Carbon Nanotube Counter Electrode Research Articles

Dye-sensitized solar cells based on MK2 dye, PMMA-based quasi-solid electrolyte, and flexible CNT counter electrode

In this paper, a dye-sensitized solar cell based on organic MK2 dye, a quasi-solid electrolyte, and a flexible counter electrode was investigated. Two types of TiO2 nanoparticles with different sizes were used to make the photoanode with a bi-layer structure. The quasi-solid electrolyte was made based on polymethylmethacrylate (PMMA) and iodide/triiodide couple. The counter electrode was fabricated by electrophoresis deposition of carbon nanotube (CNT) mixed with diallyl dimethylammonium chloride (PDDA) on a flexible stainless-steel mesh. A cellulose separator was used to improve the stability of the solar cell. A simple and low-cost sealing method using polypropylene-based tape has been proposed and used for conducting the stability test. The maximum conversion efficiency of 2.5% (under simulated AM 1.5) was obtained with the fabricated quasi-solid dye-sensitized solar cells.

CNTs/Cf based counter electrode for highly efficient hole-transport-material-free perovskite solar cells

A carbon nanotubes (CNTs)/carbon fiber (Cf) has been prepared and used as a counter electrode (CE) for hole-transport-material-free perovskite solar cells (PSCs). It was found that CNTs/Cf material effectively increased the contact area between perovskite and carbon layer, correspondingly decreased the charge exchange resistance and enhanced hole extraction ability at perovskite/CE interface. In addition, hole transfer in CNTs/Cf CE was accelerated due to the existence of “highway” hole transfer path derived from CNTs/Cf structure, which reduced photoluminescence peak intensity. As a result, the PSC based on CNTs/Cf CE with high-efficiency hole extraction ability and fast hole transfer performance had a high power conversion efficiency (PCE) of 11.80 % compared with that of CNTs CE (8.93 %) and Cf CE (7.47 %).

Enhancing DSSC Photoanode Performance by Using Ni-Doped TiO2 to Fabricate Scattering Layers

Titanium dioxide powder (TDP) and nickel-doped titanium dioxide powder (NiTDP) were synthesized by simple processes based on the sol–gel method. Nickel can be doped into titanium dioxide to narrow its energy bandgap; as a result, the visible-light photoactivity can be improved. In this study, the particle size of the fabricated TDP and NiTDP were larger than 100 nm, which is suitable for fabricating the light scattering layer (LSL) of the photoanode of dye-sensitized solar cells (DSSCs). The photoanode of our DSSCs comprised two layers: (1) a light absorbent layer made of commercial P25 titanium dioxide nanoparticles and (2) an LSL made of TDP or NiTDP. The DSSC used an organic MK-2 dye sensitizer, iodine-based redox electrolyte, and a multiwalled carbon nanotube counter electrode. Experimental results show that the photocurrent was significantly enhanced when the LSL was used. The DSSC with the absence of the LSL exhibited a conversion efficiency of 2.15%, while those of the DSSCs with the TDP-based LSL and NiTDP-based LSL were 2.37% and 2.78%, respectively. These results combined with UV–Vis spectra data, confirm the effectiveness of the extended visible-light photoactivity of the NiTDP-based LSL on the performance of the photoanode.

Application of polypyrrole/sodium dodecyl sulfate/carbon nanotube counter electrode for solid-state dye-sensitized solar cells and dye-sensitized solar cells

The replacement of the expensive Pt counter electrode (CE) for solid-state dye-sensitized solar cells (ss-DSSCs) and dye-sensitized solar cells (DSSCs) is necessary to reduce cell fabrication cost. With this objective, two CE films PPy + SDS (polypyrrole + sodium dodecyl sulfate as a surfactant), and PPy + SDS + CNT (carbon nanotubes) were prepared by a simple electrochemical polymerization method. These films were effectively used as the CE in DSSCs and ss-DSSCs. Tafel curves and impedance spectroscopy data showed that the PPy + SDS + CNT has a low surface resistance, which causes excellent electrocatalytic activity in both devices. DSSCs with a PPy + SDS + CNT CE show good power conversion efficiency (PCE) compared to ss-DSSCs. Both devices show comparable PEC to the Pt counterpart, and the PPy + SDS + CNT film can be used as a CE for DSSCs and ss-DSSCs and is a viable alternative to a sputtered Pt electrode.

