Copper Bipyridyl Redox Mediators for Dye-Sensitized Solar Cells with High Photovoltage

0466347 - ÚFCH JH 2017 RIV US eng J - Článek v odborném periodiku
Saygili, Y. - Söderberg, M. - Pellet, N. - Giordano, F. - Cao, Y. - Munoz-García, A. B. - Zakeeruddin, S. M. - Vlachopoulos, N. - Pavone, M. - Boschloo, G. - Kavan, Ladislav - Moser, J. E. - Grätzel, M. - Hagfeldt, A. - Freitag, M.
Copper Bipyridyl Redox Mediators for Dye-Sensitized Solar Cells with High Photovoltage.
Journal of the American Chemical Society. Roč. 138, č. 45 (2016), s. 15087-15096. ISSN 0002-7863. E-ISSN 1520-5126
Grant CEP: GA ČR GA13-07724S
Institucionální podpora: RVO:61388955
Klíčová slova: Conversion efficiency * Copper * Dye-sensitized solar cells
Kód oboru RIV: CG - Elektrochemie
Impakt faktor: 13.858, rok: 2016

Redox mediators play a major role determining the photocurrent and the photovoltage in dye-sensitized solar cells (DSCs). To maintain the photocurrent, the reduction of oxidized dye by the redox mediator should be significantly faster than the electron back transfer between TiO2 and the oxidized dye. The driving force for dye regeneration with the redox mediator should be sufficiently low to provide high photovoltages. With the introduction of our new copper complexes as promising redox mediators in DSCs both criteria are satisfied to enhance power conversion efficiencies. In this study, two copper bipyridyl complexes, Cu(II/I)(dmby)2TFSI2/1 (0.97 V vs SHE, dmby = 6,6′-dimethyl-2,2′-bipyridine) and Cu(II/I)(tmby)2TFSI2/1 (0.87 V vs SHE, tmby = 4,4′,6,6′-tetramethyl-2,2′-bipyridine), are presented as new redox couples for DSCs. They are compared to previously reported Cu(II/I)(dmp)2TFSI2/1 (0.93 V vs SHE, dmp = bis(2,9-dimethyl-1,10-phenanthroline). Due to the small reorganization energy between Cu(I) and Cu(II) species, these copper complexes can sufficiently regenerate the oxidized dye molecules with close to unity yield at driving force potentials as low as 0.1 V. The high photovoltages of over 1.0 V were achieved by the series of copper complex based redox mediators without compromising photocurrent densities. Despite the small driving forces for dye regeneration, fast and efficient dye regeneration (2-3 μs) was observed for both complexes. As another advantage, the electron back transfer (recombination) rates were slower with Cu(II/I)(tmby)2TFSI2/1 as evidenced by longer lifetimes. The solar-to-electrical power conversion efficiencies for [Cu(tmby)2]2+/1+, [Cu(dmby)2]2+/1+, and [Cu(dmp)2]2+/1+ based electrolytes were 10.3%, 10.0%, and 10.3%, respectively, using the organic Y123 dye under 1000 W m-2 AM1.5G illumination.
Trvalý link: http://hdl.handle.net/11104/0264665