Effect of Extractant pH and Concentration of Ageratum Conyziodes L on the Optical Properties of Photosensitizer and Performance of Dye-Sensitized Solar Cell

ZnO is an interesting material for application in the dye-sensitized solar cell (DCS) related to the large variety of low-temperature synthesis methods that allow for easy manipulation of the morphology and texture of the material. In particular, electrodeposition of crystalline ZnO can be achieved at room temperature, making it an excellent method for the preparation of solar cells based on flexible plastic substrates. We will present results on the performance of dye-sensitized solar cells based on electrodeposited ZnO, describing the electrodeposition method in detail, and compare the results to ZnO-based solar cells prepared using sol-gel synthesis and CVD. The morphology and texture are expected to influence the performance of the dye solar cell via a variety of effects. For instance, the exposed crystal facets may affect the dye bonding, dye coverage, and injection efficiency, the electron transfer kinetics to the solution, and the trap state distribution [1]. Using these materials, we have compared the electron transport and recombination properties using small-signal perturbation techniques [2]. We have also addressed the influence of solution additives on the performance of ZnO-based dye-sensitized solar cells and rationalized the results. The influence of surface facet exposure on dye bonding is highlighted.

Contact angle measurement: A preliminary diagnostic method for evaluating the performance of ZnO platelet-based dye-sensitized solar cells

Chapter 5 - TiO2-based dye-sensitized solar cells

This study reports the effect of sintering time on the performance of the dye-sensitized solar cells with turmeric dyes as sensitizers. Sintering TiO2 semiconductors were conducted at a temperature of 450°C for 30, 50, 90, 120, 150, and 180 minutes. The natural dye was extracted from dried turmeric powders with ethanol solvent. The results show that size of grains and the opening area of TiO2 semiconductor depended on the sintering time. The improvement of the properties of TiO2 semiconductor allowed more turmeric dyes were adsorbed by the semiconductors and then improved the performance of solar cells. The sintering time of 150 minutes produced large grains with an average diameter of 68.87 nm, and a porosity area of 26.51% caused the performance of DSSCs was the highest among other sintering time. The Voc, Jsc, and efficiency of DSSCs with turmeric-based natural dyes 0.64 V, 0.47 mA/cm2, and 0.2%, respectively.

Nanoporous TiO2 thin film electrodes were fabricated based on incorporating various amounts of carbon spheres into TiO2 paste followed by thermal treatment. The size of carbon spheres was prepared from 100 to 200 nm. The TiO2 electrodes modified with carbon spheres were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and UV-visible spectrophotometer. The performances of dye-sensitized solar cells with carbon-sphere-modified TiO2 anodes were investigated. The experimental results indicated that 1.0 wt% of carbon spheres with the size of 100 nm added into TiO2 anode had the most favorable effect on the performance of dye-sensitized solar cells compared with other quantities and sizes. The incipient performance of the dye-sensitized solar cell in the investigation was: a Voc of 0.71 V, a Jsc of 12.00 mA cm-2, a i¬ll factor of 56.92% and an efficiency of 4.85%, which was enhanced comparing with that of carbon-free TiO2 electrode under the same experimental conditions. The results revealed the possibility of fabricating dye-sensitized solar cells using nanometer-sized carbon spheres. Key words: Carbon spheres, TiO2 films, dye-sensitized solar cell.

To clarify the relationships between the performance of dye-sensitized solar cells and their internal resistances, we applied ac impedance spectroscopy to the analysis of the cells. Impedance and measurements of solar cells were carried out for various cell compositions and measurement conditions such as different kinds of conductive glass substrates, two kinds of counter electrodes, calcination temperature, applied bias, and distance between electrodes; in order to separate internal resistances which occur at different interfaces. Impedance spectra of dye-sensitized solar cells showed that their internal resistance consisted of at least five components. It was found that the resistance of a conductive glass substrate appeared as ohmic resistance, and that electron transfer at F-doped (FTO)/ Pt/electrolyte, and /electrolyte interfaces was identified as the internal resistances determinative to the performance of dye-sensitized solar cells. Internal resistances at Pt/electrolyte and the resistance of conductive glass affected the fill factor. Internal resistances at and /electrolyte mainly affected the photocurrent. Particularly, the /electrolyte was significant as the interface controlling photocurrent of the dye-sensitized solar cell. The impedance stemming from the diffusion of the electrolyte had little effect on the performance of the cells. © 2005 The Electrochemical Society. All rights reserved.

