Large Area Dye-sensitized Solar Cells Research Articles

Effects of counter electrode geometry on the power conversion efficiency of large-area dye-sensitized solar cells

In order to design electrode with reasonable geometry for large-area dye-sensitized solar cells (DSSCs), the effect of counter electrode geometry on the power conversion efficiency (PCE) of DSSCs has been investigated. The fill factor and shunt resistance decrease with the increase of active area, which results in a relatively low PCE in large-area DSSCs. If the F-doped SnO2 (FTO) substrate of counter electrode is replaced by metal substrate while keeping the electrode geometry unchanged, the drop in PCE will be smaller, which indicates that Ag grids can’t help inject electrons to counter electrode as effective as those help collect electrons in photoanode. The variation of the PCE of DSSCs with same length and different width suggests that the PCE can be improved greatly by reducing active area from the width rather than the length, which is proportional to the distance between positive and negative ohmic contact, and a reference value related to the series resistance (Rs) is proposed that the PCE of DSSCs are influenced by the deviation between theoretical Rs and Rs obtained by measurement.

Synthesis of germanium-platinum nanoparticles as high-performance catalysts for spray-deposited large-area dye-sensitized solar cells (DSSC) and the hydrogen evolution reaction (HER).

GePt3 and Ge2Pt nanoparticles were synthesized via a solution colloidal method as catalysts for dye-sensitized solar cells (DSSC) and the hydrogen evolution reaction (HER). The shape, size, arrangement, phases and crystalline structures of Ge-Pt nanoparticles were determined, and the ability to be dispersed in nonpolar solvents enabled them to form a catalyst ink with a stable ejection for the spray coating technique. A series of electrochemical analyses confirmed the catalytic properties of Ge-Pt nanoparticles toward the I-/I3- redox reaction system. The DSSC using GePt3 nanoparticles as the counter electrode exhibited excellent power conversion efficiency (PCE) of 8.04% at 0.16 cm2, which was comparable to that of a DSSC using Pt as the counter electrode (8.0%); it also exhibited an average PCE of 7.26% even at a large working area (2 cm2). In addition, the GePt3 catalyst exhibited excellent HER electrocatalytic performance with a large current density and a low Tafel slope, and it could stably operate at a working area of up to 5 cm2 with a low over potential (<0.06 V) to achieve 10 mA cm-2 cathodic current. This study provides fundamental insights into the preparation of germanium-platinum intermetallic compound catalysts at the nanoscale, which can be beneficial for the design and development of clean energy devices.

Enhanced efficiency of large-area dye-sensitized solar cells by light-scattering effect using multilayer TiO2 photoanodes

In order to reduce the usage of photoactive dye and improve light harvesting by the photoanode of dye-sensitized solar cells (DSSCs), TiO2 scatting layers were introduced. We have investigated the light-scattering effect in large-area DSSCs with an active area of 100.6 cm2 that contain diffusing or reflective layers. The result shows that the light-scattering effect is more important than the dye adsorption capacity for the light harvesting property of TiO2 photoanodes with same thickness, and the light-scattering effect is shown to enhance the light absorption in the red part of the solar spectrum. The highest power conversion efficiency of 7.52% has been obtained by the cell with optimized high dye adsorption layer and high light-scattering layer, which is 9.5% higher than that of the cell without the light-scattering layer (6.87%).

Development of stable current collectors for large area dye-sensitized solar cells

The substrate sheet resistance effect in a large area dye-sensitized solar cell (DSC) device is still the main factor responsible for low energy conversion efficiencies. In this work, current collectors made of metal lines were applied by magnetron sputtering on a transparent conducting glass substrate. The introduction of these metal lines enabled a decrease in the sheet resistance from 7.26Ω·□−1 to 2.52Ω·□−1, by depositing an optimized 1.0μm tungsten thick layer on the top of 1.5μm thick molybdenum lines. These Mo/W lines withstanded long-term stability when in contact with iodide/triiodide redox couple. Large area dye-sensitized solar cells with 36cm2 of active area were assembled and the power conversion efficiency increased from 0.54% to 1.62% when ten metal lines were applied in both electrodes. As a final design, Mo/W lines were only applied onto the counter-electrode and protected with an indium-tin oxide layer; the resulting device showed a power conversion efficiency of 3.43%, compared with the reference efficiency of 2.38%.

