In present work we report that the observation of Meyer Neldel rule and crystallization rate constant stability of Se93-x Zn2Te5Inx (0 ≤x≤ 10) chalcogenide glasses. A strong correlation has been observed between the pre-exponential factor (K 0) and activation energy of crystallization (E c). Such a strong correlation between K 0 and E c indicates that the presence of compensation effect under the non-isothermal crystallization processes. Further, obtained results also demonstrate that the crystallization rate constant stability is higher at 6 at.wt.% of indium.

Cu doped cadmium sulfide (CdS:Cu) nanoparticles were prepared with a wet chemical synthesis by mixing the reactants in a double distilled water solvent. Thioglycerol (TG) was employed as the capping agent and also as the reaction catalyst. Properties of the particles were investigated using UV absorption; photoluminescence spectroscopy (PL) and X-ray diffraction analysis (XRD). The particle size of the prepared CdS:Cu nanoparticles was estimated to be about 4 nm. The XRD pattern of CdS:Cu nanoparticles reveals a hexagonal crystal structure at room temperature. Variation of the TG concentration does not shift the position of the excitonic peak in the absorption spectrum but the PL intensity increases as the TG concentration is increased. The PL intensity decreases with increasing Cu concentration.

In this work, we investigate the emission of the nano-hole array in an ultrathin silver film at infrared regime. It is shown that when the incident light illuminates the nano-hole array, the localized surface plasmons are excited and serve as electric dipoles. The emission of the nano-hole array presents a strong directivity. The maximum radiation is located at infrared regime, and it can be tuned by the period of the nano-hole array, the incidence angle and the polarization of the excitation light. These findings extend our understandings of optical property of metallic nano-structures and provide a unique way to achieve infrared antenna arrays, which may achieve potential applications in photovoltaics and telecommunication.

Ba2Ca(BO3)2: Eu2+ green phosphors were prepared by sol-gel process. The crystallization processes of the phosphor precursors were characterized by X-ray diffraction (XRD) and thermogravimetric analysis (TG). The photoluminescence (PL) results showed that this phosphor was efficiently excited by ultraviolet (UV)-visible light in the wavelength range from 300 to 500 nm and emitted intensely green light with a broad peak at around 520 nm, causing in to exhibit a bright green emission. The critical quenching concentration of Eu2+ in Ba2Ca(BO3)2: Eu2+ phosphor was about 0.10 mol. Based on the experimental results, it is identified that the dipole-dipole interaction in the mechanism of concentration quenching of Eu2+ in the Ba2Ca(BO3)2: Eu2+ phosphor. The CIE of the optimized sample was calculated (x, y) = (0.23, 0. 63).

In this paper, a new calculation approach is developed and applied, for the first time, to different dielectric scales using the thermal step method (TSM). The thermal aspect of the approach concerns insulating materials from nano to macro-scales. The theoretical approach is based on the ballistic-diffuse transport taking into account the relaxation time of heat phonons and their effects on the trapped space charges. These effects are revealed on the temporal evolution of the induced image charges that constitute the electrical signal of the thermal step method. The temperature distributions and the TSM induced image charges are obtained by applying the numerical finite element method, the Newmark direct integration, the mean value theorem and the composite Simpson approximation. In a first step, the results of the temperature distributions are validated with those obtained by Boltzmann and Chen models for nano-polyethylene sample. In a second step, our approach is validated with TSM previous works using the Fourier's model for space charge characterizations in the micro and macro-dielectrics. The validated results of the TSM induced image charges for micro and macro-scales show good agreements, and prove that our approach is a consistent tool to be applied in space charge characterizations for different dielectric scales.

ZnSe nanorods are grown by varying the amount of reducing agent Sodium borohydride and keeping the amount of zinc chloride, selenium powder constant. The samples are characterized using electron diffraction techniques. Simultaneously optical absorption, photoluminescence and longtime photorelaxation of these samples are studied at room temperature. An increase in band gap is observed in each case as compared to bulk ZnSe. Also the formation of nanorods is found to be favourable at particular ratio of reducing agent. An attempt is made to explain the growth and correlate the structural, optical and electrical properties.

The present paper reports the study of a porous silicon based microcavity for a potential chemical sensing application using tris-(8-hydroxyquinoline) aluminum (Alq3) molecules. Porous silicon based planar microcavity was first designed and fabricated using the electrochemical etching technique. Photoluminescence emission of a single porous silicon layer after immersion in an Alq3 solution was first carried out in order to verify that the Alq3 molecules were bound to the porous surface. A wide green band centered at 519 nm, typical of a nano-structured Alq3 film, was observed. Reflectivity measurements of the porous silicon microcavity were then performed for different aluminum concentrations of the Alq3 solution. The microcavity device showed a good sensibility for the Alq3 molecules and an important shift of the microcavity photonic resonance was observed. This device might be considered for a potential aluminiun sensing application.

