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1.
We demonstrate intrinsic white light emission from hybrid light emitting diodes fabricated using an inorganic–organic hybrid junction grown at 50 °C on a paper substrate. Cyclotene was first spin coated on the entire substrate to act as a surface barrier layer for water and other nutrient solutions. The active area of the fabricated light emitting diode (LED) consists of zinc oxide nanorods (ZnO NRs) and a poly(9,9‐dioctylfluorene) (PFO) conducting polymer layer. The fabricated LED shows clear rectifying behavior and a broad band electroluminescence (EL) peak covering the whole visible spectrum range from 420 nm to 780 nm. The color rendering index (CRI) was calculated to be 94 and the correlated color temperature (CCT) of the LED was 3660 K. The low process temperature and procedure in this work enables the use of paper substrate for the fabrication of low cost ZnO–polymer white LEDs for applications requiring flexible/disposable electronic devices. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Jia-Hong Wu Shu-Yi Liu Shuti Li Yu-long Jiang Guo-Ping Ru Xin-Ping Qu 《Applied Physics A: Materials Science & Processing》2012,109(2):489-495
Light-emitting diodes (LEDs) were formed by hydrothermally growing n-ZnO nanostructures on p-GaN with or without seed layers. The performance of the fabricated LEDs was studied. The seed layers not only have a great influence on the morphology and density of the ZnO nanostructures but also determine the lighting bias and emitting mechanism. The LEDs without seed layers and with sputtered seed layers exhibit light emission only under reverse bias, which is believed due to the GaN buffer layer/p-GaN p–n junction. The LEDs with sol–gel seed layers exhibit light emission under both forward and reverse biases. With the increase of the forward bias, the LEDs first demonstrate a red electroluminescence emission coming from the sol–gel seed layers and then demonstrate an orange emission coming from the ZnO nanorods. The sol–gel seed layer and the interface play a very important role in the electroluminescence. 相似文献
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Efficient polymer white-light-emitting diodes (WPLEDs) have been fabricated with a single layer of fluorescent polymer blend. The device structure consists of ITO/PEDOT/PVK/emissive layer/Ba/Al. The emissive layer is a blend of poly(9,9-dioctylfluorene) (PFO), phenyl-substituted PPV derivative (P-PPV) and a copolymer of 9,9-dioctylfluorene and 4,7-di(4-hexylthien-2-yl)-2,1,3-benzothiadiazole (PFO-DHTBT), which, respectively, emits blue, green and red light. The emission of pure and efficient white light was implemented by tuning the blend weight ratio of PFO: P-PPV: PFO-DHTBT to 96:4:0.4. The maximum current efficiency and luminance are, respectively, 7.6 cd/A at 6.7 V and 11930 cd/m2 at 11.2 V. The CIE coordinates of white-light emission were stable with the drive voltages. 相似文献
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S. Kishwar K. ul HasanN.H. Alvi P. KlasonO. Nur M. Willander 《Superlattices and Microstructures》2011
Vertically well aligned zinc oxide nanorods (ZnO NRs) were grown on p-GaN by electrodeposition (ED) and aqueous chemical growth (ACG) techniques and the structures were employed to fabricate white light emitting diodes (LEDs). Room temperature current voltage (I–V), photoluminescence (PL), and electroluminescence (EL) measurements were performed to investigate and compare both LEDs. In general, the I–V characteristics and the PL spectra of both LEDs were rather similar. Nevertheless, the EL of the ED samples showed an extra emission peak shoulder at 730 nm. Moreover, at the same injection current, the EL spectrum of the ED light emitting diode showed a small UV shift of 12 nm and its white peak was found to be broader when compared to the ACG grown LED. The broadening of the EL spectrum of the LED grown by ED is due to the introduction of more radiative deep level defects. The presented LEDs have shown excellent color rendering indexes reaching a value as high as 95. These results indicate that the ZnO nanorods grown by both techniques possess very interesting electrical and optical properties but the ED is found to be faster and more suitable for the fabrication of white LEDs. 相似文献
