Influence of pyrazole on the photovoltaic performance of dye-sensitized solar cell with polyvinylidene fluoride polymer electrolytes

We investigate the influence of the pyrazole content on the polyvinylidene fluoride (PVDF)/KI/I2 electrolytes for dye-sensitized solar cells (DSSCs). The solid polymer electrolyte films consisting of different weight percentage ratios (0 20,30,40, and 50%) of pyrazole doped with PVDF/KI/I2have been prepared by solution casting technique using N,N- dimethyl formamide (DMF) as a solvent. The as-prepared polymer electrolyte films were characterized by various techniques such as Fourier transform infrared spectroscopy (FT-IR spectroscopy), differential scanning calorimetry (DSC), X-ray diffractometer (XRD), alternate current (AC)-impedance analysis, and scanning electron microscopy (SEM). The 40 wt% pyrazole-PVDF/KI/I2 electrolyte exhibited the highest ionic conductivity value of 9.52×10− 5 Scm− 1 at room temperature. This may be due to the lower crystallinity of PVDF and higher ionic mobility of iodide ions in the electrolyte. The DSSC fabricated using this highest ion conducting electrolyte showed an enhanced power conversion efficiency of 3.30% under an illumination of 60 mW/cm2 than that of pure PVDF/KI/I2 electrolyte (1.42%)

Synthesis of High Surface Area WN and Co–W–N Nitrides by Chemical Routes

This study investigates the synthesis of high surface area W 2 N and Co–W–N nitrides by nitridation of various precursors obtained by chemical routes. For the synthesis of W 2 N nitride, WO 3 precursors were obtained by acidifying Na 2 WO 4 ·2H 2 O (acid route) and by thermal decomposition of the tungstate–citrate precursor. The solid-state reactivity, BET surface areas and pore structures of the nitride materials have been investigated in detail. Co–W–N nitride was obtained from CoWO 4 synthesized by co-precipitation. W 2 N and Co–W–N nitrides crystallize in β-W 2 N structure. The single-point BET surface areas were estimated to be 58, 55 and 60 m 2 /g for the β-W 2 N nitride materials synthesized using commercial WO 3 and WO 3 obtained from acid and citrate precursor, respectively. The maximum surface areas (40 m 2 /g) are obtained for Co–W–N nitrides synthesized at 700 °C. We have investigated the change in pore volume and pore diameter when the synthesis conditions are changed. The thermogravimetric and differential thermal analysis studies corroborate the fine particle nature of the materials

Mesoporous Vanadium Nitride Synthesized by Chemical Routes

Nanocrystalline vanadium nitride (VN) materials are synthesized by two different routes, namely, the urea route and the ammonia route, using various V 2 O 5 precursors obtained by citric acid–based sol–gel method. The VN nanomaterials obtained are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and BET method. The XRD patterns show the presence of pure cubic phase with line broadening. The lattice parameters were found to be 4.1266 and 4.1136 Å for the urea route and 4.1125 and 4.1120 Å for the ammonia route using V 2 O 5 precursors heat treated at 350 and 550 °C, respectively. The estimated crystallite sizes are found to be 9 and 7 nm for the urea route and 22 and 28 nm for the ammonia route using V 2 O 5 precursors synthesized at 350 and 550 °C, respectively. The SEM images show the presence of agglomerates having particle dimensions of 115 and (300 × 15) nm for the urea route and 111 and 68 nm for the ammonia route using V 2 O 5 precursors heat treated at 350 and 550 °C, respectively. The maximum BET surface area of 57 m 2 /g was obtained for VN sample synthesized by the urea route using V 2 O 5 precursors synthesized at 350 °C. The isotherms show typical Type IV with H2 hysteresis, which is characteristic of the mesoporous particles. The production of high-surface-area nitride materials has been correlated to synthetic procedure, precursor used and formation of mesopores in the material

Effect of tetrabutylammonium iodide content on PVDF-PMMA polymer blend electrolytes for dye-sensitized solar cells

The influence of tetrabutylammonium iodide on the polyvinylidene fluoride-poly(methyl methacrylate)-ethylene carbonate (PVDF-PMMA-EC)-I2 polymer blend electrolytes was investigated and optimized for use in a dye-sensitized solar cell. The different weight ratios (50, 60, 70, and 80 %) of tetrabutylammonium iodide (TBAI)-added PVDF-PMMA-EC-I2 polymer electrolytes were prepared. The prepared solid polymer blend electrolytes were characterized by using various techniques such as Fourier transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC), and electrochemical impedance spectroscopy (EIS). The FT-IR spectra revealed the interaction among all composition of polymer electrolytes. The influence of TBAI salt on the ionic conductivity of polymer electrolytes was studied using electrochemical impedance spectroscopy. The polymer electrolyte containing 60 % of TBAI in PVDF-PMMA-EC-I2 showed the highest room temperature conductivity of 5.10 × 10−3 S cm−1. The fabricated DSSC using PVDF-PMMA-EC-I2 polymer electrolytes with 60 % of TBAI showed the best performance with a short-circuit current density of 8.0 mA cm−2, open-circuit voltage of 0.66 V, fill factor of 0.65, and the overall power conversion efficiency of 3.45 % under an illumination of 100 mW cm−2. Hence, the weight content of organic iodide salt in polymer electrolytes influences the overall performance of dye-sensitized solar cells

Synthesis of α-Mo2C by Carburization of α-MoO3 Nanowires and Its Electrocatalytic Activity towards Tri-iodide Reduction for Dye-Sensitized Solar Cells

Nanowire-shaped α-MoO3 was synthesized on a large scale by hydrothermal route. Nanocrystalline α-Mo2C phase was obtained by the carburization of α-MoO3 nanowires with urea as a carbon source precursor. The phase purity and crystalline size of the synthesized materials were ascertained by using powder X-ray diffraction. The shape and morphology of synthesized materials were characterized by field-emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HR-TEM). The electrocatalytic activity of α-Mo2C for I−/I3− redox couple was investigated by the cyclic voltammetry. The synthesized α-Mo2C was subsequently applied as counter electrode in dye-sensitized solar cells to replace the expensive platinum

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