Graphene-based Counter Electrode Research Articles

Efficiency of the dye from Spinacia olerace linn for augmentation of charge transfer to Tio2 in dye sensitized solar cell

A chlorophyll-rich dye was made from the leaves of Spinaciaoleracealinn using ethanol and a TiO2 nanoparticle-coated FTO substrate immersed in the dye to achieve ideal binding to maximize absorption of photon energy. The dye's visible light absorbance ranges from 400 nm to 700 nm, with a notable peak at 657 nm and the existence of functional groups allowing perfect binding to the semiconductor material. oxide was confirmed by UV–Visible and FTIR spectroscopy. The SEM image of the dye-impregnated TiO2-coated FTO shows a uniform dispersion of the dye over the entire surface for better photon absorption. Dye-sensitive solar cells are made using a graphene-based counter electrode and an electrolyte of the redox pair I-/I-3. The bonding characteristics of the fabricated solar cells were analyzed to predict the solar cell parameters, and it was found that the fabricated solar cells produced 0.78% efficiency with open circuit voltage., short circuit current, current density and fill factor are 0.49 V., 2.01 mA/cm2 and 0.54 respectively.

Stimulated carbon from Jackfruit wood with TiO2 on FTO substrate as an active counter electrode in DSSC

An effort has been taken to carbonize Jackfruit wood at 750 °C and NaOH which is used for the synthesis of activated carbon. XRD, SEM and EDAX are taken and analyzed for the confirmation of the activated carbon and precise results are presented. As prepared activated carbon is incorporated on the TiO2 coated FTO substrate to be percolated as counter electrode in Dye Sensitized Solar Cell. Dye from the leaves of Saraca Asoca is extracted and subjected to FTIR and UV–Visible spectroscopy to find the presence of chemical constituents. The influence of natural dye in photoanode and activated carbon in counter electron has boosted the photoconversion efficiency of 40% higher than the graphene-based counter electrode. The proposed cell has enhanced photocatalytic activity for the redox couple I-/I3- with low charge transfer resistance of 32.7 Ω. The cell has given short circuit photocurrent density of 3.608 mA/cm2 will fill factor of 0.588 and improved light scattering respectively.

Metal organic frameworks derived high-performance photoanodes for DSSCs

Metal organic frameworks (MOFs) and reduced graphene oxide (RGO) are used to modify photoanodes of dyes sensitized solar cells (DSSCs) to improve their photovoltaic performances. The MOFs are found that bring about a significant enhancement of the BET area of photoanodes, which endows a high dye adsorption capacity. Moreover, the added MOFs introduces an improved incident photon to electron efficiency because of the remarkably enhanced scattering power for the incident light. On the other hand, in the presence of RGO provides a fast transport channel for photo-induced electrons, which depresses the dark current of the resulting devices. After optimizing the mass fraction of MOFs and RGO, the synergy has been achieved. Moreover, by using a graphene-based counter electrode, the photovoltaic performances of the resulting full-carbon DSSCs are detected. The short-circuit current, open-circuit voltage, fill factor (FF) and energy conversion efficiency (η) reach 18.6 mAcm−2, 682 mV, 0.608 and 7.67%, indicating the potential application prospection of the as-prepared photoanodes.

Effects of Electric Field on the Performance of Graphene-Based Counter Electrodes for Dye-Sensitized Solar Cells: A Theoretical Study

We have investigated the influence of an external electric field on the performance of graphene-based counter electrode (CE) materials such as pristine, boron-doped graphene (BC5), and nitrogen-dop...

Electrocatalytic activity of disulfide/thiolate with graphene nanosheets as an efficient counter electrode for DSSCs: A DFT study

An interaction between the redox mediator, disulfide/thiolate (T2/T‒), and catalytic based monolayer graphene nanosheets (GNSs) in a counter electrode of a dye‒sensitized solar cell (DSSC) has been investigated. Two different structures, pristine prefect and defective GNSs, were modeled and used as substrates for catalytic activity toward the reduction reaction of T2 to T‒. The electrocatalytic potentials of the counter electrode, i.e., its energetic, electronic and thermodynamic properties, were investigated using density functional theory calculations. It was found that pristine GNSs can achieve high reactivity to T2/T‒ via an exothermic adsorption reaction. Thermodynamic considerations imply that exothermic and spontaneous cationic and anionic adsorption reactions occurred. These calculations can model the catalytic mechanism and be used for designing high performance counter electrodes for DSSCs. This may be helpful in future experiments using graphene based counter electrodes in DSSCs.

