Low-cost Counter Electrode Research Articles

Construction of efficient counter electrodes for dye-sensitized solar cells: Fe2O3 nanoparticles anchored onto graphene frameworks

Exploiting cost-effectiveness and highly efficient counter electrodes (CEs) has been a persistent objective for large-scale practical application of dye-sensitized solar cells (DSSCs). Here, we propose an alternative design for the fabrication of low-cost and Pt-free CE materials by constructing fast electron transport network and creating highly active sites on the electron pathway using graphene and Fe2O3 nanoparticles. The hybridized structure of three-dimensional (3D) graphene frameworks (GFs) supported Fe2O3 nanoparticles is prepared by a simple hydrothermal self-assembly process. Due to the superior electrocatalytic activity originated from the uniformly dispersed Fe2O3 nanoparticles and enriched edges and defects on graphene frameworks, along with the incorporation of 3D GFs which provide effective transport pathways for electrons transfer, the DSSC with Fe2O3/GFs as CE display a power conversion efficiency of 7.45%, which is superior to that of Pt as CE (7.29%). Therefore, the Fe2O3/GFs composites exhibit great potential in low-cost and highly efficient CE materials for DSSCs.

Silver nanoparticles-decorated porous silicon as the counter electrode of dye-sensitised solar cell

Silver nanoparticles-decorated porous silicon (Ag@PSi) films are investigated as the counter electrodes for dye-sensitized solar cells (DSSCs). The surface morphology, crystal structure and photoluminescence (PL) of the Ag@PSi counter electrode are analysed by means of field-emission scanning electron microscope, X-ray diffractometer and PL spectroscopy, respectively. After being characterised under the AM 1.5 simulated solar light of 100 mW cm− 2, the power conversion efficiency of the DSSC with the Ag@PSi counter electrode reaches 1.02%, which is comparable to that of the control DSSC with platinum (Pt) counter electrode (1.22%). The remarkable photovoltaic performance of the DSSCs with the Ag@PSi conter electrodes can be attributed to the combined catalytic activities of the porous silicon (PSi) films and the silver nanopartciles. Our results have demonstrated that Ag@PSi films may be used as the low-cost counter electrodes for highly efficient DSSCs.

ZnO nanorods decorated graphene/ZnO nanoparticle composite as the counter electrode of dye-sensitised solar cells

A counter electrode based on graphene, ZnO nanoparticles and ZnO nanorods was designed for dye-sensitized solar cells (DSSCs). In this counter electrode, a 200 nm thick composite film of graphene with ZnO nanoparticles served as the scaffolds while vertically aligned ZnO nanorods with the lengths of about 730 nm and the diameters of about 50 nm were employed to decorate these scaffolds. The surface morphology, crystal structure, photoluminescence of the graphene/ZnO composite counter electrodes were analysed by means of field-emission scanning electron microscope, X-ray diffractometer and photoluminescence spectroscopy, respectively. Under 1-Sun illumination (100 mW cm− 2, AM 1.5), J–V measurements were performed to characterise the photovoltaic performance of the DSSCs with the graphene/ZnO composite counter electrode. The power conversion efficiency of the DSSCs with the graphene/ZnO composite counter electrode was 0.17%, which was slightly higher than that of the DSSC with the Pt counter electrode (0.15%). The reasonable photovoltaic performance of the DSSCs can be attributed to the large surface area for the reduction of and direct pathway for electron transport from counter electrode to electrolyte. Our results have demonstrated that graphene/ZnO composite may be used as the low-cost counter electrodes for highly efficient DSSCs.

