Use In Dye-sensitized Solar Cells Research Articles

Charge transfer from an adsorbed ruthenium-based photosensitizer through an ultra-thin aluminium oxide layer and into a metallic substrate.

The interaction of the dye molecule N3 (cis-bis(isothiocyanato)bis(2,2-bipyridyl-4,4'-dicarbo-xylato)-ruthenium(II)) with the ultra-thin oxide layer on a AlNi(110) substrate, has been studied using synchrotron radiation based photoelectron spectroscopy, resonant photoemission spectroscopy, and near edge X-ray absorption fine structure spectroscopy. Calibrated X-ray absorption and valence band spectra of the monolayer and multilayer coverages reveal that charge transfer is possible from the molecule to the AlNi(110) substrate via tunnelling through the ultra-thin oxide layer and into the conduction band edge of the substrate. This charge transfer mechanism is possible from the LUMO+2 and 3 in the excited state but not from the LUMO, therefore enabling core-hole clock analysis, which gives an upper limit of 6.0 ± 2.5 fs for the transfer time. This indicates that ultra-thin oxide layers are a viable material for use in dye-sensitized solar cells, which may lead to reduced recombination effects and improved efficiencies of future devices.

CeO2-TiO2 photoanode for solid state natural dye-sensitized solar cell

The main challenge facing liquid electrolyte-based dye-sensitized solar cells (DSSCs) is the leakage and valorization of organic solvents limiting the long-term durability and practical use of DSSC. Therefore, the solidification of the electrolyte used in these devices has been one of the most crucial research directions in the field of DSSC. In the present work, we have assembled a dye-sensitized solar cell based on a new nanocomposite polymer electrolyte system which is composed of polyvinyl alcohol as a host polymer, mixture of EC and PC as a plasticizer, LiI:I2 as a redox couple, and TiO2 as a filler. A novel photoanode CeO2-TiO2 sensitized with betacyanin natural dye was used in order to reduce recombination rate by providing inherent energy barrier. The obtained solar energy conversion efficiency was of 2.8 % with a current density JSC of 7.22 mA/cm2 using an irradiation of 100 mW/cm2 at 25 °C.

Graphene materials and their use in dye-sensitized solar cells.

Graphene materials and their use in dye-sensitized solar cells.

Performance of metalloporphyrin malonic acids as dye sensitizers for use in dye-sensitized solar cells assessed by density functional theory

The performance of metallo (Zn, Cd, Hg) tetra (4-methylphenyl) porphyrin malonic acids as dye sensitizers for use in dye-sensitized solar cells (DSSCs) is assessed by means of ab initio molecular electronic structure calculations. The results reveal that malonic acid side chain cannot be described as an acceptor moiety, and the photo-to-current conversion efficiencies of the DSSCs that are based on organic semiconducting Cd and Hg tetra (4-methylphenyl) porphyrin malonic acid donors and a series of oxide semiconducting acceptors are expected to be greater than the reference porphyrin dye Zn tetra (4-methylphenyl) porphyrin malonic acid under standard global AM 1.5 solar conditions. This result is confirmed and characterized in terms of charge transfer, band gaps, density of states, polarizabilities, dipole moments, molecular electrostatic potential contours, electronic absorption energies, and infrared vibrational frequencies. The study emphasizes the role of metal centers, and provides alternatives to DSSCs with expensive materials.

Computational study on zinc porphyrin analogs for use in dye-sensitized solar cells

The density functional theory (DFT) and time-dependent DFT (TD-DFT) approaches have been applied to obtain the optimized geometries, electronic structures, molecular orbitals and absorption spectra of a series of meso-substituted zinc porphyrin analogs with phenyl and thiophene groups as the π bridging unit and cyanoacrylic acid as the acceptor unit. The results showed that the introduction of thiophene group increases the orbital splitting and changes the absorption spectra properties significantly. It is indicated that when there is only one thiophene group included in the π bridge, the oscillator strength of B absorption band is much stronger. The increasing length of thiophene chain just changes the scope of specific absorption enhancement. The effect of attaching an additional electron-donating group diphenylamine instead of phenyl to the porphyrin core also has been shown. It is found that the diphenylamine group reduces the band gap, and leads to facile intramolecular charge transfer from diphenylamine and porphyrin ring unit to acceptor unit. These kinds of zinc porphyrin analogs have the LUMO energy close to the conduction band of TiO 2 and more red-shifted absorption spectrum compared with phenyl substituted analogs.

