首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到10条相似文献,搜索用时 19 毫秒
1.
路慧敏  陈根祥 《中国物理 B》2011,20(3):37807-037807
GaN-based irregular multiple quantum well(IMQW) structures assembled two different types of QWs emitting complementary wavelengths for dichromatic white light-emitting diodes(LEDs) are optimized in order to obtain near white light emissions.The hole distributions and spontaneous emission spectra of the IMQW structures are analysed in detail by fully considering the effects of strain,well-coupling,valence band-mixing and polarization effect through employing a newly developed theoretical model from the k · p theory.Several structure parameters such as well material component,well width,layout of the wells and the thickness of barrier between different types of QWs are employed to analyse how these parameters together with the polarization effect influence the electronic and the optical properties of IMQW structure.Numerical results show that uniform hole distributions in different types of QWs are obtained when the number of the QWs emitting blue light is two,the number of the QWs emitting yellow light is one and the barrier between different types of QWs is 8nm in thickness.The near white light emission is realized using GaN-based IMQW structure with appropriate design parameters and injection level.  相似文献   

2.
A Dy3+-doped LiYF4 single crystal capable of generating white light by simultaneous blue and yellow light emission of phosphorescent centers is produced.Chromaticity coordinates and photoluminescence intensity vary with excitation wavelength.Under 350,365,and 388 nm excitation,the crystal shows excellent white light emission.The most efficient wavelength for white light is 388 nm.The CIE coordinates are x=0.316 and y =0.321,and the color temperature(Tc) is 6 368 K.These results indicate that the studied crystal is a potential candidate for ultraviolet light-excited white light-emitting diodes.  相似文献   

3.
Novel Dy^3+-doped GdPO4 white light phosphors with a monoclinic system are successfully synthesized by the hydrothermal method at 240℃. The strong absorption at around 147nm in the excitation spectrum is assigned to the host absorption. It is suggested that the vacuum ultraviolet excited energy is transferred from the host to the Dy^3+ ions. The f - d transition of the Dy^3+ ion is observed to be located at 182nm, which is consistent with the calculated value using Dorenbos's expression. Under 147nm excitation, Gd0.92PO4:0.08Dy^3+ phosphor exhibits two emission bands located at 572 nm (yellow) and 478 nm (blue), which correspond to the hypersensitive transitions ^4 F9/2-^6 H13/2 and ^4 F9/2-^6 H15/2. The two emission bands lead to the white light. Because of the strong absorption at about 147nm, Gd0.92PO4:0.08Dy^3+ under vacuum ultraviolet excitation is an effective white light phosphor, and has promising applications to mercury-free lamps.  相似文献   

4.
The dependence of light intensities of organic light-emitting diodes (OLEDs) on the distance of emission zone to metal cathode is investigated numerically. The investigation is based on the half-space optical model that accounts for optical interference effects of metal cathode. We find that light intensities of OLEDs are functions of the distance of emission zone from the metal cathode because of the effect of interference of the metal cathode.This interference leads to an optimal location of emission zone in OLEDs for the maximum of light intensities.Optimal locations of emission zone are numerically shown in various emitting colour OLEDs with different metalcathodes and these results are expected to give insight into the preparation of high efficiency full colour or white light OLEDs.  相似文献   

5.
Spherical organic-bonded ZnS nanocrystals with 4.0 4-0.2 nm in diameter are synthesized by a liquid-solid-solution method. The photoluminescence spectrum of sample ([S^2-]/[Zn^2+] = 1.0) shows a strong white emission with a peak at 490nm and - 170 nm full widths at half maximum. By Gauss fitting, the white emission is attributed to the overlap of a blue emission and a green-yellow emission, originating from electronic transitions from internal S^2- vacancies level to valence band and to the internal Zn^2+ vacancy level, respectively. After sealingZnS nanocrystals onto InGaN chips, the device shows CIE coordinates of (0.29,0.30), which indicates their potential applications for white light emitting diodes.  相似文献   

