We present a series of organic photovoltaic (PV) cells based on the bulk-distributed heterojunction where $\pi $ -conjugated polymer poly[1-(4-trimethylsilylphenyl)-2-phenylvinylene], PSDPhV, acts as the donor upon photoexcitation and the substituted perylene based low-molecular-weight compound: N,N`-di(pent-3-yl)-perylene-3,4:9,10-bis(dicarboximide), DPe-PTCDI, as the acceptor of photogenerated electrons. According to both absorption spectra and AFM images of the thin films spin-coated from solution of DPe-PTCDI and PSDPhV in toluene, the DPe-PTCDI is molecularly dissolved in conjugated polymer matrix. Upon exposition of layers to toluene vapors, microcrystals of DPe-PTCDI are progressively formed. The influence of the morphology of DPe-PTCDI inside the polymer matrix on PV cell performance is investigated.

Polycrystalline electroceramics have been prepared by varying modifier to former (Bi/La) ratios ( $z/1-z$ ) according to the complex formula Pb0.92[La $_{1-z}$ Biz ] 0.08[Zr0.65Ti0.35] 0.98O3 (PLBZT), where z = 0.0, 0.3, 0.6. The electrical properties of PLBZT compounds were studied using the ac impedance spectroscopy technique over a wide range of temperature (30–500 °C) in the frequency range of 100 Hz–1 MHz. Nyquist plots recorded at different temperatures show a decrease in the bulk resistance (R b ) with rise in temperature for PLZT material (z = 0.0) i.e., NTCR behavior like semiconductors. The Nyquist plots also indicates that the bulk resistance of the material has been observed to be concentration dependent and decreased in two order of magnitude with higher Bi-addition in PLZT matrix. Bismuth (Bi) substitution at the lanthanum (La) position not only resulted in lowering of the electrical resistance with its higher concentration but also has changed the NTCR behavior of PLZT (z = 0.0) to PTCR (positive temperature coefficient of resistance) for PLBZT. Electrical property studied by complex impedance spectroscopic method also indicates the evidence of (i) single electrical relaxation attributed to the presence of bulk contribution to the electrical properties, (ii) presence of temperature dependent electrical relaxation phenomenon and (i) diminution in the barrier to the mobility of charge carrier on Bi-substitution.

While silicon is not the best semi-conductor material to design Hall effect sensors, it is widely used because Hall devices are fully compatible with standard processes such as CMOS or Bi-CMOS.Hall effect sensors can thus take advantage of on-chip circuitry to counterbalance the poor intrinsic metrological characteristics of silicon Hall devices, and low cost integrated smart magnetometers can be designed using standard technologies.Conventional Hall plate as well as the spinning-current method, which is the present state of the art technique to improve performances of integrated Hall devices, are reviewed in this paper.Then a new multi-strips Hall device and its specific biasing circuit are introduced.This new device allows to multiply by n the absolute sensitivity of the Hall sensor where n is the number of strips, but it suffers from offset.To overcome this drawback, a Hall sensors network which also allows to increase the sensitivity while reducing the offset is proposed.Finally a comparison between the Hall sensors network and the spinning-current is done, showing that both techniques are complementary and should be combined to design high resolution Hall sensor systems.

The synthesis and properties of two semiconducting donor-acceptor (D-A) block copolymers and their application in nanostructured bulk heterojunction solar cells are reported. The donor segments were obtained via nitroxide mediated polymerization of either bis(4-methoxyphenyl)-4'-vinylphenylamine or N,N'-bis(4-methoxyphenyl)-N-phenyl-N'-4-vinylphenyl-[1,1'biphenyl]-4,4'-diamine. Narrow-distributed macroinitiators, poly{bis(4-methoxyphenyl)-4'-vinylphenylamine} (PvDMTPA) and poly{N,N'-bis(4-methoxyphenyl)-N-phenyl-N'-4-vinylphenyl-[1,1'biphenyl]-4,4'-diamine} (PvDMTPD) were used to polymerize the acceptor monomer perylene diimide acrylate (PerAcr) to yield block copolymers with well-defined molecular weights. Different diblock copolymers, PvDMTPA-block-PPerAcr and PvDMTPD-block-PPerAcr, with high perylene diimide weight fractions were prepared. The block copolymers exhibited efficient fluorescence quenching. Transmission electron microscopy revealed wire-like and worm-like nanostructures throughout bulk samples. Thin film photovoltaic devices showed short circuit currents $J_{\it SC}$ of up to 1.21 mA/cm2 and power conversion efficiencies ηof 0.32% under AM 1.5 illumination conditions.

