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Sample records for electroluminescent devices based

  1. Hybrid electroluminescent devices

    DOEpatents

    Shiang, Joseph John; Duggal, Anil Raj; Michael, Joseph Darryl

    2010-08-03

    A hybrid electroluminescent (EL) device comprises at least one inorganic diode element and at least one organic EL element that are electrically connected in series. The absolute value of the breakdown voltage of the inorganic diode element is greater than the absolute value of the maximum reverse bias voltage across the series. The inorganic diode element can be a power diode, a Schottky barrier diode, or a light-emitting diode.

  2. Hybrid electroluminescent device based on MEH-PPV and ZnO

    NASA Astrophysics Data System (ADS)

    Hewidy, Dina.; Gadallah, A.-S.; Fattah, G. Abdel

    2017-02-01

    Hybird organic/inorganic electroluminescent device based on the structure of glass/ITO/PEDOT:PSS/MEH-PPV/ZnO/ZnO submicrorods/Al has been manufactured. Spin coating has been used to deposit both PEDOT:PSS and MEH-PPV. Two-step process has been used to synthesis ZnO submicrorods, namely, spin coating and chemical bath deposition. Changing the dimensions of the ZnO submicrorods in this layer structure has been investigated to improve the performance of the organic/inorganic electroluminescence device. Such layer structure provides electroluminescence with narrow emission bands due to a high gain with this structure. X-ray diffraction patterns and scanning electron microscope images show that ZnO submicrorods have hexagon structure. Current-voltage curve for the structure has been reported. Electroluminescence curves (electroluminescence intensity versus wavelength) at different bias voltages have been presented and these results show narrowing in full width at half maximum in the spectra at high current density compared to photoluminescence excitation. The narrowing in the spectrum has been explained.

  3. Mechanisms of efficiency enhancement in the doped electroluminescent devices based on a europium complex

    NASA Astrophysics Data System (ADS)

    Zhou, Liang; Zhang, Hongjie; Shi, Weidong; Deng, Ruiping; Li, Zhefeng; Yu, Jiangbo; Guo, Zhiyong

    2008-12-01

    In this study, we investigated the dependence of electroluminescence (EL) efficiency on carrier distribution in the light-emitting layer (EML) of the device based on Eu(TTA)3phen (TTA=thenoyltrifluoroacetone, phen=1,10-phenanthroline) doped 4,4'-N,N'-dicarbazole-biphenyl (CBP) system. We found that EL efficiency increases monotonously with increasing hole injection even when holes are the majority carriers. This phenomenon was attributed to the accumulation of holes in EML, which improves the balance of holes and electrons on Eu(TTA)3phen molecules, thus enhancing the EL efficiency. To further improve the balance of holes and electrons on Eu(TTA)3phen molecules, the injection of electron was gently decreased by modulating the thickness of Al and LiF layers. Interestingly, EL efficiency increases gradually to a maximum and then decreases rapidly with decreasing electron injection. As a result, the device with 80 nm Al and 1.2 nm LiF obtained the maximal current efficiency of 9.53 cd/A, power efficiency of 5.35 lm/W, and external quantum efficiency of 5.15%. Our experimental results demonstrated that the balance of holes and electrons on dye molecules is the precondition for the doped device to obtain high EL efficiency, when carrier trapping is the dominant EL mechanism.

  4. Fabrication of a white electroluminescent device based on bilayered yellow and blue quantum dots.

    PubMed

    Kim, Jong-Hoon; Lee, Ki-Heon; Kang, Hee-Don; Park, Byoungnam; Hwang, Jun Yeon; Jang, Ho Seong; Do, Young Rag; Yang, Heesun

    2015-03-12

    Until now most work on colloidal quantum dot-light-emitting diodes (QLEDs) has been focused on the improvement of the electroluminescent (EL) performance of monochromatic devices, and multi-colored white QLEDs comprising more than one type of QD emitter have been rarely investigated. To demonstrate a white EL as a result of color mixing between blue and yellow, herein a unique combination of two dissimilar QDs of blue- CdZnS/ZnS plus a yellow-emitting Cu-In-S (CIS)/ZnS is used for the formation of the emitting layer (EML) of a multilayered QLED. First, the QLED consisting of a single EML randomly mixed with two QDs is fabricated, however, its EL is dominated by blue emission with the contribution of yellow emission substantially weaker. Thus, another EML configuration is devised in the form of a QD bilayer with two stacking sequences of CdZnS/ZnS//CIS/ZnS QD and vice versa. The QLED with the former stacking sequence shows an overwhelming contribution of blue EL, similar to the mixed QD EML-based device. Upon applying the oppositely stacked QD bilayer of CIS/ZnS//CdZnS/ZnS, however, a bicolored white EL can be successfully achieved by means of the effective extension of the radiative excitonic recombination zone throughout both QD EML regions. Such QD EML configuration-dependent EL results, which are discussed primarily using the proposed device energy level diagram, strongly suggest that the positional design of individual QD emitters is a critical factor for the realization of multicolored, white emissive devices.

  5. Fabrication of a white electroluminescent device based on bilayered yellow and blue quantum dots

    NASA Astrophysics Data System (ADS)

    Kim, Jong-Hoon; Lee, Ki-Heon; Kang, Hee-Don; Park, Byoungnam; Hwang, Jun Yeon; Jang, Ho Seong; Do, Young Rag; Yang, Heesun

    2015-03-01

    Until now most work on colloidal quantum dot-light-emitting diodes (QLEDs) has been focused on the improvement of the electroluminescent (EL) performance of monochromatic devices, and multi-colored white QLEDs comprising more than one type of QD emitter have been rarely investigated. To demonstrate a white EL as a result of color mixing between blue and yellow, herein a unique combination of two dissimilar QDs of blue- CdZnS/ZnS plus a yellow-emitting Cu-In-S (CIS)/ZnS is used for the formation of the emitting layer (EML) of a multilayered QLED. First, the QLED consisting of a single EML randomly mixed with two QDs is fabricated, however, its EL is dominated by blue emission with the contribution of yellow emission substantially weaker. Thus, another EML configuration is devised in the form of a QD bilayer with two stacking sequences of CdZnS/ZnS//CIS/ZnS QD and vice versa. The QLED with the former stacking sequence shows an overwhelming contribution of blue EL, similar to the mixed QD EML-based device. Upon applying the oppositely stacked QD bilayer of CIS/ZnS//CdZnS/ZnS, however, a bicolored white EL can be successfully achieved by means of the effective extension of the radiative excitonic recombination zone throughout both QD EML regions. Such QD EML configuration-dependent EL results, which are discussed primarily using the proposed device energy level diagram, strongly suggest that the positional design of individual QD emitters is a critical factor for the realization of multicolored, white emissive devices.Until now most work on colloidal quantum dot-light-emitting diodes (QLEDs) has been focused on the improvement of the electroluminescent (EL) performance of monochromatic devices, and multi-colored white QLEDs comprising more than one type of QD emitter have been rarely investigated. To demonstrate a white EL as a result of color mixing between blue and yellow, herein a unique combination of two dissimilar QDs of blue- CdZnS/ZnS plus a yellow-emitting Cu

  6. Highly Stretchable and Waterproof Electroluminescence Device Based on Superstable Stretchable Transparent Electrode.

    PubMed

    You, Banseok; Kim, Youngmin; Ju, Byeong-Kwon; Kim, Jong-Woong

    2017-02-15

    Realization of devices with enhanced stretchability and waterproof properties will significantly expand the reach of electronics. To this end, we herein fabricate an elastic transparent conductor that comprises silver nanowires (AgNWs) on a hydroxylated polydimethylsiloxane (PDMS) substrate covered by polyurethane urea (PUU), which is fully compatible with both materials. Carboxylic acid groups of PUU was designed to form hydrogen bonds with the carbonyl groups of poly(vinylpyrrolidone) on the AgNW surface, resulting in an enhanced affinity of AgNWs for PUU. Exceptionally strong hydrogen bonds between PUU and the hydroxylated PDMS thus facilitate the achievement of water sealable, mechanically stable, and stretchable transparent electrodes. To fabricate stretchable electroluminescence (EL) devices, ZnS particles were mixed with PUU, and the mixture was coated onto the AgNWs/hydroxylated PDMS, followed by a face-to-face lamination with another identical electrode. The devices could be stretched up to 150% without a severe reduction in the emission intensity, and they survived 5000 cycles of 100% stretch-release testing. The high adhesion between PUU and PDMS even in water is responsible for the good waterproof characteristics of the EL devices. These results pave the way for realization of fully stretchable and waterproof electronic devices.

  7. RAPID COMMUNICATION: Self-quenching of excited europium ions in Eu(DBM)3bath-based organic electroluminescent devices

    NASA Astrophysics Data System (ADS)

    Liang, C. J.; Wong, T. C.; Hung, L. S.; Lee, S. T.; Hong, Z. R.; Li, W. L.

    2001-06-01

    Luminance-current characteristics of organic electroluminescent devices based on the europium complex of europium(dibenzoylmethanato)3 (bathophenanthroline) (Eu(DBM)3bath) have been investigated. Transient measurements were carried out to study the decay process of excited Eu3+ ions. A comparison of experimental data and theoretical calculation shows that biexcitonic quenching among the excited Eu3+ ions is an important channel in their decay process, and this quenching process is a primary cause for our observation of a rapid decrease in quantum efficiency with increasing current density. Extending the recombination zone is found to be beneficial to reducing this defective effect. The mechanism of the quenching process is also discussed.

  8. Infrared and visible emission from organic electroluminescent devices based on praseodymium complex

    NASA Astrophysics Data System (ADS)

    Hong, Ziruo; Liang, Chunjun; Li, Ruigang; Zang, Faxin; Fan, Di; Li, Wenlian; Hung, L. S.; Lee, S. T.

    2001-09-01

    Praseodymium(dibenzoylmethanato)3(bathophenanthroline) [Pr(DBM)3bath] was employed as an emitting and electron transport layer, and N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1, 1'-biphenyl-4,4'-diamine (TPD) as a hole transport layer in organic electroluminescent (EL) devices. Bilayer device TPD/Pr(DBM)3bath and trilayer devices TPD/TPD:Pr(DBM)3bath/Pr(DBM)3bath with a different ratio of TPD to the Pr-complex were fabricated. Emission bands at 608 nm (1D2→3H6), 890 nm (1D2→3F2), 1015 nm (1D2→3F3), 1065 nm (1D2→3F4) and 1550 nm (1D2→1G4) originating from the internal f-f transitions of a Pr3+ ion were observed from EL devices using both bilayer and trilayer structures. Decreasing the ratio of TPD to the Pr-complex, the emission of the 1D2→3H6 transition was promoted and that from the exciplex suppressed, which was explained in terms of energy transfer from the ligand to the central ion.

  9. Progress and Prospects in Stretchable Electroluminescent Devices

    NASA Astrophysics Data System (ADS)

    Wang, Jiangxin; Lee, Pooi See

    2017-03-01

    Stretchable electroluminescent (EL) devices are a new form of mechanically deformable electronics that are gaining increasing interests and believed to be one of the essential technologies for next generation lighting and display applications. Apart from the simple bending capability in flexible EL devices, the stretchable EL devices are required to withstand larger mechanical deformations and accommodate stretching strain beyond 10%. The excellent mechanical conformability in these devices enables their applications in rigorous mechanical conditions such as flexing, twisting, stretching, and folding.The stretchable EL devices can be conformably wrapped onto arbitrary curvilinear surface and respond seamlessly to the external or internal forces, leading to unprecedented applications that cannot be addressed with conventional technologies. For example, they are in demand for wide applications in biomedical-related devices or sensors and soft interactive display systems, including activating devices for photosensitive drug, imaging apparatus for internal tissues, electronic skins, interactive input and output devices, robotics, and volumetric displays. With increasingly stringent demand on the mechanical requirements, the fabrication of stretchable EL device is encountering many challenges that are difficult to resolve. In this review, recent progresses in the stretchable EL devices are covered with a focus on the approaches that are adopted to tackle materials and process challenges in stretchable EL devices and delineate the strategies in stretchable electronics. We first introduce the emission mechanisms that have been successfully demonstrated on stretchable EL devices. Limitations and advantages of the different mechanisms for stretchable EL devices are also discussed. Representative reports are reviewed based on different structural and material strategies. Unprecedented applications that have been enabled by the stretchable EL devices are reviewed. Finally, we

  10. Transparent organic photodiodes stacked with electroluminescence devices

    NASA Astrophysics Data System (ADS)

    Komatsu, Takahiro; Sakanoue, Kei; Fujita, Katsuhiko; Tsutsui, Tetsuo

    2005-10-01

    Stacked devices that consisted of transparent organic photodiodes (TOPDs) and organic electroluminescence devices (OELs) were demonstrated. TOPDs were prepared by poly-(2-methoxy-5- (2'-ethylhexyloxy)-1,4-phenylene vinylene (MEH-PPV) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) blend films as an active layer and transparent Au cathode (10 nm thick). These TOPDs showed about 45 % transmittance on average in visible light region (380-780 nm) and good correlation between incident light intensity and output photocurrent. Based on these results, the stacked devices were prepared by introducing OELs on TOPDs through a SiO insulating layer. The structure of OELs was ITO/Carbon/TPD/Alq3/LiF/Al. These stacked devices work as light emitting devices and also photo diodes. Since TOPDs have transparency, OELs can illuminate a paper put on the glass substrate through TOPDs and TOPDs can receive reflective light from the paper. Although the TOPDs also absorb light from OELs directly, the output signals from TOPDs changed according to the black and white pattern of the paper. These results show that the devices act as an image sensor having light emitting layer and light receiving layer in a same area.

  11. Organic electroluminescent devices having improved light extraction

    DOEpatents

    Shiang, Joseph John

    2007-07-17

    Organic electroluminescent devices having improved light extraction include a light-scattering medium disposed adjacent thereto. The light-scattering medium has a light scattering anisotropy parameter g in the range from greater than zero to about 0.99, and a scatterance parameter S less than about 0.22 or greater than about 3.

  12. Intrinsic Polarization and Tunable Color of Electroluminescence from Organic Single Crystal-based Light-Emitting Devices

    PubMed Central

    Ding, Ran; Feng, Jing; Zhou, Wei; Zhang, Xu-Lin; Fang, Hong-Hua; Yang, Tong; Wang, Hai-Yu; Hotta, Shu; Sun, Hong-Bo

    2015-01-01

    A single crystal-based organic light-emitting device (OLED) with intrinsically polarized and color-tunable electroluminescence (EL) has been demonstrated without any subsequent treatment. The polarization ratio of 5:1 for the transversal-electric (TE) and transversal-magnetic (TM) polarization at the emission peak of 575 nm, and 4.7:1 for the TM to TE polarization at the emission peak of 635 nm, respectively, have been obtained. The emitting color is tunable between yellow, yellow-green and orange by changing the polarization angle. The polarized EL and the polarization-induced color tunability can be attributed to the anisotropic microcavity formed by the BP3T crystal with uniaxial alignment of the molecules. PMID:26207723

  13. Rare Earth Complex as Electron Trapper and Energy Transfer Ladder for Efficient Red Iridium Complex Based Electroluminescent Devices.

