AVS 64th International Symposium & Exhibition
    Nanometer-scale Science and Technology Division Wednesday Sessions
       Session NS+SS+SU-WeM

Paper NS+SS+SU-WeM10
Magnetron Sputtered Nanostructured TiO2 Thin Films for Dye Sensitized Solar Cells Applications

Wednesday, November 1, 2017, 11:00 am, Room 19

Session: Nanotechnology for Renewable Energy
Presenter: Pierre-Antoine Cormier, ChIPS, University of Mons, Belgium
Authors: P.-A. Cormier, ChIPS, University of Mons, Belgium
J. Dervaux, ChIPS, University of Mons, Belgium
Y. Pellegrin, CEISAM, University of Nantes, France
F. Odobel, CEISAM, University of Nantes, France
R. Snyders, ChIPS, University of Mons, Belgium
Correspondent: Click to Email
Among the many advantages of Dye Sensitive Solar Sells (DSSCs), their non-toxic and low cost components, their lightweight and their high performances under diffuse light and high temperatures are very interesting. DSSCs are therefore considered as a promising alternative to conventional Si and chalcogenide based solar cells. In DSSCs, the light is absorbed by dye molecules inducing an electron injection into a TiO2 nanoparticles (NPs)-based photo-anode. Although this allows a high photon collection, the charge transport is limited by charge recombination at the NPs boundaries limiting the solar to conversion efficiency [1]. Many efforts have been devoted to rule this problem such as replacing NPs by nanofils, nanotubes or hierarchical nanostructured thin films which offer a direct path way to electrons [1]. We previously shown that such hierarchical structure can be obtained by reactive magnetron sputtering (RMS) at grazing incidence which allows to tune the film morphology from slanted nanoculmns, to zigzag or pillars [2].

In this work, such films were synthesized and annealed during 2h at 773 K under atmospheric pressure in order to obtain nanocolumns composed by a single anatase crystal as verified by TEM. These films were used as photo-anode in liquid DSSCs, which were characterized under simulated AM1.5 Global spectrum and 1sun illumination. Different morphologies (slanted columns, zigzag and pillars) and different thicknesses of slanted columns based films were studied. In addition, the dye grafting efficiency on these structures was evaluated by absorbance measurements performed by UV-Visible spectrophotometry.

The slanted columns-based cells present the best performances followed by zigzag and pillar based ones. This result is directly related to the corresponding specific surface area which is the highest for the slanted columns films. By increasing the thickness of the slanted films from 1.2 to 4.3 μm, the cell efficiency increases from 1.2 to 2.6 %. As the short-circuit current density also increased while the open circuit voltage was not affected, it was concluded that the critical parameter limiting the cell efficiency is the adsorbed dye density, which is enhanced for thicker films

To overcome this limitation still using thin films, the slanted columns films were impregnated by TiO2 NPs (~20nm). This allows for an enhancement of the cell efficiency by 2.2% attributed to a synergetic effect between: (i) a higher dye adsorption and (ii) and the very good charge transport through the single crystalline columns.

[1] A. Hagfeldt et al. “Dye-Sensitized Solar Cells,” 2010

[2] J. Dervaux et al., Vacuum, vol. 114, pp. 213–220, Nov. 2014.