Platinum-based Counter Electrode Research Articles

Voltage- and Power-Conversion Performance of Bi-functional ZrO2 : Er3+ / Yb3+ Assisted and Co-sensitized Dye Sensitized Solar Cells for Internet of Things Applications.

Giant power conversion efficiency is achieved by using bifunction ZrO2 : Er3+ /Yb3+ assisted co-sensitised dye-sensitized solar cells. The evolution of the crystalline structure and its microstructure are examined by X-ray diffraction, scanning electron microscopy studies. The bi-functional behaviour of ZrO2 : Er3+ /Yb3+ as upconversion, light scattering is confirmed by emission and diffused reflectance studies. The bi-function ZrO2 : Er3+ /Yb3+ (pH=3) assisted photoanode is co-sensitized by use of N719 dye, squaraine SPSQ2 dye and is sandwiched with Platinum based counter electrode. The fabricated DSSC exhibited a giant power conversion efficiency of 12.35 % with VOC of 0.71 V, JSC of 27.06 mA/cm2 , FF of 0.63. The results, which motivated the development of a small DSSC module, gave 6.21 % and is used to drive a tiny electronic motor in indoor and outdoor lighting conditions. Small-area DSSCs connected in series have found that a VOC of 4.52 V is sufficient to power up Internet of Things (IoT) devices.

Scalable, solution-based dye-sensitized photovoltaic fibers with an electrolytic solid-state ion conductor

We have created a textile with solid-state dye-sensitized photovoltaic fibers (DSPFs) fabricated using a unique combination of inexpensive, commercial-off-the-shelf materials and solution-based processing deposition techniques. DSPFs were made possible by macroscopic support of liquid state components in both the electrolyte and photoanode of the DSPFs. A plastic crystal system of succinonitrile was doped with iodide salts to achieve a solid-state ion-conducting electrolyte. Similarly, utilization of a mesoporous TiO2 photoanode created an adsorptive scaffold for photoactive dyes in a liquid solution. An inexpensive pairing of coated carbon and stainless steel, replacing the traditional and expensive platinum-based counter electrode, was used as a catalytic counter electrode. A solid-state DSPF including both electrodes aligned in comparative orientations provided peak power of up to 0.4 µW/mm with open-circuit voltage (VOC) of 0.7 V. A module of solid-state DSPFs was then incorporated into a simple weave in a mini-loom to demonstrate textile capability. Solid-state DSPFs woven and connected in series in the loom produced peak power of over 50 µW and VOC of 4.5 V. Creation of the flexible DSPFs was achieved through a series of simple and scalable solution-based coating processes, and to the best of our knowledge, has not been previously reported in literature to produce fully encapsulated solid-state dye-sensitized photovoltaic cells with a fiber form factor. Low cost, high throughput processing of this technology can potentially support the manufactural transition for the next generation of commercial energy harvesting wearable electronics.

Electrophoretic Codeposition of MoOx/MoS2 Thin Film for Platinum-Free Counter Electrode in Quantum Dot Solar Cells

The MoOx/MoS2 thin films were manufactured on conducting glass (FTO) from the ethanolic mixture of colloidal molybdenum disulfide (MoS2) and molybdenum oxides (MoOx) by electrophoretic deposition method and were used for counter electrode of quantum dot solar cells. Different ramp-rate conditions for electrophoretic deposition as well as bias potential were investigated in an attempt to get the highest possible electrocatalytic activity of polysulfide (S2-/Sn2-) redox couple. In this research, interestingly, by simply using CdS/CdSe/ZnS photoanode and polysulfide electrolyte under 1000 W.m−2 AM 1.5 G illumination, the power conversion efficiency of MoOx/MoS2-counter-electrode-based QDSC was achieved up to 2.01%, which was double compared to platinum-based counter electrode of QDSCs.