    PubMed

    Zhou, Liang; Li, Leijiao; Jiang, Yunlong; Cui, Rongzhen; Li, Yanan; Zhao, Xuesen; Zhang, Hongjie

    2015-07-29

    In this work, we experimentally demonstrated the new functions of trivalent rare earth complex in improving the electroluminescent (EL) performances of iridium complex by codoping trace Eu(TTA)3phen (TTA = thenoyltrifluoroacetone, phen = 1,10-phenanthroline) into a light-emitting layer based on PQ2Ir(dpm) (iridium(III)bis(2-phenylquinoly-N,C(2'))dipivaloylmethane). Compared with a reference device, the codoped devices displayed higher efficiencies, slower efficiency roll-off, higher brightness, and even better color purity. Experimental results demonstrated that Eu(TTA)3phen molecules function as electron trappers due to its low-lying energy levels, which are helpful in balancing holes and electrons and in broadening recombination zone. In addition, the matched triplet energy of Eu(TTA)3phen is instrumental in facilitating energy transfer from host to emitter. Finally, highly efficient red EL devices with the highest current efficiency, power efficiency and brightness up to 58.98 cd A(-1) (external quantum efficiency (EQE) of 21%), 61.73 lm W(-1) and 100870 cd m(-2), respectively, were obtained by appropriately decreasing the doping concentration of iridium complex. At certain brightness of 1000 cd m(-2), EL current efficiency up to 51.94 cd A(-1) (EQE = 18.5%) was retained. Our investigation extends the application of rare earth complexes in EL devices and provides a chance to improve the device performances.

  14. Method for producing high energy electroluminescent devices

    DOEpatents

    Meyerson, Bernard S.; Scott, Bruce A.; Wolford, Jr., Donald J.

    1992-09-29

    A method is described for fabricating electroluminescent devices exhibiting visible electroluminescence at room temperature, where the devices include at least one doped layer of amorphous hydrogenated silicon (a-Si:H). The a-Si:H layer is deposited on a substrate by homogeneous chemical vapor deposition (H-CVD) in which the substrate is held at a temperature lower than about 200.degree. C. and the a-Si:H layer is doped in-situ during deposition, the amount of hydrogen incorporated in the deposited layer being 12-50 atomic percent. The bandgap of the a-Si:H layer is between 1.6 and 2.6 eV, and in preferrable embodiments is between 2.0 and 2.6 eV. The conductivity of the a-Si:H layer is chosen in accordance with device requirements, and can be 10.sup.16 -10.sup.19 carriers/cm.sup.2. The bandgap of the a-Si:H layer depends at least in part on the temperature of the substrate on which the layer is deposited, and can be "tuned" by changing the substrate temperature.

  15. White light-emitting organic electroluminescent device based on a new orange organometallic iridium complexes

    NASA Astrophysics Data System (ADS)

    Shieh, Tien-shou; Huang, Heh-lung; Liu, Pey-ching; Tseng, Mei-Rurng; Liu, Jia-Ming

    2007-09-01

    We develop the white organic light-emitting diodes (WOLEDs) with a new orange electrophosphorescent emission, and the blue electrofluorescent or electrophosphorescent sensitizer. The new orange phosphorescent sensitizer is the thieno-pyridine framework organo-iridium complexes (PO-01). The blue phosphorsensitized electrofluorescent is 4,4'-Bis(9-ethyl-3-carbazovinylene)-1,1'- biphenyl (DSA) doped into 4,4'-Bis(2,2-diphenyl-ethen-1-yl) diphenyl (DPVBi). Beside, the blue phosphorescent sensitizer is Bis(3,5-difluoro-2-(2-pyridyl)phenyl- (2-carboxypyridyl)iridium (FirPic). The Device Type I of WOLED based on the PO-01 and the DSA doped into DPVBi has an efficiency of 5.7 lm/W (10.6Cd/A) at 500 Cd/m2, a CIE coordinates of (0.33, 0.31), and a CRI of 71. However, the Device Type II of WOLED has an efficiency of 5.5 lm/W (10.3Cd/A) at 500 Cd/m2 and a CIE coordinates of (0.30, 0.42), while the FirPic replaces the DPVBi doped with DSA. The spectra of the Device Type II and I both response insensitive to drive current. Nevertheless, the Device Type I relatively achieves a balanced whit emission with CIE coordinates of (0.33, 0.33). They are good suitability to use in OLED lighting and full-color LCD backlights.

  16. Single-layer electroluminescent devices based on fluorene-1H-pyrazolo[3,4-b]quinoxaline co-polymers

    NASA Astrophysics Data System (ADS)

    Pokladko-Kowar, Monika; Danel, Andrzej; Chacaga, Łukasz

    2013-11-01

    A fluorene based copolymer was synthesized for electroluminescent application. To the main chain of polymer the nitrogen heterocyclic, 1H-pyrazolo[3,4-b]quinoxaline, unit was introduced. The incorporation of this derivative tuned the emission from the blue to yellow-green one. A simple, single layered device was fabricated with the configuration ITO/PEDOT/co-poly-FLU-PQX/Ca/Mg.

  17. Dielectric relaxation in AC powder electroluminescent devices

    NASA Astrophysics Data System (ADS)

    Zhang, Shuai; Su, Haibin; Tan, Chuan Seng; Wong, Terence Kin Shun; Teo, Ronnie Jin Wah

    2017-01-01

    The dielectric properties of AC powder electroluminescent devices were measured and analyzed using complex impedance spectroscopy to determine the relaxation processes occurring within the devices. The relaxation processes identified were ascribed to the electrode polarization caused by ion accumulation at the electrode/resin interfaces, the Maxwell-Wagner-Sillars effects at the (ZnS or BaTiO3) particle/resin interfaces, and the dipolar reorientation of polymer chains in the resin matrix. Each relaxation process was represented by its corresponding equivalent circuit component. Space charge polarization at the electrodes were represented by a Warburg element, a resistor, and a constant phase element. The resin matrix, ZnS/resin and BaTiO3/resin interfaces could each be modeled by a resistor and a capacitor in parallel. The simulated equivalent circuits for three different printed structures showed good fitting with their experimental impedance results.

  18. Non-Doped Deep Blue and Doped White Electroluminescence Devices Based on Phenanthroimidazole Derivative.

    PubMed

    Chen, Shuo; Wu, Yukun; Hu, Shoucheng; Zhao, Yi; Fang, Daining

    2017-03-01

    A novel deep-blue emitter PhImPOTD based on phenathroimidazole was synthesized, which is incorporated by an electron-donating dibenzothiophene unit and electron-withdrawing phenanthroimidazole and diphenylphosphine oxide moieties. Furthermore, the weak π-π stacking and intermolecular aggregation render the photoluminescence quantum yield is as high as 0.34 in the solid state. Non-doped organic light emitting diodes (OLEDs) based on PhImPOTD emitter exhibits a low turn-on voltage of 3.6 V, a favorable efficiency of 1.13 cd A(-1) and a deep blue emission with Commission Internationale de l'Eclairage (CIE) coordinates of (0.15, 0.08). The CIE is very close to the NTSC (National Television Standards Committe) blue standard (CIE: 0.14, 0.08). PhImPOTD is also utilized as blue emitter and the host for a yellow emitter (PO-01) to fabricate white organic light-emitting diodes (WOLEDs). This gives a forward-viewing maximum CE of 4.83 cd A(-1) and CIE coordinates of (0.32, 0.32) at the luminance of 1000 cd m(-2). Moreover, the single-carrier devices unambiguously demonstrate that typical bipolar-dominant characteristics of PhImPOTD. This work demonstrates not only that the phenanthroimidazole unit is an excellent building block to construct deep blue emission materials, but also the introduction of a diphenylphosphine oxide deprotonation substituent is an efficient tactic for harvesting deep-blue emitting devices.

  19. White light-emitting organic electroluminescent devices

    DOEpatents

    Shiang, Joseph John; Duggal, Anil Raj; Parthasarathy, Gautam

    2006-06-20

    A light-emitting device comprises a light-emitting member, which comprises two electrodes, at least two organic electroluminescent ("EL") materials disposed between the electrodes, a charge blocking material disposed between the electrodes, and at least one photoluminescent ("PL") material. The light-emitting member emits electromagnetic ("EM") radiation having a first spectrum in response to a voltage applied across the two electrodes. The PL material absorbs a portion of the EM radiation emitted by the light-emitting member and emits EM radiation having second spectrum different than the first spectrum. Each of the organic EL materials emits EM radiation having a wavelength range selected from the group consisting of blue and red wavelength ranges.

  20. Theoretical and material studies on thin-film electroluminescent devices

    NASA Technical Reports Server (NTRS)

    Summers, C. J.; Brennan, K. F.

    1986-01-01

    Electroluminescent materials and device technology were assessed. The evaluation strongly suggests the need for a comprehensive theoretical and experimental study of both materials and device structures, particularly in the following areas: carrier generation and multiplication; radiative and nonradiative processes of luminescent centers; device modeling; new device concepts; and single crystal materials growth and characterization. Modeling of transport properties of hot electrons in ZnSe and the generation of device concepts were initiated.

  1. Solid state carbon nanotube device for controllable trion electroluminescence emission

    NASA Astrophysics Data System (ADS)

    Liang, Shuang; Ma, Ze; Wei, Nan; Liu, Huaping; Wang, Sheng; Peng, Lian-Mao

    2016-03-01

    Semiconducting carbon nanotubes (CNTs) have a direct chirality-dependent bandgap and reduced dimensionality-related quantum confinement effects, which are closely related to the performance of optoelectronic devices. Here, taking advantage of the large energy separations between neutral singlet excitons and charged excitons, i.e. trions in CNTs, we have achieved for the first time all trion electroluminescence (EL) emission from chirality-sorted (8,3) and (8,4) CNT-based solid state devices. We showed that strong trion emission can be obtained as a result of localized impact excitation and electrically injected holes, with an estimated efficiency of ~5 × 10-4 photons per injected hole. The importance of contact-controlled carrier injection (including symmetric and asymmetric contact configurations) and EL spectral stability for gradually increasing bias were also investigated. The realization of electrically induced pure trion emission opens up a new opportunity for CNT film-based optoelectronic devices, providing a new degree of freedom in controlling the devices to extend potential applications in spin or magnetic optoelectronics fields.Semiconducting carbon nanotubes (CNTs) have a direct chirality-dependent bandgap and reduced dimensionality-related quantum confinement effects, which are closely related to the performance of optoelectronic devices. Here, taking advantage of the large energy separations between neutral singlet excitons and charged excitons, i.e. trions in CNTs, we have achieved for the first time all trion electroluminescence (EL) emission from chirality-sorted (8,3) and (8,4) CNT-based solid state devices. We showed that strong trion emission can be obtained as a result of localized impact excitation and electrically injected holes, with an estimated efficiency of ~5 × 10-4 photons per injected hole. The importance of contact-controlled carrier injection (including symmetric and asymmetric contact configurations) and EL spectral stability for

  2. Electroluminescent devices formed using semiconductor nanocrystals as an electron transport media and method of making such electroluminescent devices

    DOEpatents

    Alivisatos, A. Paul; Colvin, Vickie

    1996-01-01

    An electroluminescent device is described, as well as a method of making same, wherein the device is characterized by a semiconductor nanocrystal electron transport layer capable of emitting visible light in response to a voltage applied to the device. The wavelength of the light emitted by the device may be changed by changing either the size or the type of semiconductor nanocrystals used in forming the electron transport layer. In a preferred embodiment the device is further characterized by the capability of emitting visible light of varying wavelengths in response to changes in the voltage applied to the device. The device comprises a hole processing structure capable of injecting and transporting holes, and usually comprising a hole injecting layer and a hole transporting layer; an electron transport layer in contact with the hole processing structure and comprising one or more layers of semiconductor nanocrystals; and an electron injecting layer in contact with the electron transport layer for injecting electrons into the electron transport layer. The capability of emitting visible light of various wavelengths is principally based on the variations in voltage applied thereto, but the type of semiconductor nanocrystals used and the size of the semiconductor nanocrystals in the layers of semiconductor nanometer crystals may also play a role in color change, in combination with the change in voltage.

  3. Electroluminescent behaviors in multilayer thin-film electroluminescent devices using 9,10-bisstyrylanthracene derivatives

    NASA Astrophysics Data System (ADS)

    Aminaka, Ei-Ichiro; Tsutsui, Tetsuo; Saito, Shogo

    1994-02-01

    Using nine 9,10-bisstyrylanthracene derivatives (BSA's) with different substituents as emission layer materials, multilayer electroluminescent (EL) devices were fabricated. Among nine BSA's, three BSA's were found to exhibit high EL performance. Four types of devices, a single-layer device with a BSA emission layer, two types of two-layer devices in which BSA emission layers were combined with a triphenylamine dimer as a hole transport layer or an oxadiazole derivative as an electron transport layer, and a three-layer device, were fabricated using the three BSA's. The relationships between the device structures and EL performances of these devices were studied. Ionization potential values in vacuum-deposited films of BSA's were measured. It was found that the introduction of an electron withdrawing group increased electron injection/transport capability, and that of electron donating groups increased hole injection/transport capability. The relative EL efficiencies of various devices were discussed in terms of the electronic nature of BSA's.

  4. A multilayer organic electroluminescent device using an organic dye salt

    NASA Astrophysics Data System (ADS)

    Feng, Xueyuan; Gu, Yongdi; Zhang, Jiayu; Cui, Yiping

    2005-01-01

    Organic electroluminescent devices have received considerable attention due to their application in flat-panel displays. To achieve full-color displays, it is necessary to obtain organic layers emitting red, green, and blue light, but it is still a challenge to obtain efficient and stable organic layer emitting red light so far. Recently, we found that an organic salt, trans-4-[p-[N-ethyl-N-(hydroxyethyl)amino]styryl]-N-methylphridinium tetraphenylborate (ASPT), exhibits efficient red-light emission. In this paper, we report a multilayer electrolumicescent device incorporating a hole-transport layer, an ASPT layer, and an electron-transport layer. The dependence of the carrier transport and the luminescence on the device structure is investigated in detail. Compared to the monolayer device, the balance between hole and electron injections is significantly improved for the multilayer device, and thus the electroluminescent efficiency and intensity are enhanced.

