Preferred Molecular Orientation of Coumarin 343 on TiO2 Surfaces: Application to Dye-Sensitized Solar Cells
ACS Applied Materials & Interfaces
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McCree-Grey, J., Cole, J., & Evans, P. (2015). Preferred Molecular Orientation of Coumarin 343 on TiO2 Surfaces: Application to Dye-Sensitized Solar Cells. ACS Applied Materials & Interfaces, 7 16404-16409. https://doi.org/10.1021/acsami.5b03572
The dye…TiO2 interfacial structure in working electrodes of dye-sensitized solar cells (DSCs) is known to influence its photovoltaic device performance. Despite this, direct and quantitative reports of such structure remain sparse. This case study presents the application of X-ray reflectometry to determine the preferred structural orientation and molecular packing of the organic dye, coumarin 343, adsorbed onto amorphous TiO2. Results show that the dye molecules are, on average, tilted by 61.1° relative to the TiO2 surface, and are separated from each other by 8.2 Å. These findings emulate the molecular packing arrangement of a monolayer of coumarin 343 within its crystal structure. This suggests that the dye adsorbs onto TiO2 in one of its lowest energy configurations, i.e. dye…TiO2 self assembly is driven more by thermodynamic rather than kinetic means. Complementary DSC device tests illustrate that this interfacial structure compromises photovoltaic performance, unless a suitably sized co-adsorbant is interdispersed between the coumarin 343 chromophores on the TiO2 surface.
Reflectometry, Dye-Sensitized Solar Cells, Coumarin 343, Molecular Orientation
J. M.-G. acknowledges ANSTO for a part-funded PhD studentship. J. M. C. is grateful to the 1851 Royal Commission for the 2014 Design Fellowship, and Argonne National Laboratory where work done was supported by DOE Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
External DOI: https://doi.org/10.1021/acsami.5b03572
This record's URL: https://www.repository.cam.ac.uk/handle/1810/249020