Ordered mesoporous carbon-decorated reduced graphene oxide as efficient counter electrode for dye-sensitized solar cells

Due to the advantages of both rapid electron transport of reduced graphene oxide (rGO) sheet and high catalytic performance of ordered mesoporous carbon (OMC), composites of OMC with rGO (G@OMC) have been prepared through the hard-template approach and used as efficient counter electrode (CE) materials for dye-sensitized solar cells (DSSCs). When compared with pure OMC, the as-obtained G@OMC composites exhibit a higher electrocatalytic activity for the reduction of triiodide, owing to the synergetic effect between rGO and OMC. As a consequence, the DSSCs assembled with this G@OMC (CE show an improved photovoltaic conversion efficiency of 6.38% compared with 5.67% for DSSCs assembled with OMC CE, which could compete with the efficiency (7.05%) produced by the Pt CE under the same conditions.     

Nanoarchitecture of variable sized graphene nanosheets incorporated into three-dimensional graphene network for dye sensitized solar cells

A novel three-dimensional (3D) nanoarchitecture consisting of hybrid graphene nanosheets (GNs)/graphene foam (GF) was fabricated on the FTO conducting substrate as a high efficient counter electrode (CE) for dye sensitized solar cells (DSSCs). The GNs with various sized such as large-sized heat-reduced graphene nanosheets (H-GNs) and small-sized laser-reduced graphene quantum dots (L-GQDs) were synthesized and used as catalytic materials incorporated into a 3D GF network, respectively. In this design, the aggregations and restacking of GNs were efficiently reduced, which is beneficial for increasing the amount of the active defective sites at the edges of graphene to the electrolyte solution. Especially, L-GQDs with smaller dimension less than 100 nm have more active defective sites at edges, providing superiority over the large-sized H-GNs in terms of electrocatalytic activity. Meanwhile, the GF network with high conductivity provides fast electron transport channels for charge injection between the GNs and FTO. The DSSC with this hybrid CE exhibited energy conversion efficiency (η) of 7.70% with an open circuit voltage (V_OC), short circuit photocurrent density (J_SC) and fill factor (FF) of 760 mV, 15.21 mA cm⁻², and 72.0%, respectively, which is comparable to that of the conventional Pt CE (7.68%).     

Effect of carbonaceous counter electrodes on the performance of ZnO-graphene nanocomposites based dye sensitized solar cells

With many advantages like low-cost preparation, excellent electrical properties, and high catalytic activity; carbon allotropes are the most expected carbon materials to substitute the expensive Platinum (Pt) as counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). In the present study, the photovoltaic behaviors of DSSCs fabricated with graphene, multiwalled carbon nanotubes (MWCNTs), and Pt films CEs, respectively, were compared. The graphene and MWCNTs CEs films were prepared by doctor blading the graphene and MWCNTs pastes on Indium tin oxides (ITOs) glass substrates. The structural, morphological, and compositional properties of these carbon CEs viz. graphene and MWCNTs were investigated by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), and energy dispersive X-ray (EDX), respectively. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed for the examination of electrochemical and catalytic properties of Pt as well as carbonaceous CEs. These low-cost graphene and MWCNTs CEs were employed in the sandwich-structured DSSCs having ZnO-graphene nanocomposite films as photoanodes. The photoconversion efficiency (η) values of as prepared DSSCs were measured under AM 1.5 illumination (100?mW?cm^?2). The DSSCs with graphene CE and MWCNTs CE performed with efficiency values of 2.26% and 2.04%, respectively. The performance of these carbonaceous CEs are comparative to that of Pt CE which indicates the practicability of carbon based nanomaterials in DSSCs as low cost alternatives to the expensive Pt.     

Graphene-based counter electrode for dye-sensitized solar cells

Graphene nanosheets (GNs) were synthesized and used as a substitute for platinum as counter-electrode materials for dye-sensitized solar cells (DSSCs). The as-synthesized GNs were dispersed in a mixture of terpineol and ethyl cellulose. GN films were screen-printed on fluorine-doped tin oxide (FTO) slides using the formed GN dispersions. GN counter-electrodes were produced by annealing the GN films at different temperatures. The annealed GN films revealed an unusual 3D network structure. Structural and electrochemical properties of the formed GN counter-electrodes were examined by field emission scanning electron microscopy, Raman spectroscopy and electrochemical impedance spectroscopy. It was found that the annealing temperature of GN materials played an important role in the quality of the GN counter-electrode and the photovoltaic performance of the resultant DSSC. The grown DSSCs with graphene-based counter-electrodes exhibited a conversion efficiency high up to 6.81%.     

