Preferred Molecular Orientation of Coumarin 343 on TiO ₂ Surfaces: Application to Dye-Sensitized Solar Cells

Journal Article · Tue Jul 21 04:00:00 EDT 2015 · ACS Applied Materials and Interfaces

DOI:https://doi.org/10.1021/acsami.5b03572· OSTI ID:1392452

McCree-Grey, Jonathan ^[1]; Cole, Jacqueline M. ^[2]; Evans, Peter J. ^[3]

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1. Cavendish Laboratory, Department of Physics, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom; Australian Nuclear Science and Technology Organisation, Lucas Heights, New South Wales 2234, Australia
2. Cavendish Laboratory, Department of Physics, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom; Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, United States
3. Australian Nuclear Science and Technology Organisation, Lucas Heights, New South Wales 2234, Australia

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.

• Research Organization: Argonne National Laboratory (ANL)
• Sponsoring Organization: USDOE Office of Science - Office of Basic Energy Sciences - Materials Sciences and Engineering Division
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 1392452
• Journal Information: ACS Applied Materials and Interfaces, Journal Name: ACS Applied Materials and Interfaces Journal Issue: 30 Vol. 7; ISSN 1944-8244
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

Reflectometry
coumarin 343
dye-sensitized solar cells
molecular orientation