Nitrogen-doped porous carbon prepared by a facile soft-templating process as low-cost counter electrode for High-performance dye-sensitized solar cells

Nitrogen-doping porous carbon (NPC) with high surface area is prepared by a simple soft-templating method and explored as a low-cost counter electrode for dye-sensitized solar cells. Nitrogen adsorption analysis shows that the as-prepared NPC has a high surface area and mesoporous structure. Electrochemical impedance spectroscopy test shows a low charge-transfer resistance of 0.77Ωcm2 for NPC electrode in iodide/triiodide redox electrolyte. Such excellent electrocatalytic activity can be attributed not only to good surface properties including high surface area and mesoporous structure but also to nitrogen doping in NPC framework. Among various nitrogen species in the NPC framework, pyridinic and quaternary nitrogen are considered to contribute significantly to the electrocatalytic activity. A conversion efficiency of 7.09% is achieved for dye-sensitized solar cells with NPC counter electrode at one sun illumination, which is comparable to that of the cell with Pt counter electrode. These results reveal that the NPC electrode is a promising counter electrode candidate for dye-sensitized solar cells.

New single-source precursor for bismuth sulfide and its use as low-cost counter electrode material for dye-sensitized solar cells

One new homoleptic [Bi(dtc)3] (1) (dtc=4-hydroxypiperdine dithiocarbamate) has been synthesized and characterized by microanalysis, IR, UV–Vis, 1H and 13C spectroscopy and X-ray crystallography. The photoluminescence spectrum for the compound in DMSO solution was recorded. The crystal structure of 1 displayed distorted octahedral geometry around the Bi(III) center bonded through sulfur atoms of the dithiocarbamate ligands. TGA indicates that the compound decomposes to a Bi and Bi–S phase system. The Bi and Bi–S obtained from decomposition of the compound have been characterized by pXRD, EDAX and SEM. Solvothermal decomposition of 1 in the absence and presence of two different capping agents yielded three morphologically different Bi2S3 systems which were deployed as counter-electrode in dye-sensitized solar cells (DSSCs).

P-type NiO nanoparticles enhanced acetylene black as efficient counter electrode for dye-sensitized solar cells

P-type nickel oxide acetylene black nanoparticles composite (NiO/AB) enables facile low cost counter electrode for dye-sensitized solar cells (DSSCs), prepared by simple chemical process and doctor-blading method. Nanocrystalline p-type NiO contributes in the improvement of holes conduction at the acetylene black surface and escalates the electrocatalytic activity, confirmed by our cyclic voltammetry and electrochemical impedance spectroscopy measurements. Owing to the improvement of electrocatalytic activity, the mutual porous acetylene black surface with p-type NiO nanoparticles counter electrode and dye-sensitized TiO2 photoanodes yielded significantly enhanced power conversion efficiency of 7.75%, which is superior to that of 6.51% and 6.96% of AB and expensive Pt in our experiment respectively.

Electrochemical deposition of molybdenum sulfide thin films on conductive plastic substrates as platinum-free flexible counter electrodes for dye-sensitized solar cells

In this study, pulsed electrochemical deposition (pulsed ECD) was used to deposit molybdenum sulfide (MoSx) thin films on indium tin oxide/polyethylene naphthalate (ITO/PEN) substrates as flexible counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). The surface morphologies and elemental distributions of the prepared MoSx thin films were examined using field-emission scanning electron microscope (FE-SEM) equipped with energy-dispersive X-ray spectroscopy. The chemical states and crystallinities of the prepared MoSx thin films were examined by X-ray photoelectron spectroscopy and X-ray diffraction, respectively. The optical transmission (T (%)) properties of the prepared MoSx samples were determined by ultraviolet–visible spectrophotometry. Cyclic voltammetry (CV) and Tafel-polarization measurements were performed to analyze the electrochemical properties and catalytic activities of the thin films for redox reactions. The FE-SEM results showed that the MoSx thin films were deposited uniformly on the ITO/PEN flexible substrates via the pulsed ECD method. The CV and Tafel-polarization curve measurements demonstrated that the deposited MoSx thin films exhibited excellent performances for the reduction of triiodide ions. The photoelectric conversion efficiency (PCE) of the DSSC produced with the pulsed ECD MoSx thin-film CE was examined by a solar simulator. In combination with a dye-sensitized TiO2 working electrode and an iodine-based electrolyte, the DSSC with the MoSx flexible CE showed a PCE of 4.39% under an illumination of AM 1.5 (100mWcm−2). Thus, we report that the MoSx thin films are active catalysts for triiodide reduction. The MoSx thin films are prepared at room temperature and atmospheric pressure and in a simple and rapid manner. This is an important practical contribution to the production of flexible low-cost thin-film CEs based on plastic substrates. The MoSx thin films produced by pulsed ECD are good candidates for catalysts in flexible DSSCs.