High-efficiency layered sulfur-doped reduced graphene oxide and carbon nanotube composite counter electrode for quantum dot sensitized solar cells

A high-efficiency layered sulfur-doped reduced graphene oxide and carbon nanotube composite counter electrode for quantum dot sensitized solar cells is prepared via ultrasonic dispersion followed with simultaneous reduction and doping by hydrothermal using Na2S as a reductant and sulfur source. Scanning and Transmission electron microscopy show the layered composite with carbon nanotube-bridges between reduced graphene sheets. An increase in sp2C/sp3C ratio of composite is revealed for the first time by the analysis of X-ray photoelectron spectra. Electrochemical tests show that the charge transfer resistance is 1.76Ω. The power conversion efficiency of 5.70% is obtained for the quantum dot sensitized solar cell based the composite counter electrode, and is 18.26%, 76.47%, and 126.19% higher than those of unsulfured composite, reduced graphene, and carbon nanotube counter electrodes, respectively. This is mainly due to the improvement of morphological and property of sulfur-doped reduced graphene and carbon nanotube composite, which presents a high specific surface area, high conductivity, providing abundant catalytic active sites and fast electron transport channels for Sn2− reduction.

Photovoltaic Characteristics of Multiwalled Carbon Nanotube Counter-Electrode Materials for Dye-Sensitized Solar Cells Produced by Chemical Treatment and Addition of Dispersant

Multiwalled carbon nanotubes (MWCNTs) have excellent electrical conductivity and good chemical stability, and are used as counter electrodes in dye-sensitized solar cells (DSSCs). The counter electrodes collect electrons from the external circuit and catalyze the redox reaction in the electrolyte. Electrocatalysis is an important step for generating energy from triiodide reduction in DSSCs. In this study, chemically treated MWCNTs were investigated for improving the photovoltaic performance of DSSCs. The MWCNTs were modified through chemical oxidation with sulfuric acid/nitric acid (H2SO4/HNO3) or potassium persulfate/sodium hydroxide (K2S2O8/NaOH). Nanocellulose (CNC) was used as a dispersant to improve the photovoltaic performance and dispersibility as an alternative material for counter electrodes in DSSCs. The counter electrodes were prepared on fluorine-doped tin oxide (FTO) glass substrates by spin coating nanofluids. Morphological and structural investigations were performed using scanning transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, and Raman spectroscopy. The electrical conductivity and UV light absorption of the DSSCs were analyzed to evaluate their photovoltaic performance. The results of these analyses showed that chemical functionalization and addition of CNC were effective for increasing the electrical conductivity and UV light absorption. Finally, all result trends were the same. Increasing the dispersibility of the counter electrode was found to improve the reduction of I3− at the interface between the MWCNTs and the electrolyte, thereby, improving the energy conversion efficiency.

Optimizing the Multiwall Carbon Nanotubes Counter Electrode by Depositing CuS Quantum Dots

For the purpose of improving the property of a multiwall carbon nanotubes (MWCNTs) counter electrode (CE), CuS quantum dots (QDs) are deposited. Three-dimension network MWCNTs as the framework are deposited onto an fluorine-doped tin oxide (FTO) glass substrate and then CuS QDs as active sites are loaded onto them with a successive ionic layer adsorption and reaction method to form a composite CE. TEM and energy dispersive X-ray (EDX) spectrum can verify the morphology and elemental composition of the composite CE that CuS QDs are loaded onto the MWCNTs CE successfully. The photoelectric properties of quantum dot sensitized solar cells (QDSCs) are analyzed with Nyquist, Tafel, and J–V curves. The results show that the catalytic ability of the CE is enhanced through the loading of CuS QDs according to electrochemical impedance spectroscopy and Tafel analyses. The effect of CuS depositing cycle times on the photoelectric properties of QDSCs is discussed. And the QDSC based on the MWCNTs CE deposited with CuS QDs in ten cycles can display the best performance within all cell samples ( $V_{{\text{oc}}}\,= \,{\text{0.874}}\,{\text{V}}$ , $J_{{\text{sc}}}\,= \,{\text{10.105}}\,{\text{mA cm}}^{- 2}$ , ${\text{FF}}\,= \,{\text{0.416}}$ , and $\eta \,= \,{\text{3.677}}\% $ ). The power conversion efficiency of this cell is almost equivalent to that of Pt CE one under the same conditions and especially its $V_{{\text{oc}}}$ is 0.118 V higher than that of the Pt CE.