The effects of changing ligand structures of cobalt complexes as electrolytes on the performance of the dye-sensitized solar cell were investigated. In this paper, cobalt(II/III) tris(2,2′-bipyridine), cobalt(II/III) tris(4,4′-dimethyl-2,2′-bipyridine) and cobalt(II/III) tris(4,4´-dimethoxy-2,2′-bipyridine) complexes as electrolytes in conjugate with organic dye D149 were investigated to consider the correlation of the cobalt complexes structural on the efficiency of the dye-sensitized solar cell. The Voc values of the prepared cells are related to the redox potential of their complexes and the maximum Voc was observed with cobalt(II/III) tris(2,2′-bipyridine) electrolyte. The obtained results represented that the cobalt(II/III) tris(4,4´-dimethyl- 2,2′-bipyridine) electrolyte has the highest efficiency in the solar cell compared with other cobalt complexes. These observed results have been interpreted by a possible interaction between the dye and cobalt complexes, which is more pronounced in the cobalt(II/III) tris(4,4´-dimethoxy- 2,2′-bipyridine) cell. This interaction should be fine-tuning with the structure of dye and complex to increase the efficiency of the dye-sensitized solar cell. In addition, the results demonstrated that a thinner layer of the TiO2 film decrease both the effects of mass transport issues and the charge recombination, therefore, it has significant advantages for cobalt electrolyte.

Au-doped mesoporous SiO2 scattering layer enhances light harvesting in quasi Solid-State dye-sensitized solar cells

Under varying certain conditions, different extraction methods (acidic solvent, mechanical and ultrasonic-assisted extractions) for improving the photovoltaic performance of dye-sensitized solar cells (DSSCs) are proposed by modifying sensitizers obtained from cornelian cherry (Cornus mas L.). The structural, optical and electrical characteristics of the samples are analyzed with Fourier transform infrared (FT-IR), UV–vis absorbance and the current-voltage measurements, respectively. FT-IR spectra of extracted dyes demonstrate the spectrum of anthocyanin. The UV–vis absorption spectra of the dye-loaded photoanodes are strongly dependent on the nature of extraction. Compared with of that of cells based on mechanical press and ultrasonic-assisted methods, a remarkable increase in the efficiency of the cell based on the acidic solvent extraction method is found. The modification of the sensitizer predominantly enhances the short circuit current. Among the extraction methods, the citric acid based solvent extraction is verified to be superior to others in terms of power conversion efficiency. Addressing this point provides a clear pathway to boost the efficiency from 0.47% to 0.98%. Our report opens a path for utilization of a novel bio-based/natural dye extracted with different methods as sensitizers for DSSCs, which might potentially improve the performance of DSSCs by determining a suitable method to extract dye from fruits.

The effect of the addition of ionic liquids with four different cations (imidazolium, pyrrolidinium, piperidinium and pyridinium) on the performance of dye-sensitized <TEX>$TiO_2$</TEX> solar cells based on electrolytes containing a t-butylpyridine (TBP) in 3-methoxypropionitrile (MPN) was studied. A total of 18 ionic liquids with mono-, di- and tri-alkyl derivatives were used in the present study, and among them a pyridinium cation with a mono-alkyl group showed better cell efficiency than the others. The best photoelectric conversion efficiency, 7.213%, was obtained using 1-hexylpyridinium iodide with an open-circuit photovoltage (<TEX>$V_{oc}$</TEX>) = 0.731 V, a short-circuit photocurrent density (<TEX>$J_{sc}$</TEX>) = 16.175 <TEX>$mA/cm^2$</TEX>, and a fill factor (ff) = 0.610 under AM1.5 and 100 <TEX>$mW/cm^2$</TEX> illumination.