Eosin-G and ethyl eosin dye sensitized CdS nanowires towards dye sensitized solar cells applications

One dimensional (1-D) CdS nanowires have been grown through a low temperature chemical route and have been sensitized with eosin-G and ethyl eosin dyes to broaden the absorption spectrum of CdS and to enhance the photoelectrochemical (PEC) performance under illumination. The used method is advantageous due to its simplicity, low cost, scalability, and controllability. Interestingly, eosin-G and ethyl eosin dyes yield nearly four- and six-fold increase in device efficiency compared to bare CdS when tested in dye-sensitized solar cell assembly. Structural, surface morphological, optical, and surface wettability studies have been formulated for CdS, whereas identification of materials along with PEC investigations were conducted through current density–voltage (J-V), external quantum efficiency (EQE), characteristics under the illumination of 94.6 mW/cm² (AM 1.5G), and electrochemical impedance spectroscopy (EIS).     

Prospects of conducting polymer and graphene as counter electrodes in dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) garner considerable research interest because of high photo-to-electric conversion efficiencies at low production cost. Platinum has been reported as an efficient metal as a counter electrode (CE) in DSSCs for its outstanding electro catalytic performance. However, the high cost and susceptibility to corrosion of Pt are paving the way for exploring new materials to replace Pt as a counter electrode in DSSCs. Various conducting polymers, graphene and conducting polymer-graphene nanocomposites have been found as counter electrodes in DSSCs with remarkable photovoltaic performances. The urge to produce composites or hybrids with nanomaterials is derived from the improvement of photovoltaic performances. This review will focus on the unique physical and chemical properties of conducting polymers and graphene, their individual photovoltaic performances as counter electrodes in DSSCs, followed by the synergistic effect of conducting polymers and graphene in conducting polymer-graphene nanocomposites as counter electrodes in DSSCs. Finally a brief outlook is provided to improve the photovoltaic performance of DSSCs using conducting polymers and graphene-based counter electrodes.     

Synthesis and characterization of Co and Ga co-doped ZnO thin films as an electrode for dye sensitized solar cells

Using a time efficient and cost effective approach so called sol‒gel dip coating route, we deposited thin films of ZnO and 1% Co & (0%, 0.5%, 1%, and 1.5%) Ga co-doped ZnO on the fluorine doped tin oxide substrates. All the films exhibited hexagonal wurtzite structure. X-rays study revealed that crystallite size increased with increase of doping. Optical parameters like absorbance, transmittance, refractive index, band gap, extinction coefficient and dielectric constants were measured using UV–Vis spectroscopy and it has been noticed that doping resulted in reduction of band gap. It has also been observed that, the films prepared with 1% Co & 1% Ga co-doped ZnO have comparatively smaller band gap and thus have high refractive index and high transmittance in visible region. The calculation of different electrically important factors for instance, high current density, small open circuit voltage, efficiency and fill factor revealed that co-doped ZnO with 1% Co and 1% Ga has relatively high efficiency of 2.43% and thus shows the potential of this composition as an electrode for solar cell devices.     

Synthesis of graphene-CoS electro-catalytic electrodes for dye sensitized solar cells

A large CoS-implanted graphene (G-CoS) film electrode was prepared using chemical vapor deposition followed by successive ionic layer absorption and reaction. HRTEM and AFM show that CoS nanoparticles are uniformly implanted on the graphene film. Furthermore, the G-CoS electro-catalytic electrode is characterized in a dye sensitized solar cells (DSSC) and is found to be highly electro-catalytic towards iodine reduction with low charge transfer resistance (R_ct ～5.05 Ω cm²) and high exchange current density (J₀～2.50 mA cm^?2). The improved performance compared to the pristine graphene is attributed to the increased number of active catalytic sites of G-CoS and highly conducting path of graphene. The comprehensive G-CoS synthesis process is a simple and scalable process which can easily adapt for large scale electro-catalytic film fabrication for several other electro-chemical energy harvesting and storage applications.     

A flexible carbon counter electrode for dye-sensitized solar cells

A pure carbon counter electrode (CE) for dye-sensitized solar cells (DSCs), has been fabricated using an industrial flexible graphite sheet as substrate and activated carbon as the catalytic material. The CE shows very low series resistance (Rs) and charge-transfer resistance (Rct) by combining the high conductivity of the flexible graphite with the high catalytic property of activated carbon. The Rs and Rct for the CE are respectively only a quarter and two-thirds of those for a platinized fluorine-doped tin oxide glass (Pt/FTO). DSCs with cell areas of 0.15 and 1 cm² fabricated with this CE show higher solar-to-electricity conversion efficiencies. The respective values are 6.46% and 5%, compared with 6.37% and 2.91% for the Pt/FTO based devices.     