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成功制备了结构为ITO/PDDOPV/PPQ/Al的异质结聚合物发光二极管。该器件在正反向偏压下均可发光。在正向偏压下的光发射主要来自PDDOPV,但在反向偏压下的光发射则包括来自PPQ的蓝光发射和PDDOPV的黄光发射。蓝光强度与黄光强度的比值随着反向偏压的增加而增加,当反向直流电压分别为22V、24V、26V、28V时,其电致发光光谱中PPQ与PDDOPV的峰高比IPPQ/IPDDOPV分别为1.092、1.329、1.605、2.046。换句话说,该器件的发光颜色是压控可调的,这对实现彩色显示是极为有利的。分析了在反向偏压下的发光机理以及IPPQ/IPDDOPV受电压控制的原因。 相似文献
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Ying He Jun-An Wang Xiao-Ban Chen Wen-Fei Zhang Xu-Yu Zeng Qiu-Wen Gu 《Journal of nanoparticle research》2010,12(1):169-176
We present a polymer-complexing soft template technique to construct the ZnO-nanowire/polymer light emitting device prototype
that exhibits blue electrically driven emission with a relatively low-threshold voltage at room temperature in ambient atmosphere,
and the ZnO-nanowire-based LED’s emission wavelength is easily tuned by controlling the applied-excitation voltage. The nearly
vertically aligned ZnO-nanowires with polymer film were used as emissive layers in the devices. The method uses polymer as
binder in the LED device and dispersion medium in the luminescence layer, which stabilizes the quasi-arrays of ZnO nanowires
embedding in a thin polymer film on silicon substrate and passivates the surface of ZnO nanocrystals, to prevent the quenching
of luminescence. Additionally, the measurements of electrical properties showed that ZnO-nanowire/polymer film could significantly
improve the conductivity of the film, which could be attributed to an increase in both Hall mobility and carrier concentration.
The results indicated that the novel technique is a low-cost process for ZnO-based UV or blue light emission and reduces the
requirement for achieving robust p-doping of ZnO film. It suggests that such ZnO-nanowire/polymer-based LEDs will be suitable
for the electro-optical application. 相似文献
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Improvement in the light extraction efficiency (LEE) of GaN-based green light emitting diodes (LEDs) with ZnO nanostructures synthesized by a hydrothermal method is reported. Formation of ZnO nanorods, hemispheres, and cones was controlled by varying the pH of the aqueous synthesis solution. The shape of the ZnO nanostructures integrated onto the LEDs shows a strong relationship with the LEE characteristics of GaN-based green LEDs. The electroluminescence (EL) intensity of LEDs covered by ZnO nanostructures increased compared to conventional LEDs. In terms of LEE, LEDs with surface-textured ZnO hemispheres showed the highest EL intensity, which can be attributed to an increase in the effective critical angle, the escape cone, and multiple scattering. Finite difference time domain (FDTD) simulation was conducted to theoretically confirm the experimental results. 相似文献
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We report on high-brightness GaN nanowire UV–blue light emitting diodes (LEDs), which are fabricated by coupling of n-GaN nanowires and p-GaN substrates using two assembly methods, random dispersion (RD) and dielectrophoresis assisted assembly deposition (DAAD). These GaN nanowire LEDs have bright UV–blue emission (411–437?nm) from the n-GaN nanowire/p-GaN substrate junction and the light emission is strong enough to be observed with the naked eye even for a single GaN nanowire LED. The results reported here should have significant implications for the fabrication of highly efficient, low-cost UV–blue LEDs with low power consumption, as compared to conventional thin-film based GaN LEDs. 相似文献
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K.H. Ibnaouf 《Optics & Laser Technology》2012,44(3):710-713
