M. A. Careem

Preparation and characterization of CdS and Cu2S nanoparticle/polyaniline composite films

Composites consisting of conducting polymers and nanosized semiconductor particles are scientifically and technologically attractive because of their unique electronic and optical properties. These properties were found to depend on the size of the embedded particles. In this study such nanocomposites with polyaniline (PANI) conducting polymers are reported. The results have shown that CdS and Cu2S nanocrystals can be successfully incorporated into a polyaniline matrix and their particle sizes can be controlled by adjusting the concentration of the additives. Photovoltaic devices with CdS/PANI systems of various CdS concentrations were fabricated and their performance were investigated. The short circuit current (ISC) and open circuit voltage (VOC) of these devices were found to increase with the concentration of CdS in the polymer matrix. The use of nanocrystals allows great flexibility in controlling the performance of the devices by changing the size, concentration and the material of the nanocrystals.

Ion movement in polypyrrole/dodecylbenzenesulphonate films in aqueous and non-aqueous electrolytes

Abstract The electrochemical characteristics during the redox process of polypyrrole (PPy) films, prepared using dodecylbenzenesulphonate (DBS−) dopant species, have been investigated using a combination of cyclic voltammetry and Electrochemical Quartz Crystal Microbalance (EQCM) measurements. Investigations were carried out using aqueous and non-aqueous electrolytes to study the effect of solvent on the ion movement during redox processes. When PPy films are cycled in aqueous electrolytes transport of both anion and cation occurs during oxidation and reduction. However, when cycled in the non-aqueous electrolyte propylene carbonate (PC) only anion movement takes place.

Paddle-wheel versus percolation mechanism for cation transport in some sulphate phases

Abstract Lithium sulphate and a few other compounds have high temperature phases which are both solid electrolytes and plastic crystals (rotor phases). Three types of experiments are here considered in order to test the validity of a “paddle-wheel mechanism” that has been proposed for cation conductivity in these phases. A single-crystal neutron diffraction study has been performed for cubic lithium sulphate. The refinement of the data gives a very complex model for the location of the lithium ions. There is definitely a void at and near the octahedral (1/2, 1/2, 1/2) position. 90% of the lithium ions are located at the tetrahedral 8c-sites (1/4, 1/4, 1/4), although significantly distored in the directions of the four neighbouring sulphate ions. The remaining 10% of the lithium ions are refined as an evenly distributed spherical shell which is sorrouding the sulphate ions. The lithium ions are transported along a slightly curved pathway of continous lithium occupation to a corressponding to a distance of about 3.7 A. Thus, lithium transport occurs in one of the six directions [110], [1 1 0], [101] etc. The electrical conductivity has been studied for solid solutions of lithium tungstate in cubic lithium sulphate. The conductivity is reduced in the one-phase region, while it is increased in a two phase (solid-melt) region. There are pronounced differenes between the rotor phases and other phases concerning how partial cation substitution affects the electrical conductivity of solids solutions. Regarding self and interdiffusion, all studied mono- and divalent cation are very mobile in the rotor phases, which lack the pronounced correlation with ionic radii that is characteristic for diffusion in other of solid classes of solid electrolytes. The quoted studies are to be considered as strong evidence against a percolation model proposed by Secco.

TiO2/Chitosan-NH4I(+I2)-BMII-Based Dye-Sensitized Solar Cells with Anthocyanin Dyes Extracted from Black Rice and Red Cabbage

Dye sensitized solar cells (DSSCs) were fabricated using anthocyanin dye and polymer electrolyte with ammonium iodide (NH4I) salt. The study was designed to focus on increasing the efficiency of the DSSC. DSSC using 26.9 wt. % chitosan-22 wt. % NH4I(

Performance of Dye-Sensitized Solar Cells with (PVDF-HFP)-KI-EC-PC Electrolyte and Different Dye Materials

A plasticized polymer electrolyte system composed of PVDF-HFP, potassium iodide (KI), and equal weight of ethylene carbonate (EC) and propylene carbonate (PC) has been used in a dye-sensitized solar cell (DSSC). The electrolyte with the composition 40 wt. % PVDF-HFP-10 wt. % KI-50 wt. % (EC

Determination of ionic carriers in polypyrrole

Abstract The successful use of conducting polymers for actuators depends on the ability to control force and position precisely by the application of a potential. The reversible oxidation and reduction of the polymer backbone is accompanied either by the insertion/expulsion of anions, by the expulsion/insertion of cations, or by a more complicated mixture of the two cases. The identity of the mobile ion has been elucidated for three polypyrrole (PPy) based systems by using the Nernst equation to interpret the dependence of the peak potentials in voltammograms on electrolyte concentration. Using the LiClO 4 /propylene carbonate electrolyte, the ClO 4 − ion is the main mobile species, whereas when using LiClO 4 /acetonitrile it is the Li + ion. The switch in mechanism caused by the change of solvent, which does not formally enter into the oxidation/reduction equation, shows that the effect depends on finely balanced interactions between the ions, the polymer and the electrolyte solvent. When using a large, immobile anion (dodecyl benzene sulphonate) incorporated in PPy, the results in the NaCl/H 2 O electrolyte indicate mainly Na + ion motion, as expected. Simultaneous cyclic voltammetry and quartz crystal microbalance measurements indicate that the Na + ions are accompanied by a large number (10–20) of H 2 O molecules. Force measurements show that the full variation in force occurs over a relatively small potential range.