Electrocatalytic activity of disulfide/thiolate with graphene nanosheets as an efficient counter electrode for DSSCs: A DFT study

An interaction between the redox mediator, disulfide/thiolate (T2/T‒), and catalytic based monolayer graphene nanosheets (GNSs) in a counter electrode of a dye‒sensitized solar cell (DSSC) has been investigated. Two different structures, pristine prefect and defective GNSs, were modeled and used as substrates for catalytic activity toward the reduction reaction of T2 to T‒. The electrocatalytic potentials of the counter electrode, i.e., its energetic, electronic and thermodynamic properties, were investigated using density functional theory calculations. It was found that pristine GNSs can achieve high reactivity to T2/T‒ via an exothermic adsorption reaction. Thermodynamic considerations imply that exothermic and spontaneous cationic and anionic adsorption reactions occurred. These calculations can model the catalytic mechanism and be used for designing high performance counter electrodes for DSSCs. This may be helpful in future experiments using graphene based counter electrodes in DSSCs.

CVD-graphene/graphene flakes dual-films as advanced DSSC counter electrodes

The use of graphene‐based electrodes is burgeoning in a wide range of applications, including solar cells, light emitting diodes, touch screens, field‐effect transistors, photodetectors, sensors and energy storage systems. The success of such electrodes strongly depends on the implementation of effective production and processing methods for graphene. In this work, we take advantage of two different graphene production methods to design an advanced, conductive oxide- and platinum-free, graphene-based counter electrode for dye-sensitized solar cells (DSSCs). In particular, we exploit the combination of a graphene film, produced by chemical vapor deposition (CVD) (CVD-graphene), with few-layer graphene (FLG) flakes, produced by liquid phase exfoliation. The CVD-graphene is used as charge collector, while the FLG flakes, deposited atop by spray coating, act as catalyst for the reduction of the electrolyte redox couple (i.e. - and Co+2/+3). The as-produced counter electrodes are tested in both - and Co+2/+3-based semitransparent DSSCs, showing power conversion efficiencies of 2.1% and 5.09%, respectively, under 1 SUN illumination. At 0.1 SUN, Co+2/+3-based DSSCs achieve a power conversion efficiency as high as 6.87%. Our results demonstrate that the electrical, optical, chemical and catalytic properties of graphene-based dual films, designed by combining CVD-graphene and FLG flakes, are effective alternatives to FTO/Pt counter electrodes for DSSCs for both outdoor and indoor applications.

SnO2/ZnO composite dye-sensitized solar cells with graphene-based counter electrodes

Abstract We have pioneered in developing dye-sensitized solar cells with interconnected nanoparticles of semiconductors other than TiO2 and we found that despite impressive properties of semiconducting materials such as ZnO and SnO2 which should theoretically give better performances than those based on TiO2, they give quite inferior performances and we explained this unprecedented fact by considering faster recombination of injected electrons in the latter semiconductor nanoparticles than those in TiO2 nanoparticles. To circumvent this problem, we introduced a novel technology in which we covered the surfaces of interconnected nanoparticles of SnO2 by an ultra-thin layer of a wide band-gap semiconductor or an insulator where the thickness of the layer is ∼1 nm or less such that electron injection from the excited dye molecules to the conduction band of the semiconductor nanoparticles is possible but injected electrons are incapable of penetrating the insulating barrier layer. In this way, we were able to suppress recombination significantly and such composite film based dye-sensitized solar cells gave efficiencies comparable to those based on TiO2 nanoparticles. We then realized that platinum used in dye-sensitized solar cell counter electrodes accounts for nearly 40% of the cost of these solar cells and hence limits their practical application. We then worked on alternative materials and found that carbon based counter electrodes can be tailored to give efficiencies closer to those of Pt counter electrode based solar cells. In extending this study we now worked on graphene as counter electrode material for composite SnO2/ZnO dye-sensitized solar cells. We report in this manuscript the optimizations of this low-cost counter electrode based dye-sensitized solar cell to give performance closer to those of expensive platinum based counterparts.

Graphene-based layers deposited onto flexible substrates: Used in dye-sensitized solar cells as counter electrodes

Abstract In this paper, new cost-effective platinum-free and flexible counter electrodes (CEs) for dye-sensitized solar cells (DSSCs) were reported. The ITO/PET CEs were produced using graphene films synthesized by CVD method and graphene flakes with addition PEDOT: PSS or PEDOT: PSS/PVP. The influence of mechanical stress arising from the bending of a flexible substrate on morphology, resistance of CEs as well as electrical properties of DSSCs was analyzed. The testing of these electrodes in DSSCs have demonstrated a power conversion efficiency of up to 3.95% to compare with the power conversion efficiency of 4.39% for DSSC with a standard Pt-based CE. After 100 bending cycles the electrodes demonstrated power conversion efficiency in range the 2.37–3.23% to compare with the power conversion efficiency of 2.08% for DSSC with a standard Pt-based CE. HRTEM investigation confirms the crystallographic structure of graphene. The obtained results demonstrate the possibility of replacing expensive platinum in DSCC by using graphene-based counter electrode.

