Transparent Counter Electrode Research Articles

Transparent metal selenide alloy counter electrodes for high-efficiency bifacial dye-sensitized solar cells.

The exploration of cost-effective and transparent counter electrodes (CEs) is a persistent objective in the development of bifacial dye-sensitized solar cells (DSSCs). Transparent counter electrodes based on binary-alloy metal selenides (M-Se; M=Co, Ni, Cu, Fe, Ru) are now obtained by a mild, solution-based method and employed in efficient bifacial DSSCs. Owing to superior charge-transfer ability for the I(-) /I3 (-) redox couple, electrocatalytic activity toward I3 (-) reduction, and optical transparency, the bifacial DSSCs with CEs consisting of a metal selenide alloy yield front and rear efficiencies of 8.30 % and 4.63 % for Co0.85 Se, 7.85 % and 4.37 % for Ni0.85 Se, 6.43 % and 4.24 % for Cu0.50 Se, 7.64 % and 5.05 % for FeSe, and 9.22 % and 5.90 % for Ru0.33 Se in comparison with 6.18 % and 3.56 % for a cell with an electrode based on pristine platinum, respectively. Moreover, fast activity onset, high multiple start/stop capability, and relatively good stability demonstrate that these new electrodes should find applications in solar panels.

Transparent Metal Selenide Alloy Counter Electrodes for High‐Efficiency Bifacial Dye‐Sensitized Solar Cells

AbstractThe exploration of cost‐effective and transparent counter electrodes (CEs) is a persistent objective in the development of bifacial dye‐sensitized solar cells (DSSCs). Transparent counter electrodes based on binary‐alloy metal selenides (M‐Se; M=Co, Ni, Cu, Fe, Ru) are now obtained by a mild, solution‐based method and employed in efficient bifacial DSSCs. Owing to superior charge‐transfer ability for the I−/I3− redox couple, electrocatalytic activity toward I3− reduction, and optical transparency, the bifacial DSSCs with CEs consisting of a metal selenide alloy yield front and rear efficiencies of 8.30 % and 4.63 % for Co0.85Se, 7.85 % and 4.37 % for Ni0.85Se, 6.43 % and 4.24 % for Cu0.50Se, 7.64 % and 5.05 % for FeSe, and 9.22 % and 5.90 % for Ru0.33Se in comparison with 6.18 % and 3.56 % for a cell with an electrode based on pristine platinum, respectively. Moreover, fast activity onset, high multiple start/stop capability, and relatively good stability demonstrate that these new electrodes should find applications in solar panels.

Cost-effective bifacial dye-sensitized solar cells with transparent iron selenide counter electrodes. An avenue of enhancing rear-side electricity generation capability

Alloy materials have established themselves as alternative electrocatalysts for electrochemical devices because of their cost-effectiveness, high conductivity, good electrocatalytic activity, and reasonable stability. Aiming at reducing fabrication cost without sacrificing power conversion efficiency of dye-sensitized solar cells (DSSCs), we report the feasibility of designing transparent and cost-effective Fe–Se alloy counter electrodes for bifacial DSSCs. Due to the rapid charge transfer ability and electrocatalytic activity, maximum front and rear efficiencies of 7.64% and 4.95% are measured for the DSSC with FeSe alloy electrode in comparison with 6.97% and 3.56% from Pt-based solar cell. The impressive results along with simple synthesis highlight the potential application of Fe–Se alloys in robust bifacial DSSCs.

3 D single-walled carbon nanotube/graphene aerogels as pt-free transparent counter electrodes for high efficiency dye-sensitized solar cells.

3D single-walled carbon nanotube (SWCNT)/graphene aerogel (NGS) was synthesized and used as an alternative to platinized fluorine-doped tin oxide (FTO) in dye-sensitized solar cells (DSSCs). An island-like structure formed on the FTO using the spin-coating method, leading to a transmittance (49.86 % at 671 nm). The resulting NGS-based counter electrodes (CEs) exhibited excellent power conversion efficiency (PCE) (8.31 %) compared to Pt (7.56 %). Surprisingly, PCE increased to 9.64 % under assisted by a mirror; The excellent performance of DSSCs can be attributed to the high electrical conductivity and good electrocatalytic activity induced by the SWCNTs and the excellent catalytic properties of graphene, coupled with the 3D structure with a larger surface area and good surface hydrophilicity for increased electrolyte-electrode interactions and electrolyte/reactant diffusion. Hence, our results demonstrate that 3D-NGS materials have considerable potential for DSSC-related applications and merit further investigation.

