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A Reappraisal of the Electron Diffusion Length in Solid-State Dye-Sensitized Solar Cells

2007; American Chemical Society; Volume: 111; Issue: 44 Linguagem: Inglês

10.1021/jp076457d

1932-7455

James R. Jennings, Laurence M. Peter,

Transition Metal Oxide Nanomaterials

The performance of dye-sensitized solar cells (DSCs) depends on the competition between transport and interfacial recombination of electrons. A key parameter in this context is the electron diffusion length, which is given by Ln = (Dτ)1/2, where D and τ are, respectively, the diffusion coefficient and lifetime of mobile electrons. A new approach to the reliable estimation of Ln is described, which involves use of a titanium contact to measure the short-circuit value of the electron quasi-Fermi level on the side of the TiO2 film furthest from the anode contact. This information is used to define conditions under which the effects of electron trapping/detrapping can be eliminated from the calculation of Ln. The method is illustrated by measurements of a solid-state DSC based on the organic hole conductor 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)9,9'-spirobifluorene (spiro-OMeTAD), which show that Ln is significantly greater than had been thought previously.