Dye-sensitized solar cells: sensitizer-dependent injection into ZnO nanotube electrodes

Synthesis of Ag/TiO2 nanocomposite via plasma liquid interactions: Improved performance as photoanode in dye-sensitized solar cell

Ag/TiO₂ nanocomposite was prepared by the atmospheric direct current plasma in aqueous solution to improve its performance in dye-sensitized solar cells (DSSCs) as the photoanode. The fabricated DSSC shows high power conversion efficiency over 6.5% and displays better long-term stability than that of referenced pure TiO₂. The comparison of photoluminescence spectra of Ag/TiO₂ and pure TiO₂ showed that only the Ag containing samples had notable photocurrent under visible light, which was attributed to the highly dispersed Ag, according to the EDS and XRD measurements. The short-circuit current density (Jsc) and open-circuit voltage (Voc) reached 13.43 mA cm^-2 and 0.72 V in Ag/TiO₂, and 9.44 mA cm^-2 and 0.68 V in pure TiO₂, respectively. The performance improvement in Ag/TiO₂ DSSC may occur due to the declined band-gap energy, retarded charge recombination and greater surface coverage of the sensitizing dye over Ag/TiO₂ nanocomposite.

Porphyrin Dye-Sensitized Zinc Oxide Aggregated Anodes for Use in Solar Cells

Porphyrin YD2-o-C8-based dyes were employed to sensitize room-temperature (RT) chemical-assembled ZnO aggregated anodes for use in dye-sensitized solar cells (DSSCs). To reduce the acidity of the YD2-o-C8 dye solution, the proton in the carboxyl group of a porphyrin dye was replaced with tetrabuthyl ammonium (TBA⁺) in this work. The short-circuit current density (Jsc) of the YD2-o-C8-TBA-sensitized ZnO DSSCs is higher than that of the YD2-o-C8-sensitized cells, resulting in the improvement of the efficiency of the YD2-o-C8-based ZnO DSSCs. With an appropriate incorporation of chenodeoxycholic acid (CDCA) as coadsorbate, the Jsc and efficiency of the YD2-o-C8-TBA-sensitized ZnO DSSC are enhanced due to the improvement of the incident-photon-to-current efficiency (IPCE) values in the wavelength range of 400-450 nm. Moreover, a considerable increase in Jsc is achieved by the addition of a light scattering layer in the YD2-o-C8-TBA-sensitized ZnO photoanodes. Significant IPCE enhancement in the range 475-600 nm is not attainable by tuning the YD2-o-C8-TBA sensitization processes for the anodes without light scattering layers. Using the RT chemical-assembled ZnO aggregated anode with a light scattering layer, an efficiency of 3.43% was achieved in the YD2-o-C8-TBA-sensitized ZnO DSSC.

Panchromatic engineering for efficient zinc oxide flexible dye-sensitized solar cells using porphyrin and indoline dyes

Panchromatic engineering of room temperature chemically assembled ZnO anodes with low acidity porphyrin and indoline dyes for use in flexible solar cells.

Synthesis, photophysical characterization, and photoelectrochemical evaluation of a palladium porphyrin sensitizer for TiO2-based dye-sensitized solar cells

An unsymmetrical (A3B) palladium porphyrin bearing a cyanoacrylic acid at one meso position has been synthesized for evaluation as a photosensitizer in dye-sensitized solar cells based on titanium dioxide ( TiO 2) as a comparison to other metalloporphyrins and as a proxy for other potential triplet-state photosensitizer compounds. The synthesis of this palladium porphyrin has provided new insight into the mechanism and product distribution of decarboxylative hydrolysis of malonic acid when attached at the porphyrin meso position. A crystal structure determination for a meso-formyl palladium porphyrin has been determined, showing saddle-distortion of the porphyrin core. The photophysical behavior of the palladium porphyrin sensitizer and its performance in photoelectrochemical cells are described and interpreted in the context of bimolecular excited state quenching pathways including oxygen sensitization, triplet–triplet annihilation and electron transfer events. Palladium porphyrins are proposed as a sensitizer class with potential for high efficiency dye-sensitized solar cells, but with the caveat that some overpotential for electron injection is necessary to compete against the multiple decay pathways that are specially available to triplet state photosensitizers.

Solid-state photogalvanic dye-sensitized solar cells

Photogalvanic cells are photoelectrochemical systems wherein the semiconductor electrode is not a participant in primary photoinduced charge formation. The discovery of photoelectrochemical systems that successfully exploit secondary (thermal) electron injection at dye-semiconductor interfaces may enable studies of electron transfer at minimal driving force for electron injection into the semiconductor. In this study, we have examined thermal electron transfer from molecular sensitizers to nanostructured semiconductor electrodes composed of titanium dioxide nanorods by means of transient spectroscopy and the assembly and testing of photoelectrochemical cells. Electron-accepting molecular dyes have been studied alongside an arylamine electron donor. Thermal injection is estimated for a naphthacenequinone radical anion as a multiexponential decay process with initial decay lifetimes of 6 and 27 ps. The ambient electric field present during charge separation at a surface-adsorbed dye monolayer causes Stark shifts of the radical ion pair absorbance peaks that confounded kinetic estimation of thermal injection for a fullerene sensitizer. Electron-accepting dyes that operate by thermal injection into titanium dioxide function better in solid-state photoelectrochemical cells than in liquid-junction cells due to the kinetic advantage of solid-state cells with respect to photoinduced acceptor-quenching to form the necessary radical anion sensitizers.

The importance of various anchoring groups attached on porphyrins as potential dyes for DSSC applications

The influence of different anchoring groups in the efficiency of porphyrin dye sensitized solar cells.

Electron transport in acceptor-sensitized polymer-oxide solar cells: the importance of surface dipoles and electron cascade effects

Fullerene and acenequinone compounds have been examined as electron mediators between a p-type semiconductive polymer and two n-type oxide semiconductors. Composite interlayer materials and photovoltaic test cells were assembled and studied for their fluorescence quenching, current-voltage, and quantum efficiency behavior to characterize the efficacy of the acceptor-sensitizers as electron-selective interlayers. The sensitizers are generally more effective with titanium dioxide than with zinc oxide, due to the difference in magnitude of dipole-induced vacuum level shifts at the respective oxide interfaces. In titanium dioxide-based solar cells, where dipole effects are weak, photovoltage and fill factor increase in a trend that matches the increase in the first reduction potential of the acceptor-sensitizers. Photosensitization of the oxide semiconductor by the acceptor-sensitizers is observed to operate either in parallel with the polymer as an alternate photosensitizer or in series with the polymer in a two-photon process, according to an acceptor-sensitizer's first reduction potential. In zinc oxide-based solar cells, where dipole effects are stronger, the acceptor-sensitizers impaired most devices, which is attributed to an upward shift of the oxide's conduction band edge caused by dipole-induced vacuum level shifts. These results have broad implications for designing electron-selective interlayers and solid-state photocells using sensitized oxide semiconductors.

Porphyrins and phthalocyanines in solar photovoltaic cells

This review summarizes recent advances in the use of porphyrins, phthalocyanines, and related compounds as components of solar cells, including organic molecular solar cells, polymer cells, anddye-sensitized solar cells. The recent report of a porphyrin dye that achieves 11% power conversion efficiency in a dye-sensitized solar cell indicates that these classes of compounds can be as efficient as the more commonly used ruthenium bipyridyl derivatives.