  5. Multilayer white light-emitting organic electroluminescent device.

    PubMed

    Kido, J; Kimura, M; Nagai, K

    1995-03-03

    Organic electroluminescent devices are light-emitting diodes in which the active materials consist entirely of organic materials. Here, the fabrication of a white light-emitting organic electroluminescent device made from vacuum-deposited organic thin films is reported. In this device, three emitter layers with different carrier transport properties, each emitting blue, green, or red light, are used to generate white light. Bright white light, over 2000 candelas per square meter, nearly as bright as a fluorescent lamp, was successfully obtained at low drive voltages such as 15 to 16 volts. The applications of such a device include paper-thin light sources, which are particularly useful for places that require lightweight illumination devices, such as in aircraft and space shuttles. Other uses are a backlight for liquid crystal display as well as full color displays, achieved by combining the emitters with micropatterned color filters.

  6. Theoretical and material studies on thin-film electroluminescent devices

    NASA Technical Reports Server (NTRS)

    Summers, C. J.; Brennan, K. F.

    1986-01-01

    A highly efficient DC electroluminescent display is presented. A variably spaced superlattice structure is used to produce high energy injection of electrons into a ZnSe:Mn active layer in which impact excitation of the Mn centers can occur. The device is predicted to operate at an applied external bias on order of magnitude less than the best DC electroluminescent device to date. The device is predicted to have comparable brightness, since it operates in the saturation regime. The improved efficiency stems from avoiding significant energy loss to phonons. The electrons sequentially tunnel through a multilayer ZnSe/CaSrF2 stack under bias and emerge into the active layer at an energy equal to the conduction band bending. The injection energy is chosen to coincide with the impact excitation energy of the Mn centers. Different device designs are presented and their performance is predicted.

  7. Optical sensors and multisensor arrays containing thin film electroluminescent devices

    DOEpatents

    Aylott, Jonathan W.; Chen-Esterlit, Zoe; Friedl, Jon H.; Kopelman, Raoul; Savvateev, Vadim N.; Shinar, Joseph

    2001-12-18

    Optical sensor, probe and array devices for detecting chemical biological, and physical analytes. The devices include an analyte-sensitive layer optically coupled to a thin film electroluminescent layer which activates the analyte-sensitive layer to provide an optical response. The optical response varies depending upon the presence of an analyte and is detected by a photodetector and analyzed to determine the properties of the analyte.

  8. In-flight gas phase passivation of silicon nanocrystals for novel inorganic-silicon nanocrystal based electroluminescent devices

    NASA Astrophysics Data System (ADS)

    Liptak, Richard William

    Silicon nanocrystals (SiNCs) have become a heavily researched material over the past several years. Researchers envision that this material can be used in many diverse applications such as electronic devices, non-toxic biological tags, optical devices such as LEDs, lasers or displays, thermoelectrics, and photovoltaic (PV) applications. For many of these proposed applications one needs to properly control the NC size and the surface chemistry via passivation. Current passivation techniques allow for the creation of highly efficient SiNC optical emitters, however the emission of these NCs are fixed in the red-NIR range. To resolve this issue several novel in-flight passivation techniques were investigated. A novel dual-plasma setup which allows for the in-flight passivation of SiNCs through a thermal or LPCVD based nitridation process was developed first. FTIR and XPS analysis were used to study the surface chemistry on of the nitride passivated NCs while TEM was used to investigate whether or not a "shell" was grown on the surface. PL measurements and thermal stability tests were performed on the nitride passivated NCs to gain a further understanding of the stability (in both air as well as other ambients) of the NCs and their surface chemistry. Tunable full color emission from SiNCs was developed for the dual-plasma reactor utilizing CF4 as both an etching and passivating source. F radicals generated in the etching plasma remove Si from the surface of the NC, while at the same time CF2 radicals lead to the formation of a fluorocarbon passivation layer on the NC surface. By controlling the parameters of the reactor (CF4 flow rate, power), the NC size and thus its color can be controlled. Red to green luminescence was observed from SiNCs and is believed to be due to the quantum confinement effect. The blue emission observed from the NCs is appears to be related to oxide related surface states. Despite the defects, high QY was observed from these CF4-etched NCs. The

  9. Electroluminescent device having improved light output

    DOEpatents

    Tyan; Yuan-Sheng; Preuss, Donald R.; Farruggia, Giuseppe; Kesel, Raymond A.; Cushman, Thomas R.

    2011-03-22

    An OLED device including a transparent substrate having a first surface and a second surface, a transparent electrode layer disposed over the first surface of the substrate, a short reduction layer disposed over the transparent electrode layer, an organic light-emitting element disposed over the short reduction layer and including at least one light-emitting layer and a charge injection layer disposed over the light emitting layer, a reflective electrode layer disposed over the charge injection layer and a light extraction enhancement structure disposed over the first or second surface of the substrate; wherein the short reduction layer is a transparent film having a through-thickness resistivity of 10.sup.-9 to 10.sup.2 ohm-cm.sup.2; wherein the reflective electrode layer includes Ag or Ag alloy containing more than 80% of Ag; and the total device size is larger than 10 times the substrate thickness.

  10. Optical properties of inorganic electroluminescent devices with nanostripe electrodes

    NASA Astrophysics Data System (ADS)

    Nonaka, Toshihiro; Yamamoto, Shin-ichi

    2016-03-01

    In this paper, we report on the luminescence (emission) characteristics of a laminated dispersion-type inorganic electroluminescent (EL) device with a nanostripe electrode made of thin Al film, instead of a conventional indium-tin oxide (ITO) transparent electrode, on the emission side of the device. The transmittance of the Al nanostripe electrode, with 60-nm line-and-space widths, was 45%. We compared an inorganic EL device positioned between two thin films of Al and the inorganic EL device with the Al nanostripe electrode using electric field simulations and actual experiments. We were able to apply the same electric field intensity to the phosphor layer in the conventional structure and to the new structure. Therefore, with an Al nanostripe electrode on one side of the EL device, it is possible to fabricate an ITO-free display.

  11. Ab initio study of phosphorescent emitters based on rare-earth complexes with organic ligands for organic electroluminescent devices.

    PubMed

    Freidzon, Alexandra Ya; Scherbinin, Andrei V; Bagaturyants, Alexander A; Alfimov, Michael V

    2011-05-12

    An ab initio approach is developed for calculation of low-lying excited states in Ln(3+) complexes with organic ligands. The energies of the ground and excited states are calculated using the XMCQDPT2/CASSCF approximation; the 4f electrons of the Ln(3+) ion are included in the core, and the effects of the core electrons are described by scalar quasirelativistic 4f-in-core pseudopotentials. The geometries of the complexes in the ground and triplet excited states are fully optimized at the CASSCF level, and the resulting excited states have been found to be localized on one of the ligands. The efficiency of ligand-to-lanthanide energy transfer is assessed based on the relative energies of the triplet excited states localized on the organic ligands with respect to the receiving and emitting levels of the Ln(3+) ion. It is shown that ligand relaxation in the excited state should be properly taken into account in order to adequately describe energy transfer in the complexes. It is demonstrated that the efficiency of antenna ligands for lanthanide complexes used as phosphorescent emitters in organic light-emitting devices can be reasonably predicted using the procedure suggested in this work. Hence, the best antenna ligands can be selected in silico based on theoretical calculations of ligand-localized excited energy levels.

  12. White electroluminescence of n-ZnO:Al/p-diamond heterostructure devices

    NASA Astrophysics Data System (ADS)

    Yang, Can; Wang, Xiao-Ping; Wang, Li-Jun; Pan, Xiu-Fang; Li, Song-Kun; Jing, Long-Wei

    2013-08-01

    An n-ZnO:Al/p-boron-doped diamond heterostructure electroluminescent device is produced, and a rectifying behavior can be observed. The electroluminescence spectrum at room temperature exhibits two visible bands centred at 450 nm-485 nm (blue emission) and 570 nm-640 nm (yellow emission). Light emission with a luminance of 15 cd/m2 is observed from the electroluminescent device at a forward applied voltage of 85 V, which is distinguished from white light by the naked eye.

  13. Theoretical and material studies of thin-film electroluminescent devices

    NASA Technical Reports Server (NTRS)

    Summers, C. J.

    1989-01-01

    Thin-film electroluminescent (TFEL) devices are studied for a possible means of achieving a high resolution, light weight, compact video display panel for computer terminals or television screens. The performance of TFEL devices depends upon the probability of an electron impact exciting a luminescent center which in turn depends upon the density of centers present in the semiconductor layer, the possibility of an electron achieving the impact excitation threshold energy, and the collision cross section itself. Efficiency of such a device is presently very poor. It can best be improved by increasing the number of hot electrons capable of impact exciting a center. Hot electron distributions and a method for increasing the efficiency and brightness of TFEL devices (with the additional advantage of low voltage direct current operation) are investigated.

  14. Mechanically flexible organic electroluminescent device with directional light emission

    DOEpatents

    Duggal, Anil Raj; Shiang, Joseph John; Schaepkens, Marc

    2005-05-10

    A mechanically flexible and environmentally stable organic electroluminescent ("EL") device with directional light emission comprises an organic EL member disposed on a flexible substrate, a surface of which is coated with a multilayer barrier coating which includes at least one sublayer of a substantially transparent organic polymer and at least one sublayer of a substantially transparent inorganic material. The device includes a reflective metal layer disposed on the organic EL member opposite to the substrate. The reflective metal layer provides an increased external quantum efficiency of the device. The reflective metal layer and the multilayer barrier coating form a seal around the organic EL member to reduce the degradation of the device due to environmental elements.

  15. Red, green, blue and white organic electroluminescent devices

    NASA Astrophysics Data System (ADS)

    Tsou, Chuan-Cheng; Lu, Huei-Tzong; Yokoyama, Meiso

    2005-06-01

    Full-color capability is an essential feature in organic electroluminescent (OEL) devices for flat panel display. This work presents novel designs for red, green, blue and white OEL devices. Indium tin oxide (ITO) was used as a glass substrate and N, N'-bis-(1-naphthyl)- N, N'-diphenyl-1,1-biphenyl-4-4'-diamine (NPB) as a hole transport layer (HTL). Bathocuproine (BCP) was used as a hole-blocking layer (HBL), DCM2, as a red fluorescent dye, was doped into the BCP layer. Tris-(8-hydroxy-quinoline) aluminum (Alq 3) was used in the electron transport layer (ETL), and aluminum (Al) was used as a cathode in OEL devices with the configuration ITO/NPB (30 nm)/BCP:DCM2 ( x%, 30 nm)/Alq 3 (40 nm)/Al. A green OEL device is obtained by employing this structure without a BCP:DCM2 ( x %) layer; a blue OEL device is obtained by using a BCP layer without the DCM2 dopant. The red OEL device is obtained by doping 10% DCM2 in the BCP layer. The white OEL device is produced by doping 1% DCM2 in the BCP layer. The CIE x and y coordinates of the white OEL device are 0.32 and 0.32, respectively.

  16. A novel electroluminescent device based on a reduced graphene oxide wrapped phosphor (ZnS:Cu,Al) and hexagonal-boron nitride for high-performance luminescence.

    PubMed

    Gupta, Bipin Kumar; Singh, Satbir; Kedawat, Garima; Kanika; Kumar, Pawan; Gangwar, Amit Kumar; Narayanan, Tharangattu N; Marti, Angel A; Vajtai, Robert; Ajayan, P M

    2017-04-06

    Reduced graphene oxide (rGO) has recently emerged as a very promising family of exotic carbon material with augmented performance in electronic and optoelectronic devices. Herein, we report an efficient and novel inorganic electroluminescent device geometry, where a new phosphor composite, reduced graphene oxide wrapped ZnS:Cu,Al, acts as an active emitting layer and an exfoliated hexagonal boron nitride (h-BN) as a dielectric layer. The roles of rGO in the active layer as a conductive support and local electric field enhancing agent are attributed to its wrinkles being unraveled compared with other carbon exotic nano-forms such as carbon nanotubes, graphite, charcoal and activated carbon, which significantly improves the brightness of the device (∼50 cd m(-2) for 0.50 wt% rGO/ZnS:Cu,Al at 10 kHz and 110 V with an external quantum efficiency of ∼6.3% ± 0.1% and current efficiency of ∼0.81 ± 0.09 cd A(-1)). This new and facile strategy to construct the luminescent devices could be a paradigm shift towards cost effective, highly stable in air (for several days) and energy efficient next generation display devices.

  17. Highly Efficient, Color-Reproducible Full-Color Electroluminescent Devices Based on Red/Green/Blue Quantum Dot-Mixed Multilayer.

    PubMed

    Lee, Ki-Heon; Han, Chang-Yeol; Kang, Hee-Don; Ko, Heejoo; Lee, Changho; Lee, Jonghyuk; Myoung, NoSoung; Yim, Sang-Youp; Yang, Heesun

    2015-11-24

    Over the past few years the performance of colloidal quantum dot-light-emitting diode (QLED) has been progressively improved. However, most of QLED work has been fulfilled in the form of monochromatic device, while full-color-enabling white QLED still remains nearly unexplored. Using red, green, and blue quantum dots (QDs), herein, we fabricate bichromatic and trichromatic QLEDs through sequential solution-processed deposition of poly(9-vinlycarbazole) (PVK) hole transport layer, two or three types of QDs-mixed multilayer, and ZnO nanoparticle electron transport layer. The relative electroluminescent (EL) spectral ratios of constituent QDs in the above multicolored devices are found to inevitably vary with applied bias, leading to the common observation of an increasing contribution of a higher-band gap QD EL over low-band gap one at a higher voltage. The white EL from a trichromatic device is resolved into its primary colors through combining with color filters, producing an exceptional color gamut of 126% relative to National Television Systems Committee (NTSC) color space that a state-of-the-art full-color organic LED counterpart cannot attain. Our trichromatic white QLED also displays the record-high EL performance such as the peak values of 23,352 cd/m(2) in luminance, 21.8 cd/A in current efficiency, and 10.9% in external quantum efficiency.

  18. Investigation of thioglycerol stabilized ZnS quantum dots in electroluminescent device performance

    NASA Astrophysics Data System (ADS)

    Ethiraj, Anita Sagadevan; Rhen, Dani; Lee, D. H.; Kang, Dae Joon; Kulkarni, S. K.

    2016-05-01

    The present work is focused on the investigation of thioglycerol (TG) stabilized Zinc Sulfide Quantum dots (ZnS QDs) in the hybrid electroluminescence (EL) device. Optical absorption spectroscopy clearly indicates the formation of narrow size distributed ZnS in the quantum confinement regime. X-ray Diffraction (XRD), Photoluminescence (PL), Energy Dispersive X-ray Spectroscopy (EDS) data supports the same. The hybrid EL device with structure of ITO (indium tin oxide)//PEDOT:PSS ((poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate)//HTL (α NPD- N,N'-diphenyl-N,N'-bis(1-naphthyl)-(1,1'-phenyl)-4,4'-diamine// PVK:ZnS QDs//ETL(PBD- 2-tert-butylphenyl- 5-biphenyl-1,3,4-oxadiazole)//LiF:Al (Device 1) was fabricated. Reference device without the ZnS QDs were also prepared (Device 2). The results show that the ZnS QDs based device exhibited bright electroluminescence emission of 24 cd/m2 at a driving voltage of 16 Volts under the forward bias conditions as compared to the reference device without the ZnS QDs, which showed 6 cd/m2 at ˜22 Volts.