A facile synthesis of bimetallic AuPt nanoparticles as a new transparent counter electrode for quantum-dot-sensitized solar cells

This study first reports the synthesis of AuPt bimetallic nanoparticles (AuPt-BNPs) on an FTO glass substrate using dry plasma reduction (DPR) and its application as an alternative transparent counter electrode (CE) for quantum-dot-sensitized solar cells (QDSCs) operated under bi-side illumination. DPR is an economically feasible and ecologically sustainable method. The formation of ultrafine crystalline AuPt-BNPs on an FTO substrate is confirmed through TEM, HRTEM with HAADF-STEM and HAADF-STEM-EDS analyses. The mechanism for controlling the size, mono-dispersity, and areal number density of nanoparticles on the substrate surface is suggested. The CE fabricated with AuPt-BNPs exhibits a high electro-catalytic activity without losing the optical transmittance of the FTO substrate. The QDSC employing the AuPt-BNP electrode reaches efficiencies of 2.4% under front-side illumination and 2.2% under back-side illumination. Bi-side illumination yields an efficiency of 3.4%, which is comparable to an efficiency of 3.7% obtained for the QDSC with the state-of-the-art CE.

Bifacial dye-sensitized solar cells with enhanced rear efficiency and power output.

Pursuing a high power conversion efficiency with no sacrifice of cost-effectiveness has been a persistent objective for dye-sensitized solar cells (DSSCs). One promising solution to this impasse is increased light harvesting. Previous efforts in light harvesting have been made on setting blocking layers or reflecting layers, or adding a light harvester, resulting in tedious procedures without reducing the expenses. We present a mild solution strategy for synthesizing transparent Ru-Se alloy counter electrodes (CEs) for bifacial DSSC applications, displaying optimal front and rear efficiencies of 8.76% and 5.90%, respectively. In comparison with pristine Pt-based solar cells, the maximum power output has also been markedly enhanced. Moreover, fast start-up, high multiple start capability, and good stability are observed in the bifacial DSSCs with transparent Ru-Se binary alloy electrodes. The impressive efficiencies along with simple preparation of the cost-effective Ru-Se alloy CEs demonstrates their potential application in robust DSSCs.

An avenue of sealing liquid electrolyte in flexible dye-sensitized solar cells

Storage of liquid electrolyte has been a persistent objective for liquid-state flexible dye-sensitized solar cells (DSSCs). We present here the feasibility of rear-irradiated flexible DSSC comprising of groove stored dye-sensitized TiO2 on a Ti foil and conductive plastic supported transparent cobalt selenide alloy counter electrode. After being injected into the groove, the liquid electrolyte containing I−/I3− redox couples can be well sealed. The flexible cells are optimized by adjusting groove depth and stoichiometry of cobalt selenide electrodes, generating a maximum power conversion efficiency of 7.52% under one sun irradiation. The research demonstrates some new insights on how to improve liquid electrolyte retention and elevate photovoltaic performances of flexible DSSCs.

Room temperature polymerization of poly(3,4-ethylenedioxythiophene) as transparent counter electrodes for dye-sensitized solar cells

Poly(3,4-ethylenedioxythiophene) (PEDOT) counter electrode is prepared with in situ polymerization of 3,4-ethylenedioxythiophene on a fluorine-doped tin oxide over-layer glass at room temperature. The cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel polarization are measured to evaluate the catalytic activity of PEDOT counter electrode for I3−/I− redox couple. Comparing the data with that of traditional thermal decomposed Pt counter electrode, it is found that PEDOT has higher catalytic activity than that of Pt counterpart. Power conversion efficiency of the dye-sensitized solar cell (DSC) with PEDOT counter electrode can attain to 7.713%, a little higher than that of the cell with Pt counter electrode (7.300%). Taking the advantage of high transparency of PEDOT counter electrode, an Ag mirror is put on the back side of PEDOT counter electrode of the DSC to reflect light back for power conversion. Power conversion efficiency of the DSC with this special structure can be further enhanced to 8.359%, which mainly stems from the improved short-circuit current density by the increased irradiated light intensity. Copyright © 2014 John Wiley & Sons, Ltd.