A novel PEDOT:PSS/SWCNH bilayer thin film counter electrode for efficient dye-sensitized solar cells

Thin platinum deposited over fluorine-doped tin oxide glass substrate is a well-known and widely used counter electrode for efficient dye-sensitized solar cells. In this paper, we investigated a potential and Pt-free bilayer thin film counter electrode based on single wall carbon nanohorn over PEDOT:PSS film. The bilayer thin film counter electrode was developed using a simple spin coat process. The results of atomic force microscope and scanning electron microscope unveil the uniform distribution of single wall carbon nanohorns over PEDOT:PSS with average size of 76 nm. The extensive electrochemical analysis demonstrated superior electrocatalytic behavior for bilayer counter electrode with lower peak-to-peak separation potential of 0.6 V, lower Rs and RCT values of 25.9 Ω and 399 Ω, and higher Jo value of 2.4 mA cm−2. The fabricated DSSC using bilayer counter electrode witnessed higher power conversion efficiency of 5.1%, compared to PEDOT:PSS (3.87%) and SWCNH (1.88%), and is almost equivalent to the platinum-based counter electrode (5.53%). The present study of bilayer counter electrode has great potential in terms of low-cost and non-platinum counter electrode for dye-sensitized solar cell applications.

Self-Assembled Graphene/MWCNT Bilayers as Platinum-Free Counter Electrode in Dye-Sensitized Solar Cells.

We describe the preparation and properties of bilayers of graphene‐ and multi‐walled carbon nanotubes (MWCNTs) as an alternative to conventionally used platinum‐based counter electrode for dye‐sensitized solar cells (DSSC). The counter electrodes were prepared by a simple and easy‐to‐implement double self‐assembly process. The preparation allows for controlling the surface roughness of electrode in a layer‐by‐layer deposition. Annealing under N2 atmosphere improves the electrode's conductivity and the catalytic activity of graphene and MWCNTs to reduce the I3 − species within the electrolyte of the DSSC. The performance of different counter‐electrodes is compared for ZnO photoanode‐based DSSCs. Bilayer electrodes show higher power conversion efficiencies than monolayer graphene electrodes or monolayer MWCNTs electrodes. The bilayer graphene (bottom)/MWCNTs (top) counter electrode‐based DSSC exhibits a maximum power conversion efficiency of 4.1 % exceeding the efficiency of a reference DSSC with a thin film platinum counter electrode (efficiency of 3.4 %). In addition, the double self‐assembled counter electrodes are mechanically stable, which enables their recycling for DSSCs fabrication without significant loss of the solar cell performance.

Laser-scribed reduced graphene oxide as counter electrode for dye-sensitized solar cell

Reduced graphene oxide (rGO) has been attracted considerable attention in the field of dye sensitized solar cells (DSSCs) to serve as a low cost and earth-abundant alternative to the conventional platinum-based counter electrodes. Recently direct laser writing technologies are emerging as an inexpensive, time-efficient and high-resolution method to produce catalytic rGO-based electrodes. Herein, we experimentally demonstrate that the laser-scribed rGO on ITO/PEN substrate was produced by a commercial LightScribe DVD burner and used as counter electrode for DSSC. SEM and Raman spectroscopy characterizations reveal that after laser-scribing rGO film presents a roughness structure with multi-layer curled or tilting graphenes. The cyclic voltammetry (CV) and electrochemical impedance spectrum (EIS) analyses were also conducted to explore its electrocatalytic activity and charge-transfer properties. Finally, the DSSC based on rGO counter electrode achieved a power conversion efficiency of 2.07% under one sun AM 1.5 G illumination. This work developed a simple and promising laser-scribing method to prepare rGO-based counter electrode materials for DSSCs applications.

