Photoelectrochemical Characterization of Nanocrystalline Thin-Film Cu2ZnSnS4 Photocathodes

Cu2ZnSnS4 (CZTS) nanocrystals, synthesized by a hot injection solution method, have been fabricated into thin films by dip-casting onto fluorine doped tin oxide (FTO) sustrates. The photoresponse of the CZTS nanocrystal films was evaluted using absorbance measurements along with photelectrochemical methods in aqueous electrolytes, Photoelectochemcial characterization revealed a p-type photoresponse when the films were illuminated in an aqueous Eu3+ redox electrolyte. The effects of CZTS stochiometry, film thickness, and low-temperature annealing on the photocurrents from front and back illuminations suggests that the minority carrier diffusion and recombination at the back contact (Via reaction of photogenerated hose with Eu2+ produced from photoreduction by minority carriers) are the main loss mechanisms in the cell. Low-temperature annealing resulted in significant increases in the photocurrents for films made from both Zn-rich and stoichiometric CZTS nanocrystals.