Fully solution-processed transparent conducting oxide-free counter electrodes for dye-sensitized solar cells: spray-coated single-wall carbon nanotube thin films loaded with chemically-reduced platinum nanoparticles.

We report fully solution-processed fabrication of transparent conducting oxide-free counter electrodes (CEs) for dye-sensitized solar cells (DSSCs) by combining spray-coating of single-wall carbon nanotubes (SWCNTs) and chemical reduction of chloroplatinic acid precursor to platinum nanoparticles (Pt NPs) with formic acid. The power conversion efficiency of a semitransparent DSSC with such SWCNT-based CE loaded with Pt NPs is comparable to that of a control device with a conventional CE. Quantification of Pt loading shows that network morphology of entangled SWCNTs is efficient in forming and retaining chemically reduced Pt NPs. Moreover, electron microscopy and electrochemical impedance spectroscopy results show that mainly Pt NPs, which are tens of nanometers in diameter and reside at the surface of SWCNT CEs, contribute to electrocatalytic activity for triiodide reduction, to which we attribute strong correlation between power conversion efficiency of DSSCs and time constant deduced from equivalent-circuit analysis of impedance spectra.

Transparent nickel selenide alloy counter electrodes for bifacial dye-sensitized solar cells exceeding 10% efficiency.

In the current work, we report a series of bifacial dye-sensitized solar cells (DSSCs) that provide power conversion efficiencies of more than 10% from bifacial irradiation. The device comprises an N719-sensitized TiO2 anode, a transparent nickel selenide (Ni-Se) alloy counter electrode (CE), and liquid electrolyte containing I(-)/I3(-) redox couples. Because of the high optical transparency, electron conduction ability, electrocatalytic activity of Ni-Se CEs, as well as dye illumination, electron excitation and power conversion efficiency have been remarkably enhanced. Results indicate that incident light from a transparent CE has a compensation effect to the light from the anode. The impressive efficiency along with simple preparation of the cost-effective Ni-Se alloy CEs highlights the potential application of bifacial illumination technique in robust DSSCs.

Charge Transfer and Performance Enhancement of Dye-Sensitized Solar Cells by Utilization of a Tandem Structure

For increasing the light-harvesting ability of dye-sensitized solar cells (DSSCs), thick TiO2 films were always utilized. However, a thicker TiO2 film also triggers a higher charge-transfer resistance. To solve the contrary effects of film thickness on the light harvest and charge transfer, a tandem-structured cell constructed by two sub-DSSCs is proposed. By using a high transparent Pt counter electrode, the light unabsorbed by the top cell can transmit trough and be utilized by the bottom cell. The performances of the tandem cells are evaluated using N719-sensitized TiO2 photoelectrodes and the thickness effects of top and bottom cells are studied. The experimental results show that the tandem structure can significantly improve the conversion efficiency of DSSCs. For the single cells studied in this work, the highest efficiency is 9.3%, achieved by a cell with 12-μm main layer and 4-μm scattering layer. For the tandem cells, the best performance appears at the structure with 12-μm top cell and 8-μm bot...

