The use of 2,6-bis (N-pyrazolyl) pyridine as an efficient dopant in conjugation with poly(ethylene oxide) for nanocrystalline dye-sensitized solar cells

Poly(ethylene oxide) (PEO)/2,6-bis (N-pyrazolyl) pyridine (BNPP) polymer electrolyte based photoelectrochemical cells have been fabricated with [cis-dithiocyanato-N, N-bis (2,2′ bipyridyl-4, 4′ dicarboxylic acid)ruthenium(II)] dihydrate (N3 dye) dye complex as the sensitizer and nanoporous TiO₂ film as photo anode. The introduction of 2,6-bis (N-pyrazolyl) pyridine into the poly (ethylene oxide) matrix reduces the crystallinity of the polymer and enhances the mobility of I⁻/I₃⁻ redox couple resulting in an improved performance with a higher conversion efficiency of 8.8% in terms of light energy to electric energy when compared to that of the corresponding dye-sensitized nanocrystalline TiO₂ solar cell.     

Effect of nano‐TiO2 dispersion on PEO polymer electrolyte property

Polymer electrolyte membranes based on poly(ethylene oxide) (PEO) doped with TiO₂ nanoparticles were synthesized by simple solution cast technique. Mesoporous TiO₂ film was prepared by doctor‐blade method. The modified polymer membranes and the mesoporous films were characterized by SEM, TEM, AFM, ionic conductivity, and J‐V measurements. Dye‐sensitized solar cells (DSSC) have been fabricated in which PEO‐polymer electrolyte doped with and without nano‐TiO₂ were sandwiched between porous TiO₂ and counter electrodes. The DSSC with nano‐TiO₂ doped polymer electrolyte shows better performance (1.68%) in comparison with pristine polymer electrolyte (1.07%), which is due to improved ionic conductivity value in polymer electrolyte system by nano‐TiO₂ doping. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Solid-state dye-sensitized hierarchically structured ZnO solar cells

A novel solid-state hierarchically structured ZnO dye-sensitized solar cell (DSC) was assembled by using TiO₂ as filler in polyethylene oxide (PEO)/polyethylene glycol (PEG) electrolytes and ZnO nanocrystalline aggregates as photoanode film. Under optimized composite polyelectrolyte containing PEO/oligo-PEG/TiO₂/LiI/I₂ the photovoltaic performance of the solid-state ZnO DSCs was significantly better, with an overall conversion efficiency (η) of 1.8% under irradiation of 100 mW/cm², which was higher than those of the cells with PEO/TiO₂/LiI/I₂ (η = 1.1%) or PEO/oligo-PEG/LiI/I₂ electrolyte (η = 1.5%). Further, the hierarchically structured ZnO-based cell showed a higher η value of 2.0% under 60 mW/cm² radiation. The morphologies, ionic conductivity of three different composite electrolytes and their performance to the DSCs were also studied by FESEM, I–V data, IPCE and EIS.     

Influences of poly(ether urethane) introduction on poly(ethylene oxide) based polymer electrolyte for solvent-free dye-sensitized solar cells

A poly(ether urethane) (PEUR)/poly(ethylene oxide) (PEO)/SiO₂ based nanocomposite polymer is prepared and employed in the construction of high efficiency all-solid-state dye-sensitized nanocrystalline solar cells. The introduction of low-molecular weight PEUR prepolymer into PEO electrolyte has greatly enhance the electrolyte performance by both improving the interfacial contact properties of electrode/electrolyte and decreasing the PEO crystallization, which were confirmed by XRD and SEM characteristics. The effects of polymer composition, nano SiO₂ content on the ionic conductivity and I₃⁻ ions diffusion of polymer-blend electrolyte are investigated. The optimized composition yields an energy conversion efficiency of 3.71% under irradiation by white light (100 mW cm⁻²).     

Formation of nanotubes in poly (vinylidene fluoride): Application as solid polymer electrolyte in DSC fabricated using carbon counter electrode

In the present work, we report the incorporation of 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) in poly(vinylidene fluoride) (PVDF) along with the redox couple (I⁻/I₃⁻). When ABTS, a π-electron donor, is used to dope PVDF, the polymer composite forms brush-like nanotubes and has been successfully used as a solid polymer electrolyte in dye-sensitized solar cells. Under the given conditions, the electrolyte composition forms nanotubes while it is doped with ABTS, a π-electron donor. With this new electrolyte, a dye-sensitized solar cell was fabricated using N3 dye adsorbed over TiO₂ nanoparticles as the photoanode and conducting carbon cement coated FTO as counter electrode.     

