Electroluminescence Research Papers - Academia.edu (original) (raw)

We report some time-resolved luminescence measurements on the conjugated polymer, MEH-PPV, that show a marked dependence on the intensity of the excitation light. At low laser powers the excited state lifetime is longer than has been... more

We report some time-resolved luminescence measurements on the conjugated polymer, MEH-PPV, that show a marked dependence on the intensity of the excitation light. At low laser powers the excited state lifetime is longer than has been reported previously and is consistent with emission from an interchain excitation that has low oscillator strength and hence a long natural radiative lifetime. We rationalise these data with a simple scheme that summarises the excited state kinetics in this and other conjugated, electroluminescent polymers.

We report the fabrication of polymer light emitting diodes from a cyano-substituted thienylene phenylene vinylene copolymer. Photoluminescence and electroluminescence studies of these devices show a broad emission spectrum which peaks in... more

We report the fabrication of polymer light emitting diodes from a cyano-substituted thienylene phenylene vinylene copolymer. Photoluminescence and electroluminescence studies of these devices show a broad emission spectrum which peaks in the near infra-red and extends out to a wavelength of 1000nm. Bilayer structures using poly(p-phenylene vinylene) as a hole transport layer and the cyano-copolymer as the emissive layer showed improved electroluminescence internal quantum efficiency of up to 0.2%..

Touch (or tactile) sensors are gaining renewed interest as the level of sophistication in the application of minimum invasive surgery and humanoid robots increases. The spatial resolution of current large-area (greater than 1 cm 2 )... more

Touch (or tactile) sensors are gaining renewed interest as the level of sophistication in the application of minimum invasive surgery and humanoid robots increases. The spatial resolution of current large-area (greater than 1 cm 2 ) tactile sensor lags by more than an order of magnitude compared with the human finger. By using metal and semiconducting nanoparticles, a ∼100-nm-thick, large-area thin-film device is self-assembled such that the change in current density through the film and the electroluminescent light intensity are linearly proportional to the local stress. A stress image is obtained by pressing a copper grid and a United States 1-cent coin on the device and focusing the resulting electroluminescent light directly on the charge-coupled device. Both the lateral and height resolution of texture are comparable to the human finger at similar stress levels of ∼10 kilopascals.

We report the demonstration of a N-polar InGaN based green light emitting diode (LED) grown by N2 plasma-assisted molecular beam epitaxy (PAMBE). High quality multiple quantum well LEDs with In0.29Ga0.71N quantum wells were grown at a... more

We report the demonstration of a N-polar InGaN based green light emitting diode (LED) grown by N2 plasma-assisted molecular beam epitaxy (PAMBE). High quality multiple quantum well LEDs with In0.29Ga0.71N quantum wells were grown at a temperature of 600 °C by applying a new growth model. LED structures exhibited green emission, and electroluminescence measurements on the test structure showed peak emission wavelengths varying from 564.5 to 540 nm. The full width at half-maximum reduced from 74 to 63 nm as the drive current was increased to 180 A/cm2. This work is the first demonstration of an N-polar LED with emission in the green wavelength range.

Use of Solar Photovoltaic (SPV) for Street Lighting Systems (SLS) is an ideal application of SPV for illumination of streets and crossroads located in areas that are not connected to the power grid. This paper presents the performance and... more

Use of Solar Photovoltaic (SPV) for Street Lighting Systems (SLS) is an ideal application of SPV for illumination of streets and crossroads located in areas that are not connected to the power grid. This paper presents the performance and degradation analysis of two pairs of the Champion PV modules which were used for SLS installed at Solar Energy Centre, India during the year 1990. These PV modules have experienced minimal degradation in their power output even after operating for 21 years. The power loss observed in all modules is less than 10%, which is less than the specified level in IEC 61215 standard. These modules showed unique behavior and the most surprising aspect is that only one of the modules in each pair is affected by browning inspite of installed at same location and under similar environmental conditions. A detailed investigation has been performed by using the I-V measurement and characterization techniques like Lock-in thermography and Electroluminescence imaging.

Jpn. J. Appl. Phys. Vol. 38 (1999) pp. 931–935 Part 1, No. 2A, February 1999 c 1999 Publication Board, Japanese Journal of Applied Physics ... Electronic Properties and Electroluminescence of Monosubstituted Polyacetylenes and Their... more

Jpn. J. Appl. Phys. Vol. 38 (1999) pp. 931–935 Part 1, No. 2A, February 1999 c 1999 Publication Board, Japanese Journal of Applied Physics ... Electronic Properties and Electroluminescence of Monosubstituted Polyacetylenes and Their Mixtures with Disubstituted Polyacetylene

Spectral emission properties of novel 4-aryloxy-1H-pyrazolo[3,4-b]quinolines were investigated. All of the compounds exhibit strong blue luminescence in the solution and in the solid state as well. Pyrazoloquinolines were used as dopants... more

Spectral emission properties of novel 4-aryloxy-1H-pyrazolo[3,4-b]quinolines were investigated. All of the compounds exhibit strong blue luminescence in the solution and in the solid state as well. Pyrazoloquinolines were used as dopants in PVK matrices in electroluminescent devices with ITO/PVK:PQ/Ca/Al light emitting diode configuration.