  19. Heck coupling of haloaromatics with octavinylsilsesquioxane: solution processable nanocomposites for application in electroluminescent devices.

    PubMed

    Sellinger, Alan; Tamaki, Ryo; Laine, Richard M; Ueno, Kazunori; Tanabe, Hiroshi; Williams, Evan; Jabbour, Ghassan E

    2005-08-07

    A new solution processable nanocomposite material has been prepared via the Heck coupling of octavinylsilsesquioxane with a selected bromoaromatic hole transport compound. Resultant electroluminescent devices show an 18% improvement in external quantum efficiencies over their small molecule analogues.

  20. Electroluminescence of carbon ‘quantum' dots - From materials to devices

    NASA Astrophysics Data System (ADS)

    Veca, L. Monica; Diac, Andreea; Mihalache, Iuliana; Wang, Ping; LeCroy, Gregory E.; Pavelescu, Emil Mihai; Gavrila, Raluca; Vasile, Eugeniu; Terec, Anamaria; Sun, Ya-Ping

    2014-10-01

    Carbon ‘quantum' dots or carbon dots have emerged as a new class of luminescent nanomaterials. While photoluminescence properties of carbon dots had targeted optical imaging and related usage, their unique excited state redox processes responsible for the luminescence emissions may find potentially significant optoelectronic applications. In this regard, we investigated the electroluminescence properties of the carbon dots integrated into multilayer light emitting diode devices. The devices emitted white light with a slight blue color, visible to naked eyes, thus validating the expectation that carbon dots may potentially serve as a new platform for electroluminescent nanomaterials.

  1. Device Optimization and Transient Electroluminescence Studies of Organic light Emitting Devices

    SciTech Connect

    Lijuan Zou

    2003-08-05

    Organic light emitting devices (OLEDs) are among the most promising for flat panel display technologies. They are light, bright, flexible, and cost effective. And while they are emerging in commercial product, their low power efficiency and long-term degradation are still challenging. The aim of this work was to investigate their device physics and improve their performance. Violet and blue OLEDs were studied. The devices were prepared by thermal vapor deposition in high vacuum. The combinatorial method was employed in device preparation. Both continuous wave and transient electroluminescence (EL) were studied. A new efficient and intense UV-violet light emitting device was developed. At a current density of 10 mA/cm{sup 2}, the optimal radiance R could reach 0.38 mW/cm{sup 2}, and the quantum efficiency was 1.25%. using the delayed EL technique, electron mobilities in DPVBi and CBP were determined to be {approx} 10{sup -5} cm{sup 2}/Vs and {approx} 10{sup -4} cm{sup 2}/Vs, respectively. Overshoot effects in the transient El of blue light emitting devices were also observed and studied. This effect was attributed to the charge accumulation at the organic/organic and organic/cathode interfaces.

  2. Guest concentration, bias current, and temperature-dependent sign inversion of magneto-electroluminescence in thermally activated delayed fluorescence devices

    NASA Astrophysics Data System (ADS)

    Deng, Junquan; Jia, Weiyao; Chen, Yingbing; Liu, Dongyu; Hu, Yeqian; Xiong, Zuhong

    2017-03-01

    Non-emissive triplet excited states in devices that undergo thermally activated delayed fluorescence (TADF) can be up-converted to singlet excited states via reverse intersystem crossing (RISC), which leads to an enhanced electroluminescence efficiency. Exciton-based fluorescence devices always exhibit a positive magneto-electroluminescence (MEL) because intersystem crossing (ISC) can be suppressed effectively by an external magnetic field. Conversely, TADF devices should exhibit a negative MEL because RISC is suppressed by the external magnetic field. Intriguingly, we observed a positive MEL in TADF devices. Moreover, the sign of the MEL was either positive or negative, and depended on experimental conditions, including doping concentration, current density and temperature. The MEL observed from our TADF devices demonstrated that ISC in the host material and RISC in the guest material coexisted. These competing processes were affected by the experimental conditions, which led to the sign change of the MEL. This work gives important insight into the energy transfer processes and the evolution of excited states in TADF devices.

  3. Guest concentration, bias current, and temperature-dependent sign inversion of magneto-electroluminescence in thermally activated delayed fluorescence devices

    PubMed Central

    Deng, Junquan; Jia, Weiyao; Chen, Yingbing; Liu, Dongyu; Hu, Yeqian; Xiong, Zuhong

    2017-01-01

    Non-emissive triplet excited states in devices that undergo thermally activated delayed fluorescence (TADF) can be up-converted to singlet excited states via reverse intersystem crossing (RISC), which leads to an enhanced electroluminescence efficiency. Exciton-based fluorescence devices always exhibit a positive magneto-electroluminescence (MEL) because intersystem crossing (ISC) can be suppressed effectively by an external magnetic field. Conversely, TADF devices should exhibit a negative MEL because RISC is suppressed by the external magnetic field. Intriguingly, we observed a positive MEL in TADF devices. Moreover, the sign of the MEL was either positive or negative, and depended on experimental conditions, including doping concentration, current density and temperature. The MEL observed from our TADF devices demonstrated that ISC in the host material and RISC in the guest material coexisted. These competing processes were affected by the experimental conditions, which led to the sign change of the MEL. This work gives important insight into the energy transfer processes and the evolution of excited states in TADF devices. PMID:28295056

  4. Modeling of electroluminescence in SrS:Ce ACTFEL display devices

    NASA Astrophysics Data System (ADS)

    Dhillon, Tarlochan Singh

    The main objective of this study was to model electroluminescence behavior of ACTFEL display devices. Qualitative comparison of the predicted results with measurable characteristics is given. It is intended to explain certain unusual behavior that other models cannot explain fully. In particular, aspects of leading and trailing edge luminance peaks, oscillations in luminance, luminance peaks due to denting in applied voltage and multiple interfacial states are analyzed. Also, optimum concentration of activators has been analytically modeled for any phosphor to get maximum light output without causing appreciable quenching. Maximum light output for ZnS:Mn yellow devices is at about 2% Mn by weight. The beginning trailing edge peak (BTE) in SrS:Ce devices can be explained based on capture of electrons by ionized activators from the bulk traps due to their proximity. Oscillations in luminance are modeled due to distinct, widely separated and deep interfacial energy states when interface of two materials is rough. It has been observed that leading edge peak and luminance peak due to denting at leading edge are intercoupled and are partially created due to impact excitation and partially due to capture of electrons by ionized activators. Luminance vs. time graph of two interfacial energy states does not match very well with the experimental results. Luminance vs. time graph for multiple energy states matches better with experimental results.

  5. Organic electroluminescent devices and method for improving energy efficiency and optical stability thereof

    DOEpatents

    Heller, Christian Maria

    2004-04-27

    An organic electroluminescent device ("OELD") has a controllable brightness, an improved energy efficiency, and stable optical output at low brightness. The OELD is activated with a series of voltage pulses, each of which has a maximum voltage value that corresponds to the maximum power efficiency when the OELD is activated. The frequency of the pulses, or the duty cycle, or both are chosen to provide the desired average brightness.

  6. Theoretical and material studies on thin-film electroluminescent devices

    NASA Technical Reports Server (NTRS)

    Summers, C. J.; Brennan, K. F.

    1986-01-01

    A theoretical study of resonant tunneling in multilayered heterostructures is presented based on an exact solution of the Schroedinger equation under the application of a constant electric field. By use of the transfer matrix approach, the transmissivity of the structure is determined as a function of the incident electron energy. The approach presented is easily extended to many layer structures where it is more accurate than other existing transfer matrix or WKB models. The transmission resonances are compared to the bound state energies calculated for a finite square well under bias using either an asymmetric square well model or the exact solution of an infinite square well under the application of an electric field. The results show good agreement with other existing models as well as with the bound state energies. The calculations were then applied to a new superlattice structure, the variablly spaced superlattice energy filter, (VSSEP) which is designed such that under bias the spatial quantization levels fully align. Based on these calculations, a new class of resonant tunneling superlattice devices can be designed.

  7. Electroluminescent devices using a layered organic-inorganic perovskite structure as emitter

    NASA Astrophysics Data System (ADS)

    Coelle, Michael; Bruetting, Wolfgang; Schwoerer, Markus; Yahiro, Masayuki; Tsutsui, Tetsuo

    2001-02-01

    Self-organizing layered perovskite compounds like (formula available in paper) naturally form a dielectric quantum-well structure in which semiconducting PbI4 layers and organic (C6H5C2H4NH3) layers are alternately piled up. Due to their low- dimensional semiconductor nature they exhibit a strong absorption and sharp photoluminescence from the exciton band. In electroluminescent devices pure green emission peaking at 520 nm with a very narrow half-width of about 10 nm has been reported. As the organic-inorganic layered structure has promising properties for EL-devices, we investigated two- and three layer structures using this perovskite as emitter material in combination with additional hole and electron injection layers. To get more insight into electrical properties and electroluminescence- mechanisms of this material, temperature dependent current- voltage-luminance characteristics have been measured, showing an increasing onset-voltage for current flow from 2.6 V at room temperature to about 8.8 V at 80 K. Electroluminescence is detected at temperatures below 150 K with onset voltages of about 13 V. At liquid nitrogen temperature efficiencies of (formula available in paper) are obtained.

  8. Fluorene-fluorenone copolymer: Stable and efficient yellow-emitting material for electroluminescent devices

    NASA Astrophysics Data System (ADS)

    Panozzo, S.; Vial, J.-C.; Kervella, Y.; Stéphan, O.

    2002-10-01

    We have synthesized and characterized a new fluorene copolymer exhibiting bright yellow luminescence. In order to ensure a complete π-stacking of the active layer, a 9-fluorenone monomeric unit (FOne) has been used as comonomer in conjunction with the more classical 9,9-di-n-nonylfluorene unit. As expected with fluorene-based materials, when excited at 370 nm, the corresponding dilute copolymer solution photoluminescence spectra exhibit a main peak centered at 450 nm in the blue part of the visible spectrum. However, in the solid state, immediate structural reorganization of the layer occurs, leading to a red-shifted emission (bright yellow emission) centered at 550 nm. The origin of the emitted light has been attributed to excimers and/or aggregates based on short FOne segments and involves mainly exciton transfer between nonaggregated fluorene segments and aggregated ones. It is noteworthy that organic light-emitting devices based on these new materials exhibit no spectral evolution upon device operation. However, although stacking leads generally to a detrimental quenching of the luminescence in the solid state, as for regular poly(alkyl-fluorene), the luminescence efficiency of the fluorene-fluorenone copolymer remains suitable for device preparation. High material stability is attributed to an efficient and fast structural reorganization of the active layer, triggered by the small proportion of fluorenone. High electroluminescence efficiency, when compared to aggregated regular poly(alkyl-fluorene), results from an improved electron injection, a better carrier transport, and the conjunction of an efficient energy transfer from fluorene segments to excimers and/or aggregates with the implication of spin triplet, which is often lacking when using regular semiconducting polymers.

  9. Determining the Origin of Half-bandgap-voltage Electroluminescence in Bifunctional Rubrene/C60 Devices

    NASA Astrophysics Data System (ADS)

    Chen, Qiusong; Jia, Weiyao; Chen, Lixiang; Yuan, De; Zou, Yue; Xiong, Zuhong

    2016-05-01

    Lowering the driving voltage of organic light-emitting diodes (OLEDs) is an important approach to reduce their energy consumption. We have fabricated a series of bifunctional devices (OLEDs and photovoltaics) using rubrene and fullerene (C60) as the active layer, in which the electroluminescence threshold voltage(~1.1 V) was half the value of the bandgap of rubrene. Magneto-electroluminescence (MEL) response of planner heterojunction diodes exhibited a small increase in response to a low magnetic field strength (<20 mT) however, a very large decay was observed at a high magnetic field strength (>20 mT). When a hole-transport layer with a low mobility was included in these devices, the MEL response reversed in shape, and simultaneously, the EL threshold voltage became larger than the bandgap voltage. When bulk heterojunction device was examined, the amplitude of MEL curves presented an anomalous voltage-dependence. Following an analysis of the MEL responses of these devices, we proposed that the EL of half-bandgap-voltage device originated from bimolecular triplet-triplet annihilation in the rubrene film, rather than from singlet excitons that formed via an interface auger recombination. This work provides critical insight into the mechanisms of OLED emission and will help advance the applications of bifunctional devices.

  10. Observation of degradation processes of Al electrodes in organic electroluminescence devices by electroluminescence microscopy, atomic force microscopy, scanning electron microscopy, and Auger electron spectroscopy

    NASA Astrophysics Data System (ADS)

    Do, L. M.; Han, E. M.; Niidome, Y.; Fujihira, M.; Kanno, T.; Yoshida, S.; Maeda, A.; Ikushima, A. J.

    1994-11-01

    Degradation of top electrodes is one of the most important factors to determine the lifetimes of organic electroluminescence (EL) devices. An organic EL device (indium thin oxide (ITO/N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD)/tris(8-hydroxy-quinoline)aluminum (Al q(sub 3))/Al) was prepared and a morphological change of the Al top electrode was observed during and/or after applying voltage by atomic force microscopy and scanning electron microscopy (SEM). The change in the electrode surface, i.e., the increase in surface roughness was observed during the current flow. The degradation process started from faint dark core parts and propagated into disks with different rates depending on the magnitude of applied voltage. Degraded sites of the Al electrode, which were analyzed as aluminum oxide by Auger electron spectroscopy, protruded into the air on the organic layers. In SEM images of a life-end electrode, discontinuities due to crevasse formation in the organic layers sandwiched by the ITO base and the metal top electrodes were observed in many places. These results confirm that one of the most crucial factors of the degradation process was deformation of metal and organic layers due to heat, gas evolution, and oxidation caused by applied voltage.

