Lead zirconate titanate (PZT) films 60 μm in thickness have been fabricated using a new sol gel based process. PZT powders are dispersed in a sol gel matrix to form a 0–3 ceramic/ceramic composite. The dielectric properties of these films have been studied as a function of powder concentration, frequency, and temperature. The characteristic Curie point is observed at 420 °C. The ferroelectric behavior measured in terms of the remanant polarization (Pr=35 μC/cm2) and coercive field (Ec=20 kV/cm) was an improvement over values quoted for thin PZT films but lower than that of bulk ceramic. The piezoelectric properties d33 (325 pC/N) and d31 (−80 pC/N) were comparable with those of the bulk ceramic.

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Current-voltage ͑J-V͒ characteristics of an organic bulk heterojunction solar cell have been modeled and compared with the measured characteristics of solar cell based on the blend of poly͑3-hexylethiophene͒ ͑P3HT͒ and phenyl ͓6,6͔ C 61 butyric acid methyl ester ͑PCBM͒. In an undoped organic double Schottky junction diode, for V Ͻ V bi the electric field remains constant and is given by ͑V bi − V͒ / d, where V bi is the built-in voltage, V is the applied voltage, and d is sample thickness. We considered the effect of this constant electric field on the charge carrier transport and solved the drift and diffusion equations to model the J-V characteristics. For V Ͻ V bi the current is found to be dominated by diffusion. A comparison of the theoretical results with the experimental data measured in dark and under different illumination intensities shows good agreement.

The temperature dependence of the dc conductivity of electrochemically polymerized films of polypyrrole, poly͑N-methyl pyrrole͒ and their copolymers, poly͑N-methyl pyrrole-pyrrole͒, having different percentage of BF 4 Ϫ ions has been investigated in the temperature range 77-350 K. The observed behavior could be explained in terms of Mott's variable range hopping model involving a single phonon process. The estimated values of polaron radius yield the realistic values of density of states at the Fermi level which are in good agreement with the values reported earlier for other polyconjugated systems.

The total measured ac conductivity σ(ω)m of lightly doped polypyrrole films has been measured in the frequency range 100 Hz–10 MHz and in the temperature range 77–350 K. In the low-temperature region the measured ac conductivity is almost independent of temperature but shows a strong dependence on frequency and can be described by a relation σ(ω) = Aωs where the exponent s has been observed to be less than unity. In the high-temperature region the frequency dependence becomes weak at low frequencies but remains strongly frequency dependent at high frequencies. The weak frequency dependence is due to the contribution of dc conductivity to the measured ac conductivity. A clear Debye-type loss peak is observed by substracting the contribution of dc conductivity. The frequency dependence of conductivity remains less than quadratic at low frequencies indicating thereby some distribution of relaxation times. This is confirmed by the measurement of dielectric constant as a function of frequency and temperature. The frequency and temperature dependence of ac conductivity can be qualitatively explained by the proposed model which considers the contributions from two mechanisms, one giving a linear dependence of conductivity on frequency and the other having distribution of relaxation times giving rise to broad dielectric loss peak.

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The present work is a detailed study of the optical, morphological and electrical properties of poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate), PEDOT:PSS, films doped with ethylene glycol (EG) and multi-walled carbon nanotubes (MWCNT). The conductivity of PEDOT:PSS films doped with EG and MWCNT is higher than pristine PEDOT:PSS film. The optical transparency of PEDOT:PSS film decreases insignificantly after addition of MWCNT and EG. The films were further studied using atomic force microscopy, x-ray diffraction, Raman spectroscopy and Kelvin probe work function measurement, after which films of PEDOT:PSS with EG and MWCNT were optimized for the fabrication of solar cells. The optimized film was used as a hole extracting layer in a typical ITO/PEDOT:PSS/ P3HT:PCBM/Al solar cell. The suitable concentration for an optimized film was found to be 4% MWCNT and 1:4 ratio of EG to PEDOT:PSS. The performance of the device with doped PEDOT:PSS was found to improve in terms of short circuit current density (J SC ) and efficiency (η). The solar cell with a doped PEDOT:PSS layer showed higher J SC and η due to the increase in the interchains among PEDOT chains along with the introduction of MWCNT channels in PEDOT:PSS matrix. The degradation behavior of the cells was studied and it was found that both pristine and doped PEDOT:PSS cells showed similar trends of degradation. The performance degradation with time was also studied under variable environmental conditions, which showed different aging rates for the two devices.

The electromagnetic interference (EMI) shielding mechanism of carbon nanotube (CNT)/polymer nanocomposites synthesized through a unique processing technique has been studied. As CNT/polymer nanocomposites evolve towards device applications, homogenous dispersion of CNTs has become a main objective to realize their full potential. In this work, dispersion of multi‐walled carbon nanotubes (MWCNTs) in polystyrene (PS) powder via dry state tumble mixing has been carried out. This involves the coating of the PS particles with the MWCNTs. Pellets were prepared by hot compression of resulted mixture. Conductivity behavior has shown that an extremely small mass fraction of 0.05 wt % MWCNTs in PS is good enough for percolation threshold. A detailed study of EMI shielding behavior of these composites is reported in addition to physical phenomena involved. The shielding effectiveness achieved is higher compared to solution mixing technique used by others. Decrease in hardness with increase in MWCNT content is little. Scanning electron microscope studies of these nanocomposites revealed a web/mesh like structure consisting of MWCNTs. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40201.