Mixtures made of poly[2-methyl-5-(2-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH–PPV) conducting polymer and cresyl violet 670 have been utilized for studying the amplified spontaneous emission characteristics (ASE) in an organic solution under laser excitation. In our earlier communication, we had shown that MEH–PPV alone could produce ASE under pulsed Nd: YAG laser excitation only in its excimeric state. In a follow up study reported here, a mixture of MEH–PPV and cresyl violet in benzene at different ratios were prepared. The results showed that when the mixture was pumped by the third harmonic of Nd: YAG (355 nm), MEH–PPV as a part of the mixture could get excited by pump laser pulse excitation, and transfer its excitation energy externally to cresyl violet to produce ASE. However, MEH–PPV represents here as a donor while CV served as an acceptor. 相似文献
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M. Sajimol Augustine P.P. Jeeju V.G. Sreevalsa S. Jayalekshmi 《Journal of Physics and Chemistry of Solids》2012,73(3):396-401
The aim of the study is to investigate the optical properties of spin-coated, highly transparent nanocomposite films of oleic acid modified ZnO (Zinc oxide) nanorods embedded in Polyvinyl alcohol (PVA) matrix. Pristine and oleic acid (OA) modified ZnO nanorods have been prepared by wet chemical synthesis and are characterized by X-ray diffraction, FESEM, TEM and FT–IR spectroscopy techniques. The optical properties of ZnO/PVA films are studied using UV–visible absorption and Photoluminescence (PL) spectroscopy. The results show that the optical absorption of the films in the UV region is quite high and more than 95% absorption is observed in films prepared from OA modified ZnO nanorods. The excellent UV absorption at around 300 nm offers prospects of applications of these films as efficient UV filters in this wavelength region. The PL spectrum of pristine ZnO nanorods shows almost white light emission whereas OA modified ZnO nanorods have a more intense peak centered in the blue region. The PL emission of OA modified ZnO/PVA film shows appreciable increase in intensity compared to the film obtained with pristine ZnO. The surface modification of ZnO by the polymer matrix removes defect states within ZnO and facilitates sharp near band edge PL emission at 364 nm. 相似文献
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ZnO nanocrystals were synthesized by hydrolysis in methanol. X-ray diffraction and photoluminescence spectra confirm that good crystallized ZnO nanoparticles were formed. Utilizing those ZnO nanoparticles and poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV), light emitting devices with indium tin oxide (ITO)/poly(3,4-oxyethyleneoxy-thiophene):poly(styrene sulfonate) (PEDOT:PSS)/ZnO:MDMO-PPV/Al and ITO/PEDOT:PSS/MDMO-PPV/Al structures were fabricated. Electroluminescence (EL) spectra reveal that EL yield of hybrid MDMO-PPV and ZnO nanocrystals devices increased greatly as compared with pristine MDMO-PPV devices. The current-voltage characteristics indicate that addition of ZnO nanocrystals can facilitate electrical injection and charge transport. The decreased energy barrier to electron injection is responsible for the increased efficiency of electron injection. 相似文献
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The spin coating method was used to assemble polymer (Poly (2,5-dibutoxy-1,4-phenylenevinylene)) (DBO-PPV) into the pores of porous alumina which was prepared by anodization. Four peaks in the photoluminescence (PL) spectra of the composite, with contributions from the DBO-PPV and porous alumina, were found. It was also found that the light emitting from the porous alumina could excite the photoluminescence of DBO-PPV. The nanometer effect of the porous alumina can lead to a blue shift of 90 nm of the PL peaks of DBO-PPV. 相似文献
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Various MoOx decorated ZnO nanorods (ZnO-MoOx) samples were fabricated by physical vapor deposition of MoOx on the surface of ZnO nanorods with varying deposition time and temperature. The microstructure and photoluminescence (PL) of the ZnO-MoOx samples were investigated. It was found that the morphology of the ZnO nanorods is changed from hexagonal prisms to lotus-roots-like shapes by the decoration of MoOx. The lotus-roots-like shapes may be formed by partial melting and evaporating of ZnO-MoOx during the MoOx decoration. This result shows that one can use the thermal