A new breakthrough for graphene/carbon nanotubes as counter electrodes of dye-sensitized solar cells with up to a 10.69% power conversion efficiency

A three-dimensional graphene/single-walled carbon nanotube counter electrode is developed for dye-sensitized solar cells via a drop-coating method. The resulting graphene/single-walled carbon nanotube counter electrode show satisfactory transmittance (56.6%) compared with that of bare fluorine-doped tin oxide glass (84.71%) at 670 nm. The obtained graphene/single-walled carbon nanotube counter electrode exhibits an excellent power conversion efficiency of 9.24%. When a mirror was set under the cells, the power conversion efficiency increased to 10.56%. Unexpectedly, in the stability test, its power conversion efficiency reached a maximum of 10.69%. This excellent performance was attributed to the three-dimensional structure, which had a large specific surface area. The cyclic voltammetry results indicate that the graphene/single-walled carbon nanotube had a higher catalytic I3− capability than that of Pt counter electrode, whereas the electrochemical impedance spectroscopy and Tafel test results prove that the graphene/single-walled carbon nanotube have a smaller resistance, which is consistent with the I-V characterization. We determine that the three-dimensional graphene/single-walled carbon nanotube counter electrode may have broad application prospects in dye-sensitized solar cells as a Pt-free material.

Preparation of CNT Counter Electrode by Electrophoresis for Dye-Sensitized Solar Cell

Carbon nanotubes are one of the materials that can replace platinum as DSSC’s counter electrode. By utilizing carbon nanotubes (CNT), which is an organic material in place of platinum it is possible to create an inexpensive solar cell. However, there are still many problems with CNT such as low conversion compared with platinum and fast degradation in CNT. At the present time, it is to be large surface area when we fabricate CNT electrode sintered at 500°C with Electrophoretic Deposition (EPD). We measured how conversion efficiency changed by changing sintering temperatures. As a result, when CNT electrode sintered at 500°C, conversion efficiency was the highest and it was 2.46%.

A transparent honeycomb-like poly(3,4-ethylenedioxythiophene)/multi-wall carbon nanotube counter electrode for bifacial dye-sensitized solar cells

A novel transparent honeycomb-like poly(3,4-ethylenedioxythiophene)/multi-wall carbon nanotube (PEDOT/MWCNT) electrode served as a counter electrode (CE) for the bifacial dye-sensitized solar cell (DSSC) has been fabricated on the fluorine-doped tin oxide (FTO) glass using a sacrificial template of poly(methyl methacrylate) for the first time. Cyclic voltammetry and electrochemical impedance spectroscopy measurements indicate that the honeycomb-like PEDOT/MWCNT CE has a higher electrocatalytic activity for the I3−/I− redox reaction and a smaller charge transfer resistance than those of the flat PEDOT CE. Ultraviolet–visible spectrophotometer measurement indicates that the PEDOT/MWCNT CE with honeycomb-like nanostructure demonstrates high transparency for the backside illumination. The bifacial DSSC based on this honeycomb-like PEDOT/MWCNT CE shows conversion efficiencies of 9.07% and 5.62% from front and rear side illumination, respectively, which are higher than those of the bifacial DSSC based on the flat PEDOT CE (7.51% and 3.49% respectively).

Elektroda iz ogljikovih nanocevk za tankoplastne barvno občutljive sončne celice

Elektroda iz ogljikovih nanocevk za tankoplastne barvno občutljive sončne celice

Rapid fabrication and photovoltaic performance of Pt-free carbon nanotube counter electrodes of dye-sensitized solar cells

We fabricated uniform multiwalled carbon nanotube (MWCNT) thin films on fluorine-doped tin oxide (FTO) glass substrates with controlled thickness by an easy and versatile spin-coating process (SCP). Aqueous dispersions of MWCNTs were dropped on the FTO glass substrates and spin-coated to form uniform MWCNT thin films, which were then used as the catalytic medium on the counter electrodes (CEs) of dye-sensitized solar cells (DSCs). For the DSC with an optimized MWCNT-thin-film thickness coated on the CE, the short circuit current density (Jsc) was more than that of the conventional Pt-based DSC (10.97±0.13mAcm−2 vs 9.58±0.17mAcm−2), while its power conversion efficiency (PCE) was comparable to that of conventional DSC (∼4.41±0.14% and ∼4.69±0.22%, respectively). This suggests that the accumulation of MWCNTs on the CE increases the interfacial contact area between the MWCNTs and liquid electrolyte in the DSC, allowing the rapid reduction of I3−. Simultaneously, it decreases the charge transfer resistance owing to rapid electron transport through the MWCNT medium with its relatively high electrical conductivity. Thus, the precisely controlled rapid accumulation of MWCNT thin films by the SCP on the CEs of DSCs is a very promising approach for replacing the expensive Pt metal that is currently used in DSC applications.

