Search results for "Diode"
showing 10 items of 469 documents
Study of voltage decrease in organic light emitting diodes during the initial stage of lifetime
2016
Abstract We report the results of lifetime DC testing at constant current of not-encapsulated organic light emitting diodes (OLEDs) based on Tris (8 idroxyquinoline) aluminum (Alq3) as emitting material. In particular, a voltage decrease during the initial stage of the lifetime test is observed. The cause of this behavior is also discussed, mainly linked to initial Joule self-heating of the device, rising its temperature above room temperature until thermal equilibrium is reached at steady state.
Generation of white LED light by frequency downconversion using a perylene-based dye
2012
A high efficiency white light emitting diode (LED) was fabricated by generation of frequency down-conversion from a GaN/InGaN blue LED. In place of conventional inorganic phosphors, a perylene-based dye was used for colour conversion. The resulting hybrid structure is analysed by focusing on the visual performance of the realised LEDs employing the most relevant photometric parameters of a light source. Preparation of the organic polymer is described as well. The thermal stability of the dye was investigated and a simple structure which avoids colour degradation is proposed.
Improving the efficiency of light-emitting diode based on a thiophene polymer containing a cyano group
2007
Abstract We report on the overall improvement of a single layer organic light-emitting diode device based on poly{[3-hethylthiophene]-co-3-[2-( p -cyano-phenoxy)ethyl]thiophene} or namely PTOPhCN. This polymer was recently developed by adding a cyano group as a side-chain substituent of the thiophenic backbone onto the main polymer chain and showed promising results for light-emitting diode devices. Using an improved device layout, bright red electroluminescence was obtained at 4 V and showed a luminance of about 400 cd/m 2 at 8 V with current densities in the order of 6000 A/m 2 .
The use of two-diode substitute model in predicting the efficiency of PV conversion in low solar conditions
2017
The article presents theoretical foundations of a two-diode equivalent model of a photovoltaic cell/module (PV), together with calculation procedures. A physical interpretation of individual components of an equivalent model was presented. Its practical application in predicting efficiency of operation of various PV cells and modules in low insulation conditions was demonstrated. The obtained predictions were verified with the actual results of their operation in open space (outdoor). The practical suitability of the “model” in early detection of ageing phenomena, such as, for example, absorber degradation taking place in PV modules, was demonstrated. The article was prepared on the basis o…
Stochastic resonance in a tunnel diode.
1994
We study stochastic resonance in a fast bistable electronic system: a tunnel diode. We investigate the phenomenon in a higher frequency regime than that studied in previous experiments. Detailed measurements of the output signal are reported for two values of the frequency of the periodic signal: ${\mathit{f}}_{\mathit{s}}$=1 kHz and ${\mathit{f}}_{\mathit{s}}$=10 kHz. We observe, in one case (${\mathit{f}}_{\mathit{s}}$=1 kHz), a nonmonotonic behavior characterized by a sharp dip in the output noise level measured at the frequency of the driving signal.
Hydrogen sensor based on a palladium-coated fibre-taper with improved time-response
2006
Abstract We report an experimental study of the response of a hydrogen sensor, based on a palladium-coated tapered optical fibre, at different temperatures in the range −30 to 80 °C. We have studied the transmission, the time-response and the initial response velocity, being able to correlate these measurements with the pressure–composition isotherms of the Pd–H system and its phase transitions. Heating of the palladium layer optically with an auxiliary laser diode permits to improve the sensor's time-response at low temperatures.
Selective Excitation of Guided Waves into Bone Phantoms by a Time-Delayed Laser Diode Array
2012
We excite selectively the Ao and So plate mode into an acrylic bone phantom using a laser diode array. This is done by controlling the time delay between the signals driving the array elements. Selective mode generation is important because it can potentially increase the sensitivity of in vivo osteoporosis screening.
Physicochemical characterisation of thermally aged anodic films on magnetron sputtered niobium
2010
The influence of thermal aging, at intermediate temperature (1h at 250°C) and in different environments, on the electronic and solid-state properties of stabilized 160 nm thick amorphous anodic niobia, grown on magnetron sputtered niobium metal, has been studied. A detailed physicochemical characterisation of the a-Nb2O5/0.5M H2SO4 electrolyte junction has been carried out by means of photocurrent and electrochemical impedance spectroscopy as well by differential admittance measurements. A change in the optical band gap (3.45 eV) of niobia film has been observed after aging (3.30 eV) at 250°C in air for 1 hour. A cathodic shift (0.15-0.2 Volt) in the flat band potential of the junction has …
SIMULTANEOUS DETERMINATION OF ATP, ITS METABOLITES AND NAD+ IN BLOOD BY HPLC WITH PHOTODIODE ARRAY DETECTOR
2013
SIMULTANEOUS DETERMINATION OF ATP, ITS METABOLITES AND NAD+ IN BLOOD BY HPLC WITH PHOTODIODE ARRAY DETECTOR Gueli Maria Concetta, Cusimano Vincenza, Lo Re Marianna, Giuseppe Salemi Dipartimento di Biomedicina Sperimentale e Neuroscienze Cliniche (BioNEC), Università degli Studi di Palermo. Nucleotides are major high-energy phosphate carriers, subunits of nucleic acids and precursors for the synthesis of nucleotide cofactors such as NAD+ and SAM. The study of purine nucleotides metabolism is very important topic for a right understanding for the cellular life. Living cells rely on ATP for growth, differentiation, and response to physiological stimuli and environmental stress. We propose a fa…
Optical, Structural and Paramagnetic Properties of Eu-Doped Ternary Sulfides ALnS2 (A = Na, K, Rb; Ln = La, Gd, Lu, Y)
2015
Eu-doped ternary sulfides of general formula ALnS2 (A = Na, K, Rb; Ln = La, Gd, Lu, Y) are presented as a novel interesting material family which may find usage as X-ray phosphors or solid state white light emitting diode (LED) lighting. Samples were synthesized in the form of transparent crystalline hexagonal platelets by chemical reaction under the flow of hydrogen sulfide. Their physical properties were investigated by means of X-ray diffraction, time-resolved photoluminescence spectroscopy, electron paramagnetic resonance, and X-ray excited fluorescence. Corresponding characteristics, including absorption, radioluminescence, photoluminescence excitation and emission spectra, and decay k…