Poly(2,5-thienylene vinylene), PTV and its soluble alkyl derivatives were synthesised using the dithiocarbamate precursor route (DTC-route) in a good yield, with high molecular weight (Mw), low polydispersity (PD), and with a high maximum absorption peak, $\lambda_{max}$ . The polymers were characterised by absorption spectroscopy, cyclic voltammetry and, X-ray diffraction.

The optical study of transmission T(λ) and reflection R(λ) spectra has enabled us to determine compounds that possess gaps close to 1.5 eV. The conditions for preparation of a ternary compound whose gap is 1.48 eV have been used to create a Pb1−x Cdx S-n/Si-p heterojunction. The heterojunction thus obtained presented a low yield (0.5%), as determined from the study of the J–V characteristic. In order to improve its efficiency, we have studied the effect of thermal treatment on the prepared heterojunction. X-ray diffraction has been used to determine the variation in the crystalline parameter and the ratio of cadmium in the Pb1−x Cdx S compound, and the dependence of its gap on the cadmium concentration. We have also used the C–V technique to determine the average concentration of impurities in the Pb1−x Cdx S compound.

We investigated mobility in the regioregular poly(3-octylthiophene) (RR-P3OT) and regioregular poly(3-hexylthiophene) (RR-P3HT) by the Charge Extraction by Linearly Increasing Voltage method (CELIV). The samples were produced by the drop-casting and spin-coating methods on the Indium-Tin-Oxide substrate and provided with Al contacts. In both materials we had observed the “negative” mobility dependence at low electric fields, i.e., the mobility used to decrease with increasing electric field (in P3HT, this was only observed here in the drop-casted sample). Such behaviour was never observed by CELIV in P3OT before. Data were analysed within the Poole-Frenkel and Gaussian disorder models. The higher energetic disorder parameters were obtained in P3OT as compared to P3HT. This could be related to the longer side-chains of P3OT. We had demonstrated that in both materials with increasing temperature conductivity grows due to the thermally activated mobility.

We have investigated properties of poly(9-vinylcarbazole) (PVK) doped with 30% wt 4-dibutylamino-4'-nitrostilbene (DBANS), depending on the orientation of the polar DBANS molecules. Appearance of the orientation-induced built-in electrical field was proven optically by the Solid Electric Field Induced Second Harmonic Generation and electrically by Current-Voltage characterization. Modification of optical properties was evidenced by the spectral dependencies of absorption coefficient. The Thermally Stimulated Currents spectra demonstrated that carrier transport and trapping are affected, too.

Thermal evaporation technique was used to prepare As20Se80−x Tlx films from bulk materials;( $5\leqslant x\leqslant 35$  at.%). The effect of TI addition on the thermoelectric properties and mobility activation energy of As-Se-Tl chalcogenide semiconductors has been studied in the homogeneous glass-forming region through temperature range (300–380 K). The thermoelectric power, TEP had a positive sign over the whole temperature range investigated, indicating p-type conductivity for As20Se80 −x Tlx films. TEP activation energy, $\Delta E_{s}$ could be calculated from TEP measurements. It was found that $\Delta E_{s}$ decreases with increasing Tl-content and is found to vary between 0.814 and 0.517 eV. The mobility activation energy, $\Delta E_{Q}$ could be calculated.

The optical absorption in organic solar cells, and hence theirefficiency to convert sunlight into electricity, is limitedby both a confined spectral absorption range and the very thin active layers which are required since polymers have short charge carrier diffusionlengths. We propose to make the most of thisapparent 'drawback' by using transparent contacts on both sides ofthe diode, leading to brilliant red-coloured semitransparent solarcells. Such cells are interesting for new, aesthetically appealingapplications where coloured glasses or foils with the additionalbenefit of providing electric power are desired. Maybe even moreimportantly – such semitransparent solar cells are essential formechanically stacked tandem arrays where two subcells arecombined. We investigated different cathodes based on Al-doped ZnO and thin LiF and Al layers. Apparently, the different cathode layer preparation conditions strongly influence the cellperformance. Our standard LiF/Al cells donot usually require annealing for improved efficiencies, incontrast to cells with sputtered cathodes. For the latter, athermal post-treatment can greatly enhance the performance,depending on the sputtering process. We could demonstrate power conversion efficiencies of up to 3.4% for single cells and up to 4.2% for stacked tandem arrays.

In order to fabricate integrated imaging and particle sensors a hydrogenated amorphous silicon (a-Si:H) p+-i-n+ photodiode technology has been developed, optimized and modelled. The realisation of a one-dimensional model of this by Chatterjee has given us a precious modelling reference. In this paper we propose a bi-dimensional model realized in finite elements approach with Atlas-Silvaco Software of particle sensor achieved by a 4 µm p+-i-n+ amorphous silicone photodiode. We will validate it by comparison with the above-mentioned one-dimensional model. The interest of the second dimension lies not only in the calibration of different structures but also in the influence between neighbouring pixels of the sensor and how this will affect their sensibility. Thus a three pixel bi-dimensional structure has been realized. The leakage and crosstalk currents between two neighbouring pixels have been studied and characterized using a uniform AM1.5 light source.

