Graphene Oxide Counter Electrodes Research Articles

Improvement of the performance of dye-sensitized solar cells employing NickelPalladium alloy-reduced graphene oxide counter electrode: Influence of palladium content

In this work, NickelPalladium-reduced graphene oxide (NiPd-rGO) films have been prepared via liquid phase deposition technique and used as free-platinum (Pt) counter electrode for dye-sensitized solar cell (DSSC). The effect of Pd content in term of various Ni:Pd ratios on the properties such as structure, optical transmission, surface morphology and elemental compositions have been studied. The morphology of NiPd-rGO sample is in the form of crumpled vertical folds in layers and white strips. The influence of Pd content on photovoltaic parameters of the device has also been investigated. The performance parameters were significantly influenced by the Pd content. The device using NiPd-rGO counter electrode prepared at Ni:Pd ratio of 20:2 demonstrated the highest PCE of 3.09%. This is due to the device owns the highest charge recombination resistance (Rrec) and shortest carrier transport time (τ). The efficiency has been improved at the optimum content of Pd. The finding from this work implies that NiPd-rGO is able to substitute Pt as counter electrode in DSSC due to its efficiency is comparable to that of the device employing Pt counter electrode.

Dye-sensitized solar cell using nickel sulfide-reduced graphene oxide counter electrode: Effect of sulphur content

The influence on sulphur content in term of thiourea (TU) concentration on the properties of nickel sulphide (NiS)-reduced graphene oxide (rGO) has been reported in this paper. The effect of sulphur content on the performance of dye-sensitized solar cell (DSSC) using NiS-rGO counter electrode (CE) has also been investigated. The source of sulphur is TU. The sample has been prepared via modified Hummers’s method assisted with spin coating technique. The cell using NiS-rGO CE prepared with 1.20 M TU yielded the highest power conversion efficiency (η) of 1.42%. This is due to this cell has the lowest series resistance (Rb) and charge transfer resistance at the interface of NiS-rGO CE/electrolyte (Rct) with the value of 0.44 and 4.09 Ω, respectively. It is also due to the sample with 1.20 M TU owns the highest reduction current (J). The finding of this work reveals that NiS-rGO is able to substitute platinum as CE for DSSC.

Facile fabrication of reduced graphene oxide counter electrodes by laser engraver for dye-sensitized solar cell applications

Exploring alternative Pt-free counter electrode with low cost and high electrocatalytic activity is always a main focus at the frontier of dye-sensitized solar cells (DSSCs). In this study, a desktop laser engraver was applied to reduce graphene oxide (GO) film on a fluorine-doped tin oxide (FTO) substrate, and the obtained graphene-based material was further used as counter electrode for DSSC. Additionally, this facile laser-scribing method was also adopted to fabricate a prototype of composite electrode via the combination of reduced graphene oxide (RGO) and carbon black (CB) to enhance the specific surface area and active sites. A variety of characterizations including scanning electron microscopy (SEM), Raman spectroscopy, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were conducted to investigate the microstructures and catalytic properties of these carbon electrodes. The findings reveal that both of the DSSCs with laser-scribed carbon electrodes show evidently increasing photovoltaic performance, and the DSSC based on RGO/CB composite electrode even presents a higher power conversion efficiency (PCE) of 4.49%, comparable to 4.14% of the conventional Pt-based DSSC.

Scalable screen-printing manufacturing process for graphene oxide platinum free alternative counter electrodes in efficient dye sensitized solar cells

The graphene oxide paste (GO) was prepared by mixing α-terpineol and ethyl cellulose, and GO films was prepared by screen printing on fluorine doped Tin oxide (FTO) glass substrates to validate as an alternative counter electrode material to platinum in dye sensitized solar cells (DSSC). The graphene oxide films were characterised by X-Ray Diffraction, Scanning Electron Microscopy, Raman spectroscopy and the catalytic properties of films were being investigated by cyclic voltammetry and electrochemical Impedance measurements. The DSSC fabricated by coupling TiO2 films soaked in N719 dye with GO as counter electrode exhibited photoconversion efficiency of 5.58% under standard one Sun illumination, whereas platinum based device showed photoconversion efficiency of 7.57%. The present study suggests that graphene oxide counter electrodes can be considered as a promising alternative to platinum, with further optimisation, which clearly has advantages in terms of its abundance and low cost processing towards industrial prospects.

Polyaniline (PANI)/reduced graphene oxide (rGO) composite as a counter electrode for dye solar cells.