  11. Highly efficient electroluminescence from a heterostructure device combined with emissive layered-perovskite and an electron-transporting organic compound

    NASA Astrophysics Data System (ADS)

    Hattori, Toshiaki; Taira, Takahiro; Era, Masanao; Tsutsui, Tetsuo; Saito, Shugu

    1996-05-01

    Two Pbl-based layer perovskite compounds, which possess cyclohexenylethylamine or phenylbutylamine as an organic ammonium layer, were newly found to exhibit efficient exciton emission due to their self-organized quantum well structure where a lead halide semiconducting layer and an organic ammonium dielectric layer are alternately piled up. We prepared heterostructure electroluminescent devices using the combination of the emissive layered perovskite and an electron-transporting oxadiazole. When the heterostructure devices were driven at 110 K, greenish emission, which corresponded well to the exciton emission, was observed. In the device using the perovskite with an organic layer of cyclohexenythylamine, a high luminance exceeding 4000 cd m -2 and high external EL quantum efficiency of 2.8% were attained at a current density of 50 mA cm -2 at an applied voltage of 24 V.

  12. Electroluminescence efficiencies of erbium in silicon-based hosts

    SciTech Connect

    Cueff, Sébastien E-mail: christophe.labbe@ensicaen.fr; Manel Ramírez, Joan; Berencén, Yonder; Garrido, Blas; Kurvits, Jonathan A.; Zia, Rashid; Rizk, Richard; Labbé, Christophe E-mail: christophe.labbe@ensicaen.fr

    2013-11-04

    We report on room-temperature 1.5 μm electroluminescence from trivalent erbium (Er{sup 3+}) ions embedded in three different CMOS-compatible silicon-based hosts: SiO{sub 2}, Si{sub 3}N{sub 4}, and SiN{sub x}. We show that although the insertion of either nitrogen or excess silicon helps enhance electrical conduction and reduce the onset voltage for electroluminescence, it drastically decreases the external quantum efficiency of Er{sup 3+} ions from 2% in SiO{sub 2} to 0.001% and 0.0004% in SiN{sub x} and Si{sub 3}N{sub 4}, respectively. Furthermore, we present strong evidence that hot carrier injection is significantly more efficient than defect-assisted conduction for the electrical excitation of Er{sup 3+} ions. These results suggest strategies to optimize the engineering of on-chip electrically excited silicon-based nanophotonic light sources.

  13. Solution-Processable Silicon Phthalocyanines in Electroluminescent and Photovoltaic Devices.

    PubMed

    Zysman-Colman, Eli; Ghosh, Sanjay S; Xie, Guohua; Varghese, Shinto; Chowdhury, Mithun; Sharma, Nidhi; Cordes, David B; Slawin, Alexandra M Z; Samuel, Ifor D W

    2016-04-13

    Phthalocyanines and their main group and metal complexes are important classes of organic semiconductor materials but are usually highly insoluble and so frequently need to be processed by vacuum deposition in devices. We report two highly soluble silicon phthalocyanine (SiPc) diester compounds and demonstrate their potential as organic semiconductor materials. Near-infrared (λ(EL) = 698-709 nm) solution-processed organic light-emitting diodes (OLEDs) were fabricated and exhibited external quantum efficiencies (EQEs) of up to 1.4%. Binary bulk heterojunction solar cells employing P3HT or PTB7 as the donor and the SiPc as the acceptor provided power conversion efficiencies (PCE) of up to 2.7% under simulated solar illumination. Our results show that soluble SiPcs are promising materials for organic electronics.

  14. Solution-Processable Silicon Phthalocyanines in Electroluminescent and Photovoltaic Devices

    PubMed Central

    2016-01-01

    Phthalocyanines and their main group and metal complexes are important classes of organic semiconductor materials but are usually highly insoluble and so frequently need to be processed by vacuum deposition in devices. We report two highly soluble silicon phthalocyanine (SiPc) diester compounds and demonstrate their potential as organic semiconductor materials. Near-infrared (λEL = 698–709 nm) solution-processed organic light-emitting diodes (OLEDs) were fabricated and exhibited external quantum efficiencies (EQEs) of up to 1.4%. Binary bulk heterojunction solar cells employing P3HT or PTB7 as the donor and the SiPc as the acceptor provided power conversion efficiencies (PCE) of up to 2.7% under simulated solar illumination. Our results show that soluble SiPcs are promising materials for organic electronics. PMID:26990151

  15. Exciplex electroluminescence and photoluminescence spectra of the new organic materials based on zinc complexes of sulphanylamino-substituted ligands

    PubMed Central

    2012-01-01

    We have investigated the electroluminescence spectra of the electroluminescent devices based on the new zinc complexes of amino-substituted benzothiazoles and quinolines containing the C-N-M-N chains in their chelate cycles. The spectra exhibit strong exciplex bands in the green to yellow region 540 to 590 nm due to interaction of the excited states of zinc complexes and triaryl molecules of the hole-transporting layer. For some devices, the intrinsic luminescence band of 460 nm in the blue region is also observed along with the exciplex band giving rise to an almost white color of the device emission. The exciplex band can be eliminated if the material of the hole-transporting layer is not a triarylamine derivative. We have also found the exciplex emission in the photoluminescence spectra of the films containing blends of zinc complex and triphenylamine material. PMID:22471942

  16. [The role of BCP in electroluminescence of multilayer organic light-emitting devices].

    PubMed

    Deng, Zhao-Ru; Yang, Sheng-Yi; Lou, Zhi-Dong; Meng, Ling-Chuan

    2009-03-01

    As a hole-blocking layer, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) is usually used in blue and white light electroluminescent devices. The ability of blocking holes of BCP layer depends on its thickness, and basically holes can tunnel through thin BCP layer. In order to know the role of BCP layer in electroluminescence (EL) of multilayer organic light-emitting diodes (OLEDs), in the present paper, the authors designed a multilayer OLED ITO/NPB/BCP/Alq3 : DCJTB/Alq3/Al and investigated the influence of thickness of BCP on the EL spectra of multilayer OLEDs at different applied voltages. The experimental data show that thin BCP layer can block holes partially and tune the energy transfer between different emissive layers, and in this way, it is easy to obtain white emission, but its EL spectra will change with the applied voltages. The EL spectra of multilayer device will remain relatively stable when BCP layer is thick enough, and the holes can hardly tunnel through when the thickness of BCP layer is more than 15 nm. Furthermore, the stability of EL spectra of the multilayer OLED at different applied voltages was discussed.

  17. Electroluminescence of Giant Stretchability.

    PubMed

    Yang, Can Hui; Chen, Baohong; Zhou, Jinxiong; Chen, Yong Mei; Suo, Zhigang

    2016-06-01

    A new type of electroluminescent device achieves giant stretchability by integrating electronic and ionic components. The device uses phosphor powders as electroluminescent materials, and hydrogels as stretchable and transparent ionic conductors. Subject to cyclic voltage, the phosphor powders luminesce, but the ionic conductors do not electrolyze. The device produces constant luminance when stretched up to an area strain of 1500%.

  18. Electroluminescence mechanisms in organic light emitting devices employing a europium chelate doped in a wide energy gap bipolar conducting host

    NASA Astrophysics Data System (ADS)

    Adachi, Chihaya; Baldo, Marc A.; Forrest, Stephen R.

    2000-06-01

    The mechanism for energy transfer leading to electroluminescence (EL) of a lanthanide complex, Eu(TTA)3phen (TTA=thenoyltrifluoroacetone,phen=1,10-phenanthroline), doped into 4,4'-N,N'-dicarbazole-biphenyl (CBP) host is investigated. With the device structure of anode/hole transport layer/Eu(TTA)3phen(1%):CPB/electron transport layer/cathode, we achieve a maximum external EL quantum efficiency (η) of 1.4% at a current density of 0.4 mA/cm2. Saturated red Eu3+ emission based on 5Dx-7Fx transitions is centered at a wavelength of 612 nm with a full width at half maximum of 3 nm. From analysis of the electroluminescent and photoluminescent spectra, and the current density-voltage characteristics, we conclude that direct trapping of holes and electrons and subsequent formation of the excitons occurs on the dopant, leading to high quantum efficiencies at low current densities. With increasing current between 1 and 100 mA/cm2, however, a significant decrease of η along with an increase in CBP host emission is observed. We demonstrate that the decrease in η at high current densities can be explained by triplet-triplet annihilation.

  19. Light-emitting device with organic electroluminescent material and photoluminescent materials

    DOEpatents

    McNulty, Thomas Francis; Duggal, Anil Raj; Turner, Larry Gene; Shiang, Joseph John

    2005-06-07

    A light-emitting device comprises a light-emitting member, which comprises two electrodes and an organic electroluminescent material disposed between the electrodes, and at least one organic photoluminescent ("PL") material. The light-emitting member emits light having a first spectrum in response to a voltage applied across the two electrodes. The organic PL material absorbs a portion of the light emitted by the light-emitting member and emits light having second spectrum different than the first spectrum. The light-emitting device can include an inorganic PL material that absorbs another portion of the light emitted from the light-emitting member and emits light having a third spectrum different than both the first and the second spectra.

  20. The Effect of the Oxygen Plasma Treatment for ITO and ZnO Nanorods on the Electroluminescence of ZnO Nanorod/MEH-PPV Heterostructure Devices

    NASA Astrophysics Data System (ADS)

    Zhao, Su-Ling; Wang, Yong-Sheng; Gao, Song; Yang, Yi-Fan; Xu, Zheng

    2013-03-01

    Series devices of ITO/ZnO/ZnO nanorods/MEH-PPV/Al have been fabricated. ITO and ZnO nanorods of some devices are treated by O2 plasma. The electroluminescence of different devices is detected under different biases. UV electroluminescence of ZnO nanorods at 380nm is observed in all the devices. The intensity of 380nm increases when both ITO and ZnO nanorods are treated. The turn-on voltage of the treated device is lower than that of the non-treated device, and the EL power is enhanced. When the thickness of MEH-PPV is sufficiently thin, only 380 nm electroluminescence, besides a weak defect emission at 760 nm, is detected. The enhancement mechanism of the electroluminescence of the treated devices is discussed.

  1. Homogeneous Synthesis and Electroluminescence Device of Highly Luminescent CsPbBr3 Perovskite Nanocrystals.

    PubMed

    Wei, Song; Yang, Yanchun; Kang, Xiaojiao; Wang, Lan; Huang, Lijian; Pan, Daocheng

    2017-03-06

    Highly luminescent CsPbBr3 perovskite nanocrystals (PNCs) are homogeneously synthesized by mixing toluene solutions of PbBr2 and cesium oleate at room temperature in open air. We found that PbBr2 can be easily dissolved in nonpolar toluene in the presence of tetraoctylammonium bromide, which allows us to homogeneously prepare CsPbBr3 perovskite quantum dots and prevents the use of harmful polar organic solvents, such as N,N-dimethylformamide, dimethyl sulfoxide, and N-methyl-2-pyrrolidone. Additionally, this method can be extended to synthesize highly luminescent CH3NH3PbBr3 perovskite quantum dots. An electroluminescence device with a maximal luminance of 110 cd/m(2) has been fabricated by using high-quality CsPbBr3 PNCs as the emitting layer.

  2. The pure white light emission from three-layer electroluminescent device

    NASA Astrophysics Data System (ADS)

    Chen, Zhijian; Ogino, Kenji; Miyata, Seizo; Lu, Youmei; Watanabe, Toshiyuki

    2002-04-01

    We have synthesized a red fluorescent dye of 4-dicyanomethylene- 2,6-di-(4-dimethylaminobenzaldehyde)-γ-pyran (DCDM), and fabricated electroluminescent devices of glass/indium-tin oxide/N,N'-diphenyl-N, N'-(3-methyphenyl)-1,1'-biphenyl-4,4'-diamine (TPD), doped with different concentration of DCDM and 2.5wt.% of 9-cyanoanthracene (CNA), 50 nm/2,9-dimethy-4,7-diphenyl-1,10-phenanthroline (BCP), 40 nm/tris-(8-hydroxyquiniline) aluminium (Alq3), 5 nm/Ag : Mg, 500 nm/Ag cap, 100 nm. The Commission International de 1' Eclairage (CIE) colour coordinates traverses along a straight line in the CIE chromaticity diagram with the concentration of DCDM. By adjusting the concentration of the fluorescent dyes, the pure white light emission was obtained at the CIE coordinates of x = 0.34 and y = 0.35.

  3. Self-Assembly of Rod-Coil Block Copolymers and Their Application in Electroluminescent Devices

    SciTech Connect

    Tao, Yuefei; Ma, Biwu; Segalman, Rachel A.

    2008-11-18

    The formation of alternating electron transporting and hole transporting 15 nm lamellae within the active layer of an organic light-emitting diode (OLED) is demonstrated to improve device performance. A new multifunctional bipolar rod-coil block copolymer containing a poly(alkoxy phenylenevinylene) (PPV) rod-shaped block as the hole transporting and emitting material and a poly(vinyloxadiazole) coil-shaped electron transporting block is synthesized. This new block copolymer is the active material of a self-assembling multicomponent electroluminescent device that can be deposited in a single step. In the thin film, grazing incidence X-ray scattering and transmission electron microscopy demonstrate that the layers form grains which are oriented bimodally: parallel and perpendicular from the anode. In this mixed orientation, the device demonstrates better performance than those with either pure PPV or a blend of the two analogous homopolymers as the active materials, i.e., higher external quantum efficiency (EQE) and brightness. This improved device performance is mainly attributed to the bipolar functionality and microphase separation of the block copolymer, which provide highly efficient hole and electron recombination at the nanodomain interfaces.

  4. Self-Assembly of Rod-Coil Block Copolymers And Their Application in Electroluminescent Devices

    SciTech Connect

    Tao, Y.; Ma, B.; Segalman, R.A.

    2009-05-26

    The formation of alternating electron transporting and hole transporting 15 nm lamellae within the active layer of an organic light-emitting diode (OLED) is demonstrated to improve device performance. A new multifunctional bipolar rod-coil block copolymer containing a poly(alkoxy phenylenevinylene) (PPV) rod-shaped block as the hole transporting and emitting material and a poly(vinyloxadiazole) coil-shaped electron transporting block is synthesized. This new block copolymer is the active material of a self-assembling multicomponent electroluminescent device that can be deposited in a single step. In the thin film, grazing incidence X-ray scattering and transmission electron microscopy demonstrate that the layers form grains which are oriented bimodally: parallel and perpendicular from the anode. In this mixed orientation, the device demonstrates better performance than those with either pure PPV or a blend of the two analogous homopolymers as the active materials, i.e., higher external quantum efficiency (EQE) and brightness. This improved device performance is mainly attributed to the bipolar functionality and microphase separation of the block copolymer, which provide highly efficient hole and electron recombination at the nanodomain interfaces.

