Search

Abstract: The properties of several types of counter electrodes based on metal, plastic, and glass substrates for use in dye-sensitized solar cells (DSCs) were investigated. High conversion efficiencies of ca. 5% for the DSCs based on a stainless steel, nickel sheet and conducting plastic film were obtained. The sheet resistances of the substrates and the platinized counter electrodes were measured. For the large-size DSCs based on the stainless steel counter electrode, the fill factor and conversion efficiency were improved by 20% by reducing the internal resistance of the cell. The stability of the metal and plastic substrates in the electrolyte and the long-term stability of the solar cell based on these counter electrodes were examined. The results revealed that the stainless steel, Ni, and ITO-PEN electrodes have good stabilities in the electrolyte. [Copyright &y& Elsevier]

The effects of the thickness and morphology of a Pt film coated on a counter electrode on the performance of a dye-sensitized solar cell (DSC) were investigated. Deposition of a Pt film ranging in thickness from 2 to 415 nm gradually decreases the sheet resistance of the counter electrode. No significant difference in the charge-transfer resistance at the electrolyte|counter electrode interface was observed for a Pt film thickness ranging from 25 to 415 nm. A high energy conversion efficiency of approximately 5% can be obtained for DSCs based on a counter electrode with a very thin Pt film of 2 nm, as well as with a 415-nm thick Pt film. These results are important for reducing production costs by reducing the required amount of expensive platinum. [Copyright &y& Elsevier]

The effects of the thickness of Pt film on the property of platinized counter electrode and the performance of the dye-sensitized solar cell (DSC) were investigated. The Pt film sputtered on an FTO glass is constructed of Pt particles, and the grain size of the Pt particles gradually increased with the increase in the Pt film thickness. When the Pt film thickness exceeds 100 nm, further Pt deposition has no significant effect on the conductivity improvement. In the range between 10 and 415 nm, the Pt film thickness has no significant influence on the performance of the DSC. A high conversion efficiency of ca. 5% was obtained by the DSC composed of the counter electrode with Pt film of 10 nm thickness. These results are important for reducing the production cost by reducing the required amount of expensive platinum. [Copyright &y& Elsevier]

An organic-medium screen-printing technique was developed for making porous TiO2 electrodes. The TiO2 pastes were prepared by mixing only 100% polyalkylene glycol and commercial nanocrystalline TiO2 powders. The obtained paste is highly printable and hard to evaporate during printing. The TiO2 electrodes have a very porous structure with large cavities. The dye-sensitized solar cell based on these meso-macroporous TiO2 electrodes exhibits high overall conversion efficiency of 4.3–5.8%, which is comparable to those of prepared by water or terpineol medium. [Copyright &y& Elsevier]

The photochemical and photoelectrochemical properties of two porphyrin derivatives with different numbers of carboxyl groups were investigated. The two porphyrin derivatives are 5-(4-carboxyphenyl)-10,15,20-tritolylporphyrin (H2TC1PP) and 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (H2TC4PP). The interaction between the porphyrin and TiO2 is determined by the UV–vis spectra. Differences in adsorption behavior of the two porphyrin derivatives on the TiO2 electrode surface were observed. The IR data suggest that both of the porphyrins adsorb by bridging or bidentate chelate coordination on the TiO2 surface. Comparing the luminescence spectra of the two porphyrins in solution and the solid state, no spectral difference was observed. However, we found that the variation in the number of carboxyl groups has an influence on the fluorescence spectra of the adsorbed TiO2 electrode. Furthermore, we measured and compared the incident photon-to-current conversion efficiency (IPCE) and the light-to-electrical conversion efficiency of the porphyrin-sensitized solar cell. These results revealed that the number of functional groups influenced the photoelectrochemical properties of the cell. [Copyright &y& Elsevier]

