Activation energy of electron transport in dye-sensitized TiO2 solar cells
2005 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, no 24, 12093-12098 p.Article in journal (Refereed) Published
Various characteristics of dye-sensitized nanostructured TiO2 solar cells, such as electron transport and electron lifetime, were studied in detail using monochromatic illumination conditions. The electron transport was found to be a thermally activated process with activation energies in the range of 0.10-0.15 eV for light intensities that varied 2 orders of magnitude. Electron lifetimes were determined using a new method and found to be significantly larger (> 1 s) than previously determined. An average potential was determined for electrons in the nanostructured TiO2 under illumination in short-circuit conditions. This potential is about 0.2 V lower than the open-circuit potential at the same light intensity. The electron transport time varies exponentially with the internal potential at short-circuit conditions, indicating that the gradient in the electrochemical potential is the driving force for electron transport in the nanostructured TiO2 film. The applicability of the conventionally used trapping/detrapping model is critically analyzed. Although experimental results can be fitted using a trapping/detrapping model with an exponential distribution of traps, the distribution parameters differ significantly between different types of experiment. Furthermore, the experimental activation energies for electron transport are smaller than those expected in a trapping/detrapping model.
Place, publisher, year, edition, pages
2005. Vol. 109, no 24, 12093-12098 p.
nanostructured tio2, photoelectrochemical cells, nanoporous tio2, back-reaction, films, diffusion, kinetics, semiconductor, photocurrent, spectroscopy
IdentifiersURN: urn:nbn:se:kth:diva-14840DOI: 10.1021/jp0513770ISI: 000229867300037ScopusID: 2-s2.0-22444435303OAI: oai:DiVA.org:kth-14840DiVA: diva2:332881
QC 201005252010-08-052010-08-05Bibliographically approved