Photovoltaic properties of TiO2–ZrO2 fiber composite electrodes for dye-sensitized solar cells

ZrO2 fibers were fabricated by sol–gel and electrospinning techniques for use in dye-sensitized solar cells (DSCs). The addition of ZrO2 fibers into TiO2 electrodes provides good dye loading and an effective electron pathway to increase the charge transfer in the TiO2/electrolyte interface over conventional TiO2 electrode. Photo-electrochemical properties of TiO2–ZrO2 fiber composite electrodes and the performance of resultant DSCs were determined from their photovoltaic-current densities. Energy conversion efficiency of DSCs with a TiO2–ZrO2-700 composite electrode was 6.2%, an increase of 26.5% than pure TiO2 electrode of 4.9%. The electron recombination times of the pure TiO2 and TiO2–ZrO2-700 electrode were 15.94 and 21.69ms, respectively.

Preparation of Fluoride-Doped Tin Oxide Films on Soda–Lime Glass Substrates by Atomized Spray Pyrolysis Technique and Their Subsequent Use in Dye-Sensitized Solar Cells

The development of a novel method for the fabrication of low-cost, transparent, conducting glass (F–-doped SnO2 layer on soda–lime glass, FTO) by a specially developed atomized spray pyrolysis tech...

Stepwise co-sensitization as a useful tool for enhancement of power conversion efficiency of dye-sensitized solar cells: The case of an unsymmetrical porphyrin dyad and a metal-free organic dye

A tertiary arylamine compound (DC), which contains a terminal cyano-acetic group in one of its aryl groups, and an unsymmetrical porphyrin dyad of the type Zn[Porph]-L-H2[Porph] (ZnP-H2P), where Zn[Porph] and H2[Porph] are metallated and free-base porphyrin units, respectively, and L is a bridging triazine group functionalized with a glycine moiety, and were synthesized and used for the fabrication of co-sensitized dye-sensitized solar cells (DSSCs). The photophysical and electronic properties of the two compounds revealed spectral absorption features and frontier orbital energy levels that are appropriate for use in DSSCs. Following a stepwise co-sensitization procedure, by immersing the TiO2 electrode in separate solutions of the dyes in different sequence, two co-sensitized solar cells were obtained: devices C (ZnP-H2P/DC) and D (DC/ZnP-H2P).The two solar cells were found to exhibit power conversion efficiencies (PCEs) of 6.16% and 4.80%, respectively. The higher PCE value of device C, which is also higher than that of the individually sensitized devices based on the ZnP-H2P and DC dyes, is attributed to enhanced photovoltaic parameters, i.e. short circuit current (Jsc=11.72mA/cm2), open circuit voltage (Voc=0.72V), fill factor (FF=0.73), as it is revealed by photovoltaic measurements (J–V curves) and by incident photon to current conversion efficiency (IPCE) spectra of the devices, and to a higher total dye loading. The overall performance of device C was further improved up to 7.68% (with Jsc=13.45mA/cm2, Voc=0.76V, and FF=0.75), when a formic acid treated TiO2ZnP-H2P co-sensitized photoanode was employed (device E). The increased PCE value of device E has been attributed to an enhanced Jsc value (=13.45mA/cm2), which resulted from an increased dye loading, and an enhanced Voc value (=0.76V), attributed to an upward shift and increased of electron density in the TiO2 CB. Furthermore, dark current and electrochemical impedance spectra (EIS) of device E revealed an enhanced electron transport rate in the formic acid treated TiO2 photoanode, suppressed electron recombination at the photoanode/dye/electrolyte interface, as well as shorter electron transport time (τd), and longer electron lifetime (τe).