TiO2 nanoparticles optimized for photoanodes tested in large area Dye-sensitized solar cells (DSSC)

Dye-sensitized solar cells (DSSCs) are still attracting great attention as a potential alternative to conventional silicon solar cells, and a lot of current research is focusing on enhancing their efficiency through the individual improvement of the DSSCs components, as well as their integration. Among all components, mesoporous TiO2 plays a major role, because it is the charge collector for the dye molecules or perovskite in liquid and solid DSSCs, respectively. Specificities of TiO2 are now well-known: an anatase crystalline structure for an optimized bandgap, small particle size to shorten the charge diffusion path, reduced grain boundaries to limit current resistivity, significant porosity to enhance integration and interaction between the photon absorbers and the charge-collecting anode. We reported previously how well-crystallized small nanoparticles were successfully synthesized via a room temperature synthesis by Hegazy and Prouzet (2012) [10], leading to very small crystallites (4–10nm) of pure TiO2 anatase. Since as-synthesized materials still contain hydration water, a major drawback in DSSCs, we report here how dehydration and crystallinity can be improved by annealing at a moderate temperature, without any sintering or significant particle coarsening. The resulting impact on properties is confirmed by testing the resulting annealed TiO2 nanopowder in photovoltaic liquid DSSCs. In addition, we describe a comprehensive study of the preparation and test of TiO2 based photoanodes, including UV exposure and HCl treatment. Photovoltaic tests were conducted on a large active surfaces (5cm2) cells to give a more realistic picture of the influence of each parameter involved in the cell performance, characterized under AM 1.5 illumination with 100mWcm−2 light intensity. The specific contribution of each parameter on the cell performance is discussed. We demonstrate why the TiO2 nanopowder developed in our previous synthesis, in connection with the suitable treatments during the photoanode preparation, can replace commercial powders, with a greater success in cell photoefficiency.

Graphene-based large area dye-sensitized solar cell modules.

We demonstrate spray coating of graphene ink as a viable method for large-area fabrication of graphene-based dye-sensitized solar cell (DSSC) modules. A graphene-based ink produced by liquid phase exfoliation of graphite is spray coated onto a transparent conductive oxide substrate to realize a large area (>90 cm(2)) semi-transparent (transmittance 44%) counter-electrode (CE) replacing platinum, the standard CE material. The graphene-based CE is successfully integrated in a large-area (43.2 cm(2) active area) DSSC module achieving a power conversion efficiency of 3.5%. The approach demonstrated here paves the way to all-printed, flexible, and transparent graphene-based large-area and cost-effective photovoltaic devices on arbitrary substrates.

Probing Electron Lifetime and Recombination Dynamics in Large Area Dye-Sensitized Solar Cells by Electrochemical Impedance Spectroscopy

A number of nanocrystalline, mesoporous large area (~0.2- 2 cm2) dye-sensitized solar cells (DSSCs) are probed by electrochemical impedance spectroscopy measurements to realize their carrier dynamics such as charge transport resistance (RCT), electron diffusion coefficient (Dη), and electron lifetime (τn) by applying an equivalent electrical model. The experimental upshots reveal that the electron lifetime relates with the device physical parameters which was neglected in previous studies. It is also found that the RCT relates negatively with the device area i.e. it decrease upon increasing photo-exposed area. The observed lowering of current density (JSC) over a series of experiments upon increasing the photoelectrode area is attributed to the decrease in RCT. The charge carriers upon injection into semiconductor layer find increased diffusion pathways and eventually recombine with the hole species when characterized by lower carrier lifetime. The thickness of the electrode film does not play an effective role indicating that the dynamics of larger area DSSCs differs largely from those of a single cell. The experimental results available indicate that a nearly complete collection of charge carriers is possible in large area modules provided the physical dimensions of photoelectrode area are considered. The results from the study hints future directions to build high efficiency DSSC modules and further asserts considering the diffusion length in two-dimensions while fabricating larger area cells.