Studies of solvent effect on the conductivity of 2‐mercaptopyridine‐doped solid polymer blend electrolytes and its application in dye‐sensitized solar cells

Solvents and electrolytes play an important role in the fabrication of dye‐sensitized solar cells (DSSCs). We have studied the poly(ethylene oxide)‐poly(methyl methacrylate)‐KI‐I₂ (PEO‐PMMA‐KI‐I₂) polymer blend electrolytes prepared with different wt % of the 2‐mercaptopyridine by solution casting method. The polymer electrolyte films were characterized by the FTIR, X‐ray diffraction, electrochemical impedance and dielectric studies. FTIR spectra revealed complex formation between the PEO‐PMMA‐KI‐I₂ and 2‐mercaptopyrindine. Ionic conductivity data revealed that 30% 2‐mercaptopyridine‐doped PEO‐PMMA‐KI‐I₂ electrolyte can show higher conductivity (1.55 × 10^?5 S cm^?1) than the other compositions (20, 40, and 50%). The effect of solvent on the conductivity and dielectric of solid polymer electrolytes was studied for the best composition (30% 2‐mercaptopyridine‐doped PEO‐PMMA‐KI‐I₂) electrolyte using various organic solvents such as acetonitrile, N,N‐dimethylformamide, 2‐butanone, chlorobenzene, dimethylsulfoxide, and isopropanol. We found that ac‐conductivity and dielectric constant are higher for the polymer electrolytes processed from N,N‐dimethylformamide. This observation revealed that the conductivity of the solid polymer electrolytes is dependent on the solvent used for processing and the dielectric constant of the film. The photo‐conversion efficiency of dye‐sensitized solar cells fabricated using the optimized polymer electrolytes was 3.0% under an illumination of 100 mW cm^?2. The study suggests that N,N‐dimethylformamide is a good solvent for the polymer electrolyte processing due to higher ac‐conductivity beneficial for the electrochemical device applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42489.     

Influence of 2,6 (N-pyrazolyl)isonicotinic acid on the photovoltaic properties of a dye-sensitized solar cell fabricated using poly(vinylidene fluoride) blended with poly(ethylene oxide) polymer electrolyte

A novel method of introducing a synthesized organic nitrogenous compound 2,6 (N-pyrazolyl)isonicotinic acid (BNIN) and its effect on the conduction behavior of poly(vinylidene fluoride) (PVdF)–poly(ethylene oxide) (PEO) polymer-blend electrolyte with potassium iodide (KI) and iodine (I₂) and the corresponding performance of the dye-sensitized solar cells (DSSCs) were studied. A systematic investigation of the blends using FTIR provides evidence of interaction of BNIN with the polymer. Differential scanning calorimetry (DSC) study proves the miscibility of these polymers. Due to the coordinating and plasticizing effects of BNIN, the ionic conductivity of polymer blend electrolytes is enhanced. The efficiency of DSSC using BNIN doped polymer blend electrolyte was 7.3% under an illumination of 60 mW cm⁻² were observed for the best performance of a solar cell in this work.     

Phase inversion process to prepare quasi-solid-state electrolyte for the dye-sensitized solar cells

A quasi-solid-state electrolyte for the dye-sensitized solar cells was prepared following the phase inversion process. The microporous polymer electrolyte based on poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) hybrid with different amount of TiO₂ nanoparticles were prepared. The surface morphologies, the differential scanning calorimetry, and the ionic conductivity of the microporous polymer electrolyte were tested and analyzed. The results indicated that the microporous polymer electrolyte with TiO₂ nanoparticles modification exhibited better ionic conductivity compared with the original P(VDF-HFP) polymer electrolyte. The optimal ionic conductivity of 0.8 mS cm⁻¹ is obtained with the 30 wt % TiO₂ nanoparticles modification. When assembled with the 30 wt % TiO₂ nanoparticles modified quasi-solid-state electrolyte, the dye-sensitized TiO₂ nanocrystalline solar cell exhibited the light to electricity conversion efficiency of 2.465% at light intensity of 42.6 mW cm⁻², much better than the performance of original P(VDF-HFP) microporous polymer electrolyte DSSC. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effects of electrolyte in dye-sensitized solar cells and evaluation by impedance spectroscopy

