This research proposes a new method for light emitting diode automotive headlight design with digital micromirror device (DMD). The optical design is advanced because of the following features. First, this optical design controls the angle of light pattern without light masking so as to achieve much higher light efficiency compared with traditional optical design for headlight systems. Second, in view of the tendency that the advanced light emitting diode automobile headlight is designed to be a low beam light module and a high beam light still needs an auxiliary lighting system, the optical system designed in this research, mainly adopting DMD module as high/low beam light switch, can switch on and off both the high and low beam lights. Because DMDs function of accepting a bidimensional image, high/low beam light patterns can be determined by DMD. Third, a light pattern will be created and compensated simultaneously by DMD, which might replace mechanical adaptive front-lighting system in the future because DMD takes advantage of fast response and simultaneous compensation. Fourth, a design using a multiple reflection curved mirror is employed in this research to adjust light energy distribution; therefore, the articulation of the light pattern can be enhanced. For this method, experimental results of light efficiency are up to 85%, which is superior to current products in the market. 相似文献
The high power GaN-based blue light emitting diode (LED) on an 80%tm-thick GaN template is proposed and even realized by several technical methods like metal organic chemical vapor deposition (MOCVD), hydride vapor-phase epi- taxial (HVPE), and laser lift-off (LLO). Its advantages are demonstrated from material quality and chip processing. It is investigated by high resolution X-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM), Rutherford back-scattering (RBS), photoluminescence, current-voltage and light output-current measurements. The width of (0002) reflection in XRD rocking curve, which reaches 173" for the thick GaN template LED, is less than that for the conventional one, which reaches 258". The HRTEM images show that the multiple quantum wells (MQWs) in 80%tm- thick GaN template LED have a generally higher crystal quality. The light output at 350 mA from the thick GaN template LED is doubled compared to traditional LEDs and the forward bias is also substantially reduced. The high performance of 80-~m-thick GaN template LED depends on the high crystal quality. However, although the intensity of MQWs emission in PL spectra is doubled, both the wavelength and the width of the emission from thick GaN template LED are increased. This is due to the strain relaxation on the surface of 80%tin-thick GaN template, which changes the strain in InGaN QWs and leads to InGaN phase separation. 相似文献
To form low-resistance Ohmic contact to p-type GaN,
InGaN/GaN multiple quantum well light emitting diode wafers are
treated with boiled aqua regia prior to Ni/Au (5~nm/5~nm) film
deposition. The surface morphology of wafers and the current--voltage
characteristics of fabricated light emitting diode devices are
investigated. It is shown that surface treatment with boiled
aqua regia could effectively remove oxide from the surface of the p-GaN
layer, and reveal defect-pits whose density is almost the same as
the screw dislocation density estimated by x-ray rocking curve
measurement. It suggests that the metal atoms of the Ni/Au transparent
electrode of light emitting diode devices may diffuse into the p-GaN
layer along threading dislocation lines and form additional leakage
current channels. Therefore, the surface treatment time with boiled
aqua regia should not be too long so as to avoid the increase of
threading dislocation-induced leakage current and the degradation of
electrical properties of light emitting diodes. 相似文献
InGaN/GaN light‐emitting diodes (LEDs) are known to exhibit a strongly non‐uniform vertical carrier distribution within the multi‐quantum well (MQW) active region. We propose to eliminate “dark” quantum wells by insertion of multiple tunnel junctions into the MQW which allow for the repeated use of electrons and holes for photon generation. In good agreement with available measurements, we demonstrate by self‐consistent numerical simulation that such tunnel junction LED design promises quantum efficiencies as high as 250% as well as a strongly enhanced output power at high input power, compared to conventional LED concepts.