Gram-Scale Synthesis of Catalytic Co9S8 Nanocrystal Ink as a Cathode Material for Spray-Deposited, Large-Area Dye-Sensitized Solar Cells

We report the development of Co9S8 nanocrystals as a cost-effective cathode material that can be readily combined with spraying techniques to fabricate large-area dye-sensitized solar cell (DSSC) devices and can be further connected with series or parallel cell architectures to obtain a relatively high output voltage or current. A gram-scale synthesis of Co9S8 nanocrystal is carried out via a noninjection reaction by mixing anhydrous CoCl2 with trioctylphosphine (TOP), dodecanethiol and oleylamine (OLA) at 250 °C. The Co9S8 nanocrystals possess excellent catalytic ability with respect to I(-)/I3(-) redox reactions. The Co9S8 nanocrystals are prepared as nanoinks to fabricate uniform, crack-free Co9S8 thin films on different substrates by using a spray deposition technique. These Co9S8 films are used as counter electrodes assembled with dye-adsorbed TiO2 photoanodes to fabricate DSSC devices having a working area of 2 cm(2) and an average power conversion efficiency (PCE) of 7.02 ± 0.18% under AM 1.5 solar illumination, which is comparable with the PCE of 7.2 ± 0.12% obtained using a Pt cathode. Furthermore, six 2 cm(2)-sized DSSC devices connected in series output an open-circuit voltage of 4.2 V that can power a wide range of electronic devices such as LED arrays and can charge commercial lithium ion batteries.

Preparation of large-area dye-sensitized solar cells based on hydrothermally synthesized nitrogen-doped TiO2 powders

Low-cost, yellowish, nanocrystalline nitrogen-doped titanium dioxide (N-doped TiO2) powder was synthesized by a hydrothermal method. The as-prepared N-doped TiO2 powder was characterized by X-ray diffraction, transmission electron microscopy (TEM), UV–Vis absorption spectra, X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller analysis techniques. The grain size of the prepared powder was around 13 nm as estimated by both Scherrer’s method and TEM images. The effect of the ratio of N-doped TiO2 particles to Degussa P25 on the photovoltaic performance of large-area dye-sensitized solar cells (DSSCs) was also investigated. The N-doped TiO2 electrode showed higher photovoltaic performance compared with that of pure P25 at constant irradiation of 100 mW cm−2, which is attributed to the large pore size and high surface area of N-doped TiO2 resulting in the introduction of extra charge carrier pathways that could be beneficial for overall charge transportation. Energy conversion efficiency of 5.12 % was achieved in a DSSC device with active area of 51.19 cm2.

FABRICATION OF AUTOMATIC ELECTROLYTE FILLING MACHINE FOR DYE-SENSITIZED SOLAR CELLS

An electrolyte filling machine, capable of filling liquid electrolyte (including viscous ionic liquid) into an enclosed cell with a single hole, has been developed. This system utilizes a vacuum-aided filling technique and has four major steps in the filling process, namely evacuation, discharging, filling, and returning extra electrolyte. The electrolyte is not open to ambient conditions throughout the filling process, and the return step minimizes the waste of electrolyte. This technique allows air bubble–free filling, better insertion of electrolyte into the mesoporous titanium oxide layer of dye-sensitized solar cells (DSC), and filling time is 40 s with a nonvolatile liquid-based electrolyte. Large area DSC modules that are 15 × 15 cm in size were tested using this machine, and conversion efficiency of 7.4% was obtained under the standard air mass (AM) 1.5 simulated sunlight.