Engineering N-reduced graphene oxide wrapped Co3O4@f-MWCNT hybrid for enhance performance dye-sensitized solar cells

Platinum-free and novel hybrid counter electrode is an important part of dye-sensitized solar cells (DSSCs). More and more researches reported that transitional metal oxide nanoparticles can be used as CEs in DSSCs. However, they are ready to be corroded by electrolyte, leading to worse stability in catalytic activities for triiodide reduction in the cyclic voltammetry (CV) test. Multiwall carbon nanotubes (MWCNTs) have tangled network, exceptional specific surface area, and unique hollow composition can be higher for use as a CE material. The electrochemical performance analysis indicates that the Co3O4 nano flakes and functionalized multiwall carbon nanotubes (f-MWCNTs), wrapped with N-doped reduced graphene oxide (Co3O4@f-MWCNTs@N-RGO) electrode has lower charge transfer resistance (Rct) on the electrolyte/electrode interface and higher catalytic ability than bare Co3O4 nano flakes. Power conversion efficiency (PCE) of the prepared hybrid has been achieved up to 8.42%, in contrast to the platinum-based counter electrode (PCE=7.81%) used in DSSCs. Besides, Co3O4@f-MWCNTs with N-RGO hybrid material shows strong catalytic activities for triiodide reduction, superior to Co3O4 nano flakes in the CV test.

Biomass-Derived Nitrogen-Doped Carbon Aerogel Counter Electrodes for Dye Sensitized Solar Cells.

Dye sensitized solar cells have emerged as an attractive alternative to conventional solar cells due to their easy processing and the abundance and low cost of their materials. However, the counter electrode in these cells employs platinum which significantly impacts their cost. Here, we report biomass-derived, nitrogen-doped carbon aerogel as an effective alternative to conventional platinum-based counter electrodes for dye sensitized solar cells. A stable suspension of biomass-derived, nitrogen-doped carbon aerogel was prepared in DMF by using oleylamine as a binder. The nitrogen-doped carbon aerogel electrode was annealed at different temperatures, and its impact on photovoltaic performance is investigated. I-V measurements confirm that the annealing temperature substantially enhances the photovoltaic parameters of these devices; these enhancements are linked to the removal of the organic binders. Electrochemical impedance spectra of the counter electrodes confirm that removal of oleylamine in nitrogen-doped carbon aerogels reduces the series resistance of the resulting electrodes. The power conversion efficiency of the solar cells from optimized nitrogen-doped carbon aerogel exhibited comparable efficiency to that of a cell fabricated using a platinum-based counter electrode. This study demonstrates the potential of biomass-derived carbon aerogels as a cheap and sustainable replacement of platinum in DSSCs.

Free-standing graphene/NiMoS paper as cathode for quasi-solid state dye-sensitized solar cells

Highly catalytic two dimensional and metal-doped two-dimensional nanomaterials (MoS2 and NiMoS) were deposited over free-standing graphene (FSG) paper using electrodeposition method and subsequently used as a counter electrode in quasi solid-state dye-sensitized solar cells (q-DSSCs). The replacement of FTO by FSG facilitates high electrical conductivity and electrodeposited metal sulphides provide electrocatalytic activity. The morphology, structural phase formation and chemical composition of FSG-MoS2 and FSG-NiMoS were investigated using FESEM, XRD, Raman and XPS analysis. The electrochemical behavior of metal sulphide decorated FSG cathodes is investigated using an electrochemical workstation and their effects on the photo-conversion efficiency of DSSCs were assessed. NiMoS with FSG substrate is an intriguing counter electrode material that can be utilized at low fabrication cost than the conventional platinum-based counter electrodes. FSG along with the metallic-two dimensional nanoparticles (NiMoS) functions as an effective catalytic material thereby allowing DSSCs to achieve enhanced efficiency of ∼7% to provide better alternative of FTO and Pt.

Evaluation of the limiting factors affecting large-sized, flexible, platinum-free dye-sensitized solar cells performance: a combined experimental and equivalent circuit analysis