A series of porphyrin derivatives containing carboxylic-, sulfo- and hydro- groups, 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (TCPP), 5,10,15,20-tetrakis(4-sulfophenyl)porphyrin (TSPP) and 5,10,15,20-tetraphenyl-porphyrin (TPP), were examined as sensitizers for porous nanocrystalline TiO2. The difference in the adsorption behavior on the TiO2 electrode surface was discussed. The interaction between the porphyrins and the TiO2 surface was determined and compared using UV–Vis spectra and X-ray photoelectron spectroscopy (XPS). The luminescence spectra of the porphyrins in DMF solution and adsorbed onto TiO2 electrodes were measured. The ionization potentials of the porphyrins in the solid state and adsorbed onto TiO2 electrodes were determined by a new approach using an apparatus for measuring the emission yield under atmospheric conditions. The importance of the binding states between the dye and TiO2 surface was discussed by comparison of the energy conversion efficiency in a dye-sensitized solar cell. The results indicate that the binding state and the amount of adsorbed dye are important factors affecting the properties of the dye-sensitized solar cell. [Copyright &y& Elsevier]

The photoelectrochemical behaviors of the dye-sensitized nanoporous TiO2 solar cell with and without microchannels were studied. A remarkably enhancement in the photocurrent of the cell with the microchannels on the TiO2 electrode was observed. The resistances of the cells were valuated by measuring the electrical impedance. It was found that the resistances of the cell with the microchannels became smaller than those of the cell without microchannnels. These results suggest that the diffusion of the iodide/triiodide species in the electrolyte was promoted. [ABSTRACT FROM AUTHOR]

Titanium films have been deposited on stainless steel metal sheets using dc magnetron sputtering technique at different substrate temperatures. The structure of the titanium films strongly depend on the substrate temperature. The titanium film deposited at the substrate temperature lower than 300°C has a loose flat sheet grains structure and the titanium film prepared at the substrate temperature higher than 500°C has a dense nubby grains structure. The DSSC assembled using stainless steel sheet coated with titanium film deposited at high substrate temperature has a low charge transfer resistance in the TiO2/Ti interface and results in a high conversion efficiency. The DSSC assembled using stainless steel sheet coated with titanium film deposited at temperature higher than 500°C has higher conversion efficiency than that assembled using titanium metal sheet as the substrate. The maximum conversion efficiency, 2.26% is obtained for DSSC assembled using stainless steel sheet coated with titanium film deposited at 700°C substrate temperature, which is about 70% of the conversion efficiency of the FTO reference cell used in this study. [ABSTRACT FROM AUTHOR]

Abstract: The Pt-like electrocatalytic activity of counter electrodes (CEs) prepared from tantalum oxides for dye-sensitized solar cells (DSCs) is demonstrated. The low ratio of oxygen to metal atom of the oxide favors the electrocatalytic activity of these CE materials for I3 − reduction in DSCs. TaO, used as a CE in DSCs, shows superior electrocatalytic activity and a high power conversion efficiency of 6.48%, up to 90.5% of the level obtained using Pt as a CE (7.16%). This work develops the use of novel tantalum oxide CE materials for low cost and high efficiency DSCs. [Copyright &y& Elsevier]

Abstract: Three different types of nanocrystalline, N-doped TiO2 electrodes were synthesized using several nitrogen dopants through wet methods. The obtained nanocrystalline, N-doped TiO2 electrodes possessed different crystallite sizes, surface areas, and N-doping amounts. Characterizations were performed to reveal the nitrogen-doping processes for the wet methods using ammonia, urea, and triethylamine as the nitrogen dopants. Additionally, a high conversion efficiency of 8.32% was achieved by the dye-sensitized solar cells, based on the N-doped TiO2 electrodes. For instance, in comparison with the commercial P25 (5.76%) and pure anatase TiO2 electrodes (7.14%), significant improvements (44% and 17%, respectively) in the efficiencies were obtained. The findings also indicated that the ammonia nitrogen dopant was more efficient than other two nitrogen dopants. The electron transports, electron lifetimes, and charge recombination in the dye-sensitized N-doped TiO2 solar cells also differed from those in the pure TiO2-based dye-sensitized solar cells (DSCs). Specifically, an enhanced photocurrent of ca. 36% in N-doped DSCs resulted from the synergistic effects of the high dye uptake and the efficient electron transport. Moreover, the relationship between charge and voltage revealed that less charge was needed to get a high open-circuit voltage in the N-doping films. [Copyright &y& Elsevier]