A novel high-performance counter electrode for dye-sensitized solar cells

A novel Pt counter electrode for dye-sensitized solar cells (DSC) was prepared by thermal decomposition of H₂PtCl₆ on NiP-plated glass substrate. The charge-transfer kinetic properties of the platinized NiP-plated glass electrode (Pt/NiP electrode) for triiodide reduction were studied by electrochemical impedance spectroscopy. Pt/NiP electrode has the advantage over the platinized FTO conducting glass electrode (Pt/FTO electrode) in increasing the light reflectance and reducing the sheet resistance leading to improve the light harvest efficiency and the fill factor of the dye-sensitized solar cells effectively. The photon-to-current efficiency and the overall conversion efficiency of DSC using Pt/NiP counter electrode is increased by 20% and 33%, respectively, compared to that of using Pt/FTO counter electrode. Examination of the anodic dissolution and the long-term test on the variation of charge-transfer resistance indicates the good stability of the Pt/NiP electrode in the electrolyte containing iodide/triiodide.     

Graphene aerogels as a highly efficient counter electrode material for dye-sensitized solar cells

Graphene aerogels (GAs) prepared with an organic sol–gel process, possessing a high specific surface area of 814 m²/g and a high electric conductivity of 850 S/m, are applied as a counter electrode material for dye-sensitized solar cells (DSSCs). The performance of the GA as the counter electrode material is found to be dependent on its film thickness, with thicker films offering more surface areas for the involved catalytic reduction reaction but at the same time increasing the charge and mass transport resistances. At an optimum GA film thickness of 4.9 μm, a power conversion efficiency of 96% of that achieved with a Pt counter electrode based DSSC is obtained. In addition, a thinner GA film of 1.7 μm, when loaded with Pt of 1 mol% through a photo-reduction process, achieves a power conversion efficiency of 98% of that obtained with a Pt counter electrode based DSSC. The excellent performances of the GA-based counter electrodes are manifested with electrochemical impedance analyses and cyclic voltammetry based catalytic activity analyses.     

Graphene-based nanohybrid materials as the counter electrode for highly efficient quantum-dot-sensitized solar cells

Dry plasma reduction is an excellent approach for easily and uniformly immobilizing Pt, Au and bimetallic AuPt nanoparticles (NPs) on a graphene nanoplatelets (GC)-coated layer under atmospheric pressure at a low temperature and without using any toxic reductants. The NPs with an average size of about 2 nm were stably and uniformly hybridized on the surface of reduced graphene nanoplatelets (RGC) after co-reduction of metal precursor ions and GC to metal atoms and RGC, respectively. Quantum-dot-sensitized solar cells exploiting AuNP/RGC, PtNP/RGC and bimetallic AuPtNP/RGC counter electrodes (CEs) exhibited power conversion efficiencies of 2.7%, 3.0% and 4.5%, respectively. The efficiencies are comparable to that of device with a conventional Au-sputtered CE (3.6%). The effect is ascribed to high electrochemical catalytic activity and high electrical conductivity of developed nanohybrid materials.     

Wurtzite copper-zinc-tin sulfide as a superior counter electrode material for dye-sensitized solar cells

Wurtzite and kesterite Cu₂ZnSnS₄ (CZTS) nanocrystals were employed as counter electrode (CE) materials for dye-sensitized solar cells (DSSCs). Compared to kesterite CZTS, the wurtzite CZTS exhibited higher electrocatalytic activity for catalyzing reduction of iodide electrolyte and better conductivity. Accordingly, the DSSC with wurtzite CZTS CE generated higher power conversion efficiency (6.89%) than that of Pt (6.23%) and kesterite CZTS (4.89%) CEs.     

Graphene supported nickel nanoparticle as a viable replacement for platinum in dye sensitized solar cells

A platinum free counter electrode for dye sensitized solar cells was developed using graphene platelets (GP) supported nickel nanoparticles (NPs) as the active catalyst. Few layered GP were prepared by chemical oxidation of graphite powders followed by thermal exfoliation and reduction. The nanoparticles of nickel were deposited directly onto the platelets by pulsed laser ablation. The composite electrodes of GP and Ni nanoparticles (GP-Ni) thus obtained showed better performance compared to conventional Pt thin film electrodes (Std Pt) and unsupported Ni NPs. The efficiencies of the cells fabricated using GP-Ni, Std Pt and Ni NP CEs were 2.19%, 2% and 1.62%, respectively. The GP-Ni composite solar cell operated with an open circuit voltage of 0.7 V and a fill factor of 0.6. Electrochemical impedance spectroscopy using the I(3)(-)/I(-) redox couple confirms lower values of charge transfer resistance for the composite electrodes, 4.67 Ω cm(2) as opposed to 7.73 Ω cm(2) of Std Pt. The better catalytic capability of these composite materials is also reflected in the stronger I(3)(-) reduction peaks in cyclic voltammetry scans.     