Effects of the electrolyte of DSCs on impedance spectra were evaluated by changing concentration of redox couple, viscosity, and additives to electrolyte. The relation with current-voltage characteristics (I-V characteristics) was investigated. In many cases, the impedance component attributed to charge transfer at TiO₂|electrolyte interface demonstrated strong relation with the I-V characteristics. The recombination of electrons in TiO₂ with I₃⁻ in electrolyte was a key factor in determining performance of DSCs. To evaluate the effect of I₃⁻, diffusion-limiting current in the electrolyte for various viscosities was evaluated by cyclic voltammetry. When the short circuit current (SCC) was almost equal to the diffusion-limiting current, strong influence of the diffusion coefficient on the impedance spectra was observed: impedance arcs were enlarged as the diffusion coefficient was decreased. On the other hand, when the diffusion-limiting current was larger than the SCC, photo-excitation and electron injection processes became dominating factors in the DSCs performance. The SCC was regulated by the charge recombination process at TiO₂|electrolyte interface, and thus the impedance component ω₃ was related to the performance in such condition.     

Influence of ionic additives NaI/I2 on the properties of polymer gel electrolyte and performance of quasi-solid-state dye-sensitized solar cells

The ionic additives NaI/I₂ in polymer gel electrolyte not only provide cations, but also affect the liquid electrolyte absorbency of the poly(acrylic acid)-poly(ethylene glycol) hybrid, which results in the change of ionic conductivity of polymer gel electrolyte and the photovoltaic performance of quasi-solid-state dye-sensitized solar cell. With the optimized components of liquid electrolyte containing 0.5 M NaI, 0.05 M I₂, 0.4 M pyridine, 70 vol.% γ-butyrolactone and 30 vol.% N-methylpyrrolidone, a 4.74% power conversion efficiency of quasi-solid-state dye-sensitized solar cell was obtained under 100 mW cm⁻² (AM 1.5) irradiation.     

A Dye-Sensitized Nanoporous TiO2 Photoelectrochemical Cell with Novel Gel Network Polymer Electrolyte

A novel gel network polymer electrolyte based on polysiloxane with internal plasticizing PEO chains was applied in fabricating solid-state dye-sensitized TiO₂ photoelectrochemical cells. Ethylene carbonate (EC)/propylene carbonate (PC) and LiI/I₂ were added as liquid plasticizer to improve the performance. The cells showed open circuit voltage of 0.69 V and short circuit current density of 1.7 mA cm^–2 under 28 mW cm^–2 white light illumination. The energy conversion efficiencies and fill factors of the cells were 2.9% and 0.72.     

Influence of solvent on the poly (acrylic acid)-oligo-(ethylene glycol) polymer gel electrolyte and the performance of quasi-solid-state dye-sensitized solar cells

The influence of solvents on the property of poly (acrylic acid)-oligo-(ethylene glycol) polymer gel electrolyte and photovoltaic performance of quasi-solid-state dye-sensitized solar cells (DSSCs) were investigated. Solvents or mixed solvents with large donor number enhance the liquid electrolyte absorbency, which further influences the ionic conductivity of polymer gel electrolyte. A polymer gel electrolyte with ionic conductivity of 4.45 mS cm⁻¹ was obtained by using poly (acrylic acid)-oligo-(ethylene glycol) as polymer matrix, and absorbing 30 vol.% N-methyl pyrrolidone and 70 vol.% γ-butyrolactone with 0.5 M NaI and 0.05 M I₂. By using this polymer gel electrolyte coupling with 0.4 M pyridine additive, a quasi-solid-state dye-sensitized solar cell with conversion efficiency of 4.74% was obtained under irradiation of 100 mW cm⁻² (AM 1.5).     

