Platinum-free Dye-sensitized Solar Cells Research Articles

Size-Controlled Cu3VSe4 Nanocrystals as Cathode Material in Platinum-Free Dye-Sensitized Solar Cells.

In this work, we report the first single-step, size-controlled synthesis of Cu3VSe4 cuboidal nanocrystals, with the longest dimension ranging from 9 to 36 nm, and their use in replacing the platinum counter electrode in dye-sensitized solar cells. Cu3VSe4, a ternary semiconductor from the class of sulvanites, is theoretically predicted to have good hole mobility, making it a promising candidate for charge transport in solar photovoltaic devices. The identity and crystalline purity of the Cu3VSe4 nanocrystals were validated by X-ray powder diffraction (XRD) and Raman spectroscopy. The particle size was determined from the XRD data using the Williamson-Hall equation and was found in agreement with the transmission electron microscopy imaging. Based on the electrochemical activity of the Cu3VSe4 nanocrystals, studied by cyclic voltammetry, the nanomaterials were further employed for fabricating counter electrodes (CEs) in Pt-free dye-sensitized solar cells. The counter electrodes were prepared from Cu3VSe4 nanocrystals as thin films, and the charge transfer kinetics were studied by electrochemical impedance spectroscopy. The work demonstrates that Cu3VSe4 counter electrodes successfully replace platinum in DSSCs. CEs fabricated with the Cu3VSe4 nanocrystals having an average particle size of 31.6 nm outperformed Pt, leading to DSSCs with the highest power conversion efficiency (5.93%) when compared with those fabricated with the Pt CE (5.85%).

Development of multi-walled carbon nanotube/polythiophene (MWCNT/PTh) nanocomposites for platinum-free dye-sensitized solar cells (DSSCs)

Platinum is utilized to a significant degree as a catalyst material in the fabrication of dye-sensitized solar cells. However, its utilization is constrained by its high cost, scarcity, requirement for high purity, poor corrosion resistance against liquid electrolytes, and energy-intensive deposition techniques. It is possible to substitute platinum with carbon allotropes or composites built of conductive polymer materials. In this study, in-situ polymerization was used to synthesize nanocomposites of multi-walled carbon nanotubes and polythiophene. X-ray Diffraction, Fourier-Transform Infrared Spectroscopy, and Scanning Electron Microscopy were used to examine the interactions between ingredients and the morphological features of composites, respectively. The results showed that the amount of multi-walled carbon nanotubes in composites affects the effectiveness of solar devices. Compared to cells based on 10% and 60 %MWCNTs/PTh, the efficiency of the cell that was made with 30 %MWCNTs/PTh exhibited a greater level of performance. The results also showed that the MWCNTs/PTh device outperformed Pt-based solar cells in terms of performance.

Development of polypyrrole/graphene (PPY/graphene) based electrocatalyst for platinum free dye-sensitized solar cells (DSSCs)

The purpose of this study was to fabricatePlatinum-free counter electrode (CE) materials for energy conversion devices. Initially, pyrrole was polymerized overnight in deionized water followed by 72 h of drying at 60 °C to obtain powdered PPY. Similarly, in-situ polymerization of pyrrole yielded PPY/graphene nanocomposite with variable graphene concentrations (2–8 wt%). Powdered samples were characterizedby SEM, XRD, and FTIR for compositional and morphological analysis. CEs of dye-sensitized solar cells (DSSCs) were made with PPY and PPY/graphene composites. The dye-sensitized TiO2 photoanodes were connected to CEs to carry out current–voltage measurements usingKeithley Solar Simulator. The DSSCs with PPY/4 %graphene CE showedthe highest efficiency (3.06%).

Enhanced Performance of Carbon-Selenide Composite with La0.9Ce0.1NiO3 Perovskite Oxide for Outstanding Counter Electrodes in Platinum-Free Dye-Sensitized Solar Cells.