Polyaniline (PANI)-reduced graphene oxide (rGO) based transparent counter electrodes have been fabricated for dye sensitized solar cells as an alternative to the expensive platinum (Pt) counter electrodes. Here, the graphene oxide (GO) added during the polymerization of PANI will subsequently reduce to rGO. The concentration of graphene oxide (GO) was varied in PANI matrix to optimize the performance of dye solar cell (DSC). With 1% GO addition in PANI, 9.68% current density was increased, consequently, 13.9% photocurrent density was found to be increased as compared to pure PANI. Electrochemical impedance spectroscopy (EIS) disclosed that the incorporation of 1% GO in PANI caused the double-layer capacitance to increase by 10 times compared to pure PANI. This implies that graphene is capable of enhancing the specific surface area and catalytic capacity of PANI. Optical transparency of PANI-1% GO counter electrode was found to be ∼67% between the wavelengths of 500 to 600 nm. Such transparency enables the construction of bifacial DSCs. Although the photo conversion efficiency (PCE) of DSC with PANI-1% GO counter electrode is still not comparable to the one with Pt counter electrode but it is sufficient to be considered as the replacement as it exhibits good photovoltaic performance and optical characteristics together with an exceptionally low cost material.

MoS2 nanosheets based counter electrodes: An alternative for Pt-free dye-sensitized solar cells

Dye-sensitized solar cells are assembled with MoS2 nanosheets based counter electrodes synthesized via hydrothermal route using ammonium molybdate tetrahydrate and thiourea as precursor materials. Basic and specific studies are followed to characterize MoS2 as counter electrode material by XRD, SEM, TEM, EDX, cyclic voltammetry and electrochemical impedance spectroscopic studies. Dye-sensitized solar cells device is fabricated by using fluorine-doped tin oxide glass plate coated with TiO2 as photoanode, Cis-bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato)ruthenium(II) dye as a light harvester, and iodine/iodide as a liquid electrolyte. The fabricated dye-sensitized solar cells device with MoS2 counter electrode showed an open circuit voltage of 795 mV, short circuit current of 19.6 mA/cm2, fill factor of 0.36, and power conversion efficiency of 6.6% upon comparing to Pt counter electrode which showed an open circuit voltage of 827 mV, short circuit current of 14.8 mA/cm2, fill factor of 0.47, and power conversion efficiency of 6.8%. In addition to this, MoS2 coupled reduced graphene oxide counter electrodes are prepared by simply dispersing reduced graphene oxide and MoS2 in isopropyl alcohol which showed the best performance with open circuit voltage of 800 mV, short circuit current of 20.5 mA/cm2, fill factor of 0.42, and power conversion efficiency of 8.1%.

Dye‐sensitised solar cell utilising gold doped reduced graphene oxide counter electrode: influence of annealing time

Gold doped reduced graphene oxide (rGO) films prepared via hummer method have been utilised as counter electrode of dye-sensitised solar cell. The samples were subjected to various annealing times at 120°C. The effect of annealing time on the dark current and photovoltaic performance has been investigated. The power conversion efficiency varies with annealing time. The highest efficiency of 0.155% was achieved by the device utilising gold doped rGO annealed for 45 min. This is due to the device employing this sample possesses the smallest leak current.

Effect of Annealing Temperature of Gold Doped Reduced Graphene Oxide Counter Electrode on the Performance of Dye-sensitized Solar Cell

Effect of Annealing Temperature of Gold Doped Reduced Graphene Oxide Counter Electrode on the Performance of Dye-sensitized Solar Cell

Cost-Effective Mo Fe Alloy/Reduced Graphene Oxide Counter Electrodes As a New Avenue for High-Efficiency Dye-Sensitized Solar Cells

MoxFe1-x/reduced graphene oxide (RGO) (0 ≤ x ≤ 1) is successfully synthesized using atmospheric pressure plasma under near room temperature and without using any toxic reagents. HRSEM, TEM, XRD and XPS measurements are conducted to analyze the morphology and chemical composition of the developed materials. Then, the developed materials are applied as Pt-free CEs in DSCs. To obtain efficient CEs, the chemical composition of the MoxFe1-x/RGO is controlled through optimizing the volume ratio of the Mo and Fe precursors during the synthesizing process. The catalytic activity of the developed CEs is carefully evaluated through EIS, CV and Tafel measurements. Finally, the effect of CEs on the efficiency of DSCs is further confirmed by J-V and IPCE performances. As the result, the high conductivity and excellent catalytic activity toward triiodide reduction in CEs of DSCs are obtained for MoxFe1-x/RGO CEs.