From crab shell to solar cell: a gel polymer electrolyte based on N-phthaloylchitosan and its application in dye-sensitized solar cells

Chitosan, a biopolymer derived from crab shells which is insoluble in common organic solvents has been converted to the organosoluble N-phthaloylchitosan (PhCh) by reaction with phthalic anhydride in dimethylformamide (DMF). The formation and structure of PhCh was confirmed by the characteristic peaks of phthalimido and aromatic groups observed at 719, 1708 and 1772 cm−1 and two sets of peaks centered at 3.0 and 7.5 ppm obtained from FTIR and 1H NMR analyses respectively. Gel polymer electrolytes consisting of PhCh, ethylene carbonate (EC), and DMF with various amounts of tetrapropylammonium iodide (TPAI) and iodine were prepared. The interaction behavior between polymer–plasticizer–salt was thoroughly investigated using FTIR spectroscopy. The gel polymer electrolyte consisting of PhCh : EC : DMF : TPAI : I2 in a weight ratio (g) of 0.1 : 0.3 : 0.3 : 0.12 : 0.012 showed the highest conductivity of 5.46 × 10−3 S cm−1 at room temperature and exhibited the best performance in DSSCs with efficiency of 5.0%, with JSC of 12.72 mA cm−2, VOC of 0.60 V and fill factor of 0.66.

Enhanced ionic conductivity of poly(ethylene imine) phosphate

The conductivity of mixtures of phosphoric acid with poly(ethylene imine) has been studied, and it was found that the conductivity of such mixtures with high acid content can be enhanced by the addition of highly dispersed silica (fumed silica). At the same time, silica addition increases the stiffness of the polymer, and macroscopically solid composites with good proton conductivity can be obtained, without significant degradation of the optical transparency of the polymer electrolyte.

Phthaloylchitosan-Based Gel Polymer Electrolytes for Efficient Dye-Sensitized Solar Cells

Phthaloylchitosan-based gel polymer electrolytes were prepared with tetrapropylammonium iodide, Pr 4 NI, as the salt and optimized for conductivity. The electrolyte with the composition of 15.7 wt.% phthaloylchitosan, 31.7 wt.% ethylene carbonate (EC), 3.17wt.% propylene carbonate (PC), 19.0 wt.% of Pr 4 NI, and 1.9wt.% iodine exhibits the highest room temperature ionic conductivity of 5.27 x 10 -3 S cm -1. The dye-sensitized solar cell (DSSC) fabricated with this electrolyte exhibits an efficiency of 3.5% with.. SC of 7.38mAcm -2,.. OC of 0.72V, and fill factor of 0.66. When various amounts of lithium iodide (LiI) were added to the optimized gel electrolyte, the overall conductivity is observed to decrease. However, the efficiency of the DSSC increases to a maximum value of 3.71% when salt ratio of Pr 4 NI : LiI is 2 : 1. This cell has.. SC,.. OC and fill factor of 7.25mAcm -2, 0.77V and 0.67, respectively.

A Suitable Polysulfide Electrolyte for CdSe Quantum Dot-Sensitized Solar Cells

A polysulfide liquid electrolyte is developed for the application in CdSe quantum dot-sensitized solar cells (QDSSCs). A solvent consisting of ethanol and water in the ratio of 8 : 2 by volume has been found as the optimum solvent for preparing the liquid electrolytes. This solvent ratio appears to give higher cell efficiency compared to pure ethanol or water as a solvent. Na2S and S give rise to a good redox couple in the electrolyte for QDSSC operation, and the optimum concentrations required are 0.5 M and 0.1 M, respectively. Addition of guanidine thiocyanate (GuSCN) to the electrolyte further enhances the performance. The QDSSC with CdSe sensitized electrode prepared using 7 cycles of successive ionic layer adsorption and reaction (SILAR) produces an efficiency of 1.41% with a fill factor of 44% on using a polysulfide electrolyte of 0.5 M Na2S, 0.1 M S, and 0.05 M GuSCN in ethanol/water (8 : 2 by volume) under the illumination of 100 mW/cm2 white light. Inclusion of small amount of TiO2 nanoparticles into the electrolyte helps to stabilize the polysulfide electrolyte and thereby improve the stability of the CdSe QDSSC. The CdSe QDs are also found to be stable in the optimized polysulfide liquid electrolyte.