The FT-IR absorption and Raman scattering were used in order to obtain information concerning the short range order in xCuO·(100-x)[ 2TeO2·PbO·0.2Ag2O](0 ≤x≤ 5 mol%) glasses. Moreover, the changes in tellurium atoms coordination that occurs with copper oxide addition were followed. Both techniques reveal that tellurium is disposed in the network structure in trigonal bipyramids (TeO4), trigonal pyramids (TeO3) along with TeO3+1 polyhedra units. Increasing the CuO content in the glasses changes the coordination of tellurium atoms from 4 to 3 through the so-called 3+1 intermediate units, simultaneously with the increase of the non-bridging oxygen (NBOs) ions amount causing a depolymerization process in the glass structure.

We report on the investigation of the electrical and optical properties of hybrid active layers for multicolor and white light-emitting organic devices consisting of a conjugated polymer – polyfluorene (PFO) mixed with inorganic nanoparticles. We have analyzed the behavior of absorption, photoluminescence (PL) spectra as well as electroluminescence (EL) of PFO-based hybrid films after introduction of inorganic nanoparticles having acceptor properties (ZnO, Si) to compare their emission efficiency. We have demonstrated the possibility to tune the PL/EL emission color from green to blue by changing the PFO/ZnO nanoparticles concentration ratio with obtaining the white color at intermediate concentration ratios.

The encapsulation of the active layers (organic semiconductors, electrodes, transparent conductive oxides, etc.) of organic electronic devices developed onto flexible polymeric substrates is one of the most challenging issues in the rapidly emerging area of organic electronics. The importance for the protection of the active layers arises from the fact that these are very sensitive when they are subjected to the atmosphere, since the permeation of the atmosphere's water vapour (H2O) and oxygen (O $_{2})$ gases induces corrosion effects, film delamination and finally, failure of the organic electronic device. In addition, the encapsulation layers contribute to the long-term stability of the whole device enabling its use in outdoor environments (e.g. in the case of flexible photovoltaic cells-OPVs). A promising approach for the encapsulation of flexible organic electronics includes the development of multilayers that consist of hybrid polymer materials and inorganic layers onto flexible polymeric substrates, such as poly(ethylene terephthalate) (PET). This approach leads to a significant improvement of the barrier performance of the whole structure, due to the synergetic effect of the confinement of the permeation to the defect zones of the inorganic layer, and the formation of chemical bonds between the hybrid polymer and the inorganic layer. The knowledge of their optical properties and their correlation with their barrier performance are of major importance since it will contribute towards the optimization of their functionality. In this work, we provide an overview on the results concerning the use of hybrid polymers as ultra high barrier materials and moreover we discuss on the effect of inclusion of SiO2 nano-particles on their optical properties and barrier performance.

The optical gaps of the low-bandgap PPVs (PM-20, PM-19, PM-18) are decreased down to 1.6-1.7 eV compared with that of MDMO-PPV (2.2 eV). The best lateral hole mobility was determined to be 2.1 × 10-3 cm2/V s (PM-18) in field effect transistors and exceeds that of MDMO-PPV (poly-[ 2-methoxy-5-(3'.7'-dimethyloctyloxy)-1.4-phenylenevinylene], 8.5 × 10-4 cm2/V s). This allows to reduce the PCBM ([6.6]-phenyl-C $_{61(71)}$ -butanoic acid methyl ester) content in solar cell devices down to 1:2 w/w giving a better $\eta_{\rm AM1.5}$ than for MDMO-PPV:[60]-PCBM cells (PM-19:[60]-PCBM 2.32% on ITO-PET, 2.86% on ITO glass). The charge transfer to PCBM as acceptor occurs quite normally and shows an effective charge separation using light-induced spin resonance spectroscopy (LESR). The [70]-PCBM $^{-\bullet}$ signals are shifted to lower field related to those of [60]-PCBM $^{-\bullet}$ and overlap more with the polaron signal of PM-19. The LESR g-factor components of [70]-PCBM $^{-\bullet}$ are reported for the first time. The external quantum efficiency peak values achieve up to 42% at ~350–400 nm and 26% at ~640 nm (PM-19:[60]-PCBM).

The growing market for flexible electronics devices is asking for reduction of manufacturing process complexity. One way to reduce complexity is to decrease the number of single components of a device by using integrated modules, i.e. device components providing multiple functions. In this article, the concept of a self-powered electrochromic graphics display device is demonstrated. The device is based on a three electrode system comprising an electrochromic electrode, a battery anode and a battery cathode, all in contact with a common electrolyte. The electrochromic electrode can be charged and discharged directly when connected to either the anode or cathode. Such a self-powered display integrates the functions of both a display and a battery. As part of a flexible electronics device, a self-powered display would be able to power other components, such as driver electronics.