Electrochemical behaviors of different pendant carbazole based oligomers have been studied for the realization of electroactive tridimensional structures. 3-substitution by hydrazone functional groups onto the pendant carbazole moieties increases the electron donor properties of the electroactive units. Electrochemical oxidation of thin films of the oligomer precursors deposited onto electrode ensures the formation of a cross-linked structure by in situ anodic coupling with the formation of biscarbazole redox sites. When the electrochemical cross-linking of the oligomers is realized in the presence of the electron acceptor polyimide (perylene based), we form a semi-interpenetrating polymer network (semi-IPN) coated as a thin layer. The electrochemical behavior of the semi-IPN shows two reversible oxidations and two reversible reduction peaks indicating respectively the p-doping of the biscarbazole entity and the n-doping of the perylene one. The presence of hydrazone substituents modifies the electron donor properties of the semi-IPN and should influence the electron transfer properties from biscarbazole to perylene units in bulk heterojunction solar cells.

Electrochemistry of perylene imide and anhydride derivatives adsorbed on semiconductor TiO2 (NT) and insulator Al2O3 (NA) metal oxide films were presented. Adsorption rates on metal oxide surface are observed to be strongly depending on molecular structure. Monoanhydride-monoimide derivatives show two reversible reductions in solution and one reversible reduction in films. Color change from red to blue and violet is observed indicating the formation of monoanion and dianion radicals. Spectroelectrochemical measurements support this interpretation. The color reversal is quite stable in NA films in comparison with NT films.

We have studied blends of poly-(3-octylthiophene) (P3OT) and graphitic nanoparticles by macroscopic transport measurements, Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD) and Scanning Force Microscopy (SFM) techniques. Their morphology as well as their mechanical and electrical properties have been characterized on a nanometer scale as a function of the carbon nanoparticle concentration in the blend. For intermediate concentrations (5–10% wt. of carbon nanoparticles) the samples present regions of pure poly-(3-octylthiophene) and round regions of polymer and carbon nanoparticles mixture, while for higher concentrations (>15% wt.) the whole sample is composed of this mixture. The interface between both regions is studied by Electrostatic Scanning Force Microscopy as a function of the applied tip-sample voltage finding evidence for the creation of new electronic states at the heterojunction. TEM images show crystalline domains of P3OT surrounded by amorphous regions. XRD measurements show that the crystallinity of the polymer increases when carbon nanoparticle concentration increases. The potential of this blends to improve the performance of organic solar cells when used as active layer is discussed.

We demonstrate, by means of light-induced EPR andoptical spectroscopy, that thermal treatment of P3HT/PCBM filmsprepared from CB solution results in a decrease of the chargetransfer yields. The improved performance of solar cells istherefore attributed to optimization of the morphology, inparticular molecular order in the P3HT regions, which could bemonitored by optical absorption and resonant Raman scattering(RRS). We further found that spin coating from slowly evaporatingsolvents leads directly (i.e., without thermal treatment) tooptimal morphologies of the P3HT/PCBM films, with similar resultsfor charge transfer, morphology and solar cell efficiencies.

An algorithm was developed for the theoretical intensities of both X-ray continuum and characteristic K-radiation (Kα1, Kα2, Kα , Kβ1, Kβ2, Kβ3, Kβ13, Kβ4 and Kβ5) of different target materials (Cr, Cu, Rh, Mo, W, Ag and Au) at different electron incidence angles (0.01° − 90°), different take-off angles of the photon emission (0.01° − 90°) and different X-ray tube voltages. It was found that the intensities of continuum and characteristic X-rays increase with increasing take-off angle and the take-off angle is inversely proportional to the absorption path of X-rays in the target. At take-off angles of 20° or more, the flux of the X-ray spectra remains practically independent of the take-off angle. Furthermore, at the optimum electron incidence angle and take-off angle of emitted X-ray photons, the dependence of X-ray tube spectra on applied voltage was also investigated.

A model organic material, namely the 36-n-alkane hexatriacontane, was etched in a dissymmetrical parallel plate RF plasma reactor and a dual distributed electron cyclotron resonance (DECR) plasma reactor, in different O2-Ar mixtures. A specific attention was paid to the role of the ion bombardment, especially when its effect is combined with the chemically active species created in an oxygen discharge. The discharge was monitored by optical emission spectroscopy (OES). The modifications induced by plasma treatment on the structure of the material were analysed by Fourier transform infrared spectroscopy (FTIR), steric exclusion chromatography (SEC) and composition analysis. We found that the ion bombardment has not only a sputtering effect but also enhances the reaction rate of the chemical species on the layer surface. It appears that plasma treatment leads to cross-linking and recombination with molecules from the room atmosphere.

