The Experts below are selected from a list of 134262 Experts worldwide ranked by ideXlab platform
Kevin P Klubek - One of the best experts on this subject based on the ideXlab platform.
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high efficiency low voltage phosphorescent organic light Emitting Diode devices with mixed host
Journal of Applied Physics, 2008Co-Authors: Marina E. Kondakova, Thomas D Pawlik, Ralph H Young, David J Giesen, Christopher T Brown, Joseph C Deaton, Jerome R Lenhard, Denis Y. Kondakov, Kevin P KlubekAbstract:We report high-efficiency, low-voltage phosphorescent green and blue organic light-Emitting Diode (PHOLED) devices using mixed-host materials in the light-Emitting layer (LEL) and various combinations of electron-injecting and electron-transporting layers. The low voltage does not rely on doping of the charge-transport layers. The mixed LEL architecture offers significantly improved efficiency and voltage compared to conventional PHOLEDs with neat hosts, in part by loosening the connection between the electrical band gap and the triplet energy. Bulk recombination in the LEL occurs within ∼10 nm of the interface with an electron-blocking layer. A “hole-blocking layer” need not have hole- or triplet-exciton-blocking properties. Optical microcavity effects on the spectrum and efficiency were used to locate the recombination zone. The effect of layer thickness on drive voltage was used to determine the voltage budget of a typical device. The behavior of undoped devices was investigated, and the electrolumines...
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Power efficiency improvement in a tandem organic light-Emitting Diode
Applied Physics Letters, 2008Co-Authors: Liang-sheng Liao, Kevin P KlubekAbstract:When a tandem light-Emitting Diode (OLED) utilizes unoptimized electroluminescent (EL) units, it is fairly easy to improve the power efficiency of such a device. However, when a tandem OLED utilizes optimized EL units, improved power efficiency can only be achieved if each intermediate connector has excellent carrier injection capabilities along with a negligible voltage drop across it. Four organic intermediate connectors were studied in this work, one of which consisting of a Li-doped 4,7-diphenyl-1,10-phenanthroline layer and a 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile layer, exhibits the best power efficiency improvement for tandem OLEDs.
M.d. Dawson - One of the best experts on this subject based on the ideXlab platform.
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High-Speed Visible Light Communications Using Individual Pixels in a Micro Light-Emitting Diode Array
IEEE Photonics Technology Letters, 2010Co-Authors: Jonathan James Donald Mckendry, R P Green, Anthony E. Kelly, Benoit Guilhabert, Er Dan Gu, Z Gong, David Massoubre, M.d. DawsonAbstract:The high-frequency modulation of individual pixels in III-nitride-based micro-pixel light-Emitting Diode arrays, where each array consists of 16 x 16 individually addressable 72-mu m-diameter pixels, are reported. The devices investigated have peak emission wavelengths at 370, 405, and 450 nm, respectively. The optical -3-dB modulation bandwidth of a typical pixel from the 450-nm-Emitting device was found to be approximately 245 MHz. Data transmission at rates of up to 1 Gb/s is demonstrated from a single pixel Emitting at 450 nm, using on-off keying nonreturn-to-zero modulation, with a bit-error ratio of less than 1x10(-10). Such devices have potential for free-space or fiber-coupled visible light communications.
Seiichi Tagawa - One of the best experts on this subject based on the ideXlab platform.
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Room temperature ultraviolet emission at 357nm from polysilane based organic light Emitting Diode
Applied Physics Letters, 2006Co-Authors: Asha Sharma, Deepak, Monica Katiyar, Shu Seki, Seiichi TagawaAbstract:We have fabricated an organic light Emitting Diode using poly(n-butylphenylsilane) which has an emission in deep ultraviolet at 357nm at room temperature. The device structure used is glass/indium tin oxide/poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)/polysilane (Emitting material)/calcium/aluminum. These devices emit ultraviolet light with a turn-on voltage of 8V. The electroluminescence spectrum of the device in the ultraviolet range is identical to the photoluminescence spectrum of the polysilane thin film. From these devices, we also observe an additional emission in the visible region, which is not present in the photoluminescence spectrum of the material. The visible emission has a color coordinate of (0.36,0.35), which can be modulated to a required white light coordinate by down converting the ultraviolet emission.
K P Homewood - One of the best experts on this subject based on the ideXlab platform.
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an efficient room temperature silicon based light Emitting Diode
Nature, 2001Co-Authors: M A Lourenco, R M Gwilliam, S Ledain, Guosheng Shao, K P HomewoodAbstract:There is an urgent requirement for an optical emitter that is compatible with standard, silicon-based ultra-large-scale integration (ULSI) technology1. Bulk silicon has an indirect energy bandgap and is therefore highly inefficient as a light source, necessitating the use of other materials for the optical emitters. However, the introduction of these materials is usually incompatible with the strict processing requirements of existing ULSI technologies. Moreover, as the length scale of the devices decreases, electrons will spend increasingly more of their time in the connections between components; this interconnectivity problem could restrict further increases in computer chip processing power and speed in as little as five years. Many efforts have therefore been directed, with varying degrees of success, to engineering silicon-based materials that are efficient light emitters2,3,4,5,6,7. Here, we describe the fabrication, using standard silicon processing techniques, of a silicon light-Emitting Diode (LED) that operates efficiently at room temperature. Boron is implanted into silicon both as a dopant to form a p–n junction, as well as a means of introducing dislocation loops. The dislocation loops introduce a local strain field, which modifies the band structure and provides spatial confinement of the charge carriers. It is this spatial confinement which allows room-temperature electroluminescence at the band-edge. This device strategy is highly compatible with ULSI technology, as boron ion implantation is already used as a standard method for the fabrication of silicon devices.
Th Amand - One of the best experts on this subject based on the ideXlab platform.
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High speed pulsed electrical spin injection in spin-light Emitting Diode
Applied Physics Letters, 2009Co-Authors: V. Truong, J. M. George, Cyrile Deranlot, Pham Huu Thanh Binh, Pierre Renucci, Aristide Lemaître, Henri Jaffrès, M. Tran, Y Lu, Th AmandAbstract:We demonstrate high speed pulsed electrical spin injection from a CoFeB/MgO spin injector into a AlGaAs/GaAs semiconductor light Emitting Diode. Under pulsed electrical excitation, time-resolved electroluminescence on nanosecond time scale exhibits a plateau of circular polarization degree as high as 15% under a 0.8 T magnetic field. It follows an initial decay that could be due to electron spin-relaxation process in the quantum well embedded in the intrinsic region of the Diode. The temporal buildup of the electronic spin polarization degree in the quantum well is much faster than the rise time of electroluminescence intensity.
