title: Role of the triiodide/iodide redox couple in dye regeneration in p-type dye-sensitized solar cells.
abstract: A series of perylene dyes with different optical and electronic properties have been used as photosensitizers in NiO-based p-type dye-sensitized solar cells. A key target is to develop dyes that absorb light in the red to near-infrared region of the solar spectrum in order to match photoanodes optically in tandem devices; however, the photocurrent produced was found to decrease dramatically as the absorption maxima of the dye used was varied from 517 to 565 nm and varied strongly with the electrolyte solvent (acetonitrile, propionitrile, or propylene carbonate). To determine the limitations of the energy properties of the dye molecules and to provide guidelines for future sensitizer design, we have determined the redox potentials of the diiodide radical intermediate involved in the charge-transfer reactions in different solvents using photomodulated voltammetry. E°(I(3)(-)/I(2)(•-)) (V vs Fe(Cp)(2)(+/0)) = -0.64 for propylene carbonate, -0.82 for acetonitrile, and -0.87 for propionitrile. Inefficient regeneration of the sensitizer appears to be the efficiency-limiting step in the device, and the values presented here will be used to design more efficient dyes, with more cathodic reduction potentials, for photocathodes in tandem dye-sensitized solar cells.
authors.affiliation: Department of Physical and Analytical Chemistry, Uppsala University, Box 259, SE-751 05 Uppsala, Sweden. elizabeth.gibson@nottingham.ac.uk
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Gibson
authors.forename: Loïc
authors.initials: L
authors.lastname: Le Pleux
authors.forename: Jérôme
authors.initials: J
authors.lastname: Fortage
authors.forename: Yann
authors.initials: Y
authors.lastname: Pellegrin
authors.forename: Errol
authors.initials: E
authors.lastname: Blart
authors.forename: Fabrice
authors.initials: F
authors.lastname: Odobel
authors.forename: Anders
authors.initials: A
authors.lastname: Hagfeldt
authors.forename: Gerrit
authors.initials: G
authors.lastname: Boschloo