Improving the photovoltaic performance of DSSCs using a combination of mixed-phase TiO2 nanostructure photoanode and agglomerated free reduced graphene oxide counter electrode assisted with hyperbranched surfactant

The role of hyperbranched surfactant, namely, sodium 1,4-bis (neopentyloxy)-3-(neopentyloxycarbonyl)-1,4-dioxobutane-2-sulphonate (TC14), in the synthesis and stabilisation of reduced graphene oxide (rGO) as counter electrode (CE) thin film was investigated for dye-sensitised solar cell (DSSCs) application. The energy conversion efficiency (η) of CE-based rGO from TC14 (TC14-rGO) was 0.0266%, with a short current density, open circuit voltage and fill factor of 0.222 mA/cm2, 0.697 V and 14.15, respectively. The efficiency of the surfactant was two times higher than that of CE-based rGO from single-tail sodium dodecyl sulphate surfactant. Graphene oxide (GO) was initially synthesised by electrochemical exfoliation method. Hydrazine hydrate was subsequently used in the production of rGO through chemical reduction process. Spraying deposition method was used to transfer GO and rGO solutions and fabricate GO and rGO CE thin films. A novel combination of hydrothermal growth and squeegee method in the synthesis and production of mixed-phase titanium dioxide (TiO2) nanostructures as photoanode was selected due to its simple and low-cost method. Rutile TiO2 nanorods and anatase TiO2 nanoparticles are essential in electron transfer process and dye adsorption, respectively. Therefore, these combinations resulted in improved photocatalytic activity and η of dye-sensitised solar cells when TC14-rGO was used.

Cost-effective CoPd alloy/reduced graphene oxide counter electrodes as a new avenue for high-efficiency liquid junction photovoltaic devices

Abstract This work presents the synthesis of Co x Pd 1-x alloys (0 ≤ x ≤ 1) on a reduced graphene oxide (RGO) surface using the dry plasma reduction method. The formation of CoPd alloys on the RGO surface is confirmed through high-resolution scanning electron microscopy (HRSEM) and X-ray photoelectron spectroscopy (XPS) measurements, and transmittance electron microscopy (TEM). Then, the developed materials are applied as Pt-free counter electrodes (CEs) in dye-sensitized solar cells (DSCs). In order to obtain efficient CEs, the chemical composition of the Co x Pd 1-x /RGO is controlled through optimizing the volume ratio of the Co and Pd precursors during the synthesizing process. Due to the optimization of the charge-transfer resistance ( R ct ) and the diffusion impedance ( Z w ) values of the Co 0.9 Pd 0.1 /RGO CE, the device using the Co 0.9 Pd 0.1 /RGO CE exhibits the highest efficiency among the fabricated cells. Note that the cells using Co/RGO and Pd/RGO exhibit efficiencies of 5.17% and 5.41%, respectively. The proposed strategy is simple and efficient; thus, it is promising for fabricating highly efficient and low-cost CE materials for DSCs.

Ultrathin-walled Co9S8 nanotube/reduced graphene oxide composite as an efficient electrocatalyst for the reduction of triiodide

A novel ultrathin-walled Co9S8 nanotube/reduced graphene oxide electrocatalyst, for the first time, is successfully prepared by a simple hydrothermal process coupling with an ion exchange process for the reduction of triiodide in dye-sensitized solar cells (DSSC). Ultrathin-walled Co9S8 nanotubes have an average diameter of 20–30 nm and a wall thickness of 3–4 nm, and the reduced graphene oxide possessing high conductivity is well dispersed in the Co9S8 nanotubes simultaneously, which contributed to the high specific surface area, well exposed active sites and excellent electric conductivity. The electrochemical performances of ultrathin-walled Co9S8 nanotube/reduced graphene oxide are evaluated by the EIS, Tafel polarization and CV measurements, exhibiting the significant improvement of electrocatalytic performance for the triiodide reduction. Optimizing the film thickness of Co9S8 nanotube/reduced graphene oxide counter electrode, the optimum photovoltaic conversion efficiency of 7.58% is obtained, which is even higher than that of the DSSC with Pt counter electrode (7.45%). In addition, the DSSC with Co9S8/reduced graphene oxide electrode exhibits a good repeatability and long-term electrochemical stability. Therefore, the ultrathin-walled Co9S8 nanotube/reduced graphene oxide is a reliable material to replace Pt.