For large-scale applications, dye-sensitized solar cells (DSSCs) require the replacement of the scarce platinum (Pt)-based counter electrode (CE) with efficient and cheap alternatives. In this respect, low-cost perovskite oxides (ABO3) have been introduced as promising additives to composite-based CEs in Pt-free DSSCs. Herein, we synthesized composites from La0.9Ce0.1NiO3 (L) perovskite oxide and functionalized-multiwall-carbon-nanotubes wrapped in selenides derived from metal-organic-frameworks (f-MWCNT-ZnSe-CoSe2, “F”). L and F were then mixed with carbon black (CB) in different mass ratios to prepare L@CB, F@CB, and L@F@CB composites. The electrochemical analysis revealed that the L@F@CB composite with a mass ratio of 1.5:3:1.5 exhibits better electrocatalytic activity than Pt. In addition, the related DSSC reached a better PCE of 7.49% compared to its Pt-based counterpart (7.09%). This improved performance is the result of the increase in the oxygen vacancy by L due to the replacement of La with Ce in its structure, leading to more active sites in the L@F@CB composites. Moreover, the F@CB composite favors the contribution to the high electrical conductivity of the hybrid carbon nanotube–carbon black, which also offers good stability to the L@F@CB CE by not showing any obvious change in morphology and peak-to-peak separation even after 100 cyclic voltammetry cycles. Consequently, the corresponding L@F@CB-based device achieved enhanced stability. Our work demonstrates that L@F@CB composites with a low cost are excellent alternatives to Pt CE in DSSCs.

Nanocomposites of Multi-walled Carbon Nanotubes and Titanium dioxide (MWCNTs/TiO2) as affective counter electrode materials for Platinum-free Dye-Sensitized Solar Cells (DSSCs)

Platinum is commonly used as a catalyst to regenerate the redox mediator in Dye-Sensitized Solar Cells (DSSCs). This work intends to replace the expensive and rare platinum with conventional and economical materials. Nanocomposites of Multi-walled Carbon Nanotubes (MWCNTs) and TiO2 can be used as active catalyst materials for the counter-electrode of DSSC. In these composites, MWCNTs provide catalytic properties, and TiO2 acts as a binder. The interaction between MWCNTs and TiO2 has been investigated by Transmission Electron Microscopy (TEM). It has been observed that DSSCs photovoltaic performance significantly depends on the concentration of MWCNTs in nanocomposites. The amount of MWCNTs has been optimized for the best performance of DSSC. The solar cell assembled with 4%MWCNTs catalyst material showed an efficiency of 8.81%, comparable to Pt-based device (9.40%), fabricated under analogous environment.

Electropolymerization of poly(spiroBiProDOT) on counter electrodes for platinum-free dye-sensitized solar cells

Poly(spiroBiProDOT) is synthesized using facile electropolymerization as a promising and cost-effective catalyst on counter electrode for dye-sensitized solar cell (DSSC) with an efficient charge mobility due to π–π conjugation and interaction.

Spray coated PbS nano-crystals as an effective counter-electrode material for platinum free Dye-Sensitized Solar Cells (DSSCs)

This work aims to replace the expansive counter electrode material such as Platinum with low-cost lead sulfide (PbS). Here, lead xanthate was used as a precursor material to synthesize PbS. The precursor material of different concentrations were spray coated on conductive glass substrates and then heated in air at different temperatures and time intervals. The cubical crystals of PbS were formed when heated at 120 °C for 2 h. Field emission scanning electron microscopy (FESEM) and X-ray powder diffraction (XRD) analyses were conducted to substantiate the PbS nanocrystals free of any precursor materials. Cyclic Voltammetry (CV) was performed to inspect the electrochemical performance of PbS crystals. The results found here show that PbS as a catalyst material shows good catalytic activity at the counter electrode of dye-sensitized solar cells (DSSCs). Under optimal conditions, DSSC with PbS shows the power-conversion-efficiency (PCE) of 4.71%, which is slightly lower than that of Pt-based device (5.34%), fabricated under similar conditions.

Polyaniline/graphene nanocomposites as counter electrode materials for platinum free dye-sensitized solar cells (DSSCSs)

Abstract The objective of this work is to fabricate the efficient and Pt-free DSSCs. Nanocomposites of PANi/graphene have been synthesized via in-situ polymerization of aniline in the graphene acidic dispersion. The morphology and the distribution of particles in composites have been analyzed by Scanning Electron Microscopy (SEM). The electrochemical performance of PANi/Graphene nanocomposites has been investigated by Tafel test. Results found here show that the graphene/polyaniline composites as catalyst materials show an outstanding electrochemical activity in DSSCs. Under optimal conditions, DSSC with PANi/Graphene shows the power-conversion-efficiency (PCE) of 7.45%, which is slightly lower than that of Pt-based DSSC (7.63%) fabricated under similar conditions.