(Invited) Point-of-Care Diagnostics with Inkjet-Printed Microchips

Multi-layer inkjet printing is applied to prepare microchips that consist of up to eight three-electrode sensors comprising a carbon nanotube (CNT) working electrode, a silver/silver chloride quasi-reference electrode and a CNT counter electrode. Optionally, the sensors contain micro-wells to measure sample volumes as small as 50 µL. The implementation of inkjet printing allows the flexible design and highly reproducible fabrication of batches of various electrode shapes and dimensions. The usage of CNTs as stand-alone working electrodes results in electroanalytical sensors with reliable and superior electrochemical response compared to tested commercial carbon paste electrodes. The sensors can be used at least up to 20 times, e.g., based on an immunoassay based strategy, or in a disposable way, e.g., when measuring in complex matrices such as blood. A gold ink is applied as alternative working electrode material. The printed sensors can be used with compact multichannel potentiostats that are suitable for point-of-care diagnostics.

Inkjet-printed microtiter plates for portable electrochemical immunoassays

Herein, we present the large-scale fabrication of multiplexed three-electrode sensors used in a point-of-care device platform that couples a magnetic bead-based immunoassay strategy with amperometric detection for rapid and highly sensitive analysis. The multiplexed sensors consisted of eight independent electrochemical cells, each with a carbon nanotube (CNT) working electrode, CNT counter electrode and a silver-silver chloride quasi-reference electrode. The microchips were fabricated on flexible polyethylene terephthalate (PET) sheets by sequential multilayer inkjet printing (IJP) of silver, CNT and insulator inks that were either simultaneously or subsequently post-processed (e.g. through UV photo-polymerization or photonic curing). Finally, plastic wells were mounted on top of the inkjet-printed patterns to obtain an eight-well microtiter plate where each well had a solution capacity of 50μL. Due to the high precision of the IJP process, the microtiter plates showed high reproducibility among the individual electrochemical cells (1–2% of deviation). Furthermore, the microchips can be reusable for at least up to 20 times as demonstrated herein. In a customized multichannel potentiostat with eight implemented magnets matching the positions of the working electrodes, the electrochemical readout of magnetic bead based sandwich and competitive immunoassays was successfully realized for the detection of thyroid-stimulating hormone (TSH) and atrazine (ATR) in aqueous and urine samples, respectively. The achieved limits of detection for ATR (i.e. 0.01μg/L) and TSH (i.e. 0.5μIU/mL) demonstrated the potential of the IJP microtiter plates for the environmental and biological quantification of analytes in a very reliable high throughput platform. This work shows that IJP has certainly reached the status of a batch production tool for electroanalytical sensing platforms.

A PVdF-based electrolyte membrane for a carbon counter electrode in dye-sensitized solar cells

This research demonstrates the design and operation of a dye-sensitized solar cell (DSSC) with a multi-walled carbon nanotube counter electrode (CE) and a pore-filled membrane consisting of polyvinylidene fluoride-co-hexafluoropropylene (PVdF-co-HFP) as an electrolyte.

Thermally Stable Boron-Doped Multiwalled Carbon Nanotubes as a Pt-free Counter Electrode for Dye-Sensitized Solar Cells

A polymeric dispersant is usually used for preparing the uniform multiwalled carbon nanotubes (CNT) film for replacing Pt as the catalyst on the counter electrode (CE) of dye-sensitized solar cells (DSSCs). However, it is necessary to remove the polymeric dispersant completely due to its nonconductive property. Herein, boron-doped CNT (BCNT) with enhanced thermal stability, as the benefit to the dispersant removal, was prepared as the catalyst on the CE of a DSSC, and the cells with pristine CNT and Pt as the catalyst on the CEs were compared. The BCNT based DSSC shows the best light-to-electricity conversion efficiency (η) of 7.91 ± 0.21%, which is higher than that of the cell with a CNT CE (η = 6.02 ± 0.19%) and is comparable to that of the cell with a Pt CE (η = 8.03 ± 0.11%).

