Electrodeposition of CZTS Thin Films for Solar Cells

Thursday, 9 October 2014: 10:50
Expo Center, 1st Floor, Universal 12 (Moon Palace Resort)
M. I. Khalil, R. Bernasconi, S. Ieffa, and L. Magagnin (Politecnico di Milano)
In the present work, Cu2ZnSnS4 (CZTS) thin films were successfully prepared using a coelectrodeposition–annealing route, in which Cu-Zn-Sn metal precursors were deposited by a novel electrolyte formula, followed by annealing in elemental sulfur environment in quartz tube furnace with N2 atmosphere on Mo substrate. The morphological, compositional, structural analyses of the films were investigated using scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction in both cases before and after sulfurization. Raman spectroscopy was also performed on the films after sulfurization to fully characterize the film. Glow discharge optical emission spectroscopy (GDOES) has also been carried out to see how composition changes along the film thickness. Results demonstrated the formation of the CZTS kesterite structure after sulfurization of the film. The result showed that CZTS crystalline properties depend on annealing times and ramping rate during sulfurization. Electrodeposition is a potentially suitable preparation method to obtain low-cost precursors films because it is inexpensive, uses an environment-friendly process, produces large deposition areas and low temperature deposition. Actually it is easier to control different process parameter during coelecrodeposition of Cu-Zn-Sn rather than sequential electrodepositon of Cu/Zn/Sn. In case of coelctrodeposited precursors, most of the researcher used an acidic electrolyte where tri sodium citrate used as complexing agent. In our studies a novel basic electrolyte formula was used where the salt of Cu2+, Zn2+ and Sn4+ were complexed in a better way with respect to the acidic electrolyte. The co-electrodeposited metallic precursor’s films were subsequently sulfurized in a quarts tube furnace in an elemental sulfur environment with N2 atmosphere. Raman spectroscopy confirmed the presence of kesterite CZTS in the films. Results on other characteristics have also shown how the annealing times and ramping rates during sulfurization influence the grain size and impurities (other binary/ ternary phases).