Increasing the Oxygen Vacancy Density on the TiO₂ Surface by La-Doping for Dye-Sensitized Solar Cells

Abstract

Facilitated by TiO2 particles absorbing La3+ in hydrosol, La-doped TiO2 was prepared by a sol-hydrothermal method. Electron paramagnetic resonance and Brunauer−Emmett−Teller (BET) surface area analysis showed that the obtained La-doped anatase TiO2 surface provided a higher density of oxygen vacancies without a change in the BET surface area. A theoretical calculation was carried out to explain the generation mechanism of the increased oxygen vacancies. The results showed that the La-doped anatase TiO2 (101) surface tends to engender oxygen vacancies. The photoelectric conversion efficiency of dye-sensitized solar cells fabricated from 1 mol % La-doped TiO2 reached 6.72%, which gave an efficiency improved by 13.5% compared with that of the cells fabricated from pure TiO2. The improvement in the efficiency was ascribed to more dye absorbed on the surface of TiO2.

Brookite TiO2 Nanoparticle Films for Dye‐Sensitized Solar Cells

“…The overall conversion efficiency of solar light to electric power achieved was 5.97 % ( Table 2). Contrary to the observed behavior with anatase TiO 2 , [23] La doping was detrimental to brookite cell performances, even after the TiCl 4 treatment.…”

“…The observed behavior is opposite to that described recently by Zhang et al for the anatase phase. [23] The brookite cell performances were evaluated by recording J-V curves under normalized illumination of the cells (Figures 4 a and 4 b and Table 2). In the first step, DSSCs were prepared with TiO 2 layers not treated with the TiCl 4 solution after sintering and prior to sensitization.…”

“…[22,23] It has been shown recently that lanthanum-containing anatase films give better cell efficiencies due to more dye adsorption, which has been linked to a higher density of oxygen vacancies at the surface. [23] Starting from these data, we have also investigated the brookite particles after their treatment with lanthanum at various concentrations before use in porous film and solar cell fabrication. We have observed that, in this case, particle sintering was improved and the cell open-circuit voltages were higher, but their overall performances were degraded due to a decrease in the short-circuit current density (J sc ).…”

Lanthanum‐Doped TiO2 Nanosheet Film with Highly Reactive {001} Facets and Its Enhanced Photocatalytic Activity

“…[26] The La 3d3/2 and La 3d5/2 peaks at binding energies of 837.6 and 854.2 eV, respectively, agree with the data reported previously for Ti-O-La bonds (Figure 3, c). [27] In summary, the XPS spectra illustrate that the La in the samples exists in the form of Ti-O-La.…”

Deposition of Photocatalytic TiO2 Coating by Modifying the Solidification Pathway in Plasma Spraying

“…The stoichiometry was further found to be a function of process parameters. Zhang et al [15] reported that oxygen vacancies at the surface remarkably prolonged the life of the photon-generated carrier. Thus, it significantly increased the activity.…”