Enhanced performance of a dye-sensitized solar cell with a modified poly(3,4-ethylenedioxythiophene)/TiO2/FTO counter electrode

ClO₄⁻-poly(3,4-ethylenedioxythiophene)/TiO₂/FTO (ClO₄⁻-PEDOT/TiO₂/FTO) counter electrode (CE) in dye-sensitized solar cells (DSSCs) is fabricated by using an electrochemical deposition method. Comparing with the DSSCs with ClO₄⁻-PEDOT/FTO counter electrode, the photocurrent-voltage (I-V) measurement reveals that the photocurrent conversion efficiency (η), fill factor (FF) and short-circuit current density (J_SC) of DSSCs with a ClO₄⁻-PEDOT/TiO₂/FTO CE increase. The enhanced performances of the DSSCs are attributed to the higher J_SC arising from the increase of active surface area of ClO₄⁻-PEDOT/TiO₂/FTO CE. Electrochemical impedance spectra (EIS) also indicate that the charge-transfer resistance on the ClO₄⁻-PEDOT/electrolyte interface decreases. Cyclic voltammetry results indicate that the ClO₄⁻-PEDOT/TiO₂/FTO electrode shows higher activity towards I₃⁻/I⁻ redox reaction than that of ClO₄⁻-PEDOT/FTO electrode.     

Effect of additives in PEO/PAA/PMAA composite solid polymer electrolytes on the ionic conductivity and Li ion battery performance

Polyethylene oxide (PEO) based-solid polymer electrolytes were prepared with low weight polymers bearing carboxylic acid groups added onto the polymer backbone, and the variation of the conductivity and performance of the resulting Li ion battery system was examined. The composite solid polymer electrolytes (CSPEs) were composed of PEO, LiClO_4, PAA (polyacrylic acid), PMAA (polymethacrylic acid), and Al₂O₃. The addition of additives to the PEO matrix enhanced the ionic conductivities of the electrolyte. The composite electrolyte composed of PEO:LiClO₄:PAA/PMAA/Li_0.3 exhibited a low polarization resistance of 881.5 ohms in its impedance spectra, while the PEO:LiClO₄ film showed a high value of 4,592 ohms. The highest ionic conductivity of 9.87 × 10⁻⁴ S cm⁻¹ was attained for the electrolyte composed of PEO:LiClO₄:PAA/PMAA/Li_0.3 at 20 °C. The cyclic voltammogram of Li⁺ recorded for the cell consisting of the PEO:LiClO₄:PAA/PMAA/Li_0.3:Al₂O₃ composite electrolyte exhibited the same diffusion process as that obtained with an ultra-microelectrode. Based on this electrolyte, the applicability of the solid polymer electrolytes to lithium batteries was examined for an Li/SPE/LiNi_0.5Co_0.5O₂ cell.     

Gel polymer electrolyte based on poly(acrylonitrile-co-styrene) and a novel organic iodide salt for quasi-solid state dye-sensitized solar cell

A gel polymer electrolyte based on poly(acrylonitrile-co-styrene) as polymer matrix and N-methyl pyridine iodide salt as I⁻ source was prepared. Controlling the concentration of polymer matrix of poly(acrylonitrile-co-styrene) at 17.5 wt.%, mixing the binary organic solvents mixture ethylene carbonate and propylene carbonate with 6:4 (w/w), and the concentration of N-methyl pyridine iodide and iodine with 0.5 and 0.05 M, respectively, the gel polymer electrolyte attains the maximum ionic conductivity (at 30 °C) of 4.63 mS cm⁻¹. Based on the gel polymer electrolyte, a quasi-solid state dye-sensitized solar cell was fabricated and its overall energy conversion efficiency of light-to-electricity of 3.10% was achieved under irradiation of 100 mW cm⁻².     