instability of a nano-material to obtain an interesting structure, although a thermal instability should often be avoided. The intensity of the ultraviolet and visible light emission the of ZnO nanorods have different dependencies on the MoOx decoration. Although the position of the ultraviolet light emission is not obviously changed by the MoOx decoration, the ultraviolet light emission intensity is greatly weakened. In contrast, the intensity and position of visible light emission is largely changed. The blue shift of the visible light emission might be related to defects introduced by melting of the ZnO nanorods. 相似文献
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Light-emitting diodes (LEDs), based on blue-emitting polyfluorenes are usually prone to the appearance of a contaminant green emission (centered around 520 nm), leading to an apparent whitish light emission. We find that, for LEDs based on poly(9,9-dioctylfluorene), PFO, the blending with the hole transporting polyvinylcarbazole, PVK, can suppress such green emission. LEDs based on a PFO/PVK blend with a 1:2 weight ratio and with aluminum cathodes show a quite stable blue emission. This result reveals the important role played by the interchain interactions on the observed contaminant green emission. In addition, we observe that in Al-based devices blending causes a decrease in EL efficiency while in Mg-based devices we obtained higher efficiencies with the blend PFO:3PVK when compared with neat PFO-based devices. 相似文献
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A. Wadeasa S. L. Beegum S. Raja O. Nur M. Willander 《Applied Physics A: Materials Science & Processing》2009,95(3):807-812
We report a demonstration of heterojunction light emitting diode (LED) based on a hybrid n-ZnO-nanorod/p-polymer layered structure.
The ZnO was grown using the aqueous chemical growth (ACG) on top of the polymer(s) which were deposited on glass. The current–voltage
(I–V) behavior of the heterojunctions showed good rectifying diode characteristics. Room-temperature electroluminescence (EL)
spectra of the LEDs provided a broad emission band over a wide LED color range (430–650 nm), in which both zinc and oxygen
vacancy peaks are clearly detected. We present here luminescent devices based on the use of ZnO-nanorods in combination with
two different blended and multi-layered p-type polymers. Electroluminescence of the first batch of devices showed that white
bluish strong emission for the presently used polymers is clearly observed. We obtained a turn-on voltage of 3 V and break-down
voltage equal to −6 V for PVK-TFB blended device. The corresponding values for the NPD-PFO multilayer device were 4 V and
−14 V, respectively. The rectification factors were equal to 3 and 10 for the two devices, respectively. The films and devices
processed were characterized by scanning electron microscopy (SEM), DEKTAK 3ST Surface Profile, Semiconductor Parameter Analyzer,
photoluminescence (PL), and electroluminescence (EL). 相似文献
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Małgorzata Norek Grzegorz Łuka Marek Godlewski Tomasz Płociński Marta Michalska-Domańska Wojciech J. Stępniowski 《Applied Physics A: Materials Science & Processing》2013,111(1):265-271
Luminescent properties of ZnO nanorods covered with Ag nanoparticles are examined. Nanorods were synthesized on AAO templates using Atomic Layer Deposition (ALD) technique. Two types of the samples were prepared with different arrangement of ZnO nanorods and doping conditions. Nanorods of the second type were codoped with Al, to stimulate defect-related emissions. The ZnO material fills heterogeneously the interior of the AAO nanopores and has hexagonal, wurtzite structure. Both types of structures exhibit a broad defect-related emission at about 440 nm, most probably related to recombination at zinc interstitial (Zni) defects. This emission in samples with a random distribution of ZnO:Al nanorods and finer Ag nanoparticles is enhanced by factor of ~2.5 upon Ag deposition. The so-obtained material is interesting from the point of view of its application in blue range emitting diodes. 相似文献