Economical and highly efficient Pt-free counter electrode for dye-sensitized solar cells

Fe-Co nanoparticle-incorporated carbon nanofibers ((Fe-Co)-CNFs) were obtained by a simple and flexible electrospinning method and were further pre-oxidized and carbonized under a high-temperature nitrogen atmosphere for application as counter electrodes for highly efficient platinum-free dye-sensitized solar cells (DSSCs). Electrochemical characterizations revealed that the (Fe-Co)-CNFs showed excellent electrocatalytic activity for the I3−/I− redox couple. Photoelectric performance tests have shown that dye-sensitized solar cells equipped with (Fe-Co)-CNF counter electrodes have comparable photovoltaic efficiency to platinum counter electrode cells. This is because the graphite properties of these fibers rendered them electronically conducting. One-dimensional nanofibers provide oriented electron transport pathways, while lapped fibers form a three-dimensional mesoporous network, enhancing the contact with the electrolyte, and hence leading to faster ionic reaction kinetics. This study demonstrates that (Fe-Co)-CNFs can be used as low-cost high-efficiency counter electrodes for DSSCs.

Nickel impregnated multi-walled carbon nanotubes (Ni/MWCNT) as active catalyst materials for efficient and platinum-free dye-sensitized solar cells (DSSCs)

The main purpose of this work is to improve the efficiency of dye-sensitized solar cells (DSSCs) by replacing the expensive platinum counter electrode material with nickel impregnated Multi-Walled Carbon Nanotubes (Ni/MWCNTs or Ni/CNTs).

Synthesis of ternary nickel cobalt phosphide nanowires through phosphorization for use in platinum-free dye-sensitized solar cells

Nickel cobalt phosphide nanowires are fabricated on titanium foil through phosphating reaction from their nickel and cobalt hydroxide precursors, which are employed as the counter electrode materials for the dye-sensitized solar cell. Electrochemical investigations demonstrate that the ternary nickel cobalt phosphide counter electrode exhibits higher catalytic activity than that of the binary nickel phosphide and cobalt phosphide counter electrodes, which is due to that the introduction of two transition metals can adjust the valence electron and provide two electron donating active sites. The dye-sensitized solar cell with the ternary nickel cobalt phosphide counter electrode achieves a competitive photoelectric conversion efficiency of 8.01%, which is higher than that of the binary nickel phosphide (3.73%) and cobalt phosphide (2.80%) counter electrodes under the same conditions and comparable photovoltaic performance to that using the conventional platinum counter electrode (8.69%) for the dye-sensitized solar cell.

Effective iron-molybdenum-disulfide counter electrodes for use in platinum-free dye-sensitized solar cells

Nanocomposites of iron disulfide (FeS2) and molybdenum disulfide (MoS2) with nanosheets structure were successfully grown on the flexible titanium foils through a facile one-step hydrothermal process, and then worked as counter electrodes (CEs) in the dye-sensitized solar cells (DSSCs). X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy dispersive spectrometer were employed to characterize the microstructure and composition of the FeS2/MoS2. Cyclic voltammogram reveals that the catalytic activity of FeS2/MoS2 CE is higher than that of FeS2, MoS2, and platinum (Pt) CEs towards triiodide/iodide (I3–/I–) redox electrolyte, owing to the superior carrier transfer properties of vertical array structure and abundant catalytic active sites of FeS2/MoS2 nanosheets. Moreover, the FeS2/MoS2 CE maintains its activity after 500 cycles, exhibiting excellent electrochemical stability. Furthermore, the power conversion efficiency (PCE) of FeS2/MoS2 CE reaches 8.67%, which is higher than that of the FeS2 (7.20%), MoS2 (7.38%) and Pt (8.16%) CEs.

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.

Carbon/carbon nanocomposites as counter electrodes for platinum free dye-sensitized solar cells

In this work, carbonaceous materials and their combinations with each other were used as counter electrodes for efficient dye-sensitized solar cells (DSSCs). A small amount of TiO2 paste was also incorporated in each electrocatalyst to increase the adhesion between the carbon material and the conductive glass substrate. The dispersion of carbonaceous materials in composite films was characterized by transmission electron microscopy (TEM). Electrocatalytic characteristics of carbon/carbon catalysts are systematically investigated by electrochemical techniques, such as cyclic voltammetry and chronoamperometry. Solar cells assembled with carbon/carbon composite counter electrodes were characterized by photocurrent–voltage characteristic and electrochemical impedance spectroscopy measurements. The results indicate that under optimal conditions, the solar cell assembled with carbon/carbon composite counter electrode containing activated carbon, multi-walled carbon nanotube and graphene, shows power conversion efficiency of 10.73%. This photovoltaic performance is comparable with 11.20% for the platinum-based dye-sensitized solar cell. The results exhibit that carbonaceous material is an encouraging alternative for low-cost DSSCs.

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%).

