A reappraisal of the electron diffusion length in solid-state dye-sensitized solar cells

J R Jennings, L M Peter

Research output: Contribution to journalArticle

78 Citations (Scopus)

Abstract

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 L-n = (D tau)(1/2), where D and tau are, respectively, the diffusion coefficient and lifetime of mobile electrons. A new approach to the reliable estimation of L-n 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 L-n. 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 L-n is significantly greater than had been thought previously.
Original languageEnglish
Pages (from-to)16100-16104
Number of pages5
JournalJournal of Physical Chemistry C
Volume111
Issue number44
DOIs
Publication statusPublished - 2007

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electron diffusion
diffusion length
solar cells
dyes
solid state
Electrons
electrons
short circuits
Titanium
Fermi level
anodes
diffusion coefficient
conductors
titanium
Short circuit currents
trapping
Anodes
life (durability)
Dye-sensitized solar cells

Cite this

A reappraisal of the electron diffusion length in solid-state dye-sensitized solar cells. / Jennings, J R; Peter, L M.

In: Journal of Physical Chemistry C, Vol. 111, No. 44, 2007, p. 16100-16104.

Research output: Contribution to journalArticle

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AB - 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 L-n = (D tau)(1/2), where D and tau are, respectively, the diffusion coefficient and lifetime of mobile electrons. A new approach to the reliable estimation of L-n 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 L-n. 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 L-n is significantly greater than had been thought previously.

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