6.
We derive an expression of the interaction between a quantum cavity field and an ultracold A-type three-level atom in which two upper levels are coupled by a coherent driving field. The effects of the driving-induced atomic coherence on the atomic emission probability are investigated. It is found that, due to the driving-induced atomic coherence, there are two transition channels for the atom interacting with the cavity field. Between the two transition channels, there is a quantum interference, which is a destructive interference. This destructive quantum interference suppresses the emission of the atom. The atomic emission probability decreases with the increasing driving field.  相似文献   

7.
陈岐岱  王龙 《中国物理快报》2004,21(9):1822-1824
Single transient cavitation bubble with luminescence has been generated in pure glycerin by using the ‘tube arrest‘ method. The analyses of high-speed photograph and light emission data suggest that the light emission would be a single bubble sonoluminescence. The luminescence pulse width is observed to vary from sub-nanosecond to about 30 ns. The width and intensity of luminescence pulses increases with the height of the liquid column height and decreases with the liquid temperature.  相似文献   

8.
Polymer white-light-emitting diodes are fabricated based on the blend of poly[9,9-di-(2-ethylhexyl)-fluorenyl-2, 7- diyl]-end capped with polysilsesquioxane (PFO) and a chelating copolymer of poly[(9,9-bis(3′-(N,N-dimethylamino) propyl)-2, 7-fluorene-alt-2, 7-(9,9-dioctylfluorene) )-co- [2, 7-(9,9-dioctlyfluorene)-alt-5,5-bis(2-(4-methyl-l-naphtha- lene) pyridine-C^2,N) iridium (III) acethylacetonate]] (PFN-NaIr). The device with the sole aluminium cathode is able to produce a comparably white electroluminescence efficiency of 1.31 cd/A to that of the device using low work function cathodes (such as Ba, Ca, etc.). The CIE coordinates of the white light emission consisting of red, green and blue three components are nearly at (0.34, 0.35). The mechanism of the white light emission from the device with the AI cathode is investigated, which is related to the efficient injection of electrons through the interface of PFN-Nalr/AI.  相似文献   

9.
A silicon-based field emission light emitting diode for low-voltage operation is fabricated in the standard 0.35 μm 2P4M salieide complementary metal-oxide-semiconduetor (CMOS) technology. Partially overlapping p^+ and n^+ regions with a salicide block layer are employed in this device to constitute a heavily doped p^+-n^+ junction which has soft "knee" Zener breakdown characteristics, thus its working voltage can be reduced preferably below 5 V, and at the same time the power efficiency is improved. The spectra of this device are spread over 500nm to 1000nm with the main peak at about 722nm and an obvious red shift of the spectra peak is observed with the increasing current through the device. During the emission process, field emission rather than avalanche process plays a major role. Differences between low-voltage Zener breakdown emission and high-voltage avalanche breakdown emission performance are observed and compared.  相似文献   

10.
谢自力  张荣  傅德颐  刘斌  修向前  华雪梅  赵红  陈鹏  韩平  施毅  郑有炓 《中国物理 B》2011,20(11):116801-116801
Wide spectral white light emitting diodes have been designed and grown on a sapphire substrate by using a metal-organic chemical vapor deposition system. Three quantum wells with blue-light-emitting, green-light-emitting and red-light-emitting structures were grown according to the design. The surface morphology of the film was observed by using atomic force microscopy. The films were characterized by their photoluminescence measurements. X-ray diffraction θ/2θ scan spectroscopy was carried out on the multi-quantum wells. The secondary fringes of the symmetric ω/2θ X-ray diffraction scan peaks indicate that the thicknesses and the alloy compositions of the individual quantum wells are repeatable throughout the active region. The room temperature photoluminescence spectra of the structures indicate that the white light emission of the multi-quantum wells is obtained. The light spectrum covers 400-700 nm, which is almost the whole visible light spectrum.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号