Reducing further the cost, increasing the application range, and scaling up of dye-sensitized solar cells (DSSCs) are important issues for their wide commercialization. The present paper constitutes a comprehensive analysis of the limiting factors affecting large-sized, flexible, platinum-free DSSCs performance. The results are interpreted using a series of materials characterization techniques, including scanning electron microscopy, atomic force microscopy, X-ray diffraction, Brunauer–Emmett–Teller analysis, ultraviolet–visible spectroscopy, diffuse reflectance spectroscopy, photoluminescence analysis, and cyclic voltammetry. Equivalent circuit analysis of DSSCs was applied, in all cases, to derive the key electrical circuit elements values, determining solar cells performance. Α satisfactory energy conversion efficiency was achieved by the implementation of the novel fabricated carbon-based counter electrodes to DSSCs, equal to the corresponding obtained by the photo-electrochemical cells employing commercially available platinum-based counter electrodes. The flexible, platinum-free DSSCs demonstrated a decreased photo-generated current and electron transport kinetics, while the charge recombination rate at TiO2/electrolyte and conductive substrate/electrolyte interfaces was increased, compared to the rigid ones. The scaling up effect was intense in the flexible devices, while the area-specific total series parasitic resistance increased, at high rates, by the solar cell active area. Equivalent circuit model successfully reproduced all experimental current–voltage characteristic curves of DSSCs, revealing that it is a powerful tool for routine analysis when designing novel photo-electrochemical cells.

Characteristics and Analyses of Various Counter Electrodes Applied in Quasi-Solid Electrolyte Dye-Sensitized Solar Cells

A carbon-based counter electrode applied in quasi-solid-state dye-sensitized cell was demonstrated. For comparison, gel/quasi-solid-state dye-sensitized cells with a platinum-based counter electrode were also investigated. Performances and electrochemical properties of solar cells were evaluated by using a solar cell measurement system and an electrochemical impendences spectrometer. As the results shown for carbon-based quasi-solid-state dye-sensitized solar cells, the power conversion efficiency, short-circuit current density, open-circuit voltage, and fill factor are 3.55%, 11.79 mA/cm2, 0.69 V, and 43.79%, respectively. The charge transfer resistance of Rct1 at the electrolyte/counter-electrode interface was increased because of the Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) polymer which can decrease the mobility of I3− ions. The charge transfer resistance of Rct2 at the TiO2/dye/electrolyte interface was decreased with the addition of PVDF-HFP polymer and TiO2 nanoparticles, due to the Ti+ cations assorting on the high fluorine electronegative polymer surface, and I− and I3− ions hopping in the channels formed in the polymeric phase by an electrostatic force. As the results of cell stability test shown, a better sealing method was suggested, because there were no pinholes at the counter electrode, the electrolyte would not leak from the hole by volatilization.

Pulsed-laser-ablation based nanodecoration of multi-wall-carbon nanotubes by Co\u2013Ni nanoparticles for dye-sensitized solar cell counter electrode applications

We report here on the use of pulsed KrF-laser deposition technique (PLD) for the decoration of Multi-wall carbon nanotubes (MWCNTs) by Co–Ni nanoparticles (NPs) to form highly efficient counter electrodes (CEs) for use in Dye-sensitized solar cells (DSSC). By varying the number of laser ablation pulses (NLP = 500–60,000) of the KrF laser, we were able to control the average size of the Co–Ni NPs and the surface coverage of the MWCNTs by the nanoparticles. The PLD-based decoration of MWCNTs by Co–Ni NPs is shown to form novel counter electrodes, which significantly enhance the power conversion efficiency (PCE) of the DSSCs. Indeed, the DSSCs based on the PLD-decorated Co–Ni counter electrodes (obtained at the optimal NLP = 40,000) are shown to exhibit a PCE value as high as 6.68%, with high short circuit current (Jsc = 14.68 mA/cm2) and open circuit voltage (Voc = 0.63 V). This represents a PCE improvement of ~190% in comparison to the DSSCs with pristine MWCNTs (PCE = 2.3%) and ~7.4% PCE increase than that of the conventional DSSC made with a sputtered Platinum-based counter electrode. By systematically investigating the local nanostructure of the Co–Ni decorated CEs, we found that the Co–Ni NPs layer exhibits a porous cauliflower-like morphology, of which surface roughness (RMS) is NLP dependent. Interestingly, both PCE and roughness of the Co–Ni NPs layer are found to exhibit the same NLP dependence, with a maximum located around the optimal NLP value of 40,000. This enabled us to establish, for the first time, a linear correlation between the achieved PCE of DSSCs and the local roughness of their CEs decorated by Co–Ni NPs. Such a correlation highlights the importance of maximizing the surface area of the Co–Ni coated MWCNTs on the CEs to enhance the PCE of the DSSCs. Finally, Ultra-violet Photoelectron Spectroscopy (UPS) measurements revealed a significant decrease in the local work function (Φ) of Co–Ni NPs decorated MWCNTs based CEs (at NLP = 40,000, Φ = 3.9 eV) with respect to that of either pristine MWCNTs (Φ = 4.8 eV) or sputtered-Pt (Φ = 4.3 eV) counter-electrodes. This Φ lowering of the Co–Ni/MWCNTs based CEs is an additional advantage to enhance the catalytic reaction of the redox couple of the electrolyte solution, and improve thereby the PCE of the DSSCs.