Fabrication of Nanoporous Twisted TiO2 Strips for Use in Dye-Sensitized Solar Cells

Fabrication of Nanoporous Twisted TiO2 Strips for Use in Dye-Sensitized Solar Cells

Bridging TiO2nanoparticles using graphene for use in dye-sensitized solar cells

SUMMARY The use of graphene to bridge TiO2 particles in the photoanode of dye-sensitized solar cell for reduced electrical resistance has been investigated. The difficulty in dispersing graphene in TiO2 paste was overcome by first dispersing graphene oxide (GO) into the TiO2 paste. The GO was then reduced to graphene after the sintering of TiO2. This is shown through transmission electron microscopy and X-ray photoelectron spectroscopy analysis. Cell performance was evaluated using a solar simulator, incident photon to electron conversion efficiency, intensity modulated photocurrent/photovoltage spectroscopy under blue light, and electrochemical impedance spectroscopy. Depending on the amount of graphene in the photoanode, the cell performance was enhanced to different degrees. A maximum increase of 11.4% in the cell efficiency has been obtained. In particular, the inclusion of graphene has reduced the electron diffusion time by as much as 23.4%, i.e. from 4.74 to 3.63 ms and increased the electron lifetime by as much as 42.3%, i.e. from 19.58 to 27.85 ms. Copyright © 2014 John Wiley & Sons, Ltd.

Comparative study of TiO<SUB align="right">2 films prepared by EPD and sol-gel techniques and their use in DSSCs

In this work, we give a comparative study of titanium dioxide (TiO 2 ) films fabricated using the electro-phoretic deposition technique (EPD) and the sol-gel one. The TiO 2 films were elaborated on commercial ITO layers and were used as photo electrodes in dye sensitised solar cells (DSSCs). To fabricate these cells, we used N 3 as the sensitising dye, the electrolyte is a KI/I 2 solution and the counter electrode is a thin aluminium film. The surface of fabricated cells is 2.5 cm 2 . Both scanning electron microscopy (SEM) and XRD characterisations show that the EPD technique leads to the formation of a thick TiO 2 layer, where grains have greater dimensions than the sol-gel one. The transmission spectra measured in the UV-Vis-NIR domain show better values in the case of sol-gel; however, the reflectivity of the film is greater when we use the EPD technique. Measured current–voltage characteristic under AM1.5 illumination of the fabricated DSS cells permits us to conclude that each one of the sol-gel and EPD techniques has not only advantages, but also some weaknesses.

1D nanorod-planted 3D inverse opal structures for use in dye-sensitized solar cells

The effectiveness of the 1D nanorod (NR)-planted 3D inverse opal (IO) structure as an electrode for dye-sensitized solar cells (DSSCs) is demonstrated here. The NRs were grown on the surface of a macroporous IO structure and their longitudinal growth increased the surface area of the structure proportional to the growth duration. NR/IO electrodes with various NR growth times were compared. A remarkable JSC was obtained for the DSSCs utilizing a NR/IO electrode. The improvement of the JSC was analyzed in terms of its efficiency in light harvesting and electron transport. The growth of the NRs improved the dye adsorption density and scattering property of the electrode, resulting in an improvement in the light harvesting efficiency. Electrochemical impedance analysis revealed that the NRs also improved its electron transport properties. Further growth of the NRs tended to limit the increase of the JSC, which could be attributed to an overlap between them.

