Electrochemical Characterization of TiO 2 Blocking Layers for Dye-Sensitized Solar Cells

Ladislav Kavan, Nicolas Tétreault, Thomas Moehl, Michael Grätzel

Research output: Contribution to journalArticlepeer-review

203 Scopus citations


Thin compact layers of TiO2 are grown by thermal oxidation of Ti, by spray pyrolysis, by electrochemical deposition, and by atomic layer deposition. These layers are used in dye-sensitized solar cells to prevent recombination of electrons from the substrate (FTO or Ti) with the hole-conducting medium at this interface. The quality of blocking is evaluated electrochemically by methylviologen, ferro/ferricyanide, and spiro-OMeTAD as the model redox probes. Two types of pinholes in the blocking layers are classified, and their effective area is quantified. Frequency-independent Mott-Schottky plots are fitted from electrochemical impedance spectroscopy. Certain films of the thicknesses of several nanometers allow distinguishing the depletion layer formation both in the TiO2 film and in the FTO substrate underneath the titania film. The excellent blocking function of thermally oxidized Ti, electrodeposited film (60 nm), and atomic-layer-deposited films (>6 nm) is documented by the relative pinhole area of less than 1%. However, the blocking behavior of electrodeposited and atomic-layer-deposited films is strongly reduced upon calcination at 500 °C. The blocking function of spray-pyrolyzed films is less good but also less sensitive to calcination. The thermally oxidized Ti is well blocking and insensitive to calcination. © 2014 American Chemical Society.
Original languageEnglish (US)
Pages (from-to)16408-16418
Number of pages11
JournalThe Journal of Physical Chemistry C
Issue number30
StatePublished - Jan 14 2014
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUS-C1-015-21
Acknowledgements: This work was supported by the EC 7th FP project SANS (contract no. NMP-246124), by the COST Action CM1104, and by the Grant Agency of the Czech Republic (contract no. 13-07724S). This work was also partially supported by the ECR Advanced Grant Agreement no. 247404 under the CE-Mesolight project and by the Center for Advanced Molecular Photovoltaics (Award No KUS-C1-015-21), made by King Abdullah University of Science and Technology (KAUST).
This publication acknowledges KAUST support, but has no KAUST affiliated authors.


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