Recent experimental studies of electrical conduction in a specially prepared silver-based material, across which a spark has been passed, are interpreted through electrical conduction via charge density waves (CDWs) moving in a dc electric field along quasi-one-dimensional chains of Ag+-ions inside the branches of the discharge pattern engraved in the material by the spark. Here we present experimental evidence that the resistance along a number N of branches connected in parallel increases in quantized steps of height $h/2e^{2}N$ with increasing voltage applied across the branches

The nanoscale morphology of the active layer in bulk-heterojunction solar cells consisting of regioregular poly(3-hexylthiophene-2, 5-diyl) (P3HT) and methanofullerene([6-6]-phenyl C61 butyric acid methyl ester) (PCBM) was extensively studied using Atomic Force Microscopy (AFM), Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD) and optical microscopy. Different weight ratios of P3HT:PCBM were investigated as a function of annealing temperature and time revealing the occurrence of crystallization of both components. Firstly, the as-prepared films can be described as a semi-crystalline blend. Secondly, it has been demonstrated that for a short annealing time (5 min) at lower annealing temperatures (75–115 °C) an increased crystallization of P3HT occurs. Thirdly, it has been observed that a prolonged annealing at the given temperature range or a short annealing at higher temperatures (≥ 120 °C) leads to the formation of a new ordered crystalline structure of PCBM. These new ordered structures, a few μm up to 100 μm in length, form a network of needle-like and even fan-shaped crystals. Key-parameters to “tune” this new ordered structure of PCBM are blend ratio and annealing conditions. The growth mechanism of these new PCBM-structures is described by means of diffusion.

In this article, a pressure-controlled sample holder for microwave dielectric measurements in the temperature range from 90–450 K is presented. The experimental set-up involves a coaxial line used to couple a microwave frequency network analyzer and an adapted sample holder in order to obtain dielectric characterization as a function of the temperature. The main innovation of the present work is the technical adaptation in the pressure control of the sample for low temperature measurements. The system was tested characterizing the complex dielectric constant of a Ca modified strontium titanate (SrTiO3) quantum paraelectric-type ceramic material, for which the main physical dielectric properties (orientational or relaxation polarization) in the high frequency region are interesting to be investigated mainly at low temperatures.

High conductive and transparent thin films based on carbon nanotube – poly(3,4-ethylene-dioxythiophene)-poly(styrene sulfonate), PEDOT-PSS blends have been used to replace the conventional indium tin oxide (ITO) as the hole collecting electrode in organic photovoltaic cells. Using PEDOT:PSS as the host material, excellent dispersion of functionalized single wall carbon nanotubes can be achieved enhancing the polymer's conductivity, while maintaining its excellent optical transparency. Photovoltaic cells with Poly(3-hexylthiophene), P3HT and [6,6]-phenyl-C61 butyric acid methyl ester (PCBM as the electron donor and acceptor on respectively on polymer-nanotube substrates have been fabricated and characterized. A power conversion efficiency of 1.3%, with a fill factor of 0.4, an open-circuit voltage of 0.6 V and a short-circuit current of 5.6 mA/cm2 under 100 mW/cm2 white light illumination are reported. These values are close with the reference cells made on ITO glass substrates with the same device structure and fabrication process. The only drawback is on the fill factor which is considerably smaller due to the high resistance of the polymer-nanotube film. Nevertheless, the results indicate that the spin casted polymer-nanotubes thin films are a low cost alternative to ITO for organic electronics.