Cobalt sulfide counter electrodes enhanced by a hydro-thermal treatment for use in platinum-free dye-sensitized solar cells

A small quantity of uncontrollable cobalt (Co) and cobalt hydroxide (Co(OH)2), remaining in the cobalt sulfide (CoS) film prepared by the cyclic voltammetry (CV) electrodeposition method, will negatively influence the catalytic activity and stability of the CoS counter electrode (CE). The residual Co and Co(OH)2 compounds are dissolved after a sodium hydrosulfide (NaHS) hydro-thermal treatment. CV, electrochemical impedance spectroscopy (EIS), and Tafel polarization curves indicate that the treated CoS CE exhibits superior electrocatalytic activity and stability for the I3− reduction. The platinum-free dye-sensitized solar cell (DSSC) using the treated CoS CE obtains an enhanced photovoltaic conversion efficiency of 7.16% compared to that using the untreated CoS CE (5.59%) under full sunlight illumination (100mWcm−2, AM1.5 G).

Dye-sensitized solar cells based on porous conjugated polymer counter electrodes

In this paper, we report platinum-free dye-sensitized solar cells that were fabricated using a grown porous poly-3-methyl-thiophene (P3MT) counter electrode. The growing of the porous P3MT was performed by an electrochemical deposition method. This method is easy and affordable unlike the common expensive deposition methods. The morphology of P3MT films was studied by scanning electron microscopy images. It was observed that polymer layers grown with a current density of 2mA/cm2 have a clear porous and rough structure as compared to layers grown with a lower current density. To understand the reaction kinetics and the catalytic activities of the counter electrodes with P3MT for 3I−/I3− redox reaction, cyclic voltammetry (CV) was performed. Based on the analysis of CV, it was shown that this layer can be used as a counter electrode for dye-sensitized solar cells. The electro deposition conditions during the growth of polymer layers such as current density, the morphology of polymer films and the duration of polymerization have a significant role in the current–voltage characterization of the fabricated solar cells. The performance of the fabricated solar cells was improved by optimization of these parameters. The highest efficiency of 2.76% was obtained by using porous P3MT in the counter electrode.

In-situ electrochemically deposited polypyrrole nanoparticles incorporated reduced graphene oxide as an efficient counter electrode for platinum-free dye-sensitized solar cells.

This paper reports a rapid and in-situ electrochemical polymerization method for the fabrication of polypyrrole nanoparticles incorporated reduced graphene oxide (rGO@PPy) nanocomposites on a ITO conducting glass and its application as a counter electrode for platinum-free dye-sensitized solar cell (DSSC). The scanning electron microscopic images show the uniform distribution of PPy nanoparticles with diameter ranges between 20 and 30 nm on the rGO sheets. The electrochemical studies reveal that the rGO@PPy has smaller charge transfer resistance and similar electrocatalytic activity as that of the standard Pt counter electrode for the I3−/I− redox reaction. The overall solar to electrical energy conversion efficiency of the DSSC with the rGO@PPy counter electrode is 2.21%, which is merely equal to the efficiency of DSSC with sputtered Pt counter electrode (2.19%). The excellent photovoltaic performance, rapid and simple fabrication method and low-cost of the rGO@PPy can be potentially exploited as a alternative counter electrode to the expensive Pt in DSSCs.

Polyaniline nanofiber/carbon film as flexible counter electrodes in platinum-free dye-sensitized solar cells

Efficient transfer of charges from a counter electrode to an electrolyte is a key process during the operation of dye-sensitized solar cells. Here, we develop a flexible counter electrode by electrochemical deposition of polyaniline nanofibers on graphitized polyimide carbon films for use in a tri-iodide reduction. As determined by the electrochemical impedance spectroscopy, the flexible counter electrode exhibited very low charge transfer resistance and series resistance. These results are due to the high electrocatalytic activity of the polyaniline nanofibers and the high conductivity of the flexible graphitized polyimide film. In combination with a dye-sensitized TiO 2 photoelectrode and electrolyte, the photovoltaic device with the polyaniline counter electrode shows an energy conversion efficiency of 6.85% under 1 sun illumination. Short-term stability tests indicate that the photovoltaic device with the polyaniline counter electrode almost maintains its initial performance.

Highly Efficient Dye-Sensitized Solar Cells Based on Carbon Black Counter Electrodes

Carbon black was employed as the catalyst for triiodide reduction on fluorine-doped tin oxide glass substrates (FTO-glass) used as counter electrodes in platinum-free dye-sensitized solar cells. The fill factors were strongly dependent on the thickness of the carbon layer, and the light energy conversion efficiency also increased up to a thickness of . The charge-transfer resistance of the carbon counter electrode decreased with the thickness of the carbon layer. The for the thicker carbon layer is less than three times that for the platinized FTO-glass. The highest cell efficiency was 9.1% under light intensity (1 sun AM 1.5 light, , , fill ).