Electrospun conductive polyaniline–polylactic acid composite nanofibers as counter electrodes for rigid and flexible dye-sensitized solar cells

Conductive polyaniline doped with 10-camphorsulfonic acid (PANI·CSA) blended with polylactic acid (PLA) composite films are directly deposited on rigid fluorine-doped tin oxide and flexible indium tin oxide-coated polyethylene naphthalate substrates by using a simple electrospinning method. The scanning electron microscope and atomic force microscope images show that the PANI·CSA–PLA film is assembled from about 200 nm-diameter nanofibers, with a generally uniform thickness of about 2 μm. The three-dimensional porous fibrous PANI·CSA–PLA films indicate good electrocatalytic performance for I3−/I− electrolyte, demonstrated by electrochemical impedance spectra and cyclic voltammetry measurements. The photoelectric conversion efficiency of the dye-sensitized solar cells (DSCs) firstly based on such rigid and flexible PANI·CSA–PLA counter electrodes achieves 5.3% and 3.1% under 1 sun illumination of 100 mW cm−2 (AM 1.5), respectively, which is close to that of sputtered Pt-based DSCs. In addition, the rigid PANI·CSA–PLA-based DSC demonstrates good stability. As the PANI·CSA–PLA counter electrodes can be obtained in a short time at room temperature, they are potentially applicable in large-area DSCs and suitable for flexible DSCs.

Bi-functional TiO 2 cemented Ag grid under layer for enhancing the photovoltaic performance of a large-area dye-sensitized solar cell

A bi-functional TiO 2 cemented Ag grid under layer for enhanced the photovoltaic performance of a large-area dye-sensitized solar cell (DSSC) is prepared with a simple way. The conductive printing paste contains micro-sized Ag powders and nano-sized TiO 2 cementing agent. The conductive printing paste can be well cemented on the FTO glass and form high conductive grids with Ag powders sintered together by the nano-sized TiO 2 particles. The formed conductive grid is protected with a TiO 2 thin layer and TiO 2 sol treatment to avoid the iodine corrosion. The addition of the TiO 2 cemented conductive grid can decrease the internal resistance of the large-area dye-sensitized solar cell when it is prepared in the photo and counter electrodes. Furthermore, the protecting TiO 2 thin layer and the TiO 2 sol treatment can be done on the whole area of the large-area photo electrode to both play as the blocking under layer at the same time, which can also enhance the photovoltaic performance of the large-area dye-sensitized solar cell.

Monolithic Module Design and Behavior Improvement of Large Area Dye-sensitized Solar Cell

A new type of simple and monolithic large size dye-sensitized solar cell(DSC) module was designed with 85% aperture ratio(ratio of active area to total area),which was much higher than that of traditional series and parallel modules.The present module reduces the transfer resistance through the electroplated nickel grid on F-doped SnO2(FTO) of anode as well as the nickel film on the FTO of counter electrode.The nickel grid and film are inside the cell and the separation of the cell is not required,which is useful to reduce the block part of light and beneficial to improve the harvest of light energy.The photoelectric conversion efficiency(η) with the active area of 510 mm2 reaches 3.00%(AM 1.5,100 mW/cm2) and the fill factor(FF) is 0.594,meanwhile the η and FF of DSC without nickel layer modification is only 0.537% and 0.251.So it is obvious that this novel designed module is very effective in the performance improvement.The underlying mechanism is understood based on the measurement of the electrochemical impedance spectroscopy(EIS) as well as the quality check of nickel film by scanning electron microscopy(SEM) and X-ray diffraction(XRD).