This paper concerns non linear dielectric spectroscopy in the SmC* phase of a ferroelectric liquid crystal. The experimental set-up and the procedure used to determine non linear permittivities are described. The results are discussed on the basis of the model proposed by Kimura et al. [Y. Kimura, S. Hara, R. Hayakawa, Phys. Rev. E 62, R5907 (2000); Y. Kimura, S. Hara, R. Hayakawa, Ferroelectrics 245, 61 (2000)]. A good agreement is obtained between the measurements and the theoretical predictions for $\epsilon^{*}_{3,3}$ and $\epsilon^{*}_{5,5}$ non linear permittivities. Some physical parameters of the material like the polarization, the rotational viscosity and the elastic term are determined. The polarization is found similar to this obtained with classical triangular wave method.

The effects of turbulence on momentum, heat and solutal transport in a typical high power laser surface alloying process are numerically investigated. The turbulent transport is accounted for by employing a standard high Reynolds number k − ε model, suitably modified to take into account a dynamic evolution of the phase changing interfaces. Phase transitions are handled by using a modified enthalpy porosity technique. Diffusive effects associated with turbulence are found to significantly affect the momentum and solutal transport in the molten pool. On the other hand, enhancements in thermal diffusion on account of turbulence turn out to be rather marginal, with the molecular and eddy thermal diffusivities approximately of the same order. The generation and dissipation rates of turbulent kinetic energy are shown to be in local equilibrium. Based on this inference, a scaling analysis is also performed, which provides order of magnitude estimates of melt pool penetration, mean surface velocity, and temperature/concentration scales. The above estimations are found to be in good agreement with numerical simulation results, in an order of magnitude sense.

This paper discusses some aspects of n-hexane soot reactivity in a multi-pin to plate pulsed corona discharge working in the nanosecond regime at atmospheric pressure. The soot-discharge interaction was quantified by measuring the densities of CO, CO2, O3 and NO2 out-coming from the discharge cell. Results showed that CO2 is the major product of soot oxidation. They also showed a strong enhancement of soot oxidation for O2 percentage greater than 10% and cathode temperatures above 425 K. The soot reactivity is significantly enhanced when the discharge frequency is increased. The results obtained were interpreted in term of the competition between the kinetics of plasma active species adsorption and oxidation product desorption.

CdSe nanocrystals were modified with small ligand molecules in order to render them compatible with a conducting polymer matrix. Modified NCs were characterized by NMR, optical spectroscopy, electrochemistry. Hybrid materials based on such modified nanocrystals and a conducting polymer (MDMO-PPV, P3HT or P3OT) were prepared, characterized, and tested in photovoltaic devices. Modified NCs quench the polymer PL in solutions as well as in films. Photovoltaic devices display modest power conversion efficiencies mainly due to phase segregation.

In this paper, we consider the two-gap Ginzburg-Landau (G-L) free energy functional including the interactions, and obtain a very simple and explicit formula which presents the relation between the critical current density and temperature. The result shows that the temperature dependence of critical current density of a two-gap superconductor is of the form J c ∝ (T c * − T)1/2 at low temperatures and J c ∝ (T c * − T)3/2 near the critical temperature. Our critical current density expression is in accord with the previous theoretical work and experimental data.

We propose a new technique for evaluating the RF voltage across the electrodes of low-pressure capacitively-coupled plasma reactors when direct measurements are not possible. It is based on determining the coordinates of the turning point in the RF breakdown curve and using known values of the electron drift velocity for the gas. The results are in good agreement with those obtained by direct measurements at the driven electrode. Furthermore it allows RF breakdown curves to be determined for different frequencies, giving results that are physically reasonable (coincidence of right-hand branches) and in agreement with other published results. The technique for determining RF voltage we proposed is valid when there is no discharge plasma between electrodes (e.g., before gas breakdown), as well as for negligibly small discharge currents (before extinction of the weak-currentdischarge mode).