In this paper, we discuss the effect of flexible substrates on the characteristics of two organic optoelectronic devices, namely P3HT:PCBM-based photovoltaic bulk heterojunctions and pentacene-based phototransistors. In addition, we have developed anode materials deposited by ion beam sputtering, a technique which satisfies the low temperature deposition requirements associated with the use of plastic substrates. The anode materials consisted of indium tin oxide (ITO) and ITO/metal/ITO tri-layers. The use of tri-layer anodes in P3HT:PCBM-based solar cells resulted in an increase in the fill factor and the power conversion efficiency reached a value of 2% with an ITO(70 nm)/Ag(14 nm)/ITO(70 nm) anode deposited on a polyphthalate carbonate substrate. In the case of phototransistors, a photosensitivity of 1.6 × 104 under illumination at 365 nm (with a power intensity of 7 mW/cm2) was obtained in the off-state of the transistor. We have fine-tuned the anode structure and deposition/annealing conditions towards flexible organic devices and optimal device characteristics.

In this paper, the fabrication and characterisation of pentacene-based photoconductors using indium tin oxide electrodes obtained by ion beam sputtering are discussed. The photoelectric properties of pentacene under red (632 nm) and ultraviolet (365 nm) illuminations were investigated. We have shown that the photocurrent was dependent on the wavelength, bias voltage and illumination side of the device. Moreover, we have demonstrated with transparent electrodes that the top contact configuration yields better performance compared to the bottom contact configuration. We obtained a maximum photoconductivity gain of approximately 3 × 103 and a faster dynamic response when the photoconductor with top contact geometry was illuminated with ultraviolet light from the semiconductor side (top illumination), with a photoconductivity estimated at 10-4  $\Omega^{-1}$  cm-1.

Preparation of highly oriented layers of organic semiconductor – dithienothiophene derivative is described. The layers were obtained by zone-casting technique – a solution based one step method that does not require the use of preoriented substrates. Unidirectional alignment of the dithienothiophene derivative molecules in the zone-cast layers was confirmed by absorption and photoluminescence polarized spectra. Anisotropy of electrical properties was characterised by means of anisotropy of charge carrier mobility in field effect transistors (FETs). The FET devices were fabricated in bottom contacts – bottom gate configuration with the channel lengths parallel and perpendicular to the crystal growth direction, respectively. The FET mobility determined in the direction parallel to the zone-casting direction is ca. 1 order of magnitude higher than those in the perpendicular direction.

The thin-film technology is the most promising technology to achieve a significant cost reduction in solar electricity. Laser scribing is an important step to preserve high efficiency of photovoltaic devices on large areas. The high-repetition-rate laser with the pulse duration of 10 ps was applied in selective ablation of multilayer thin-film a-Si solar cells deposited on flexible and rigid substrates. Two types of solar cells with flexible and rigid substrates have been investigated. The first type of solar cells was made of 400 nm a-Si layer coated on both sides with 2  $\mu $ m transparent ZnO:Al contact layers deposited by CVD technique on the glass plate. The second type of solar cells was made of a flexible polyimide substrate coated with the Al back-contact, a-Si light absorbing layer and the ITO top-contact. Selection of the right laser wavelength is important to keep the energy coupling in a well defined volume at the interlayer interface. Well-defined shapes of scribes were produced by laser ablation through layers of the solar cell on the glass substrate. Localization of the coupled energy at the inner interface led to the “lift-off” type process rather than evaporation of the top ITO layer when the 355 nm radiation was applied. All laser scribes did not indicate any material melting or other thermal damage caused by laser irradiation. Ultra-short picosecond pulses ensured the high energy input rate into absorbing material therefore peeling of the layers had no influence on the remaining material.

The characteristics of organic light-emitting devices based on aluminum tris-(8-hydroxy-quinoline) (Alq3), N,N'-bis(3-methylphenyl)-N,N'-diphenylbenzidine (TPD) with novel p-isopropenyl-calix[8]arenestyrene copolymer buffer layer and Al cathode were investigated. The devices with TPD/Alq3/Al were also fabricated in the same way for comparison. The p-isopropenylcalix[8]arenestyrene copolymer used as buffer layer greatly improved the performance of the device and increased the device efficiency and stability.

Nanocomposite organic-inorganic dye-sensitised solar cells have been constructed by using solution processed materials that are easily deposited, they do not necessitate sealing or encapsulation and offer satisfactory efficiency. The main components of the cell are a nanocrystalline titania layer made of commercial Degussa P25 and a solid gel electrolyte made of a ureasil precursor. Details on cell construction are given and show that the whole procedure can be upscaled for massive production.

Undoped and Al and In doped ZnO films were deposited on flexible PET substrates by Reactive Pulsed Laser Deposition (R-PLD). The morphological and structural characteristics of the obtained structures were investigated by AFM, SEM and XRD respectively. The transmittance spectra were recorded in the 300–1200 nm wavelength range and the electrical conductivity was measured. The samples appeared as granular and polycrystalline with high transparency and had a good electrical conductivity. The crystallinity of the undoped ZnO films improved with increasing pressure of the reactive oxygen gas. Doping of ZnO with Al or In modified the energy band gap and the resistivity of the material. The possibility for the application of such structures for the development of hybrid photovoltaic cells on flexible substrates will be demonstrated.