White polymer light emitting diode (PLED) has attracted the interest of researchers by the advantage of having low cost, flexible light sources. One of the major advantages of PLED is that it can be able to fabricate in flexible plastic substrate instead of glass substrate. Generally PLED??s requires a substrate of high refractive index to enhance the amount of trapped light in the device, but the refractive index of flexible plastic substrate is low (n?<?1.6). In this paper, we present a white PLED on a flexible plastic substrate with a new enhancement method. In which the semi-transparent gold layer is sandwiched between the layers of tantalum oxide and molybdenum oxide which does not require a high refractive index substrate. Using this design, the extraction efficiency of the device is increased from 1.5 to 2.1 cw compared to that of the device using glass substrate. 相似文献
We observed a significant increase in electro luminescence from GaSb based mid-wave infrared (MWIR) LED device through coupling with localized surface plasmon of a single layer Au nano-particles. We fabricated an interband cascade (IC) LED device with nine cascade active/injection layers with InAs/Ga1−x InxSb/InAs quantum well (QW) active region. Thin Au plasmon layer of 20 nm thickness is deposited on top anode electrode by e-beam technique, which resulted in 100% increase in light output for 50 μm square mesa device. We also observed a reduction in the device turn on voltage and increase in the apparent black body emission temperature due to nano-structure surface plasmon layer. 相似文献
The high power GaN-based blue light emitting diode (LED) on an 80-μ-thick GaN template is proposed and even realized by several technical methods like metal organic chemical vapor deposition (MOCVD), hydride vapor-phase epitaxial (HVPE), and laser lift-off (LLO). Its advantages are demonstrated from material quality and chip processing. It is investigated by high resolution X-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM), Rutherford back-scattering (RBS), photoluminescence, current-voltage and light output-current measurements. The width of (0002) reflection in XRD rocking curve, which reaches 173" for the thick GaN template LED, is less than that for the conventional one, which reaches 258". The HRTEM images show that the multiple quantum wells (MQWs) in 80-μm-thick GaN template LED have a generally higher crystal quality. The light output at 350 mA from the thick GaN template LED is doubled compared to traditional LEDs and the forward bias is also substantially reduced. The high performance of 80-μm-thick GaN template LED depends on the high crystal quality. However, although the intensity of MQWs emission in PL spectra is doubled, both the wavelength and the width of the emission from thick GaN template LED are increased. This is due to the strain relaxation on the surface of 80-μm-thick GaN template, which changes the strain in InGaN QWs and leads to InGaN phase separation. 相似文献
A kind of green organic light-emitting diodes (OLED) was prepared via vacuum thermal evaporation, of which the multilayer structure was indium-tin oxide (ITO)/copper-phthalocyanine (CuPc) (200 Å)/N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (α-NPD) (600 Å)/N′-diphenyl-N,N′-tris(8-hydroxyquinoline) aluminium (Alq3) (400 Å):10-(2-benzothiazolyl)-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-(l)benzopyropyrano(6,7,8-i, j)quinolizin-11-one (C545T) (2%)/Alq3 (200 Å)/LiF (10 Å)/Al (1000 Å). And we used both traditional glass encapsulation and thin film encapsulation (TFE) technologies to protect the device, reducing impact of vapor and oxygen. Organic film offered an excellent surface morphology, while inorganic film was nearly a perfect barrier to vapor and oxygen. Both of them constituted the encapsulation unit of TFE. According to the results of acceleration life test, the operation lifetime of device using TFE was 22% less than that of device using traditional glass cap encapsulation. So, the technology of TFE should be optimized further, and the quality of TFE needs a great improvement. There is a long way to go and a lot of hard work before realizing flexible display with OLED, but the dream will be true one day. 相似文献
Abstract Hydrogenated amorphous silicon nitride-based heterojunction pin diode was electroformed under sufficiently high forward bias stress leading to its instant nanocrystallization at room temperature. In order to investigate the origin of the accompanying bright visible light emission, current-voltage and electroluminescence (EL) characteristics of the electroformed diode were scanned over temperature. Electrical transport mechanism was analysed in the low, medium and high electric field regimes. Temperature and field dependence of thermal activation energy were discussed. EL characteristics were studied using the spectral energy distribution and the injection current dependence of its intensity. Thermal quenching data of EL and photoluminescence intensities were compared. Finally, the relationship between the electrical transport and luminescence phenomena was attempted to be interpreted within the frame of a self-consistent model. 相似文献
Enhanced near-infrared (NIR) electroluminescence (EL) of a metal-oxide-semiconductor light emitting device (MOSLED) made on CO2 laser-annealed SiOx film is demonstrated. 相似文献
<正>Light emitting diode(LED) sources have been widely used for illumination.Optical design,especially freedom compact lens design is necessary to make LED sources applied in lighting industry,such as large-range interior lighting and small-range condensed lighting.For different lighting requirements,the size of target planes should be variable.In our paper we provide a method to design freedom lens according to the energy conservation law and Snell law through establishing energy mapping between the luminous flux emitted by a Lambertian LED source and a certain area of the target plane.The algorithm of our design can easily change the radius of each circular target plane,which makes the size of the target plane adjustable.Ray-tracing software Tracepro is used to validate the illuminance maps and polar-distribution maps.We design lenses for different sizes of target planes to meet specific lighting requirements. 相似文献
In this article, we report an optical design for a light emitting diode that can achieve high illumination quality using two
hyperbolic reflectors. The relative movements of the reflectors and the light source produce a zoom function that can change
the illumination beam from convergence to divergence. This study uses optical software ZEMAX for system simulation, and optimization
was performed to select reflector parameters with the objectives of both improving floodlight uniformity and spotlight efficiency.
Finally, experiments were conducted to verify the validity of the design, and the results corresponded well to the zoom illumination
simulations. 相似文献