Carbon Nanotubes Counter Electrode for Dye-Sensitized Solar Cells Application

AbstractThe influence of the carbon nanotubes counter electrode deposited on the FTO glass substrates on the structure and optoelectrical properties of dye-sensitized solar cells counter electrode (CE) was analysed. Carbon materials have been applied in DSSC s in order to produce low-cost solar cells with reasonable efficiency. Platinum is a preferred material for the counter electrode because of its high conductivity and catalytic activity. However, the costs of manufacturing of the platinum counter electrode limit its use to large-scale applications in solar cells. This paper presents the results of examining the structure and properties of the studied layers, defining optical properties of conductive layers and electrical properties of dye-sensitized solar cells manufactured with the use of carbon nanotubes.Such counter electrodes are promising for the future fabrication of stable, low-cost and effective dye-sensitized solar cells.

Surfactant Effect in Polypyrrole and Polypyrrole with Multi Wall Carbon Nanotube Counter Electrodes: Improved Power Conversion Efficiency of Dye-Sensitized Solar Cell.

In our present study, polypyrrole-1 (PPy1), polypyrrole-2 (PPy2), and polypyrrole-2/multi wall carbon nanotube composite film (PPy2/MWCNT) were proposed as counter electrodes (CEs) in dye-sensitized solar cells (DSSCs) to replace the precious Pt CE. These films were fabricated on fluorine-doped tin oxide substrates by using a facile electrochemical polymerization route, and served as CEs in DSSCs. It is shown that the introduction of anionic surfactant, sodium dodecyl sulfate (SDS), enhanced the catalytic activity, thus leading to an improvement in the performance of PPy2. Further, introduction of MWCNT resulted in increase in conversion efficiency of DSSCs with PPy2/MWCNT composite film. The Tafel and electrochemical impedance analysis revealed that the PPy2 and PPy2/MWCNT CEs prepared with anionic surfactant possessed more catalytic activity and lower charge transfer resistance in comparison with PPy1 -based CE. This resulted in a better conversion efficiency of 5.88% for PPy2/MWCNT-based DSSC under 1 sun condition, reaching 86% of the DSSC based on reference Pt counter electrode (6.86%). These results indicate that the composite film with high catalytic properties for I3- reduction can potentially be used as the CE in a high-performance DSSC.

Facile fabrication of highly efficient carbon nanotube thin film replacing CuS counter electrode with enhanced photovoltaic performance in quantum dot-sensitized solar cells

An ideal counter electrode (CE), with high electrocatalytic activity, high performance stability, cost-efficient and applicable fabrication simplicity, is necessary to give full play to the advantages of quantum dot-sensitized solar cells (QDSSCs). Herein, we report a facile one-step preparation for carbon nanotubes (CNTs) have been explored as an electrocatalyst and low-cost alternative to platinum (Pt) and cuprous sulfide (CuS) CEs for polysulfide reduction in QDSSCs. QDSSC using this newly prepared CNT as a CE achieves a higher power conversion efficiency of 4.67% than those with a CuS (3.67%) or Pt CE (1.56%). Besides, a preliminary stability test reveals that the new CNT CE exhibits good stability. The results of Tafel polarization and electrochemical impedance spectroscopy measurements revealed that the CNTs had higher electrocatalytic activity for the polysulfide redox reaction and a smaller charge transfer resistance (8.61 Ω) at the CE/electrolyte interface than the CuS (21.87 Ω) and Pt (54.99 Ω) CEs. These results indicate that the CNT CE has superior electrocatalytic activity and can potentially replace CuS and Pt as CEs in QDSSCs. The preparation method of the CNT CE is simple and shows much promise as an efficient, stable, cost-effective and environmentally friendly CE for QDSSCs.

Electro-polymerization of polypyrrole/multi-wall carbon nanotube counter electrodes for use in platinum-free dye-sensitized solar cells

In the development of the dye-sensitized solar cell (DSSC), it is critically important, but remains challenging to discover new counter electrode (CE) materials to replace the expensive and precious platinum (Pt). Herein we electro-polymerize the polypyrrole (PPy) on the multi-wall carbon nanotube (MWCNT)-coated F-doped tin oxide substrate by a facile cyclic voltammetry method to obtain the PPy/MWCNT composite CE. The resultant composite CE shows that the MWCNT is wrapped with 15nm thickness of PPy nanoparticles, which takes advantage of the high surface area and good conductivity of the MWCNT and good catalytic activity of the PPy for the reduction of triiodide to iodide, providing the fast electron transport and diffusion channels and plenty of interfacial catalytic active sites. The DSSC based on the PPy/MWCNT composite CE shows an excellent photoelectric conversion efficiency of 7.15% under full sunlight illumination (100mWcm−2, AM 1.5G), which is much higher than that of the MWCNT (1.72%) and PPy (5.72%) based DSSCs, and 92.14% that of the Pt-based DSSC (7.76%).