Pt-free spray coated reduced graphene oxide counter electrodes for dye sensitized solar cells

Graphene oxide (GO) was synthesized using a modified Hummers method and was reduced by using focused sunlight to obtain solar reduced graphene oxide (SRGO). GO and SRGO are then used as Pt-free counter electrode materials in dye sensitized solar cells (DSSCs). GO and SRGO counter electrodes were prepared by a simple spray coating method to produce homogeneous electrode layers. The DSSCs with GO and SRGO counter electrodes exhibited an overall power conversion efficiencies of ∼3.4 and ∼4%, respectively. Cyclic voltammetry and electrochemical impedance spectroscopy reveal that the DSSC with SRGO counter electrode exhibits higher electro-catalytic activity and lower charge transfer resistance at the electrode/electrolyte interface (in comparison to the DSSC with GO) resulting in higher conversion efficiency. Moreover, the microstructural features of SRGO are found to be suitable for its improved interaction with the liquid electrolyte and the enhanced electro-catalytic activity at its surface.

Low Cost Fabrication of Graphene Oxide Films As Efficient Counter Electrode for Dye-Sensitized Solar Cells (DSSC)

Graphene-oxide was prepared by screen printing to validate as an alternative counter electrode material to platinum in dye sensitized solar cells. The synthesis of graphene oxide was carried out by modified Hummer’s method using graphite flakes. Subsequently, graphene oxide paste was prepared by mixing α-terpineol and ethyl cellulose, which was screen-printed on FTO glass (TEC8) substrates. The screen printed films were subjected to annealing at 450°C for 30 minutes. The graphene oxide films were characterised by X-Ray Diffraction, Scanning Electron Microscopy and Raman spectroscopy for the required identification. The device fabrication was carried out by coupling TiO2 films soaked in N719 dye with Surlyn as the spacer between the electrodes. The J-V measurements were carried out with the help of the solar Simulator AM1.5G condition under standard one Sun illumination. The DSSC fabricated with graphene oxide as counter electrode exhibited photoconversion efficiency of 5.58% whereas, platinum based devices showed photoconversion efficiency of 7.57%. The catalytic properties of graphene oxide films are being investigated by cyclic voltammetry and electrochemical Impedance spectroscopy. The present study suggests that graphene oxide counter electrodes can be considered as a promising alternative to platinum, with further optimisation, which clearly has advantages in terms of its abundance and low cost processing towards industrial prospects.

Investigation of Graphene Oxide-TiO2 Photoelectrodes with Different Compact Layers and Counter Electrodes

Modified Hummer’s method was adopted for the preparation of graphene oxide (GO) using graphite flakes. Graphene-oxide was incorporated in the TiO2 paste and the films are prepared by screen printing on FTO glass (TEC8) substrates. The screen printed films were subjected to heat treatment cycle at 375°C for 5 min, 375 °C for 5 min, 450°C for 15 min and finally at 500°C for 15 minutes. The crystallinity and phase purity of the GO samples were characterised by X-ray diffraction using Cu-Kα radiation. The morphology of the GO is investigated using transmission electron microscopy and the chemical structures of GO are analysed by XPS. Photovoltaic properties were measured by a computer-controlled digital source meter (Keithley 2400) under simulated one sun illumination at AM 1.5G (100mW/cm2) from a solar simulator (92250 A, Newport, USA). The electrochemical impedance spectroscopy (EIS) is carried out using Metrohm Autolab in the frequency range of 1MHz to 0.1Hz with amplitude of 20 mV under dark conditions. The device was assembled by coupling GO-TiO2 films soaked in N719 dye with Surlyn as the spacer between the electrodes. The performance of the GO-TiO2 composite photoelectrodes were tested with different compact layers and different counter electrodes. The DSSC fabricated with graphene oxide as counter electrode exhibited photoconversion efficiency of 4.6% whereas, platinum based devices showed photoconversion efficiency of 4.7%. The present study suggests that graphene oxide counter electrodes can be considered as a promising alternative to platinum, with further optimisation, which clearly has advantages in terms of its abundance and low cost processing towards industrial prospects.

Characterization of graphene-oxide-based composite structures as counter electrodes for dye-sensitized solar cells

Graphene oxide (GO) was synthesized by using a “top-down” approach with the Hummers method; 2-dimensional (2-D) GO sheets were obtained starting from bulk graphite. The GO sheets were cut into nanoparticles by using ultrasonic dispersion in deionized water. The GO nanoparticle solution was deposited on fluorine-doped tin-oxide glass by using electrophoretic deposition (EPD). We applied the deposition current and voltage by using the results of cyclic voltammetry. The EPD process was monitored during the deposition times by using real-time chronoamperometery. The deposited GO films showed over 80% transmittance at 550 nm in spite of the composite structure consisting of porous particles and 2-D sheets. We prepared GO-based composite structures as counter electrodes for dye-sensitized solar cells. From the results of the electrochemical impedance spectroscopy, the electron transfer in the composite counter electrode was better than that of the graphite or the platinum. Also, the energy conversion efficiency was enhanced to 6.02% by using the suggested GO counter electrodes.

