Influence of surface area on charge transport and recombination in dye-sensitǐzed TiO2 solar cells

Kai Zhu, Nikos Kopidakis, Nathan R. Neale, Jao Van De Lagemaat, Arthur J. Frank*

*Corresponding author for this work

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189 Citations (Scopus)


The dependence of the electron transport and recombination dynamics on the internal surface area of mesoporous nanocrystalline TiO2 films in dye-sensitized solar cells was investigated. The internal surface area was varied by altering the average particle size in the films. The scaling of the photoelectron density and the electron diffusion coefficient at short circuit with internal surface area confirms the results of a recent study (Kopidakis, N.; Neale, N. R.; Zhu, K.; van de Lagemaat, J.; Frank, A. J. Appl. Phys. Lett. 2005, 87, 202106) that transport-limiting traps are located predominately on the surfaces of the particles. The recombination current density was found to increase superlinearly (with an exponent of 1.40 ± 0.12) with the internal surface area. This result is at odds with the expected linear dependence of the recombination current density on the surface area when only the film thickness is increased. The observed scaling of the recombination current density with surface area is consistent with recombination being transport-limited. Evidence is also presented confirming that photoinjected electrons recombine with redox species in the electrolyte via surface states rather than from the TiO2 conduction band.

Original languageEnglish
Pages (from-to)25174-25180
Number of pages7
JournalJournal of Physical Chemistry B
Issue number50
Publication statusPublished - 21 Dec 2006
Externally publishedYes


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