Investigation of low cost carbonaceous materials for application as counter electrode in dye-sensitized solar cells

The structural and morphologic properties of different carbonaceous materials were studied by X-ray diffraction (XRD), Brunauer–Emmet–Teller (BET) porosimetry and transmission electron microscopy (TEM) analyses. The electrochemical behaviour of these powders used as counter electrode in dye-sensitized solar cells (DSSCs) was investigated by polarization experiments and electron impedance spectroscopy. Results were compared with DSSC using Pt as counter electrode. All DSSCs based on the carbonaceous materials showed conversion efficiencies higher than those equipped with Pt. Among the various carbon materials investigated, Acetylene Black in conjunction with graphite showed the best performance. This was interpreted from the physico-chemical analysis as due to a compromise between pores accessibility for the I₃ ^? reactant presents in electrolyte and appropriate surface graphiticity index of this carbonaceous material. A high degree of graphitization for the carbon black was found to enhance electron conduction and charge transfer properties.     

Micro–meso hierarchical porous carbon as low-cost counter electrode for dye-sensitized solar cells

A micro–meso hierarchical porous carbon with low crystallinity was prepared by a combination of self-assembly and post activation and explored as a counter electrode in dye-sensitized solar cells. Pore structure analysis showed that the pristine mesopores were basically preserved during activation and the micropores were mainly generated within the mesopore wall. Due to its low crystallinity and unique pore-structure including both mesopores and micropores, hierarchical porous carbon exhibited a relatively higher electrocatalytic activity for triiodide reduction, as compared with the pristine mesoporous carbon electrode. This enhanced electrocatalytic activity is beneficial for improving the photovoltaic performance of dye-sensitized solar cells. Under irradiation of 100 mW cm⁻², the dye-sensitized solar cell with hierarchical porous carbon counter electrode showed an overall conversion efficiency of 6.48%, which was 11.5% higher than that of the cell with pristine mesoporous carbon counter electrode.     

染料敏化太阳电池介孔薄膜电极的研究进展

介绍了染料敏化太阳电池多孔二氧化钛薄膜电极的结构、工作原理及其制备方法,并进一步阐述了减小电荷复合速率、改进薄膜电极性能、提高器件的光电转化效率的方法,主要涉及多孔二氧化钛薄膜电极的复合、掺杂和表面包覆等表面改性处理技术。指出了基于有序二氧化钛薄膜电极、柔性二氧化钛薄膜电极的染料敏化太阳电池和叠层薄膜结构的太阳电池高效的转化效率和应用方便的特点,并在此基础上展望了未来的研究方向。     

Carbon nanotube counter electrode for high-efficient fibrous dye-sensitized solar cells

ABSTRACT: High-efficient fibrous dye-sensitized solar cell with carbon nanotube (CNT) thin films as counter electrodes has been reported. The CNT films were fabricated by coating CNT paste or spraying CNT suspension solution on Ti wires. A fluorine tin oxide-coated CNT underlayer was used to improve the adherence of the CNT layer on Ti substrate for sprayed samples. The charge transfer catalytic behavior of fibrous CNT/Ti counter electrodes to the iodide/triiodide redox pair was carefully studied by electrochemical impedance and current-voltage measurement. The catalytic activity can be enhanced by increasing the amount of CNT loading on substrate. Both the efficiencies of fibrous dye-sensitized solar cells using paste coated and sprayed CNT films as counter electrodes are comparative to that using Pt wires, indicating the feasibility of CNT/Ti wires as fibrous counter electrode for superseding Pt wires.     

Reverse micelle facilitated synthesis of nanostructured polyaniline as the counter electrode materials in dye-sensitized solar cells

ABSTRACT

We report a reverse-micelle emulsion polymerization of nanostructured PANI using a nonionic surfactant Polyglyceryl-2-Dipolyhydroxystearate (PGPH) at various concentrations from 2% to 6% (v/v). SEM images show that the obtained morphologies are irregular agglomerates at low PGPH concentration and relatively regular granules at high PGPH concentration. FTIR and Raman spectra show that the synthesized PANI is in the form of Emeraldine salt (PANI ES) with electrical conductivity around 10^?3 S cm^?1. Photovoltaic current-voltage (J-V) measurements show the highest power conversion efficiency is achieved at 1.71% at 6% (v/v) of PGPH.     

The application of a three dimensional CNT-sponge as the counter electrode for dye-sensitized solar cells

A sponge-like three dimensional carbon nanotube (CNT) framework has been applied as the counter electrode for a dye-sensitized solar cell (DSC). The CNT-sponge shows high catalytic activity to the counter electrode reduction reactions of I^?/I₃^? redox couple and a photoelectric conversion efficiency of 6.21% has been achieved. Compared with previous carbon-based counter electrode materials for DSCs, the CNT sponge retains highly flexibility and good mechanical strength. Its soft structure makes it possible to directly transfer it onto a substrate to make DSC devices.