Metal sulfide counter electrodes for dye-sensitized solar cells: A balanced strategy for optical transparency and electrochemical activity

Dye-sensitized solar cells (DSSCs) have obtained exciting progress in improving energy conversion efficiency and cutting material cost in recent years. It is found that many kinds of inorganic compounds have promising potential to replace platinum as counter electrode materials for DSSCs. Actually, to a thin film electrode, preparation of the thin film is the same important as choice of active materials, because quality of the films has a direct effect on electrochemical and optical performance of the final counter electrodes. In this paper, a general strategy is developed to prepare transparent and high-efficient metal sulfide counter electrodes. In the route, the Group VIIIB metal sulfides are formed as compact, homogenous and stable films on fluorine-doped tin oxide conductive glass from a precursor organic solution by spin coating, and the film thickness can be readily converted to reach the balance between optical transparency and electrochemical activity. Among the Group VIIIB metal sulfides, the nickel sulfide film with the thickness of 100 nm shows the high transparency and energy conversion efficiency of 7.37%, higher than that of the DSSC using platinum electrode. The results provide a new and facile alternative to prepare high-efficient and transparent sulfide counter electrodes for DSSCs.

Highly transparent and efficient counter electrode using SiO2/PEDOT-PSS composite for bifacial dye-sensitized solar cells.

A highly transparent and efficient counter electrode was facilely fabricated using SiO2/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) inorganic/organic composite and used in bifacial dye-sensitized solar cells (DSCs). The optical properties of SiO2/PEDOT-PSS electrode can be tailored by the blending amount of SiO2 and film thickness, and the incorporation of SiO2 in PEDOT-PSS provides better transmission in the long wavelength range. Meanwhile, the SiO2/PEDOT-PSS counter electrode shows a better electrochemical catalytic activity than PEDOT-PSS electrode for triiodide reduction, and the role of SiO2 in the catalytic process is investigated. The bifacial DSC with SiO2/PEDOT-PSS counter electrode achieves a high power conversion efficiency (PCE) of 4.61% under rear-side irradiation, which is about 83% of that obtained under front-side irradiation. Furthermore, the PCE of bifacial DSC can be significantly increased by adding a reflector to achieve bifacial irradiation, which is 39% higher than that under conventional front-side irradiation.

Effect of Reflective Platinum Film on the Performance of Flexible Dye Solar Cell (DSC)

Robust and flexible dye solar cell (DSC) made up of nanocrystalline TiO2 encapsulated in polyethylene naphthalate (PEN) substrate will be able to fulfill the demand for indoor power applications as it has lower energy and manufacturing cost, produces electricity in low light conditions even under artificial light. The fabrication using PEN substrate has the advantage of scalability and compatible with the roll to roll manufacturing method. This paper reports the study on the effect of platinum film reflectance on the counter electrode to the DSC performance and efficiency. The reflective counter electrode uses the commercially available Pt/Ti PEN film with 100% reflectance properties. The transparent counter electrode with 20.9% reflectance is prepared using pre-treated indium doped tin oxide (ITO). The platinum film is sintered at 170°C followed by direct heat of 150°C to achieve a good bonding between the ITO and the deposited platinum film. Both cells uses TiO2 coated ITO PEN as the working electrode. The DSC test cell with reflective counter electrode increases the cell efficiency compared to the non-reflective counter electrode as there is a higher light spectrum response on the reflective DSC cell.

Transparent platinum counter electrode for efficient semi-transparent dye-sensitized solar cells

A method for fabrication of highly transparent platinum counter electrodes (CEs) has been developed based on spray coating of Pt nanoparticles (NPs) on hot substrates. This method leads to 86% reduction in Pt consumption reducing the Pt cost per peak watt of counter electrode from $0.79/Wp down to $0.11/Wp compared to the conventional Pt counter electrodes made by sputter deposition. The simplicity and low cost of this method provide a basis for an up-scalable fabrication process. The Pt NP layer is over 88% transparent, leading to overall transparency of 80% when incorporated with indium tin oxide/glass substrates for functional counter electrodes. This counter electrode exhibits a large surface area and high catalytic activity, comparable to that of the conventional opaque CEs. Semi-transparent dye-sensitized solar cells fabricated based on this counter electrode showed 6.17% power conversion efficiency.