Flexible carbon nanotube/polypropylene composite plate decorated with poly(3,4-ethylenedioxythiophene) as efficient counter electrodes for dye-sensitized solar cells

In this study, we fabricate an efficient, flexible and low-cost counter electrode (CE) composed of a plasma-etched carbon nanotubes/polypropylene (designated as ECP) composite plate decorated with poly(3,4-ethylene dioxythiophene) (PEDOT) for dye-sensitized solar cells (DSCs). The PEDOT-decorated monolithic ECP CEs are fabricated via series of processes including high-temperature refluxing, thermal compression, oxygen plasma etching, and electropolymerization. The bottom ECP plate is used to replace conventional transparent conducting oxide (TCO) as a conductive substrate, and the top PEDOT layer is employed as catalyst for I3− reduction. According to the extensive electrochemical measurements, the as-fabricated flexible PEDOT coated ECP CE demonstrates a Pt-like electrocatalytic for I3− reduction. The DSC based on the flexible PEDOT-decorated ECP CE yields impressive energy conversion efficiency of 6.82% (or 6.77% even after the bending test), which is comparable to that of the DSC using the Pt CE (7.20%) under similar device architecture conditions. Therefore, the PEDOT-decorated ECP based CEs show the possibility of serving as low-cost and flexible CEs for efficient DSCs.

In Situ Controllable Growth of Cu2SnS3 Film as Low-Cost Counter Electrodes for Dye-Sensitized Solar Cells

Morphology-controllable Cu2SnS3 thin films on Mo-glass were prepared via a facile in situ one-step solvothermal process and used in dye-sensitized solar cells as counter electrodes. The effects of different solvents on the morphology of films were investigated. DSC based on the porous net-like Cu2SnS3 thin film as counter electrodes showed a power conversion efficiency of 2.30%, which was improved to 3.35% after annealing.

Sulfur-doped porous carbon as metal-free counter electrode for high-efficiency dye-sensitized solar cells

In this study, we demonstrate a high performance of sulfur-doped porous carbon (S-PC) as metal-free low-cost counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). The S-PC material is synthesized by using pitch as carbon source and basic magnesium sulfate (BMS) whiskers as both template and S source. The doped sulfur is mainly present in the C–S–C configuration. The enhanced electrocatalytic performance can be attributed to the S atoms doped into the carbon framework which has large effective surface areas due to their porous or rough morphology. Therefore, it enhances the asymmetry of the atomic charge density in C atoms, leading to a large number of reduction sites and low charge transfer resistance. The S-PC significantly enhances the performance compared to the pure porous carbon (PC) due to the lower charge-transfer resistance. The DSSC with S-PC as the CE exhibits a high conversion efficiency of 6.97% which is comparable to that of the traditional Pt CE (7.28%).

NH3-treated WO3 as low-cost and efficient counter electrode for dye-sensitized solar cells.

A novel low-cost and efficient counter electrode (CE) was obtained by treating catalytic inert tungsten trioxide (WO3) nanomaterial in NH3 atmosphere at elevated temperatures. The formation of tungsten oxynitride from WO3 after NH3 treatment, as evidenced by X-ray photoelectron spectroscopy and X-ray diffraction, increases the catalytic activity of the CE. Correspondingly, the power conversion efficiency (PCE) of the DSC is significantly increased from 0.9% for pristine WO3 CE to 5.9% for NH3-treated WO3 CE. The photovoltaic performance of DSC using NH3-treated WO3 CE is comparable to that of DSC using standard Pt CE (with a PCE of 6.0%). In addition, it is also shown that NH3 treatment is more efficient than H2 or N2 treatment in enhancing the catalytic performance of WO3 CE. This work highlights the potential of NH3-treated WO3 for the application in DSCs and provides a facile method to get highly efficient and low-cost CEs from catalytic inert metal oxides.

