Design and characterization of a chloride-free organic copper solution: Electrochemical synthesis of Zn/Cu/Sn precursor stack for CZTS-based photoconversion devices

• Published in: Electrochimica acta 2021-03, Vol.372, p.137857, Article 137857
• Main Authors: Panzeri, G., Dell'Oro, R., Sansotera, M., Marchionna, S., Parravicini, J., Acciarri, M., Binetti, S., Magagnin, L.
• Format: Article
• Language: English
• Subjects: Aqueous solutions; Bias; Chemical synthesis; Complexation; Copper; Correlation analysis; Current efficiency; Diethanolamine; Displacement; Ethylene glycol; Heterostructures; Organic medium; Photoelectric effect; Photoelectric emission; Photoelectrode; Precursors; Raman spectroscopy; Submerging; Tin; Water splitting; X-ray diffraction; Zinc
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2021.137857

•Innovative procedure to electrodeposit copper onto zinc from an ethylene-glycol-based copper solution.•Immersion potential measurements demonstrate a slower displacement reaction rate at increasing diethanolamine concentration.•Diethanolamine (DEA) can form amine-complexes with copper in an ethylene-glycol-based solution.•Mo(sub)/Zn/Cu/Sn stack can be obtained by plating copper on zinc. In the present study, an ethylene glycol-based electrolyte is used to electrodeposit copper onto zinc for the synthesis of the Zn/Cu/Sn stack, precursor of Cu2ZnSnS4. The employed solution contains diethanolamine (DEA) which supports the formation of amine-complexes, whose features are studied by UV–vis absorption, ESI-MS, and FTIR measurements, providing insight on the optimal concentration of DEA for copper complexation. Cyclic voltammetries (CVs) are carried out at increasing [DEA]/[Cu2+] ratios, highlighting the amine effect on the reduction potential of the copper species. The displacement reaction between copper and zinc is investigated by immersion potential measurements, showing a direct correlation to the voltammetric data. The optimized copper solution resulted in a negligible displacement contribution, allowing the electrochemical synthesis of Mo(sub)/Zn/Cu/Sn stack on a relatively large area (4 cm2). The metallic precursor is analyzed by SEM/EDS, AFM, XRD, and GDOES techniques. Finally, the kesterite CZTS phase is obtained through reactive annealing with elemental sulfur and it is characterized by SEM/EDS, XRD, and Raman spectroscopy. Photoelectrochemical water splitting on CZTS/CdS/Pt heterostructure is carried out in an aqueous solution at pH 6.85, showing a photocurrent of -5.05 mA/cm2 at 0 V vs RHE. A maximum applied bias photon-to-current efficiency (ABPE) value of 2.15% was found at 0.84 V bias. [Display omitted]