  5. Incorporation of electroluminescence and electrochemiluminescence in one organic light-emitting device

    NASA Astrophysics Data System (ADS)

    Zhen, Changgua; Chuai, Yutao; Lao, Chunfeng; Huang, Lan; Zou, Dechun; Lee, Do Nam; Kim, Byeong Hyo

    2005-08-01

    The incorporation of electroluminescence and electrochemiluminescence in one light-emitting device with the configuration of indium tin oxide (ITO)/[Ru(bpy)2(dimbpy)](PF6)2/Alq3(30nm)/NPB(45nm)/Ag(60nm) is investigated. When the ITO and Ag electrodes are negatively and positively biased respectively, the color of the emission changes from green to light yellow-white within 100 s. So there is only one recombination zone in the bulk of the Alq3 at the initial stage of the operation, followed by the formation of another recombination zone in the bulk of the [Ru(bpy)2(dimbpy)](PF6)2. This directly indicates the existence of unipolar injection (electron injection) process in the ruthenium complex layer. The external quantum efficiency of the device is 1.4% compared with 0.45% of the ITO /[Ru(bpy)2(dimbpy)](PF6)2/Ag device, improved by twofold. Furthermore, this hybrid device provides a feasible way to control the emission of a wide spectrum of colors including red, green, yellow, and white.

  6. Electroluminescence from metal-oxide-semiconductor devices with erbium-doped CeO{sub 2} films on silicon

    SciTech Connect

    Lv, Chunyan; Zhu, Chen; Wang, Canxing; Gao, Yuhan; Ma, Xiangyang Yang, Deren

    2015-04-06

    We report on erbium (Er)-related electroluminescence (EL) in the visible and near-infrared (NIR) from metal-oxide-semiconductor (MOS) devices with Er-doped CeO{sub 2} (CeO{sub 2}:Er) films on silicon. The onset voltage of such EL under either forward or reverse bias is smaller than 10 V. Moreover, the EL quenching can be avoidable for the CeO{sub 2}:Er-based MOS devices. Analysis on the current-voltage characteristic of the device indicates that the electron transportation at the EL-enabling voltages under either forward or reverse bias is dominated by trap-assisted tunneling mechanism. Namely, electrons in n{sup +}-Si/ITO can tunnel into the conduction band of CeO{sub 2} host via defect states at sufficiently high forward/reverse bias voltages. Then, a fraction of such electrons are accelerated by electric field to become hot electrons, which impact-excite the Er{sup 3+} ions, thus leading to characteristic emissions. It is believed that this work has laid the foundation for developing viable silicon-based emitters using CeO{sub 2}:Er films.

  7. Quantum-dot-based white lighting planar source through downconversion by blue electroluminescence.

    PubMed

    Lee, Ki-Heon; Kim, Jong-Hoon; Jang, Ho Seong; Do, Young Rag; Yang, Heesun

    2014-03-01

    We report the unprecedented fabrication of a planar white lighting quantum dot light-emitting diode (QD-LED) through integrating a CdZnS QD-based blue electroluminescence (EL) device with a free-standing polymethyl methacrylate (PMMA) composite film embedded with orange-emitting Cu-In-S (CIS) green-greenish yellow-emitting Cu-In-Ga-S (CIGS) QDs. The hybrid device successfully generates bicolored white emission that comprises blue EL and downconverted QD photoluminescence. The hybrid QD-LEDs loaded with the composite film embedded with one type of QDs exhibit a limited white spectral coverage, consequently producing low values (<65) in color rendering index (CRI). Thus, the QD-PMMA film consisting of a blend of green CIGS and orange CIS QD downconverters is applied for obtaining a higher-CRI white light through the spectral extension, resulting in a much improved CRI of 75-77. Various EL performances of the hybrid planar white device versus the reference blue QD-LED are also characterized in details.

  8. High performance organic integrated device with ultraviolet photodetective and electroluminescent properties consisting of a charge-transfer-featured naphthalimide derivative

    SciTech Connect

    Wang, Hanyu; Wang, Xu; Yu, Junsheng E-mail: jsyu@uestc.edu.cn; Zhou, Jie; Lu, Zhiyun E-mail: jsyu@uestc.edu.cn

    2014-08-11

    A high performance organic integrated device (OID) with ultraviolet photodetective and electroluminescent (EL) properties was fabricated by using a charge-transfer-featured naphthalimide derivative of 6-(3,5-bis-[9-(4-t-butylphenyl)-9H-carbazol-3-yl]-phenoxy)-2- (4-t-butylphenyl)-benzo[de]isoquinoline-1,3-dione (CzPhONI) as the active layer. The results showed that the OID had a high detectivity of 1.5 × 10{sup 11} Jones at −3 V under the UV-350 nm illumination with an intensity of 0.6 mW/cm{sup 2}, and yielded an exciplex EL light emission with a maximum brightness of 1437 cd/m{sup 2}. Based on the energy band diagram, both the charge transfer feature of CzPhONI and matched energy level alignment were responsible for the dual ultraviolet photodetective and EL functions of OID.

  9. Mechanism of hot electron electroluminescence in GaN-based transistors

    NASA Astrophysics Data System (ADS)

    Brazzini, Tommaso; Sun, Huarui; Sarti, Francesco; Pomeroy, James W.; Hodges, Chris; Gurioli, Massimo; Vinattieri, Anna; Uren, Michael J.; Kuball, Martin

    2016-11-01

    The nature of hot electron electroluminescence (EL) in AlGaN/GaN high electron mobility transistors is studied and attributed to Bremsstrahlung. The spectral distribution has been corrected, for the first time, for interference effects due to the multilayered device structure, and this was shown to be crucial for the correct interpretation of the data, avoiding artefacts in the spectrum and misinterpretation of the results. An analytical expression for the spectral distribution of emitted light is derived assuming Bremsstrahlung as the only origin and compared to the simplified exponential model for the high energy tail commonly used for electron temperature extraction: the electron temperature obtained results about 20% lower compared to the approximated exponential model. Comparison of EL intensity for devices from different wafers illustrated the dependence of EL intensity on the material quality. The polarization of electroluminescence also confirms Bremsstrahlung as the dominant origin of the light emitted, ruling out other possible main mechanisms.

  10. Electroluminescence of quantum-dash-based quantum cascade laser structures

    SciTech Connect

    Liverini, V.; Bismuto, A.; Nevou, L.; Beck, M.; Faist, J.

    2011-12-23

    We developed two mid-infrared quantum cascade structures based on InAs quantum dashes. The dashes were embedded either in AlInGaAs lattice-matched to InP or in tensile-strained AlInAs. The devices emit between 7 and 11 {mu}m and are a step forward in the development of quantum cascade lasers based on 3-D confined active regions.

  11. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: A New Conducting Polymer Electrode for Organic Electroluminescence Devices

    NASA Astrophysics Data System (ADS)

    Qu, Shu; Peng, Jing-Cu

    2008-08-01

    Conducting polymer polydimethylsiloxane (PDMS) is studied for the high performance electrode of organic electroluminescence devices. A method to prepare the electrode consisting of a SiC thin film and PDMS is investigated. By using ultra thin SiC films with different thicknesses, the organic electroluminescence devices are obtained in an ultra vacuum system with the model device PDMS/SiC/PPV/Alq3, where PPV is poly para-phenylene vinylene and Alq3 is tris(8-hydroxyquinoline) aluminium. The capacitance-voltage (C - V), capacitance-frequency (C - F), current-voltage (I - V), radiation intensity-voltage (R - V) and luminance efficiency-voltage (E - V) measurements are systematically studied to investigate the conductivity, Fermi alignment and devices properties in organic semiconductors. Scanning Kelvin probe measurement shows that the work function ofPDMS/SiC anode with a 2.5-nm SiC over layer can be increased by as much as 0.28 eV, compared to the conventional ITO anode. The result is attributed to the charge transfer effect and ohmic contacts at the interface.

  12. Electroluminescence emission patterns of organic light-emitting transistors based on crystallized fluorene-type polymers

    NASA Astrophysics Data System (ADS)

    Kajii, Hirotake; Ohtomo, Takahiro; Ohmori, Yutaka

    2017-03-01

    The electroluminescence (EL) emission patterns of organic light-emitting transistors (OLETs) based on crystallized poly(9,9-dioctylfluorene) (F8), poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) and poly(9,9-dioctylfluorene-co-dithienyl-benzothiadiazole) (F8TBT) films are investigated. For the single-layer devices and the mixed-layer device without an F8/F8BT interface, only line-shaped EL emission patterns are observed between source/drain (S/D) electrodes. For an F8BT (F8TBT)/F8 heterostructure device, a localized electric field is generated by the positive (negative) charges of the accumulated holes (electrons) in the F8 upper layer, which allow the injection of electrons (holes) in the F8BT (F8TBT) lower layer at a lower (higher) gate voltage. The F8/F8BT device exhibits unique light emission properties with a surface like EL emission pattern between S/D electrodes at a lower gate voltage. The interfacial structure is important for forming field-effect transistor channels along different organic layers to obtain a surface like emission between S/D electrodes. For the F8TBT/F8 OLET, the hole carrier transport mainly occurs at the F8TBT lower layer, and line-shaped EL emission patterns are observed in the vicinity of the source electrode upon varying the gate voltages owing to the worse carrier balance between the F8TBT lower layer and the F8 upper layer.

  13. Intense green-yellow electroluminescence from Tb+-implanted silicon-rich silicon nitride/oxide light emitting devices

    NASA Astrophysics Data System (ADS)

    Berencén, Y.; Wutzler, R.; Rebohle, L.; Hiller, D.; Ramírez, J. M.; Rodríguez, J. A.; Skorupa, W.; Garrido, B.

    2013-09-01

    High optical power density of 0.5 mW/cm2, external quantum efficiency of 0.1%, and population inversion of 7% are reported from Tb+-implanted silicon-rich silicon nitride/oxide light emitting devices. Electrical and electroluminescence mechanisms in these devices were investigated. The excitation cross section for the 543 nm Tb3+ emission was estimated under electrical pumping, resulting in a value of 8.2 × 10-14 cm2, which is one order of magnitude larger than one reported for Tb3+:SiO2 light emitting devices. These results demonstrate the potentiality of Tb+-implanted silicon nitride material for the development of integrated light sources compatible with Si technology.

  14. Electroluminescence from a diamond device with ion-beam-micromachined buried graphitic electrodes

    NASA Astrophysics Data System (ADS)

    Forneris, J.; Battiato, A.; Gatto Monticone, D.; Picollo, F.; Amato, G.; Boarino, L.; Brida, G.; Degiovanni, I. P.; Enrico, E.; Genovese, M.; Moreva, E.; Traina, P.; Verona, C.; Verona Rinati, G.; Olivero, P.

    2015-04-01

    Focused MeV ion microbeams are suitable tools for the direct writing of conductive graphitic channels buried in an insulating diamond bulk, as demonstrated in previous works with the fabrication of multi-electrode ionizing radiation detectors and cellular biosensors. In this work we investigate the suitability of the fabrication method for the electrical excitation of color centers in diamond. Differently from photoluminescence, electroluminescence requires an electrical current flowing through the diamond sub-gap states for the excitation of the color centers. With this purpose, buried graphitic electrodes with a spacing of 10 μm were fabricated in the bulk of a detector-grade CVD single-crystal diamond sample using a scanning 1.8 MeV He+ micro-beam. The current flowing in the gap region between the electrodes upon the application of a 450 V bias voltage was exploited as the excitation pump for the electroluminescence of different types of color centers localized in the above-mentioned gap. The bright light emission was spatially mapped using a confocal optical microscopy setup. The spectral analysis of electroluminescence revealed the emission from neutrally-charged nitrogen-vacancy centers (NV0, λZPL = 575 nm), as well as from cluster crystal dislocations (A-band, λ = 400-500 nm). Moreover, an electroluminescence signal with appealing spectral features (sharp emission at room temperature, low phonon sidebands) from He-related defects was detected (λZPL = 536.3 nm, λZPL = 560.5 nm); a low and broad peak around λ = 740 nm was also observed and tentatively ascribed to Si-V or GR1 centers. These results pose interesting future perspectives for the fabrication of electrically-stimulated single-photon emitters in diamond for applications in quantum optics and quantum cryptography.

  15. Synthesis, photophysical and electroluminescent properties of novel iridium (III) complexes based on 5-methyl-2-phenylbenzo[d]oxazole derivatives

    NASA Astrophysics Data System (ADS)

    Li, Xiao; Chi, Hai-Jun; Dong, Yan; Xiao, Guo-Yong; Lei, Peng; Zhang, Dong-Yu; Cui, Zheng

    2013-12-01

    A new series of phosphorescent iridium (III) complexes based on 5-methyl-2-phenylbenzo[d]oxazole derivatives as main ligands, i.e. bis(5-methyl-2- phenylbenzo[d]oxazole-N,C2‧)iridium(acetylacetonate) [(mpbo)2Ir(acac)], bis(2-(4-fluorophenyl)-5-methylbenzo[d]oxazole-N,C2‧)iridium(acetylacetonate) [(fmbo)2Ir(acac)] and bis(5-methyl-2-p-tolylbenzo[d]oxazole-N,C2‧) iridium(acetylacetonate) [(mtbo)2Ir(acac)], were synthesized for organic light-emitting diodes (OLEDs), and their photophysical, electroluminescent properties were investigated. All complexes have high thermal stability and emit intense phosphorescence from green to yellow at room temperature with high quantum efficiencies and relatively short lifetimes. The OLED based on (fmbo)2Ir(acac) as dopant emitter showed very high luminance of 26,004 cd m-2 and luminance efficiency of 18.5 cd A-1. The evidences indicated that this series of iridium (III) complexes were potential candidates for applications in organic electroluminescent devices.

  16. Near-field measurement of ZnS:Mn nanocrystal and bulk thin-film electroluminescent devices.

    PubMed

    Grmela, L; Macku, R; Tomanek, P

    2008-02-01

    A near-field study of the electro-optical phenomena and aging characteristics of nanostructured and bulk ZnS:Mn alternating-current thin-film electro-optical devices is presented. ZnS:Mn nanocrystals embedded in the glass matrices as well as ZnS:Mn thin-film phosphors contain four different concentrations of Mn (from 0.05 to 1.0 mol%). The activator impurity in the phosphor influences the spectral properties and, to a large extent, the temporal properties of optical emission and an aging process of the devices. Therefore, a local photoluminescence and electroluminescence investigation using a scanning near-field optical microscope technique is provided and the aging characteristics of ZnS:Mn nanocrystal structure also presented.

  17. Ultraviolet-visible electroluminescence from metal-oxide-semiconductor devices with CeO{sub 2} films on silicon

    SciTech Connect

    Lv, Chunyan; Zhu, Chen; Wang, Canxing; Li, Dongsheng; Ma, Xiangyang Yang, Deren

    2015-03-15

    We report on ultraviolet-visible (UV-Vis) electroluminescence (EL) from metal-oxide-semiconductor (MOS) devices with the CeO{sub 2} films annealed at low temperatures. At the same injection current, the UV-Vis EL from the MOS device with the 550 °C-annealed CeO{sub 2} film is much stronger than that from the counterpart with the 450 °C-annealed CeO{sub 2} film. This is due to that the 550 °C-annealed CeO{sub 2} film contains more Ce{sup 3+} ions and oxygen vacancies. It is tentatively proposed that the recombination of the electrons in multiple oxygen-vacancy–related energy levels with the holes in Ce 4f{sup 1} energy band pertaining to Ce{sup 3+} ions leads to the UV-Vis EL.