Encapsulant discoloration is a common type of degradation in photovoltaic (PV) modules, which significantly affects its performance and reliability under field conditions. This paper presents the non-destructive characterization... more

Encapsulant discoloration is a common type of degradation in photovoltaic (PV) modules, which significantly affects its performance and reliability under field conditions. This paper presents the non-destructive characterization techniques for investigation of encapsulant discoloration in crystalline-silicon PV modules. These characterization techniques have been channelized and applied to investigate various aspects of discoloration effects on 20 years old field-exposed PV modules. Dark lock-in ther-mography (DLIT) has been exploited for investigation of temperature variation and defects caused by uneven discoloration over the cells, while electroluminescence (EL) imaging has been proposed for relative quantification of extent of discoloration in a PV module. The spatially-resolved images obtained from both the techniques provided the qualitative and quantitative information about the optical and electrical effects of discoloration in a module, which is not possible by the conventional visual inspection method alone. The electrical methods including proposed differential current analysis, I–V measurement and insulation resistance test have also been used to aid this investigation. The results obtained from these techniques show that the power degradation due to discoloration was attributed to significant reduction in fill factor by non-uniform discoloration and increase in series resistance of cell contacts, and to some extent by its direct effect of light reduction. Electrical mismatch appeared to play an important role in accelerating the encapsulant discoloration in the module. These nondestructive characterization approaches can enable to inspect large number of PV modules in their actual encapsulated form by fast and efficient manner.

Efforts are being made in direct Dark Matter search experiments to detect the primary ionisation in the liquid by extracting the electrons to the gas phase and use the secondary ionization produced in the micropattern electron multipliers... more

Efforts are being made in direct Dark Matter search experiments to detect the primary ionisation in the liquid by extracting the electrons to the gas phase and use the secondary ionization produced in the micropattern electron multipliers for signal amplification in noble-liquid dual-phase TPCs. We have studied the secondary scintillation yield of a single Gas Electron Multiplier (GEM) and of a Micro-Hole & Strip Plate (MHSP) for xenon at room temperature. Values for secondary scintillation yield between 5.0 × 10^3 and 1.3 × 10^3 photons per primary electron were obtained for the GEM and between 7.2 × 10^4 and 1.8 × 10^3 photons per primary electron for the MHSP, as the pressure increased from 1.0 to 2.5 bar in the GEM-setup and from 1.0 to 3.3 bar in the MHSP-setup, respectively. These values can be more than one order of magnitude higher than what has been obtained in the uniform-field scintillation gaps of the XENON and ZEPLIN-III experiments. Although in the present setups the amount of secondary scintillation obtained is sufficient in view of the use of PMTs, if a different type of readout is considered, such as large area avalanche photodiodes, it will be important to increase the amount of secondary scintillation. The attained results demonstrate the clear advantage of reading the secondary scintillation instead of the charge produced in the electron avalanches of micropattern electron multipliers, in low-background and low-rate experiments, as is the case in direct Dark Matter search.

Research on efficient light emission from silicon devices is moving toward leading-edge advances in components for nano-optoelectronics and related areas. A silicon laser is being eagerly sought and may be at hand soon. A key advantage is... more

Research on efficient light emission from silicon devices is moving toward leading-edge advances in components for nano-optoelectronics and related areas. A silicon laser is being eagerly sought and may be at hand soon. A key advantage is in the use of silicon-based materials and processing, thereby using high yield and low-cost fabrication techniques. Anticipated applications include an optical emitter for integrated optical circuits, logic, memory, and interconnects; electro-optic isolators; massively parallel optical interconnects and cross connects for integrated circuit chips; lightwave components; high-power discrete and array emitters; and optoelectronic nanocell arrays for detecting biological and chemical agents. The new technical approaches resolve a basic issue with native interband electro-optical emission from bulk Si, which competes with nonradiative phonon- and defect-mediated pathways for electron-hole recombination. Some of the new ways to enhance optical emission efficiency in Si diode devices rely on carrier confinement, including defect and strain engineering in the bulk material. Others use Si nanocrystallites, nanowires, and alloying with Ge and crystal strain methods to achieve the carrier confinement required to boost radiative recombination efficiency. Another approach draws on the considerable progress that has been made in high-efficiency, solar-cell design and uses the reciprocity between photo- and light-emitting diodes. Important advances are also being made with silicon-oxide materials containing optically active rare-earth impurities.