Rapid atmospheric pressure plasma jet processed reduced graphene oxide counter electrodes for dye-sensitized solar cells.

In this work, we present the use of reduced graphene oxide (rGO) as the counter electrode materials in dye-sensitized solar cells (DSSCs). rGO was first deposited on a fluorine-doped tin oxide glass substrate by screen-printing, followed by post-treatment to remove excessive organic additives. We investigated the effect of atmospheric pressure plasma jet (APPJ) treatment on the DSSC performance. A power conversion efficiency of 5.19% was reached when DSSCs with an rGO counter electrode were treated by APPJs in the ambient air for a few seconds. For comparison, it requires a conventional calcination process at 400 °C for 15 min to obtain comparable efficiency. Scanning electron micrographs show that the APPJ treatment modifies the rGO structure, which may reduce its conductivity in part but simultaneously greatly enhances its catalytic activity. Combined with the rapid removal of organic additives by the highly reactive APPJ, DSSCs with APPJ-treated rGO counter electrode show comparable efficiencies to furnace-calcined rGO counter electrodes with greatly reduced process time. This ultrashort process time renders an estimated energy consumption per unit area of 1.1 kJ/cm(2), which is only one-third of that consumed in a conventional furnace calcination process. This new methodology thus saves energy, cost, and time, which is greatly beneficial to future mass production.

Fabrication and Characterization of Reduced Graphene Oxide Counter Electrode for Dye-Sensitized Solar Cells

To improve performance of dye-sensitized solar cell(DSSC), thermally reduced graphene oxide(rGO) was investigated as Pt-free counter electrodes(CE) material. The DSSCs with rGO were fabrcated by simple spin coating method under different temperature and ambient atmospheres like Ar, N2 and air. When the rGO CE was reduced at 450°C under the Ar atmosphere, it was obtained the power conversion efficiency of 6.02%, which showed the high catalytic activity and performance of DSSC as much as Pt. This value means the thermally reduced rGO CEs under the Ar gas will be suitable as a substitute for Pt CEs.

Highly Efficient Metal-Free Sulfur-Doped and Nitrogen and Sulfur Dual-Doped Reduced Graphene Oxide Counter Electrodes for Dye-Sensitized Solar Cells

Developing metal-free electrocatalysts with both high performance and low cost for the reduction reaction at the cathode of dye-sensitized solar cells (DSCs) is critical for further cost reduction and large-scale implementation of DSCs. Here, sulfur-doped reduced graphene oxide (SRGO) and nitrogen and sulfur dual-doped reduced graphene oxide (NSRGO) were applied as highly efficient metal-free electrocatalysts for DSCs in disulfide/thiolate redox electrolytes. It was found that SRGO and NSRGO exhibited outstanding electrochemical performance toward catalyzing the disulfide/thiolate redox couple. The DSC devices based on SRGO and NSRGO counter electrodes showed power conversion efficiency of 4.23% and 4.73%, respectively. In addition, the obtained SRGO and NSRGO also presented catalytic activity higher than that of the platinum electrodes for Co(bpy)33+/2+ redox mediators. The currently reported SRGO and NSRGO demonstrate not only the attractive feasibility of replacing platinum cathodes with abundant carbon materials for novel iodine-free electrolytes but also that the judicious heteroatom doping of graphene oxide might open promising directions for further cathode candidates for iodine-free DSCs.

Transparent graphene oxide–Pt composite counter electrode fabricated by pulse current electrodeposition-for dye-sensitized solar cells

To use as counter electrode in dye-sensitized solar cells (DSSCs) highly transparent graphene oxide (GO)–Pt composite film was fabricated via spin-coating of synthesized GO followed by pulse current (PC) electrodeposition of Pt, which has many benefits such as controlling of particle size and density, remarkable adhesion, uniform morphology, and simple and atmospheric pressure method without any use of vacuum systems. Compared to GO counter electrode, uniform distribution of Pt nanoparticles with a size of ~30nm on GO leads to dramatic improvement of electrocatalytic activity toward the I3−+2e−=3I− reaction, and thus overall power conversion efficiency was increased from 3.99% to 7.10%. Moreover, GO–Pt composite counter electrode showed superior characteristics to PC electrodeposited Pt counter electrode showing ununiform distribution of Pt nanoparticles on rough fluorine-doped tin oxide (FTO) coated glass substrates.