  18. Electroluminescence-based quality characterization of quantum wells for solar cell applications

    NASA Astrophysics Data System (ADS)

    Toprasertpong, Kasidit; Inoue, Tomoyuki; Delamarre, Amaury; Watanabe, Kentaroh; Guillemoles, Jean-François; Sugiyama, Masakazu; Nakano, Yoshiaki

    2017-04-01

    Material quality is a critical factor which determines the performance, particularly the open-circuit voltage, of multiple quantum well (MQW) solar cells. In this study, we report an electroluminescence-based characterization technique for evaluating luminescence efficiency and Shockley-Read-Hall recombination lifetime in MQW structures as a measure of the material quality. As a demonstration, various structures of InGaAs/GaAsP MQWs inserted in GaAs solar cells are investigated. The complete compensation of strain and the insertion of GaAs interlayers between heterointerfaces result in significant improvement of electroluminescence homogeneity, external luminescence efficiency, and lifetime, agreeing well with the tendency of the open-circuit voltage. We show that this characterization technique can detect even subtle degradations, which are not easily detectable by other typical techniques, such as in-situ reflection, X-ray diffraction, and spectral and transient photoluminescence, but still have a significant impact on the performance of solar cells.

  19. Preparation, characterization and electroluminescence studies of ZnO nanorods for optoelectronic device applications

    NASA Astrophysics Data System (ADS)

    Singh, Anju; Vishwakarma, H. L.

    2015-07-01

    In this work, ZnO nanorods were achieved by a simple chemical precipitation method in the presence of capping agent Poly Vinyl Pyrrolidone (PVP) at room temperature. X-Ray Diffraction (XRD) result indicates that the synthesized undoped ZnO nanorods have wurtzite hexagonal structure without any impurities. It has been seen that the growth orientation of the prepared ZnO nanorods were (101). XRD analysis revealed that the nanorods having the crystallite size 49 nm. The Scanning Electron Microscopy (SEM) image confirmed the size and shape of these nanorods. The diameter of nanorods has been found that 1.52 µm to 1.61 µm and the length of about 4.89 µm. It has also been found that at room temperature Ultra Violet Visible (UV-VIS) absorption band is around 355 nm (blue shifted as compared to bulk). Electroluminescence (EL) studies show that emission of light is possible at very small threshold voltage and increases rapidly with increasing applied voltage. It is seen that smaller ZnO nanoparticles give higher electroluminescence brightness starting at lower threshold voltage. The brightness is also affected by increasing the frequency of AC signal.

  20. Preparation, characterization and electroluminescence studies of ZnO nanorods for optoelectronic device applications

    SciTech Connect

    Singh, Anju; Vishwakarma, H. L.

    2015-07-31

    In this work, ZnO nanorods were achieved by a simple chemical precipitation method in the presence of capping agent Poly Vinyl Pyrrolidone (PVP) at room temperature. X-Ray Diffraction (XRD) result indicates that the synthesized undoped ZnO nanorods have wurtzite hexagonal structure without any impurities. It has been seen that the growth orientation of the prepared ZnO nanorods were (101). XRD analysis revealed that the nanorods having the crystallite size 49 nm. The Scanning Electron Microscopy (SEM) image confirmed the size and shape of these nanorods. The diameter of nanorods has been found that 1.52 µm to 1.61 µm and the length of about 4.89 µm. It has also been found that at room temperature Ultra Violet Visible (UV-VIS) absorption band is around 355 nm (blue shifted as compared to bulk). Electroluminescence (EL) studies show that emission of light is possible at very small threshold voltage and increases rapidly with increasing applied voltage. It is seen that smaller ZnO nanoparticles give higher electroluminescence brightness starting at lower threshold voltage. The brightness is also affected by increasing the frequency of AC signal.

  1. Simultaneous enhancement of photo- and electroluminescence in white organic light-emitting devices by localized surface plasmons of silver nanoclusters

    NASA Astrophysics Data System (ADS)

    Yu, Jingting; Zhu, Wenqing; Shi, Guanjie; Zhai, Guangsheng; Qian, Bingjie; Li, Jun

    2017-02-01

    White organic light-emitting devices (WOLEDs) with enhanced current efficiency and negligible color shifting equipped with an internal color conversion layer (CCL) were fabricated. They were attained by embedding a single layer of silver nanoclusters (SNCs) between the CCL and light-emitting layer (EML). The simultaneous enhancement of the photoluminescence (PL) of the CCL and electroluminescence (EL) of the EML were realized by controlling the thickness and size of the SNCs to match the localized surface plasmon resonance spectrum with the PL spectrum of the CCL and the EL spectrum of the EML. The WOLED with optimal SNCs demonstrated a 25.81% enhancement in current efficiency at 60 mA cm‑2 and good color stability over the entire range of current density.

  2. Reduction of molecular aggregation and its application to the high-performance blue perylene-doped organic electroluminescent device

    NASA Astrophysics Data System (ADS)

    Mi, B. X.; Gao, Z. Q.; Lee, C. S.; Lee, S. T.; Kwong, H. L.; Wong, N. B.

    1999-12-01

    A nonplanar derivative of perylene, 2,5,8,11-tetra-tertbutylperylene (TBPe), was synthesized via the Friedel-Crafts alkylation reaction. Electroluminescent (EL) devices were made using TBPe or perylene as a dopant in bis(2-methyl-8-quinolinolato)(para-phenylphenolato)aluminum(III) and their EL performance was compared. Similar to the device doped with the parent perylene molecule, the device doped with TBPe also emitted strongly in the blue. As the concentration of TBPe increased from 1% to 5%, the color coordinates in CIE 1931 chromaticity of the TBPe-doped device changed only slightly from (0.168,0.273) to (0.175,0.273), whereas the perylene-doped device exhibited a much larger shift from (0.165,0.196) to (0.178,0.252). The constancy of EL color and efficiency with respect to TBPe dopant concentration is attributable to diminishing molecular aggregation in the nonplanar perylene derivative, TBPe, due to the steric hindrance of the tert-butyl groups.

  3. Observation of near infrared and enhanced visible emissions from electroluminescent devices with organo samarium(III) complex

    NASA Astrophysics Data System (ADS)

    Chu, B.; Li, W. L.; Hong, Z. R.; Zang, F. X.; Wei, H. Z.; Wang, D. Y.; Li, M. T.; Lee, C. S.; Lee, S. T.

    2006-11-01

    Samarium (dibenzoylmethanato)3 bathophenanthroline (Sm(DBM)3 bath) was employed as an emitting and electron transport layer in organic light emitting diodes (OLEDs), and narrow electroluminescent (EL) emissions of a Sm3+ ion were observed in the visible and near infrared (NIR) region, differing from those of the same devices with Eu3+- or Tb3+-complex EL devices with the same structure. The EL emissions of the Sm3+-devices originate from transitions from 4G5/2 to the lower respective levels of Sm3+ ions. A maximum luminance of 490 cd m-2 at 15 V and an EL efficiency of 0.6% at 0.17 mA cm-2 were obtained in the visible region, and the improved efficiency should be attributed to introducing a transitional layer between the N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-diphenyl-4,4'-diamine (TPD) film and the Sm(DBM)3 bath film and the avoidance of interfacial exciplex emission in devices. Sharp emissions of Sm3+ ions in the NIR region were also observed under a lower threshold value less than 4.5 V.

  4. White-light emitting thin film electroluminescent devices with stacked SrS:Ce/CaS:Eu active layers

    NASA Astrophysics Data System (ADS)

    Ono, Yoshimasa A.; Fuyama, Moriaki; Onisawa, Ken-ichi; Tamura, Katsumi; Ando, Masahiko

    1989-12-01

    By stacking blue-green emitting SrS:Ce and red-emitting CaS:Eu active layers, white-light emitting electroluminescent (EL) devices were fabricated. Luminance improvement and EL characteristics of SrS:Ce and CaS:Eu EL devices were discussed. The electrooptical characteristics of white-light emitting EL devices with stacked SrS:Ce/CaS:Eu active layers were presented. Color changed from blue-green to white by changing the voltage or frequency. Finally, feasibility of multicolor EL devices by using the fabricated white-light emitting EL devices with color filters were discussed. UFpg5523,5527 UFid992922JAP UFttIn situ ac magnetic susceptibility of gadolinium thin films UFauF. H. SalasSUPa),b) and M. Mirabal-GarciaaSUPc) UFloInstitut fuur Atom- und Festkourperphysik, Freie Universitaut Berlin, D-1000 Berlin 33, ufquadFederal Republic of Germany UFsd(Received 27 April 1989; accepted for publication 3 August 1989) UFabWe report measurements of the ac magnetic susceptibility on Gd(0001)/W(110) thin films grown in ultrahigh vacuum. The measurements were made by using a pickup coil, in which the geometry and the number of turns were optimized. We applied an alternating magnetic field of about 2 Grms at frequencies of 180 and 340 Hz. The growth mode and the deposition rate of the Gd films were determined by performing conventional Auger electron spectroscopy during film growth. In films with thickness larger than 10 nm our technique is sensitive up to 1016 atoms/Grms , which allowed us to study the critical behavior of the magnetic susceptibility as the Curie temperature is approached from above, TT+C . A sharp maximum, which may be related to the Hopkinson effect, is observed at a temperature TH 289 K.

  5. Conversion process of the dominant electroluminescence mechanism in a molecularly doped organic light-emitting device with only electron trapping

    NASA Astrophysics Data System (ADS)

    Zhou, Liang; Zhang, Hongjie; Deng, Ruiping; Li, Zhefeng; Yu, Jiangbo; Guo, Zhiyong

    2007-09-01

    In this work, the detailed conversion process of the dominant electroluminescence (EL) mechanism in a device with Eu(TTA)3phen (TTA =thenoyltrifluoroacetone, phen =1,10-phenanthroline) doped CBP (4,4'-N,N'-dicarbazole-biphenyl) film as the emitting layer was investigated by analyzing the evolution of carrier distribution on dye and host molecules with increasing voltage. Firstly, it was confirmed that only electrons can be trapped in Eu(TTA)3phen doped CBP. As a result, holes and electrons would be situated on CBP and Eu(TTA)3phen molecules, respectively, and thus creates an unbalanced carrier distribution on both dye and host molecules. With the help of EL and photoluminescence spectra, the distribution of holes and electrons on both Eu(TTA)3phen and CBP molecules was demonstrated to change gradually with increasing voltage. Therefore, the dominant EL mechanism in this device changes gradually from carrier trapping at relatively low voltage to Förster energy transfer at relatively high voltage.

  6. Large Size Color-tunable Electroluminescence from Cationic Iridium Complexes-based Light-emitting Electrochemical Cells

    PubMed Central

    Zeng, Qunying; Li, Fushan; Guo, Tailiang; Shan, Guogang; Su, Zhongmin

    2016-01-01

    Solution-processable light-emitting electrochemical cells (LECs) with simple device architecture have become an attractive candidate for application in next generation lighting and flat-panel displays. Herein, single layer LECs employing two cationic Ir(III) complexes showing highly efficient blue-green and yellow electroluminescence with peak current efficiency of 31.6 cd A−1 and 40.6 cd A−1, respectively, have been reported. By using both complexes in the device, color-tunable LECs with a single spectral peak in the wavelength range from 499 to 570 nm were obtained by varying their rations. In addition, the fabrication of efficient LECs was demonstrated based on low cost doctor-blade coating technique, which was compatible with the roll to roll fabrication process for the large size production. In this work, for the first time, 4 inch LEC devices by doctor-blade coating were fabricated, which exhibit the efficiencies of 23.4 cd A−1 and 25.4 cd A−1 for the blue-green and yellow emission, respectively. The exciting results indicated that highly efficient LECs with controllable color could be realized and find practical application in large size lighting and displays. PMID:27278527

  7. Large Size Color-tunable Electroluminescence from Cationic Iridium Complexes-based Light-emitting Electrochemical Cells

    NASA Astrophysics Data System (ADS)

    Zeng, Qunying; Li, Fushan; Guo, Tailiang; Shan, Guogang; Su, Zhongmin

    2016-06-01

    Solution-processable light-emitting electrochemical cells (LECs) with simple device architecture have become an attractive candidate for application in next generation lighting and flat-panel displays. Herein, single layer LECs employing two cationic Ir(III) complexes showing highly efficient blue-green and yellow electroluminescence with peak current efficiency of 31.6 cd A‑1 and 40.6 cd A‑1, respectively, have been reported. By using both complexes in the device, color-tunable LECs with a single spectral peak in the wavelength range from 499 to 570 nm were obtained by varying their rations. In addition, the fabrication of efficient LECs was demonstrated based on low cost doctor-blade coating technique, which was compatible with the roll to roll fabrication process for the large size production. In this work, for the first time, 4 inch LEC devices by doctor-blade coating were fabricated, which exhibit the efficiencies of 23.4 cd A‑1 and 25.4 cd A‑1 for the blue-green and yellow emission, respectively. The exciting results indicated that highly efficient LECs with controllable color could be realized and find practical application in large size lighting and displays.

  8. Color-tunable electroluminescence from Eu-doped TiO(2)/p(+)-Si heterostructured devices: engineering of energy transfer.

    PubMed

    Zhu, Chen; Lv, Chunyan; Wang, Canxing; Sha, Yiping; Li, Dongsheng; Ma, Xiangyang; Yang, Deren

    2015-02-09

    We report on color-tunable electroluminescence (EL) from TiO(2):Eu/p(+)-Si heterostructured devices using different TiO(2):Eu films in terms of Eu content and annealing temperature. It is found that the Eu-related emissions are activated by the energy transferred from TiO(2) host via oxygen vacancies, at the price of weakened oxygen-vacancy-related emissions. Both the higher Eu content and the higher annealing temperature for TiO(2):Eu films facilitate the aforementioned energy transfer. In this context, the dominant EL from the TiO(2):Eu/p(+)-Si heterostructured devices can be transformed from oxygen-vacancy-related emissions into Eu-related emissions with increasing Eu-content and annealing temperature for TiO(2):Eu films, exhibiting different colors of emanated light. We believe that this work sheds light on developing silicon-based red emitters using the Eu-doped oxide semiconductor films.

