1,254 research outputs found

    Immunizations in immunocompromised hosts : effects of immune modulating drugs and HIV on the humoral immune response

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    The immune response upon (influenza, pneumococcal and rabies) vaccination in immunocompromized patients (HIV, anti-TNF, HSCT patients) has been studied.Abbott; Boehringer Ingelheim BV; Gilead; GlaxoSmithKline; Janssen-Cilag BV; Merck Sharp and Dome; Pfizer BV; Roche Nederland BV; Viiv; Wyeth PharmaceuticalsUBL - phd migration 201

    Trap-Assisted Charge Generation and Recombination in State-of-the-Art Organic Photodetectors

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    The performance of organic photodetectors is steadily improving, and the specific detectivity, as a key figure of merit, has reached values of 1012–1013 Jones, i.e., comparable to that of silicon diodes but still considerably lower than the intrinsic limit. As with other semiconductor devices, the electrical performance of state-of-the art organic photodiodes (OPDs) is presently determined to a high degree by the presence of chemical impurities or structural defects which create carrier trapping states within the bandgap of organic active layer. This review aims to provide a comprehensive and timely account of trap-assisted charge generation and recombination in OPDs, with emphasis on the impact of these phenomena on photodetector performance parameters such as, noise and dark current density, responsivity, response speed, and ultimately, specific detectivity.</p

    Degradation Mechanisms in Organic Lead Halide Perovskite Light‐Emitting Diodes

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    Organic-inorganic metal halide perovskites have attracted significant attention for low‐cost, high‐efficiency, color‐pure light‐emitting applications. However, as seen in many reports so‐far, perovskite light‐emitting diodes (PeLED) suffer from poor operational lifetime, limiting their practical use. The underlying degradation mechanism is a topic of crucial importance. Here, the degradation mechanisms of methylammonium lead bromide based PeLED are investigated. When the PeLED is electrically biased, there is an initial raise in the luminance followed by a rapid reduction in luminance and current density. Microscopic studies reveal the formation of micrometer‐sized spots that are photoluminescent but not electroluminescent. It is demonstrated that this degradation is due to the formation of gaseous compounds that leads to local delamination of the cathode, thereby reducing the electroluminescence. When the degraded cathode is substituted with a fresh cathode, the initial luminance is largely recovered. By further analyzing the buried interface of the cathode, the formation of lead bromide and gaseous methylamine due to the degradation of the perovskite layer are revealed. These insights will help to further improve the lifetime of PeLEDs. As an example, it is shown that substituting methylammonium cations by cesium leads to longer lifetimes

    Reconfigurable Complementary Logic Circuits with Ambipolar Organic Transistors

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    Ambipolar organic electronics offer great potential for simple and low-cost fabrication of complementary logic circuits on large-area and mechanically flexible substrates. Ambipolar transistors are ideal candidates for the simple and low-cost development of complementary logic circuits since they can operate as n-type and p-type transistors. Nevertheless, the experimental demonstration of ambipolar organic complementary circuits is limited to inverters. The control of the transistor polarity is crucial for proper circuit operation. Novel gating techniques enable to control the transistor polarity but result in dramatically reduced performances. Here we show high-performance non-planar ambipolar organic transistors with electrical control of the polarity and orders of magnitude higher performances with respect to state-of-art split-gate ambipolar transistors. Electrically reconfigurable complementary logic gates based on ambipolar organic transistors are experimentally demonstrated, thus opening up new opportunities for ambipolar organic complementary electronics.115Ysciescopu

    Design trade-offs in amorphous indium gallium zinc oxide thin film transistor based bio-signal sensing front-ends

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    With the advent of the Internet of things, wearable sensing devices are gaining importance in our daily lives for applications like vital signal monitoring during sport and health diagnostics. Amorphous indium gallium zinc oxide (a-IGZO) thin film transistors (TFTs) fabricated on flexible large-area substrates are a very interesting platform to build wearable sensing devices due to their flexibility, conformability to the human body, and low cost. For this paper four different bio-signal sensing front-end circuits based on a-IGZO TFTs are designed, fabricated, measured and compared, focusing on three performance indicators which are in a trade-off: power efficiency factor (PEF), area occupation and input impedance. Considering a 200 Hz bandwidth, the measured PEF varies between 4.7 × 105 and 7.5 × 106. The area occupation spans from 4.2 to 37 mm2, while the input impedance at 1 Hz varies from 5.3 to 55.3 MΩ. The front-ends based on diode-load amplifiers are compact but have the lowest input impedance and need external capacitors; a front-end exploiting positive feedback impedance boosting has the highest input impedance and is fully integrated on foil, but occupies the largest area

    Correlated theory of triplet photoinduced absorption in phenylene-vinylene chains

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    In this paper we present results of large-scale correlated calculations of triplet photoinduced absorption (PA) spectrum of oligomers of poly-(para)phenylenevinylene (PPV) containing up to five phenyl rings. In particular, the high-energy features in the triplet PA spectrum of oligo-PPVs are the focus of this study, which, so far, have not been investigated theoretically, or experimentally. The calculations were performed using the Pariser-Parr-Pople (PPP) model Hamiltonian, and many-body effects were taken into account by means of multi-reference singles-doubles configuration interaction procedure (MRSDCI), without neglecting any molecular orbitals. The computed triplet PA spectrum of oligo-PPVs exhibits rich structure consisting of alternating peaks of high and low intensities. The predicted higher energy features of the triplet spectrum can be tested in future experiments. Additionally, theoretical estimates of exciton binding energy are also presented.Comment: To appear in Phys. Rev.

    Origin of multiple memory states in organic ferroelectric field-effect transistors

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    In this work, we investigate the ferroelectric polarization state in metal-ferroelectric-semiconductor-metal structures and in ferroelectric field-effect transistors (FeFET). Poly(vinylidene fluoride-trifluoroethylene) and pentacene was used as the ferroelectric and semiconductor, respectively. This material combination in a bottom gate—top contact transistor architecture exhibits three reprogrammable memory states by applying appropriate gate voltages. Scanning Kelvin probe microscopy in conjunction with standard electrical characterization techniques reveals the state of the ferroelectric polarization in the three memory states as well as the device operation of the FeFET
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