Electrochemical Characterization of TiO2 Blocking Layers for Dye-Sensitized Solar Cells
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- 作者：Ladislav Kavan ; Nicolas T茅treault ; Thomas Moehl ; Michael Gr盲tzel
- 刊名：Journal of Physical Chemistry C
- 出版年：2014
- 出版时间：July 31, 2014
- 年：2014
- 卷：118
- 期：30
- 页码：16408-16418
- 全文大小：518K
- ISSN：1932-7455
文摘
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鈥揝chottky 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 掳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.