Double-N doping: a new discovery about N-doped TiO2applied in dye-sensitized solar cells

In this paper, we first investigated the optimal amount of ammonia to add, using ammonia as the single dopant for use in dye-sensitized solar cells (DSSCs). Using this optimal amount of ammonia, urea was introduced as the second N dopant. The DSSCs produced by double-N doped samples combine the advantages of increased visible light absorption with ammonia as the nitrogen dopant and enlarged interface area with urea as the second nitrogen dopant. Not only was Voc increased, but Jsc was also enhanced. We observed that the double-N doped sample forms a new microstructure with more mesopores, which enhance the transfer of electrolyte. Because these mesopores are the combination core of generated electrons and holes, they need to be kept in delicate balance. When urea is brought in as the double-N dopant, the doped amount of N atoms was improved. As a result, η is increased to 7.58%, a 14% improvement compared with single-N doped TiO2.

Photovoltaic properties of bis(octyloxy)benzo-[c][1,2,5]thiadiazole sensitizers based on an N,N-diphenylthiophen-2-amine donor

Three sensitizers with N,N-diphenylthiophen-2-amine as the donor were synthesized for use in dye-sensitized solar cells, in which the furan-based sensitizer showed an efficiency of 7.16%.

Porous NiOx nanostructures templated by polystyrene-block-poly(2-vinylpyridine) diblock copolymer micelles

A facile synthetic route to NiOx nanostructures using various amphiphilic polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymers as templates was investigated. The synthesis targets NiOx nanostructures with a large surface area in order to allow an efficient functionalization, e.g., through loading with dyes to enable photo-induced hole injection for use in dye-sensitized solar cells or in (photo-)catalytic systems. The complete synthetic process to NiOx contains several steps: (i) the dissolution of the diblock copolymer, (ii) the subsequent addition of Ni2+, followed by the formation of core–corona micelles and eventually, (iii) further addition of Ni2+, resulting in the formation of a macroscopic precipitate. In all cases, (iv) deposition onto different substrates and calcination yielded NiOx films. All intermediates were thoroughly investigated using scanning or transmission electron microscopy, dynamic light scattering, and UV-vis spectroscopy. In contrast to the well-established synthetic route via the commercially available Pluronic F108 triblock copolymer, in our case a variety of different morphologies was found, i.e. spherical particles, toroid structures, or networks. Furthermore, the obtained BET area of about 50 m2 g−1 is comparable to the value for conventionally obtained NiOx surfaces. First dye sensitization experiments with coumarine 343 confirm that the dye binds to the surface, which is a prerequisite for using the material as a photo-electrode. The presented route to porous NiOx is easy and provides superior control over the morphology of the intermediates involved in nanostructure formation.

Investigation of 35 Elements as Single Metal Oxides, Mixed Metal Oxides, or Dopants for Titanium Dioxide for Dye-Sensitized Solar Cells

A total of 35 elements were investigated as single component metal oxides and as dopants for TiO2 for use in dye-sensitized solar cells (DSCs). An array dispenser and scanner system was utilized for high-throughput testing of the single component metal oxides and hundreds of doped TiO2 compositions. The optimal dopant concentrations were identified and summarized according to their effect on short circuit current (ISC) and open circuit voltage (VOC). New dopant candidates were discovered, including several post-transition metals, which showed improvements in DSC performance when incorporated at compositions of 6% In TiO2, 6% Sn TiO2, and 6% Sb TiO2 (metals basis). These compositions were used to synthesize scaled-up DSC devices for detailed characterization. Incorporation of 6% In into TiO2 enhanced VOC substantially and increased ISC slightly, 6% Sn improved ISC while preserving VOC, and 6% Sb increased ISC significantly but decreased VOC. When coincorporated, Cr and Sb showed a complementary interaction, which reduced resistance to charge transport in the DSC device. The 2% Cr, 6% Sb TiO2 showed higher ISC and VOC values than 6% Sb TiO2 and considerably higher ISC than 2% Cr TiO2. The fill-factor for 2% Cr, 6% Sb TiO2 was relatively low, but the maximum power was higher than the other compositions due to the higher currents. The VOC values for DSC devices with different compositions correlated linearly with the measured flat-band potentials (EFB).