Abstract: Twenty natural dyes, extracted from natural materials such as flowers, leaves, fruits, traditional Chinese medicines, and beverages, were used as sensitizers to fabricate dye-sensitized solar cells (DSCs). The photoelectrochemical performance of the DSCs based on these dyes showed that the open circuit voltages (Voc) varied from 0.337 to 0.689V, and the short circuit photocurrent densities (Jsc) ranged from 0.14 to 2.69mAcm−2. Specifically, a high Voc of 0.686V was obtained from the dye extracted from mangosteen pericarp sensitizer. The photo-to-electric conversion efficiency of the DSC sensitized by the ethanol extract of mangosteen pericarp without purification reached 1.17%. Moreover, various components of the ethanol extract were extracted using different organic solvents. The photoelectrochemical performance of these extracts demonstrated that rutin was the most effectual component of the sensitizer for DSC. [Copyright &y& Elsevier]

Abstract: A series of nitrogen-doped and undoped TiO2 nanocrystals was prepared by several simple methods. Needle-like N-doped TiO2 nanocrystals and nanoparticles were obtained from commercial TiO2 powders. Several dye-sensitized solar cells (DSCs) were fabricated based on N-doped and undoped TiO2 electrodes. The N-doped DSCs achieved a high conversion efficiency of 10.1% and 4.8% using an organic electrolyte and an ionic liquid electrolyte, respectively. Systemic investigations were carried out on the properties of N-doped and undoped TiO2 powders, films, and DSCs. The electron transport time and electron lifetime were investigated by intensity-modulated photocurrent and photovoltage spectroscopy (IMPS/IMVS). Moreover, the electron injection of N-doped DSCs was studied by surface photovoltage spectroscopy (SPS). The synergetic effect of higher dye uptake, faster electron transport and higher photovoltage contributes to a higher conversion efficiency of N-doped DSCs. The stability test also demonstrated that the photodegradation of the DSCs was not accelerated and the DSC system was stabilized by the introduction of nitrogen into the TiO2 photoelectrode. These results indicate that the N-doped TiO2 nanocrystals prepared by our approach from commercial TiO2 are ideal semiconductor materials for DSCs. [Copyright &y& Elsevier]

Abstract: Surface treatment of ruthenium dye (Bu4N)2[Ru(dcbpyH)2(NCS)2]-sensitized TiO2 films using diethyl 4-methylphenylphosphonate as a coadsorbent results in large improvements in DSC performance, 24% larger overall conversion efficiency and 55mV higher open-circuit voltage without current penalty. Introducing another two coadsorbents ethyl 4-methylphenylphosphonate and 4-methoxyphenylphosphonic acid brings in negative effects. Analysis by impedance spectroscopy indicated that this was attributed to different numbers of proton-releasing hydroxyl groups of the coadsorbents and consequently different proton-adsorbing chemical environments on the surface of TiO2 photoanodes. [Copyright &y& Elsevier]

Abstract: All-transparent and all-flexible dye-sensitized solar cells (DSCs) were fabricated using a novel, facile, and low-lost friction-transfer technique, which involved assembling TiO2 films on flexible substrates via high-temperature sintering. This friction-transfer technique led to a 25% enhancement in conversion efficiency compared with the compression method. The efficiency of the optimized all-flexible DSC reached 5.7%, which is approximately 73% higher than that of the all-flexible DSC prepared by the low-temperature sintering method (3.3%). [Copyright &y& Elsevier]