Electrochemical Properties of Cu(II/I)-Based Redox Mediators for Dye-Sensitized Solar Cells. (10th February 2017)

• Record Type: Journal Article
• Authors: Kavan, Ladislav; Saygili, Yasemin; Freitag, Marina; Zakeeruddin, Shaik M.; Hagfeldt, Anders; Grätzel, Michael
• Is Part Of: Electrochimica acta. Volume 227(2017)
• Page Start: 194
• Page End: 202
• Publication Date: 2017-02-10
• Subjects: Graphene -- Dye sensitized solar cell -- Cu-complexes -- Redox mediators; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2016.12.185
• Languages: English
• ISSNs: 0013-4686

Abstract

Graphical Abstract: Highlights: The electrocatalytic activity of graphene-based catalysts is outperforming that of platinum for the Cu(II/I) redox mediators. The charge-transfer kinetics and the diffusion rate significantly slowdown in the presence 4 -tert -butylpyridine. Electrochemically clean Cu(II)-bipyridine complexes are prepared by electrochemical oxidation of the parent Cu(I) complexes. Abstract: Three Cu(II/I)-phenanthroline and Cu(II/I)-bipyridine redox mediators are studied on various electrodes and in variety of electrolyte solutions using cyclic voltammetry and impedance spectroscopy on symmetrical dummy cells. Graphene-based catalysts provide comparably high activity to PEDOT, and both catalysts outperform the activity of platinum. The charge-transfer kinetics and the diffusion rate significantly slowdown in the presence 4 -tert -butylpyridine. This effect is specific only for Cu-mediators (is missing for Co-mediators), and is ascribed to a sensitivity of the coordination sphere of the Cu(II)-species to structural and substitutional changes. The 'Zombie Cells' made from symmetrical PEDOT/PEDOT devices exhibit enhanced charge-transfer rate and enhanced diffusion resistance. Electrochemically clean Cu(II)-bipyridine species are prepared, for the first time, by electrochemical oxidation of the parent Cu(I) complexes. Our preparative electrolysis brings numerous advantages over the standard chemical syntheses of the Cu(II)-bipyridine complexes. The superior performance of electrochemically-grown clean Cu(II)-bipyridine complex is demonstrated on practical dye-sensitized solar cells.