Dye-sensitised photoelectrochemical solar cells with polyacrylonitrile based solid polymer electrolytes

Novel all solid state dye-sensitised photolectrochemical solar cells of the type, FTO-TiO₂-dye-PAN, EC, PC, Pr₄N⁺I⁻, I₂-Pt-FTO, have been fabricated and characterised using current-voltage characteristics and action spectra. Liquid electrolyte generally used for such solar cells has successfully replaced by a quasi solid electrolyte comprised of polyacrylonitrile (PAN) with ethylene carbonate (EC) and propylene carbonate (PC) as plasticisers and Pr₄N⁺I⁻/I₂ redox couple with tetrapropylammoniumiodide as the complexing salt. For the polymer electrolyte, the optimum conductivity of 2.95×10⁻³ S cm⁻¹ was obtained for the electrolyte composition, PAN:EC:PC=15:35:50 (wt.%). The short circuit current density (J_SC) and the open circuit voltage (V_OC) obtained for an incident light intensity of 600 W m⁻² were 3.73 mA cm⁻² and 0.69 V, respectively. This corresponds to an overall quantum efficiency of 2.99%. From the action spectrum, the maximum incident photon conversion efficiency (IPCE) of 33% was obtained for incident light of wavelength 480 nm.     

Pure and (zinc or iron) doped titania powders prepared by sol-gel and used as photocatalyst

Pure and doped (zinc and iron) nanocrystalline titania powders were prepared by the sol-gel route. Doping tends to change the existing crystalline phases and their degree of crystallinity, but particle size distribution and morphology of the particles are also affected. In the pure titania system, the main crystalline phase is anatase but rutile is also present. The doped (Zn and Fe) titania crystallizes only as anatase. The undoped titania shows a bimodal distribution of particles size: fine (20-40 nm) and coarse (300-500 nm) grains. The doped TiO₂ powder also exhibits a much more uniform particle size distribution, with all grains under 40 nm.The photocatalytic efficiency of suspended powders was tested on the decolouration of Orange II aqueous solutions under visible artificial light irradiation. The maximum decolouration reached by the pure TiO₂ was 81% at a rate of 3.6 × 10⁻³ min⁻¹. Iron doping decreases the photocatalytic activity; the maximum dye degradation was only 43% at a rate of 1.3 × 10⁻³ min⁻¹. On the contrary, the performance of Zn-doped titania was better, having a decolouration rate of 17.7 × 10⁻³ min⁻¹.     

Vanadium doped ceramic matrix Li6.7La3Zr1.7V0.3O12 enabled PEO-based solid composite electrolyte with high lithium ion transference number and cycling stability

Solid polymer electrolytes (SPEs) have attracted much attention because of their potential in improving energy density and safety. Vanadium doped ceramic matrix Li_6.7La₃Zr_1.7V_0.3O₁₂ (LLZVO) was synthesized by high-temperature annealing, and formed a composite electrolyte with polyethylene oxide (PEO). Compared with pure PEO electrolyte membrane, the composite electrolyte membrane exhibited better ionic conductivity (30 °C: 3.2 × 10^?5 S cm^?1; 80 °C: 3.6 × 10^?3 S cm^?1). The combination of LLZVO was beneficial to improve the lithium ion transference number (t_Li⁺) of SPE, which was as high as 0.81. The Li/SPE/LiFePO₄ battery shows good cycling ability, with a specific capacity of 142 mAh g^?1 after a stable cycle of 150 cycles. Meanwhile, the symmetrical lithium battery with composite electrolyte can work continuously for 1200 h without short circuit at the current density of 0.1 mA cm^?2 at 50 °C, and the capacity is 0.176 mAh. Vanadium doped ceramic matrix LLZVO as an active ionic conductor, improved the overall performance of solid electrolyte.     

Morphology,crystallinity, and electrochemical properties of in situ formed poly(ethylene oxide)/TiO2 nanocomposite polymer electrolytes

A method to produce nanocomposite polymer electrolytes consisting of poly(ethylene oxide) (PEO) as the polymer matrix, lithium tetrafluoroborate (LiBF₄) as the lithium salt, and TiO₂ as the inert ceramic filler is described. The ceramic filler, TiO₂, was synthesized in situ by a sol–gel process. The morphology and crystallinity of the nanocomposite polymer electrolytes were examined by scanning electron microscopy and differential scanning calorimetry, respectively. The electrochemical properties of interest to battery applications, such as ionic conductivity, Li⁺ transference number, and stability window were investigated. The room‐temperature ionic conductivity of these polymer electrolytes was an order of magnitude higher than that of the TiO₂ free sample. A high Li⁺ transference number of 0.51 was recorded, and the nanocomposite electrolyte was found to be electrochemically stable up to 4.5 V versus Li⁺/Li. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2815–2822, 2003