Investigation of cobalt redox mediators and effects of TiO₂ film topology in dye-sensitized solar cells

Abstract

One-electron outer-sphere redox couples, such as cobalt metal-organic complexes, represent an interesting alternative as redox mediators in dye-sensitized solar cells since they show weak visible light absorption and available redox potentials may lead to higher open circuit voltage values. Here, we have studied the effect of using different substituents on bipyridyl and phenanthroline ligands in cobalt redox shuttles, giving the following complexes: Co[tris(4,4 0 -dimethoxy-2,2 0 -bipyridine)(PF 6 ) 2 ], Co[tris(4,4 0dichloro-2,2 0 -bipyridine)(PF 6 ) 2 ] and Co[tris(4,7-dichloro-1,10-phenanthroline)(CF 3 SO 3 ) 2 ], displaying a range of CoII/CoIII redox potentials from +0.37 to +0.79 V vs. NHE. The regeneration kinetics of the organic dye D35 was found to depend systematically on the redox mediator potential, which was explained using Marcus theory. The mass transport of cobalt mediators in dye-sensitized solar cells is highly dependent on the porosity, effective surface area and roughness of the mesoporous TiO 2 films.Therefore, films with different TiO 2 pore sizes were prepared and investigated to gain an insight into the topological effects of TiO 2 film preparation in order to obtain optimum solar cell performance.

Cyclic voltammetry data of polypyridine ligands and Co(II)-polypyridine complexes

“…1.63 V vs FcH/FcH + (preliminary assigned to anionic nitrate oxidation). The data obtained in this data article, compares well with available published data on some of the redox events for some of the complexes, namely complex 1 [5] , [6] , [7] , [8] , [9] , [10] , complex 2 [11] , [12] , [13] and complex 5 [11] ; obtained under different experimental conditions (different solvents, scan rates and supporting electrolytes). The linear responses obtained for the graphs of the peak currents vs the square root of the scan rate, for three main redox events in the CV of complex 1 (see Fig.…”

Electrochemical data of Co(II) complexes containing phenanthroline functionalized ligands

“…Data for the irreversible anionic nitrate oxidation peak at ca 1.63 V vs FcH/FcH + , is not included in the tables. The data obtained in this study, compare good with available published data on some of the complexes, namely complex 2 [5] , complex 4 [6] , [7] , [8] , [9] , complex 7 [9] and complex 8 [9] , obtained under different experimental conditions (different solvents, scan rates and supporting electrolytes).

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Solar energy conversion using first row d-block metal coordination compound sensitizers and redox mediators

“…They concluded that porosity and pore size must be modied for different combinations of dyes and electrolytes in order to minimize the diffusion limitations of the cobaltbased redox mediator, 91 and these conclusions are consistent with those of Boschloo and coworkers. 92 Co 3+ /Co 2+ redox mediators: ruthenium(II) dyes…”