Synergistic effects of high temperature and impact compaction on the nano-TiO2 film for the significant improvement of photovoltaic performance of flexible dye-sensitized solar cells

In dye-sensitized solar cells (DSSCs), materials classified as Transparent Conducting Oxides (TCOs) have the capacity to conduct electricity and transmit light at the same time. Their exceptional blend of optical transparency and electrical conductivity makes them popular choices for transparent electrodes in DSSCs. Fluorine Tin Oxide (FTO) was utilized in this experiment. The optical and electrical characteristics of TCOs may be negatively impacted by their frequent exposure to hostile environments and potential for deterioration. TCOs are coated with passivating layers to increase their performance, stability, and defense against environmental elements including oxygen, moisture, and chemical pollutants. Because of its superior dielectric qualities, strong chemical stability, and suitability with TCO materials, aluminum oxide (Al2O3) was utilized as a passivating layer for the FTO. In this research work, Al2O3 was deposited via atomic layer deposition (ALD) to form thin mesoporous layers as a passivator in the photoanode (working electrode). The work focuses on finding an appropriate thickness of Al2O3 for optimum performance of the dye-sensitized solar cells. The solar simulation and sheet resistance analysis clearly showed 200 cycles of Al2O3 to exhibit an efficiency of 4.31%, which was the most efficient performance. The surface morphology and topography of all samples were discussed and analyzed.

A flat thin TiO2 film was employed as the photo-electrode of a dye sensitized solar cell (DSSC), on which only a geometrical mono-layer of dye was attached. The effect of surface protonation by HCl chemical treatment on the performance of DSSCs was studied. The results showed that the short-circuit current Jsc increased significantly upon the HCl treatment, while the open-circuit voltage Voc decreased slightly. Compared to the untreated DSSC, the Jsc and energy conversion efficiency was increased by 31% and 25%, respectively, for the 1 mol/L HCl treated cell. TiO2 surface protonation improved electronic coupling between the chemisorbed dye and the TiO2 surface, resulting in an enhanced electron injection. The decreased open-circuit voltage after TiO2 surface protonation was mainly due to the TiO2 conduction band edge downshift and was partially caused by increased electron recombination with the electrolyte. In situ Raman degradation study showed that the dye stability was improved after the TiO2 surface protonation. The increased dye stability was contributed by the increased electron injection and electron back reaction with the electrolyte under the open-circuit condition.

We report preparation and improvement in photovoltaic performance of N719-based dye-sensitized solar cells (DSSCs) using pressurized carbon dioxide (CO2) as a co-solvent for the absorption process on the TiO2 photoelectrode surface. Effective absorption of the N719 molecules on the TiO2 surface was achieved using CO2 processing, and the absorption time was shortened drastically from 24 h (in the dip process) to less than 3 h. The cells prepared under pressurized CO2 for the absorption showed greater photovoltaic performance, especially higher short-circuit current density and conversion efficiency, compared with that from typical dip method. It was revealed that the suitable CO2 pressure for the absorption was 5 MPa and the efficiency was achieved to be more than 7.5 %. Prevention of back electron transfer reactions from TiO2 to oxidized dyes or iodides was caused currently, because the homogeneous coverage of N719 molecules on the TiO2 surface was obtained by the use of pressurized CO2.

Five novel perylene molecules with different intramolecular charge-transfer (ICT) characters have been synthesized. The relation between the ICT character for different donating groups and the results for their electro- and photochemical properties as well as their performance in nanostructured dye-sensitized solar cells (nDSC) are reported. With the stronger donors, we obtain a shift of the lowest unoccupied molecular orbital (LUMO) to more negative potential versus normal hydrogen electrode (NHE) as well as an increase the charge separation in the dye upon excitation. Ab initio calculations were used to analyze the effects on orbital energies and electron distribution with the different donors. Incorporating the dyes in nDSCs, we see a drastical improvement in the performance for the more polar dyes. In particular, we find a much improved photovoltage because of higher LUMO levels, allowing conduction band tuning in the TiO2 as well as a contribution from the permanent dipoles in the dyes. The photocurr...