title: Tetracoordinated Bis-phenanthroline Copper-Complex Couple as Efficient Redox Mediators for Dye Solar Cells.
abstract: A tetracoordinated redox couple, made by [Cu(2-mesityl-4,7-dimethyl-1,10-phenanthroline)2][PF6], 1, and its Cu(II) form [Cu(2-mesityl-4,7-dimethyl-1,10-phenanthroline)2][PF6]2, 2, has been synthesized, and its electrochemical and photochemical features have been investigated and compared with those of a previously published Cu(2+)/Cu(+) redox shuttle, namely, [Cu(2,9-dimethyl-1,10-phenanthroline)2][PF6], 3, and its pentacoordinated oxidized form [Cu(2,9-dimethyl-1,10-phenanthroline)2Cl][PF6], 4. The detrimental effect of the fifth Cl(-) ancillary ligand on the charge transfer kinetics of the redox shuttles has been exhaustively demonstrated. Appropriately balanced Cu-based electrolytes have been then formulated and tested in dye solar cells in combination with a π-extended benzothiadiazole dye. The bis-phenanthroline Cu-complexes, 1 and 2, have been found to provide an overall 4.4% solar energy conversion efficiency, which is more than twice that of the literature benchmark couple, 3 and 4, employing a Cl-coordinated oxidized species and even comparable with the performances of a I(-)/I3(-) electrolyte of analogous concentration. A fast counter-electrode reaction, due to the excellent electrochemical reversibility of 2, and a high electron collection efficiency, allowed through the efficient dye regeneration kinetics exerted by 1, represents two major characteristics of these copper-based electron mediators and may constitute a pivotal step toward the development of a next generation of copper-based efficient iodine-free redox shuttles.
authors.affiliation: Dipartimento di Chimica, Università di Milano , UdR dell'INSTM, Via Golgi, Milano, Italy.
authors.forename: Mirko
authors.initials: M
authors.lastname: Magni
authors.affiliation: CBN-Fondazione Istituto Italiano di Tecnologia, Via Barsanti, Arnesano (Lecce), Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Giannuzzi
authors.affiliation: Dipartimento di Chimica, Università di Milano , UdR dell'INSTM, Via Golgi, Milano, Italy.
authors.forename: Alessia
authors.initials: A
authors.lastname: Colombo
authors.affiliation: CBN-Fondazione Istituto Italiano di Tecnologia, Via Barsanti, Arnesano (Lecce), Italy.
authors.forename: Maria Pia
authors.initials: MP
authors.lastname: Cipolla
authors.affiliation: Dipartimento di Chimica, Università di Milano , UdR dell'INSTM, Via Golgi, Milano, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Dragonetti
authors.affiliation: Dipartimento di Scienze Chimiche e Farmaceutiche, Università di Ferrara , Via F. di Mortara, Ferrara, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Caramori
authors.affiliation: Dipartimento di Scienze Chimiche e Farmaceutiche, Università di Ferrara , Via F. di Mortara, Ferrara, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Carli
authors.affiliation: CBN-Fondazione Istituto Italiano di Tecnologia, Via Barsanti, Arnesano (Lecce), Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Grisorio
authors.affiliation: CBN-Fondazione Istituto Italiano di Tecnologia, Via Barsanti, Arnesano (Lecce), Italy.
authors.forename: Gian Paolo
authors.initials: GP
authors.lastname: Suranna
authors.affiliation: Dipartimento di Scienze Chimiche e Farmaceutiche, Università di Ferrara , Via F. di Mortara, Ferrara, Italy.
authors.forename: Carlo Alberto
authors.initials: CA
authors.lastname: Bignozzi
authors.affiliation: Dipartimento di Chimica, Università di Milano , UdR dell'INSTM, Via Golgi, Milano, Italy.
authors.forename: Dominique
authors.initials: D
authors.lastname: Roberto
authors.affiliation: CBN-Fondazione Istituto Italiano di Tecnologia, Via Barsanti, Arnesano (Lecce), Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Manca