Thermal Processing and Characterizations of Dye-Sensitized Solar Cells Based on Nanostructured TiO₂

Abstract

This work reports an extensive study about the effects of thermal treatments on the performance of TiO 2based dye-sensitized solar cells. The morphologic, structural, luminescence, and electrical properties of the as-prepared TiO 2 electrode are first analyzed by using several diagnostic techniques. In particular, by extensive cathodoluminescence and photocurrent measurements it is possible to determine the energy band diagram of the material intragap levels and to observe their influence in both radiative and photoinduced transport properties. The TiO 2 electrodes have been annealed at 500 °C for 1, 4, and 8 h in argon or in oxygen environment and then used to develop different DSSCs. The oxygen annealed solar cells show a monotonic increase in the efficiency from 6.75 up to 7.30; meanwhile, the argon-annealed solar cells have an efficiency that remains slightly constant around 6.85. By comparing the behavior of all cells parameters with the CL properties of the annealed TiO 2 electrodes, it is possible to determine a correspondence between the short circuit current densities of the DSSCs and the variation of the intragap states in the semiconductor layer induced by annealing.

Single oxygen vacancies of (TiO2)35as a prototype reduced nanoparticle: implication for photocatalytic activity

“…27,64,65 Therefore PBEx functional seems to be appropriate for the DFT calculation of TiO 2 NP on the basis of the calculated ∆ H-L value. Hence, the structures and data calculated using PBEx are mainly presented for the sake of simplicity.…”

“…24 The defect states originating from trapped electrons appear around 1.0 eV below the conduction band minimum (CBM), which induces band gap narrowing as optimal value for photocatalyst. 23,[25][26][27] Herein, we systemically investigate the properties of stoichiometric (TiO 2 ) 35 anatase NP and neutral single oxygen removed one. The bipyramidal (TiO 2 ) 35 NP, maintaining anatase structure after geometrical relaxation, seems to be a proper model to study the physical and electronic properties of oxygen vacancy in TiO 2 NP by comparing those of bulk and slab surface.…”

Metastability of anatase: size dependent and irreversible anatase-rutile phase transition in atomic-level precise titania

“…To explain the metastability of anatase and the phase difference in the crystal-nucleus-size titania, we have proposed a kinetic control nucleation model from a combinational viewpoint of polymer chemistry and coordination chemistry instead of thermodynamics. The basic understanding of the thermal properties contributes to improving the energy conversion efficiency of DSCs by 10% through the thermal annealing process of TiO 2 nanocrystalline film for better connection between nanocrystals without the phase change and size growth, as recently reported50. Since the phase control is important for nano materials and devices, we still need the further works to understand and control the crystal phase of nanocrystals.…”

Laser-Induced Anatase-to-Rutile Transition in TiO2 Nanoparticles: Promotion and Inhibition Effects by Fe and Al Doping and Achievement of Micropatterning

“…8 In addition, it has been recently found that a mixed anatase/rutile phase exhibits an enhancement of the TiO 2 photocatalytic performance, 9,10 with relevant consequences in the improvement of the production of hydrogen from water or the efficiency of dye-sensitized solar cells. 7 Hence, optimized TiO 2 applicability in this field can be achieved through precise control of the phase composition. In that way, efforts are directed toward the controlled growth of stabilized anatase and rutile single and mixed phases, as well as the understanding of the anatase to rutile transition.…”