AuNP/graphene nanohybrid prepared by dry plasma reduction as a low-cost counter electrode material for dye-sensitized solar cells

Au nanoparticles (NPs) with a radius ranging from 4 ∼ 18nm (mostly 11nm) were stably and uniformly hybridized on the surface of reduced graphene oxide (RGO) after co-reduction of Au precursor ions and graphene oxide (GO), to Au atoms and RGO, respectively. The hybridization was provided by dry plasma reduction (DPR) operated under atmospheric pressure and at a low temperature without any toxic chemicals. The structure of the AuNP/RGO nanohybrid was characterized by SEM, TEM, XPS, XRD and Raman spectroscopy. Raman spectra indicated that DPR induced an increase in the degree of clustering of the sp2 phase in addition to sp2 bond restoration. Increasing the number of AuNP/RGO layers yielded a decrease in the transmittance and sheet resistance of the AuNP/RGO nanohybrid. A developed electrode based on the AuNP/RGO nanohybrid showed high electrochemical catalytic activity and high conductivity in comparison with the AuNP and GO electrodes. Thus, the AuNP/RGO nanohybrid fabricated by DPR could be an excellent material for a low-cost counter electrode for dye-sensitized solar cells using Co2+/Co3+ redox electrolyte.

Electrocatalytic properties of iron chalcogenides as low-cost counter electrode materials for dye-sensitized solar cells

Three iron chalcogenides were successfully prepared and tested as CE materials in DSSCs. The devices using FeS2, FeSe2 and FeTe2 obtained high photovoltaic conversion efficiencies of 8.00, 7.92 and 7.21%, respectively, which were also confirmed by theoretical calculations.

Influence of earth-abundant bimetallic (Fe–Ni) nanoparticle-embedded CNFs as a low-cost counter electrode material for dye-sensitized solar cells

Earth-abundant bimetallic (Fe–Ni) nanoparticle-embedded carbon nanofibers (CNFs) have been prepared by electrospinning technique and used as counter electrode (CE) material for dye-sensitized solar cells (DSSCs).

Recent advances in alternative counter electrode materials for Co-mediated dye-sensitized solar cells.

Recently, considerable attention has been paid to dye-sensitized solar cells (DSSCs) which are based on Co(2+)/Co(3+) redox shuttles, because of their unparalleled merits including higher redox potential, reduced corrosiveness towards metallic conductors, low costs and high power conversion efficiencies (PCE) (13%). The counter electrode (CE) is an essential component in DSSCs, and plays a crucial role in catalyzing Co(3+) ion reduction in Co-based DSSCs. In this mini-review, we review recent developments in CE materials for Co-mediated DSSCs including: noble metal platinum (Pt), carbon materials, transition metal compounds (TMCs), polymers, and their corresponding hybrids, highlighting important contributions worldwide that promise low cost, efficient, and robust Co-mediated DSSC systems. Additionally, the crucial challenges associated with employing these low-cost CE catalysts for Co-based redox couples in DSSCs are stressed.

N-Doped ZnO Nanoparticle-Carbon Nanofiber Composites for Use as Low-Cost Counter Electrode in Dye-Sensitized Solar Cells

【Nitrogen-doped ZnO nanoparticle-carbon nanofiber composites were prepared using electrospinning. As the relative amounts of N-doped ZnO nanoparticles in the composites were controlled to levels of 3.4, 9.6, and 13.8 wt%, the morphological, structural, and chemical properties of the composites were characterized by means of field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). In particular, the carbon nanofiber composites containing 13.8 wt% N-doped ZnO nanoparticles exhibited superior catalytic properties, making them suitable for use as counter electrodes in dye-sensitized solar cells (DSSCs). This result can be attributed to the enhanced surface roughness of the composites, which offers sites for $I_3{^-}$ ion reductions and the formation of Zn3N2 phases that facilitate electron transfer. Therefore, DSSCs fabricated with 13.8 wt% N-doped ZnO nanoparticle-carbon nanofiber composites showed high current density ( $16.3mA/cm^2$ ), high fill factor (57.8%), and excellent power-conversion efficiency (6.69%); at the same time, these DSSCs displayed power-conversion efficiency almost identical to that of DSSCs fabricated with a pure Pt counter electrode (6.57%).】