A simple route to making counter electrode for dye sensitized solar cells (DSSCs) using sucrose as carbon precursor

Dye sensitized solar cells (DSSCs) have attracted much attention in recent years due to low cost fabrication as compared to silicon-based and thin film solar cells. Though, platinum is an excellent catalytic material for use in preparation of counter electrodes (CEs) for DSSCs it is expensive. Alternatives to replacement of platinum (Pt) that have been examined are carbon materials, conductive polymers and hybrids. In this work, counter electrode for DSSCs was fabricated using carbon material obtained from graphitization of sucrose at high temperature. A slurry of the carbon produced from sucrose graphitization was made with polyvinylpyrrolidone (PVP) as a surfactant and a coating was obtained by doctor blading the slurry over the FTO glass substrate. The current density (Jsc) and open circuit voltage (VOC) of fabricated cell (area 0.25cm2) was 10.28mAcm−2 and 0.76V respectively. The efficiency of the cell was 4.33% which was just slightly lower than that obtained for similar cells using platinum based counter electrode.

Influence of Solvents and Surface Treatment on Photovoltaic Response of DSSC Based on Natural Curcumin Dye

Dye-sensitized solar cells have recently drawn much attention because of their cost effectiveness and easy manufacturing process. However, the challenge lies in minimizing the cost of sensitizer dyes and the platinum-based counter electrode. Natural dyes such as red cabbage, red perilla, rosella, blue pea, and curcumin represent a low-cost, environmentally friendly alternative to costly ruthenium-based complexes for sensitization of nc-TiO $_2$ . Attempts are being made to improve the efficiency of a cell based on natural dyes by way of selecting a proper sensitizer, modifying the surface of a working electrode by chemical treatment, and replacing a platinum-based counter electrode. We have adopted two approaches to improve the photovoltaic response of a cell, i.e., 1) modifying the surface of a working electrode by treating it with HCl and TiCl $_4$ and 2) using different organic solvents to enhance the extent of sensitization. PEDOT:PSS grown over graphite-coated fluorine-doped tin oxide is used as a counter electrode to catalyze the reduction of triiodide ( ${\rm I}_3^ -$ ) to iodide (I $^-$ ). A TiCl $_4$ -treated photoelectrode, on sensitization with curcumin, gives maximum power conversion efficiency. The impact of the solvent's polarity in dye diffusion was determined with cyclic voltametry. Kelvin probe, SEM, and Raman spectroscopy are employed to justify the surface modification of nc-TiO $_2$ induced by TiCl $_4$ treatment.

Room-temperature fabrication of graphene films on variable substrates and its use as counter electrodes for dye-sensitized solar cells

Graphene films with controllable thicknesses, electrical and optical properties are fabricated on variable substrates at room temperature by a simple, efficient and low-cost solution-based method. This process is completely compatible with flexible substrates (polyethylene terephthalate, PET), fluorine-doped tin oxide (FTO) conductive glasses, and even glassy carbon electrodes. The graphene films show excellent conductivity and electrochemical activity. The films prepared on FTO conductive glasses, as an alternative to ubiquitously employed platinum-based counter electrodes (CEs) for dye-sensitized solar cells (DSSCs), are demonstrated. The results suggest a new start in the direction of graphene CEs for the development of next generation of optoelectronics.