An electrical model for a dielectric barrier discharge (DBD) is proposed, with the aim of its application in power supply design process. An identification method, which finds the actual value of the parameters in a model, is presented. The specific modelling of a XeCl exciplex lamp is developed, along with the identification procedure of the parameters, using a sinusoidal and a pulsed experiment. Electrical representation of the model is done in two different simulators. The applicability of the identified model is proved with different experiments. Differences between experimental and simulated waveforms are minor, encouraging the use of the model in the construction of the converter for the DBD lamp.

The rapid crystallization of amorphous silicon utilizing a very-high-frequency (VHF) inductive coupling thermal microplasma jet of argon is demonstrated. Highly crystallized Si films were synthesized by adjusting the translational velocity of the substrate stage and flow rate of argon. The H concentration in the crystallized Si films decreased from 1021 cm−3 to 1019 cm−3 with no marked increases in oxygen and nitrogen impurity concentrations and defect density. The thin-film transistors of a 40-nm-thick crystallized a-Si film showed a field-effect mobility of 30–55 cm2/V s with a threshold voltage of 3–5 V. P-i-n thin-film solar cells were also fabricated for 1.5-μm-thick crystallized a-Si films, which showed an efficiency of 5.5% and filled factor of 0.52. The crystallization proceeded with time constants of $\sim $ 10 ms, which was of 4–6 orders of magnitude lower than the conventional laser-crystallization of a-Si. The crystallization process is discussed in terms of the viscous flow of Si-network, due to the rapid local heating and melting of a-Si.

A stable corona discharge in a two conductors-to-plane configuration is analysed in this paper. A linear biased probe, without end-effect, has been adapted to a linear geometry and is used for the first time to measure the ground-plane current density and electric field during the bipolar corona. The values of the electric field and the current density are maximum under the two coronating conductors and decrease when moving away from them. Furthermore, a hybrid technique is developed to obtain a general solution of the governing equations of the coupled space-charge and electric field problem. The technique is to use the finite-element method (FEM) to solve Poisson's equation, and the method of characteristic (MOC) to find the charge density from a current-continuity relation. The model avoids resorting to the Deutsch assumption. The computed values are in good agreement with experimental data.

The influence of H2 addition on the discharge characteristics of Ne-Xe in a AC-PDP macro-cell was studied in this paper. The experimental results show that there are remarkable decreases of the firing voltage and the minimum sustaining voltage, and a remarkable increase of the discharge current, and an increase of the sustaining voltage memory margin by an amount of H2 addition in Ne + 4%Xe mixture when the sustaining voltage frequency is in the range of 12.5–93.5 kHz. As for H2% = 0.12 and f = 15.5 kHz, the discharge current is 6 times of the discharge current without H2 addition in Ne + 4%Xe mixture. The maximum value of the increase of discharge current can be obtained at f = 32.5 kHz as well as the firing voltage and the minimum sustaining voltage have the decreases of 12 V and 11 V. The maximum value of the sustaining voltage can be obtained at H2% = 0.12 and f = 93.5 kHz. The firing voltage and sustaining voltage can be depressed remarkably without deterioration of the voltage memory margin by an amount of H2 addition in Ne + 4%Xe.

Oxygen plasmas have found numerous applications in plasma processing, such as reactive sputtering, dry etching of polymers, oxidation, and resist removal of semiconductors. Swarm and transport coefficients are essential for better understanding and modelling of these gas discharge processes. The electron swarms in a gas under the influence of an electric field can be simulated with the help of a Monte Carlo method. The swarm parameters evaluated are compared with experimental results.

Various poly[3-(4-octylphenyl)thiophene]s (POPTs) were prepared either by oxidative polymerisation or by chain-growth Grignard metathesis (GRIM). In accordance with previous results, the former polymerisation yielded polydisperse POPT. The method based on the GRIM reaction made possible the preparation of medium and higher molecular weight polymers with lower polydispersities. The POPTs were found to have band-gaps of ca. 1.7 eV. The photovoltaic characteristics of POPTs-blend-[6,6]-phenyl C61 butyric acid methyl ester (PCBM) composites under AM 1.5 conditions in standard ITO/PEDOT-blend-PSS/POPT-blend-PCBM/LiF/Al solar cells were studied. It was found that POPT prepared via GRIM could deliver greater efficiencies than its equivalent prepared by oxidative polymerisation. It is expected that access to even higher molecular weight POPTs may improve the efficiencies of such devices.

We discuss the possibility of simultaneous and sequential synchronisation in vertical and horizontal arrays of unidirectionally coupled discrete systems. This is realized for the specific case of two dimensional Gumowski-Mira maps. The synchronised state can be periodic, thereby bringing in control of chaos, or chaotic for carefully chosen parameters of the participating units. The synchronised chaotic state is further characterised using variation of the time of synchronisation with coupling coefficient, size of the array, etc. In the case of the horizontal array, the total time of synchronisation can be controlled by increasing the coupling coefficient step wise in small bunch of units.