Synthesis of organic dye containing an alkylenesulfanyl-bridged bithienyl π-linker and its use in dye-sensitized solar cells

Abstract The synthesis and photovoltaic characteristics of a new organic dye, CU-L2, which has a unique and flexible alkylenesulfanyl-bridged bithienyl bridging framework between the phenylamino donor unit and cyanoacrylic acceptor unit, were demonstrated. CU-L2 exhibited better photovoltaic performance, with an enhanced photocurrent due to the redshifted optical absorption and reduced interfacial recombination, as compared to CU-L1, with its rigid dithienothiophene bridging motif between the same donor and acceptor units. The dye-sensitized solar cell fabricated with CU-L2 under optimized processing conditions presented a high power conversion efficiency of 6.63%.

In-situ formation of dispersed ZnO nanoparticles in mesoporous carbon counter electrode for efficient dye-sensitized solar cells

The high electronic-mobility ZnO was developed as binder with a mesoporous carbon (MC) as catalytic material to fabricate a novel ZnO–MC counter electrode through in-situ formation technique. The homogeneous MC blended paste containing the ZnO sol was first coated on the conductive substrate, and then annealed in ambient atmosphere to obtain the ZnO–MC electrode. The annealing temperature is a key factor to obtain the high-performance ZnO–MC electrode. When annealed at 300°C, the in-situ formed and dispersed ZnO nanoparticles are functioned as bridges to bind the MC particles and to strengthen the adhesion of the carbon film to the substrate, providing enough conductive paths for the transportation of the electrons to participate timely in the reduction of tri-iodide (I3−), and further improving the electrochemical performances of the electrode. As a result, the efficiency of the ZnO–MC electrode for use in dye-sensitized solar cells (DSCs) enhances from 2.5% to 6.37% compared with the binder-free MC electrode. Importantly, the ZnO–MC electrode exhibits higher catalytic activity for the I3− reduction than the MC electrode using carboxymethyl cellulose (CMC) as binder, leading to an increase of 14.2% in the efficiency of the cell, which is mainly from the high electronic-mobility of the ZnO. Furthermore, the efficiency of the low cost ZnO–MC based DSCs reaches 90.4% of that of the Pt based ones. Noted that compared with the Pt electrode, the ZnO–MC electrode is beneficial to obtain a device with higher open-circuit voltage.

Application of graphene-based nanostructures in dye-sensitized solar cells

The paper reviews recent advances in the application of graphene and related materials, viz. graphene nanoplatelets (GNP), functionalized graphene sheets (FGS), graphene oxide (GO), and reduced graphene oxide (rGO) as electrode building materials in dye-sensitized solar cell (DSC). Graphene promises multifaceted use in DSC: as prospective sensitizer, photoanode additive, current collector, and electrocatalyst for the redox-shuttle turnover. Of particular significance is the use of graphene as cathode catalyst in the state of art Co-mediated solar cells. Here, it can successfully replace platinum without any compromise on the electrode's catalytic activity, associated with good optical transparency.

Design of high-performance chlorine type dyes for dye-sensitized solar cells

Intrinsic defect of electronic structure for the chlorine-type porphyrin 1, which was synthesized for use in dye-sensitized solar cell (DSSC), is found by theoretical calculation including density functional method (DFT), time-dependent DFT, and C+/C− function. It is believed that the limited cell performance obtained by using dye 1 as the sensitizer is due to the existence of this electronic defect. To avoid this defect, a series of novel molecules with electron deficient π bridge were designed. The subsequent theoretical calculation indicated that the electron deficient π bridge in the newly designed molecule is quite effective in offsetting the electronic defect observed for dye 1. The parameters for the designed molecules closely associated with open-circuit voltage and short-circuit current density including dipole moment of dye vertical to the surface of semiconductor and light-harvesting efficiency were then evaluated. By comparing these parameters of designed dyes with those of dye 1, we can predict that the DSSC based on dye 4 (2, 6-cyan benzoic acid as anchoring group) should possess enhanced performance, which would be a valuable theoretical guidance for the practical work. © 2013 Wiley Periodicals, Inc.