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.

Characterisation of graphene-based layers for dye-sensitised solar cells application

The influence of the graphene-based counter electrode on the structure, optical properties and electrocatalytic activity of dye-sensitised solar cells (DSCC) was analysed. The graphene and reduced graphene oxide were deposited by CVD and spin-coating method on the FTO glass substrate, respectively. HRTEM investigation confirms the crystallographic structure of graphene. The investigated layers show flat transmittance spectra across the visible and near-infrared region. The charge transfer resistance of the graphene-based film was analysed by electrochemical impedance measurement. The obtained results show the possibility of replacing expensive platinum in DSCC by using graphene-based counter electrode.

Performance of FTO-free conductive graphene-based counter electrodes for dye-sensitized solar cells

Network structure graphene is used as an efficient counter electrode for DSSCs which is made from modified graphene after UV irradiation. The DSSCs with FTO-free graphene-based counter electrode exhibit an energy conversion efficiency of 9.33%.

Optimum strategy for designing a graphene-based counter electrode for dye-sensitized solar cells

In this study, we developed a cost-effective method to enhance the electro-catalytic activity and conductivity of graphene-based counter electrodes (CEs) by diminishing the oxygen content in graphene nanoplatelets (GNPs) through dry plasma reduction (DPR). As a result, the efficiency of dye-sensitized solar cells (DSCs) based on GNPs with an average surface area of 750m2/g treated by DPR was enhanced by 15% over that of devices with pristine graphene oxide electrodes. The next step in the design strategy for improving DSC performance suggested the immobilization of platinum nanoparticles (PtNPs) on the electrode surface through DPR. DSCs based on the newly developed CEs had an increase in efficiency by 50.3% over that of the Pt-free device, and by 10.4% over the efficiency of state-of-the-art DSCs. The introduction of PtNPs on the surface of a CE through DPR along with removal of the oxygen functional groups from the surface of the GNP electrode reduces the charge-transfer resistance at the electrolyte/CE interface and the diffusion impedance of triiodide ions. PtNPs hybridization on the surface of CE facilitates the electron conductivity in the PtNPs/CE structure by creating a conductive network in the sp3 phase for charge carriers delocalized in a sp2 matrix.

Transparent graphene-based counter-electrodes for iodide/triiodide mediated dye-sensitized solar cells

A new highly transparent and low cost counter-electrode for dye-sensitized solar cells was fabricated, comprised of a structured graphene film over nickel nanoparticles. Annealed nickel particles induced an enhanced restoration of graphene double bonds, which led to cells with energy conversion efficiencies similar to those using a conventional platinum electrode.

Dye-sensitized solar cells equipped with graphene-based counter electrodes with different oxidation levels

This study examines the performance of dye-sensitized solar cells (DSCs) equipped with graphene nanosheet (GN) counter electrodes having different oxidation levels. A thermal deposition is adopted to adjust the O/C atomic ratio and surface oxygen functionalities on graphene sheets. By decreasing the O/C ratio, the GN electrode displays high catalytic activity toward the I3−/I− redox reaction and lower charge-transfer resistance, as analyzed by cyclic voltammetry and electrochemical impedance spectroscopy. The DSC fabricated with the GN counter electrode also offers an improved incident photon-to-current efficiency and power conversion efficiency, in comparison with that equipped with graphene oxide electrodes. This improvement of cell performance could be attributed to the fact that the GN electrode, with a two-dimensional crystal of sp2 carbon, serves as a semi-metal or a zero-bandgap semiconductor with remarkable high electron mobility.

Reduced graphene oxide films as transparent counter-electrodes for dye-sensitized solar cells

Abstract Stand-alone graphene-based films were prepared from graphene oxide (GO) nanoplatelets and their use as counter-electrodes (CEs) in dye-sensitized solar cells (DSCs) was investigated. The graphene-based CEs were produced by spray deposition of GO and chemically reduced GO, followed by thermal annealing under an inert atmosphere. These GO-based CEs were shown to have similar transparency as a reference CE made of Pt. Consistent with impedance data from symmetrical half-cells, DSCs assembled with such GO-based CEs exhibited relative efficiencies of ca. 75% comparatively to the reference Pt CE. The possibility of obtaining transparent (transmittance higher than 80%) and reasonable catalytic films for DSCs (energy conversion efficiency of 2.64%) from GO nanoplatelets was demonstrated. The need for reduction of the graphene oxide nanoplatelets prior to deposition was not observed, allowing for a simplified CE manufacturing process. However, further work is still needed to equal or surpass the performance of Pt CEs.

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%.