Fabrication of high performance Pt/Ti counter electrodes on Ti mesh for flexible large-area dye-sensitized solar cells

High performance and homogeneous platinum (Pt) nanoparticles is electrodeposited onto titanium (Ti) mesh to form counter electrodes for use in large-area flexible dye-sensitized solar cells (DSSCs). The obtained Pt/Ti counter electrode shows high electrocatalytic activity for the I 3 −/I − redox reaction, low charge transfer resistance (49.57 Ω cm 2 with an area of 80 cm 2) and good light transmittance (92.31%). Based on the counter electrode, a light-to-electric energy conversion efficiency of 6.13% is achieved for a flexible DSSC with an area of 80 cm 2, and a maximum power output of 0.443 W is reached for a flexible DSSC with an area of 160 cm 2, under an outdoors natural light irradiation with an intensity of 55 mW cm −2. The present findings should accelerate the practical application of flexible DSSCs.

Large area dye-sensitized solar cells with titanium based counter electrode

Construction of dye-sensitized solar cell of large area using platinum sputtered titanium metal counter electrode is demonstrated. An impressive increase in the fill factor and consequently the efficiency compared to the conventional platinized conducting glass based counter electrodes result from very low sheet resistance of the titanium plate and a cell of active area 151cm2 with parallel silver collecting grids delivered an efficiency of 7.4%. The possibility of using this technique for commercial production of dye-sensitized solar cells was discussed giving details of fabrication procedure.

Fabrication of Large Area Dye-Sensitized Solar Cell Using Thermal Spraying Method

not Available.

Dye-Sensitized Solar Cell Constructed with Titanium Mesh and 3-D Array of TiO2 Nanotubes

We have designed and constructed dye sensitized solar cells based on new, 3-D configurations of TiO(2) nanotubes. The overall efficiency of our best cells is 5.0% under standard air mass 1.5 global (AM 1.5 G) solar conditions, and the incident photon-to-current efficiency exceeds 60% over a broad part of the visible spectrum. Unlike prior nanotube-based cells where tubes are grown vertically in a 2-D array, the anodes of the present cells consist of tubes that extend radially in a 3-D array from a grid of fine titanium wires. The nanotubes are tens of micrometers in length, and the radial nature of the anode allows the photon absorption path length to exceed the electron transport distance (nanotube length). The cells are front-illuminated and do not require a transparent conductive oxide substrate at either the anode or cathode. The use of 3-D configured nanotubes and low-resistance titanium metal substrates are expected to enhance the performance and simplify the construction of large area dye-sensitized solar cells.

Metallic Titanium-Based Photoelectrode for Large Area Dye-Sensitized Solar Cells

not Available.

PV Efficiency Improved Large-area Dye-sensitized Solar Cells

Several techniques including current-collecting metal fingers and double-layer TiO2 electrode were applied to improve the conversion efficiency of large area dye-sensitized solar cells (DSSCs). Silver paste was used to fabricate the current-collecting metal fingers on the fluorine-doped tin oxide (FTO) glass substrate by screen-printing process. Then a single- or double-layer TiO2 electrode was fabricated by using screen-printing process. The double-layer TiO2 electrode consists of a transparent TiO2 layer and a light-scattering TiO2 layer. Results showed that applying the current-collecting metal fingers and double-layer TiO2 electrode could effectively improve the conversion efficiency. The conversion efficiency of 5.89% was achieved in a DSSC module with an area of 50mm×50mm by using the current-collecting metal finger cell of 45mm×3.5mm and double-layer TiO2 electrode under global air mass 1.5 condition.

Large area dye-sensitized solar cells: material aspects of fabrication

Dye-sensitized photoelectrochemical solar cells of large area are fabricated using highly conducting and optically transparent glass consisting of an inner layer of indium-tin oxide and an outer layer of fluorine doped tin oxide. A method is described for the deposition of nanocrystalline films of TiO2 consisting of large and small median size particles (30 and 5 nm, respectively) which promote porosity and light scattering. Incorporation of trace quantities of magnesium oxide into TiO2 increased the efficiency of the cells. The energy conversion efficiency of a cell (AM 1·5, 1000 W m−2 simulated sunlight) of area 21 cm2 was found to be 7·2% compared to 5·6% in the absence of magnesium oxide. The mechanisms by which the magnesium oxide improves the cell performance are discussed. Copyright © 2006 John Wiley & Sons, Ltd.