-laser Raman spectroscopy, scanning electronic microscopy, energy-dispersive X-ray spectroscopy, UV?Vis spectroscopy and photoelectrochemical techniques. Raman spectroscopy and X-ray diffraction results confirmed the formation of crystalline CZTS after sulfurization. Photocurrent analysis confirmed the p-type nature of the semiconductor. Cu2ZnSnS4 films obtained with short electrodeposition times are good-quality absorbers suitable to be used in superstrate thin films solar cells. The bath composition together with the acidity level of the precursor bath needs to be adjusted together, in order to adequate the electrodeposition of Cu2ZnSnS4 to the characteristics of different substrates. The most promising results were obtained when using the lowest citrate concentration. This is likely related to the proportion of Zn in the precursor deposit. The incorporation of S to the precursor bath resulted in no particular benefit. This element is efficiently incorporated during annealing in sulfur vapor and seems to be detrimental for the morphology when present in the electrodeposition precursor bath.