Unique ZnS nanobuns decorated with reduced graphene oxide as an efficient and low-cost counter electrode for dye-sensitized solar cells

Unique ZnS nanobuns decorated with reduced graphene oxide (RGO) was synthesized and found to exhibit a synergetic effect as a highly efficient and low-cost counter electrode (CE) in dye-sensitized solar cells (DSCs). Using this ZnS-RGO CE, a power conversion efficiency (PCE) of 7.03% was achieved. This value was 53% and 41% higher than those of pure ZnS and RGO CEs, respectively. The ZnS-RGO nanocomposite is indeed an efficient and cost-effective Pt-like alternative for iodine reduction reaction.

Novel one pot stoichiometric synthesis of nickel sulfide nanomaterials as counter electrodes for QDSSCs

Solution combustion synthesis has been used for the first time to synthesize metal sulfide nanomaterials. Selective stoichiometric synthesis of nickel sulfide nanomaterials was achieved in a single step by using combustion synthesis under ambient conditions and the samples were tested as counter electrodes in a typical quantum dot sensitized solar cell (QDSSC). By varying the oxidant/fuel ratio, different stoichiometric nickel sulfide nanomaterials were obtained. Interestingly, a maximum of fourfold increase in efficiency (1.1%) was achieved with nickel sulfide counter electrode when compared to the Pt counter electrode (0.25%). This can be attributed to the less charge transfer resistance offered by nickel sulfide samples compared to Pt, which was confirmed by electrochemical impedance spectroscopy. Among different stoichiometric compositions of nickel sulfide, Ni3S2 was found to exhibit the least charge transfer resistance and superior solar cell efficiency. The present study describes a novel selective stoichiometric synthetic approach and facile fabrication procedure for low cost counter electrode materials in QDSSCs.

Recent Progress of Counter Electrode Catalysts in Dye-Sensitized Solar Cells

To realize long-term developments and practical application of the dye-sensitized solar cells (DSCs) requires a robust increase of the power conversion efficiency (PCE) and a significant decrease of the production cost. Fortunately, a new record PCE value of 12.3% was achieved by using cobalt-based redox couples combined with organic dye. Evidently, dye design is the key path to improve the PCE, while developing low cost counter electrode (CE) catalysts is one of the promising paths to reduce the production cost of DSCs by replacing the expensive Pt CE. In this article, we review the recent progress of CE catalysts involving Pt, carbon materials, inorganic materials, multiple compounds, polymers, and composites. We discuss the advantages and disadvantages of each catalyst and put forward ideas for designing new CE catalysts in future research for DSCs and other application fields.

Low-Cost Counter Electrodes From CoPt Alloys For Efficient Dye-Sensitized Solar Cells

Dye-sensitized solar cell (DSSC) is a promising solution to global energy and environmental problems because of its merits on clean, low cost, high efficiency, good durability, and easy fabrication. However, the commercial application of DSSCs has been hindered by the high expenses of counter electrodes (CEs) and limited power conversion efficiency. With an aim of significantly enhancing the power conversion efficiency, here we pioneerly synthesize CoPt alloys using an electrochemically codeposition technique which are employed as CEs for DSSCs. Owing to the rapid charge transfer, electrical conduction, and electrocatalysis, power conversion efficiencies of CoPt-based DSSCs have been markedly elevated in comparison with the DSSC using Pt CE. The DSSC employing CoPt0.02 alloy CE gives an impressive power conversion efficiency of 10.23%. The high conversion efficiency, low cost in combination with simple preparation, and scalability demonstrates the potential use of CoPt alloys in robust DSSCs.