A method has been developed to link the geometry of the trapped charge distribution within irradiated insulators to the mirror plot shape, in a scanning electron microscope. We give a detailed analysis of the geometrical optic approximation which is used to evaluate the mirror image formation. We establish then analytical mirror relations obtained for diverse trapped charge distributions such as homoïdal charge distribution, bipunctual and cylindrical ones. Knowledge of the charge distribution first moments enables us to investigate then their effect on the first terms of the mirror expression limited development. Finally, we apply these analytical expressions to evaluate certain characteristics of the charge distribution from an experimental mirror plot.

This article deals with the analysis of small sample volume by using a planar microcoil and a micromachined cavity. This microcoil is used as a nuclear magnetic resonance (NMR) radio frequency detection coil in order to perform in vitro NMR analysis of the sample introduced into the microcavity.It is a real challenging task to develop microsystem for NMR spectrum extraction for smaller and smaller sample volume. Moreover, it is advantageous that these microsystems could be integrated in a Micro Total Analysing System ( $\mu $ -TAS) as an analysing tool. In this paper, NMR theory, description, fabrication process and electrical characterization of planar microcoils receiver are described. Results obtained on NMR microspectroscopy experiments have been performed on water and ethanol, using a 1 mm diameter planar coil. This microcoil is tuned and matched at 85.13 MHz which is the Larmor frequency of proton in a 2 T magnetic field.

We report measurements of the birefringence-induced losses in silicon single crystals for [001] and [111] crystallographic orientation and for different doping levels. These results are compatible with the so-called spatial-dispersion-induced birefringence in cubic crystals. These angular maps have been used to fix some tolerances for the next generation of optics in the Virgo gravitational-wave detector.

Sub-bandgap absorption features ( $\alpha \le 100$  cm−1) have been detected in organic and inorganic semiconductors and their heterojunctions. Photothermal deflection spectroscopy (PDS) is used to increase the detection limit considerably with respect to common absorption spectroscopy. Results are presented on discotic liquid crystals, donor-acceptor complex formation in P3HT:PCBM solar cells and UV-induced defect generation in nanoporous $\mathrm{TiO_2}$ .

Efficient charge transfer between a newly synthesizedlow band gap (LBG) conjugated polymer and the C60 derivativePCBM is demonstrated. Spectral and time-resolved photoluminescence(PL) measurements show strong quenching and charge separation inthe picosecond time range. The charge transfer is furtherconfirmed by light-induced electron paramagnetic resonance (EPR)measurements of both the positive polarons and the fullereneradicals, which can be resolved in high-frequency EPR. Thepotential for the LBG polymer to act as acceptor was examined inblends with the para-phenylene-vinylene polymer MDMO-PPV. Nocharge transfer, but instead energy transfer from MDMO-PPV to LBGoccurs in these blends, as shown by PL spectroscopy.

This paper aims to evaluate the spatial resolution achievable with immersion objective lenses for electron emission microscopy. The simulations, using Simion 7 software, follow a brief reminder of objective lens properties as determined by analytical studies. In general, the aperture and chromatic aberrations should be characterised concurrently since the aperture stop causes an energy-dependent angular discrimination. This last effect adds to the longitudinal chromatic shift produced during the initial electron acceleration. The simulation is applied first to monochromatic electron beams for PEEM objective lenses described in the literature and for several other lens configurations. Then, for energy dispersed electron beams (0.2–2, 0.2–4,..., 0.2–10 eV), the image quality is deduced from density plots involving convolution weighting factors which include the change in angular acceptances. It is shown that PEEM objective lenses associated with an aperture stop of a diameter of 30 µm, may provide resolutions below 2 nm for electrons emitted within the initial energy window 0–10 eV. However for the same aperture stop and a moderate acceleration voltage of 4000 V other objective lenses might provide equally good resolutions. The acceleration bias mode for the focussing element seems especially promising since all along their paths the electron beams keep high energy and are thus less submitted to residual magnetic fields. Also the misalignment effects caused by the electrostatic field disturbances on the sample surface are reduced when a quite long acceleration length is used: the object nodal point being removed far from the emitting surface.