Dependence of TiO₂ Nanoparticle Preparation Methods and Annealing Temperature on the Efficiency of Dye-Sensitized Solar Cells

Abstract

Performances of dye-sensitized solar cells prepared from nanoporous TiO 2 films with different TiO 2 nanoparticle preparation methods and different annealing temperatures are studied with various film thicknesses. The results show that the solar cells prepared at higher annealing temperatures have higher energy conversion efficiencies. Regarding film thickness, thin film electrode solar cells annealed at low-temperature show comparable efficiencies with those of the cells annealed at high temperature. The difference of the efficiency between the cells with the film annealed at different temperatures increases with the film thickness. To explain the observations, the surface area of the films, the amount of the adsorbed dye, and the diffusion coefficient and lifetime of electrons are measured. The amount of adsorbed dye per unit area is found to be independent of annealing temperature, while the diffusion coefficient and lifetime increase with the temperature. With trapping models, the measured increases of the diffusion coefficient with annealing temperature are interpreted with the change of the charge-trap density and neck growth between particles, which are suggested by transmission electron microscope and surface area measurements of the films. Diffusion lengths of electrons for each solar cell estimated from the diffusion coefficient and lifetime increase with annealing temperature. From the comparison between the short circuit currents of the solar cells with the diffusion lengths, it is concluded that the higher efficiencies of the solar cells prepared from high-temperature annealed films are attributed to their longer diffusion lengths of electrons.

Laser Forward Transfer of Electronic and Power Generating Materials

“…In the current work, cells made with an optimum thickness of 15 m exhibited a J sc of 10.1 mA/cm 2 , V oc of 0.64 V, a fill factor (ff) of 0.65, and a light power conversion efficiency () of ~ 4.3 %. The conversion efficiency is comparable to those reported earlier for analogous cells fabricated with commercial TiO 2 powders (P25) using traditional techniques (Okuya, 2002;Nakada, 2002;Hinsch, 2001). …”

“…10. Over the last decade, DSSCs based on nc-TiO 2 films have been extensively studied as possible alternatives to silicon-based solar cells due to their high power conversion efficiencies (~ 10%) and expected low materials and manufacturing costs (O'Regan, 1991;Nazeeruddin, 1993;Barbe, 1997;Nakada, 2002). Mesoporous nc-TiO 2 layers with high surface area are essential for achieving high efficiency in the DSSC system because a large amount of dye can be adsorbed on the surface of the nc-TiO 2 particles resulting in an increased solar light absorption and an increased reacting interface per unit area.…”

Excited state properties of anodic TiO2 nanotubes

“…An optimum annealing temperature of 400-500 C was found to result in efficient charge transfer. 17,18 TiO 2 nanostructures annealed below 400 C exhibit low charge collection efficiency. The latter has been rationalized on grounds of small electron diffusion coefficients, owing to altered trap state distributions and sintering of crystallites inside the nanostructures.…”

“…The latter has been rationalized on grounds of small electron diffusion coefficients, owing to altered trap state distributions and sintering of crystallites inside the nanostructures. 16,18 In the present work, we report on the impact of thermal treatments on the photophysical properties of TiO 2 nanotubes and compare the results with commercially available TiO 2 nanoparticles. For this, optically transparent samples were obtained by fabrication of TiO 2 nanostructures on a glass support.…”

Recent Overview of Solar Photocatalysis and Solar Photo-Fenton Processes for Wastewater Treatment

“…A batch mode reactor exposed to sunlight using a mirror concentrator. 12 International Journal of Photoenergy Sol-gel method using titanium butoxide 16 International Journal of Photoenergy nanoparticles, and TiO 2 thin films strongly depends on the synthesis methods [144][145][146][147][148][149]. Three different phases of TiO 2 have been reported which depend on the heat treatment like anatase, rutile, and brookite, anatase and rutile phases being commonly prepared [8,9,11,145,149].…”