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 (H 2 O) 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 Supprimé : response Supprimé : response 2 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 SiO 2 nano-particles on their optical properties and barrier performance.
The replacement of the anode material in tantalum capacitors by a new generation of high CV niobium powders offers the possibility to get an economical alternative to tantalum for a wide range of applications. Due to the high CV potential of niobium powder there is also an alternative to low voltage aluminum electrolytic capacitors. We developed a new niobium capacitor which shows stable electrical values. By optimizing the structure of the dielectric and the cathodic layers as well as the process parameters we gained a capacitor which can be used up to105 °C. Electrical characteristics and lifetest behavior of niobium capacitors out of 100 k–150 k CV/g powder will be discussed.
Following an annealing process of several hours duration at a temperature of at least 1100 °C, reactively sputtered cerium-oxide films with film thicknesses ranging from 0.5 to 3 μm show a dependence of electric conductivity on oxygen partial pressure similar to that of polycrystalline bulk material within the temperature range studied (700 to 1000 °C). But films with comparatively small grain structures have specific electrical conductivities that are as much as an order of magnitude higher than those of large-grained structures, let alone bulk materials. This outcome justifies the supposition that the carrier transport in CeO2−x thin films occurs in a grain barrier layer within which electrons are enriched. This negative carrier enrichment layer may be due to a positive surface charge. An investigation of the interaction between oxygen vacancies of CeO2−x thin films and the oxygen of the environment showed that for layer thickness of from 1 to 3 μm and temperatures of 700–1000 °C, the reaction of the oxygen molecules at the surface is always the kinetics-governing step. Above 950 °C the transport reaction through the laminar boundary zone on the surface determines the reaction kinetics. Under these conditions the volume diffusion of oxygen vacancies in the thin film proceeds more rapidly than the surface reaction or the gas-phase transport of oxygen molecules.
Simultaneous Hall and conductivity measurements have been performed on sputtered polycrystalline thin films and on bulk ceramic specimens of nearly stoichiometric CeO, in the temperature range between 900" and 1040°C. The measurements have been performed in air using lowfrequency alternating current. In the case of the bulk ceramic specimens, an upper limit for the carrier mobility of 50.2 cm2/(V.s) has been obtained, which is in accordance with data from the literature for bulk samples. The conductivity of the thin films ( U ( 0 . m ) at 1000°C) is in accordance with data from the literature for bulk ceramics. The carrier density derived from the Hall measurements (3 X l0l6/cm3 at 1000°C) increases with increasing temperature, whereas the Hall mobility (4 cm*/(V.s) at 1000°C) decreases with increasing temperature. These values differ from literature data for bulk ceramic specimens. The difference may be due to the small grain diameters (-200 nm) in the 1-pm-thick thin films.
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