Thickness-self-controlled synthesis of porous transparent polyaniline-reduced graphene oxide composites towards advanced bifacial dye-sensitized solar cells

A powerful synthesis strategy is proposed for fabricating porous polyaniline-reduced graphene oxide (PANI-RGO) composites with transparency up to 80% and thickness from 300 to 1000 nm for the counter electrode (CE) of bifacial dye-sensitizing solar cells (DSSCs). The first step is to combine the in-situ positive charge transformation of graphene oxide (GO) through aniline (ANI) prepolymerization and the electrostatic adsorption of ANI oligomer-GO to effectively control the thickness of ultrathin PANI-GO films by adjusting pH of the polymerization media. In the second step, PANI-GO films are reduced with hydroiodic acid to simultaneously enhance the apparent redox activity for the I3−/I− couple and their electronic conductivity. Incorporating the RGO increases the transparency of PANI and facilitates the light-harvesting from the rear side. A DSSC assembled with such a transparent PANI-RGO CE exhibits an excellent efficiency of 7.84%, comparable to 8.19% for a semi-transparent Pt-based DSSC. The high light-harvesting ability of PANI-RGO enhances the efficiency retention between rear- and front-illumination modes to 76.7%, compared with 69.1% for a PANI-based DSSC. The higher retention reduces the power-to-weight ratio and the total cost of bifacial DSSCs, which is also promising in other applications, such as windows, power generators, and panel screens.

Role of Transparent Electrodes for High Efficiency TiO2 Nanotube Based Dye-Sensitized Solar Cells

In the present work, we investigate the performance of anodic TiO2 nanotube layers in dye-sensitized solar cells under front- and back-side illumination configurations. To fabricate transparent TiO2 nanotube electrodes, we evaporated 5 μm thick metallic Ti layers on FTO glass—then the metal layers are completely anodized to form aligned nanotube layers. We compare different types of FTO glass (conductivity and transparency) and use them for working electrodes as well as transparent platinized counter electrodes. The results show that for TiO2 nanotube electrodes the resulting light conversion efficiency in DSSCs is highly affected by the type of glass used (efficiency range—depending on configuration from 4.62% to 7.58%).

MoS2atomic layers with artificial active edge sites as transparent counter electrodes for improved performance of dye-sensitized solar cells

A novel MoS2 transparent counter electrode for dye-sensitized solar cells is reported. In order to enhance the catalytic activity of the electrode, active edge sites are created artificially by patterning holes on MoS2 atomic layers. Electrochemical analysis shows that the electrochemical activity is significantly improved after the patterning of holes. The photon-to-electron efficiency of the dye-sensitized solar cells based on MoS2 atomic layer counter electrodes is increased remarkably from 2% to 5.8% after the hole patterning.

Pt-free transparent counter electrodes for cost-effective bifacial dye-sensitized solar cells

In this feature article, we pay special attention to the recent advances in the development of Pt-free transparent CEs and highlight their applications in bifacial DSCs.

Morphology dependence of molybdenum disulfide transparent counter electrode in dye-sensitized solar cells

Molybdenum disulfide attracts additional attention due to its layered structure which allows transformation into a two-dimensional morphology, like graphene. In this paper, three kinds of molybdenum disulfides with distinguishable morphologies, i.e. multilayers, a few layers and nanoparticles, are prepared and used as counter electrode materials for dye-sensitized solar cells (DSSCs). The characterization results from X-ray diffraction (XRD) and transmission electron microscopy (TEM) demonstrate that the molybdenum disulfides have an obviously different edge area to basal-plane ratio, with the order: synthesized MoS2 nanoparticles (MoS2-NPs) > multilayered MoS2 (ML-MoS2) > few-layered MoS2 (FL-MoS2). It is interesting that the MoS2 counter electrodes show the same order as above in the energy conversion efficiency measurements of the corresponding DSSCs. Electrochemical impedance spectra (EIS) show that the MoS2-NPs electrode has the minimum charge-transfer resistance, while the FL-MoS2 electrode provides the maximum. Combined with the results from triiodine ion adsorption experiences and N2-adsorption measurements, it is proposed that the catalytically active sites of molybdenum disulfide lie on the edges of the typical layered material, but not on the basal planes. In addition, the transparency of the FL-MoS2 electrode is obviously higher than that of the other MoS2 and Pt electrodes.