  9. Improved efficiency for green and red emitting electroluminescent devices using the same cohost composed of 9,10-di(2-naphthyl) anthracene and tris-(8-hydroxyquinolinato) aluminum

    NASA Astrophysics Data System (ADS)

    Zhu, Jianzhuo; Li, Wenlian; Chu, Bei; Yang, Dongfang; Zhang, Guang; Liu, Huihui; Chen, Yiren; Su, Zisheng; Wang, Junbo; Wu, Shuanghong

    2009-12-01

    We demonstrate highly efficient green and red fluorescence dyes-doped electroluminescent devices using cohost strategy. The cohost system is composed of tris-(8-hydroxyquinolinato) aluminum (Alq) and 9,10-di(2-naphthyl) anthracene (ADN). The maximum current efficiencies are increased by 54% and 104% for green and red devices by optimizing the ratio between ADN and Alq in the cohost compared to the conventional Alq single-host devices, respectively. We attribute the improvement of efficiencies to balanced hole and electron injection into the emitting layer, the enlarged width of recombination region and the multiple emission processes.

  10. Electroluminescence of ZnO nanocrystal in sputtered ZnO-SiO2 nanocomposite light-emitting devices.

    PubMed

    Chen, Jiun-Ting; Lai, Wei-Chih; Chen, Chi-Heng; Yang, Ya-Yu; Sheu, Jinn-Kong; Lai, Li-Wen

    2011-06-06

    We have demonstrated the electroluminescence (EL) of Ga:ZnO/i-ZnO-SiO2 nanocomposite/p-GaN n-i-p heterostructure light-emitting devices (LEDs). ZnO nano-clusters with sizes distributing from 2 to 7nm were found inside the co-sputtered i-ZnO-SiO2 nanocomposite layer under the observation of high-resolution transparent electron microscope. A clear UV EL at 376 nm from i-ZnO-SiO2 nanocomposite in these p-i-n heterostructure LEDs was observed under the forward current of 9 mA. The EL emission peak at 376 and 427nm of the Ga:ZnO/i-ZnO-SiO2 nanocomposite/p-GaN n-i-p heterostructure LEDs were attributed to the radiative recombination from the ZnO clusters and the Mg acceptor levels in the p-GaN layer, respectively.

  11. Nanostructured Sublayers for Improved Light Extraction of Top-Emitting and Transparent Organic Electroluminescent Devices

    DTIC Science & Technology

    2007-05-01

    fabrication of top-emitting red, green, and blue OLEDs with various light emitting and hole transport layer thicknesses. (b) The layered structures of...the top-emitting red, green, and blue devices. (c) The materials used as hole transport layers, light emitting hosts, and dopants. Figure 4...transmittance of dielectric mirror with structure of TiO2 54nm /SiO2 90nm / TiO2 54nm /Glass Figure 12. Light emitting spectra of green microcavity

  12. Large magneto-conductance and magneto-electroluminescence in exciplex-based organic light-emitting diodes at room temperature

    NASA Astrophysics Data System (ADS)

    Ling, Yongzhou; Lei, Yanlian; Zhang, Qiaoming; Chen, Lixiang; Song, Qunliang; Xiong, Zuhong

    2015-11-01

    In this work, we report on large magneto-conductance (MC) over 60% and magneto-electroluminescence (MEL) as high as 112% at room temperature in an exciplex-based organic light-emitting diode (OLED) with efficient reverse intersystem crossing (ISC). The large MC and MEL are individually confirmed by the current density-voltage characteristics and the electroluminescence spectra under various magnetic fields. We proposed that this type of magnetic field effect (MFE) is governed by the field-modulated reverse ISC between the singlet and triplet exciplex. The temperature-dependent MFEs reveal that the small activation energy of reverse ISC accounts for the large MFEs in the present exciplex-based OLEDs.

  13. Effect of solution combusted TiO2 nanopowder within commercial BaTiO3 dielectric layer on the photoelectric properties for AC powder electroluminescence devices.

    PubMed

    Park, Sung; Choi, Gil Rak; Kim, Youn Cheol; Lee, Jae Chun; Lee, Ju Hyeon

    2013-05-01

    A unique synthesis method was developed, which is called solution combustion method (SCM). TiO2 nanopowder was synthesized by this method. This SCM TiO2 nanopowder (-35 nm) was added to the dielectric layer of AC powder electroluminescence (EL) device. The dielectric layer was made of commercial BaTiO3 powder (-1.2 microm) and binding polymer. 0, 5, 10 and 15 wt% of SCM TiO2 nanopowder was added to the dielectric layer during fabrication of AC powder EL device respectively. Dielectric constant of these four kinds of dielectric layers was measured. The brightness and current density of AC powder EL device were also measured. When 10 wt% of SCM TiO2 nanopowder was added, dielectric constant and brightness were increased by 30% and 101% respectively. Furthermore, the current density was decreased by 71%. This means that the brightness was double and the power consumption was one third.

  14. Correlating electroluminescence characterization and physics-based models of InGaN/GaN LEDs: Pitfalls and open issues

    SciTech Connect

    Calciati, Marco; Vallone, Marco; Zhou, Xiangyu; Ghione, Giovanni; Goano, Michele Bertazzi, Francesco; Meneghini, Matteo; Meneghesso, Gaudenzio; Zanoni, Enrico; Verzellesi, Giovanni; Zhu, Dandan; Humphreys, Colin

    2014-06-15

    Electroluminescence (EL) characterization of InGaN/GaN light-emitting diodes (LEDs), coupled with numerical device models of different sophistication, is routinely adopted not only to establish correlations between device efficiency and structural features, but also to make inferences about the loss mechanisms responsible for LED efficiency droop at high driving currents. The limits of this investigative approach are discussed here in a case study based on a comprehensive set of current- and temperature-dependent EL data from blue LEDs with low and high densities of threading dislocations (TDs). First, the effects limiting the applicability of simpler (closed-form and/or one-dimensional) classes of models are addressed, like lateral current crowding, vertical carrier distribution nonuniformity, and interband transition broadening. Then, the major sources of uncertainty affecting state-of-the-art numerical device simulation are reviewed and discussed, including (i) the approximations in the transport description through the multi-quantum-well active region, (ii) the alternative valence band parametrizations proposed to calculate the spontaneous emission rate, (iii) the difficulties in defining the Auger coefficients due to inadequacies in the microscopic quantum well description and the possible presence of extra, non-Auger high-current-density recombination mechanisms and/or Auger-induced leakage. In the case of the present LED structures, the application of three-dimensional numerical-simulation-based analysis to the EL data leads to an explanation of efficiency droop in terms of TD-related and Auger-like nonradiative losses, with a C coefficient in the 10{sup −30} cm{sup 6}/s range at room temperature, close to the larger theoretical calculations reported so far. However, a study of the combined effects of structural and model uncertainties suggests that the C values thus determined could be overestimated by about an order of magnitude. This preliminary

  15. Ultraviolet-light-emitting AlN:Gd thin-film electroluminescence device using an energy transfer from Gd3+ ions to N2 molecules

    NASA Astrophysics Data System (ADS)

    Toyama, Toshihiko; Ota, Jun; Adachi, Daisuke; Niioka, Yasumasa; Lee, Dong-Hun; Okamoto, Hiroaki

    2009-04-01

    An ultraviolet (UV)-light-emitting AlN:Gd thin-film electroluminescence device (TFELD) was demonstrated for application to flat-panel lighting. AlN:Gd thin films were deposited by rf magnetron sputtering at 200 °C and applied to an ac-voltage-driven TFELD with a double-insulating structure as an emission layer. UV-light emission was observed over a threshold voltage of 270 V for a 5 kHz sinusoidal ac voltage. Electroluminescence (EL) spectra were compared with photoluminescence and cathodoluminescence spectra of AlN:Gd originating from Gd3+ P6j→S87/2 transitions and with an emission spectrum of the second positive system (C3Πu→B3Πg) of N2 molecules. As a result, an energy transfer from Gd3+ P6j→S87/2 to N2 C3Πu→B3Πg is discussed as a likely mechanism for the UV EL. Finally, a preliminary result, associated with the conversion from UV light into blue-green light via a phosphor, is demonstrated for the color tunability of the TFELD.

  16. Photo- and electroluminescent properties of zinc(II) complexes with tetradentate Schiff bases, derivatives of salicylic aldehyde

    NASA Astrophysics Data System (ADS)

    Vashchenko, A. A.; Lepnev, L. S.; Vitukhnovskii, A. G.; Kotova, O. V.; Eliseeva, S. V.; Kuz'mina, N. P.

    2010-03-01

    It is studied how the introduction of various substituents into the composition of organic ligands affects the photoluminescence spectra of new zinc(II) complexes with tetradentate Schiff bases H2L (derivatives of salicylic aldehyde (H2SAL1, H2SAL2) and o-vanillin (H2MO1, H2MO2) with ethylenediamine and o-phenylenediamine) in the form of bulk solids and thin films. It is demonstrated that the emission spectra of bulk solid complexes without o-phenylenediamine bridges (ZnSAL1 and ZnMO1) contain additional long-wavelength bands compared to the spectra of corresponding thin films. In the case of films obtained from [ZnSAL1]2 dimer complexes, the long-wavelength band is dominant. At the same time, the photoluminescence spectra of ZnSAL2 and ZnMO2 complexes with o-phenylenediamine bridges are similar in the case of solid samples and thin films. The electroluminescent properties of organic light-emitting diodes (OLEDs) with the ITO/α-NPD/ZnL/Ca:Al structure are studied. The bathochromic shift of the electroluminescence peaks of OLEDs with respect to the photoluminescence spectra of bulk solid samples and thin films is probably related to the formation of exciplexes at the α-NPD/ZnL interface. The electroluminescence spectra of OLEDs based on [ZnSAL1]2 show a hypsochromic shift of the emission maximum, which can be caused by a shift of the recombination region into the α-NPD layer.

  17. High-efficiency blue electroluminescence based on coumarin derivative 3-(4-(anthracen-10-yl)phenyl)-benzo[5,6]coumarin.

    PubMed

    Zhang, Hui; Chai, Haifang; Yu, Tianzhi; Zhao, Yuling; Fan, Duowang

    2012-11-01

    The electroluminescent (EL) properties of a new coumarin derivative, 3-(4-(anthracen-10-yl)phenyl)-benzo[5,6]coumarin (APBC), were investigated. The results show that the EL devices comprised of vacuum vapor-deposited films using the derivative as dopant exhibited blue emission that is identical to the photoluminescence of the thin film. The electroluminescence device of ITO/2-TNATA (5 nm)/NPB (40 nm)/CBP : APBC (1.0 wt%, 30 nm)/PBD (30 nm)/LiF (1 nm)/Al (100 nm) gives a maximum luminous efficiency of 2.3 cd/A at the current density of 20 mA/cm(2), and maximum luminance of 5169 cd/m(2) at 16 V. The external quantum efficiency of the device is 1.85 %.

  18. Magnetically modulated electroluminescence from hybrid organic/inorganic light-emitting diodes based on electron donor-acceptor exciplex blends

    NASA Astrophysics Data System (ADS)

    Pang, Zhiyong; Baniya, Sangita; Zhang, Chuang; Sun, Dali; Vardeny, Z. Valy

    2016-03-01

    We report room temperature magnetically modulated electroluminescence from a hybrid organic/inorganic light-emitting diode (h-OLED), in which an inorganic magnetic tunnel junction (MTJ) with large room temperature magnetoresistance is coupled to an N,N,N ',N '-Tetrakis(4-methoxyphenyl)benzidine (MeO-TPD): tris-[3-(3-pyridyl)mesityl]borane (3TPYMB) [D-A] based OLED that shows thermally activated delayed luminescence. The exciplex-based OLED provides two spin-mixing channels: upper energy channel of polaron pairs and lower energy channel of exciplexes. In operation, the large resistance mismatch between the MTJ and OLED components is suppressed due to the non-linear I-V characteristic of the OLED. This leads to enhanced giant magneto-electroluminescence (MEL) at room temperature. We measured MEL of ~ 75% at ambient conditions. Supported by SAMSUNG Global Research Outreach (GRO) program, and also by the NSF-Material Science & Engineering Center (MRSEC) program at the University of Utah (DMR-1121252).

  19. Electroluminescent layers based on ZnS:Cu deposited into matrices of porous anodic Al2O3

    NASA Astrophysics Data System (ADS)

    Valeev, R. G.; Petukhov, D. I.; Chukavin, A. I.; Bel'tyukov, A. N.

    2016-02-01

    It is suggested to use a new nanocomposite material—nanostructures of copper-doped zinc sulfide in a matrix of porous aluminum oxide—as a light-emitting layer of electroluminescent sources of light. The material was deposited by thermal evaporation in a vacuum. The microstructure of the layers, impurity distribution in the electroluminescent-phosphor layer, and electroluminescence spectra at various copper concentrations in ZnS:Cu were studied.

  20. Observation of red electroluminescence from an Eu2O3/p +-Si device and improved performance by introducing a Tb2O3 layer

    NASA Astrophysics Data System (ADS)

    Yin, Xue; Wang, Shenwei; Mu, Guangyao; Wan, Guangmiao; Huang, Miaoling; Yi, Lixin

    2017-03-01

    We report red electroluminescence (EL) from an Eu2O3/p +-Si device with Eu2O3 film annealed in oxygen ambient at 700 °C. The red EL is ascribed to the characteristic emissions of Eu3+ ions in Eu2O3 film and the luminescence mechanism is discussed in detail. In order to optimize the device performance, Eu2O3/Tb2O3 multiple films were deposited on Si wafer, and the result showed EL intensity of the device was obviously enhanced and the turn-on voltage was reduced to about 10 V. Moreover, intensity ratio I(5D0–7F2)/I(5D0–7F1) was also significantly increased with the hypersensitive transition 5D0–7F2 as the most prominent group at about 611 nm. The improved performance was attributed to the added Tb2O3 film that it can be served as the hole-injection layer to afford extra holes injected into the Eu2O3 layer.

  1. A novel violet/blue light-emitting device based on Ce2Si2O7

    NASA Astrophysics Data System (ADS)

    Li, Ling; Wang, Shenwei; Mu, Guangyao; Yin, Xue; Ou, Kai; Yi, Lixin

    2015-11-01

    Rare-earth silicates are highly efficient materials for silicon-based light sources. Here we report a novel light-emitting device based on Ce2Si2O7. Intense violet/blue electroluminescence was observed, with a turn-on voltage of about 13 V. The violet/blue emission is attributed to 4f-5d transitions of the Ce3+ ions in Ce2Si2O7, which are formed by interfacial reaction of CeO2 and Si. Electroluminescence and photoluminescence mechanisms of the Ce2Si2O7 light-emitting device are also discussed.

  2. A novel violet/blue light-emitting device based on Ce2Si2O7

    PubMed Central

    Li, Ling; Wang, Shenwei; Mu, Guangyao; Yin, Xue; Ou, Kai; Yi, Lixin

    2015-01-01

    Rare-earth silicates are highly efficient materials for silicon-based light sources. Here we report a novel light-emitting device based on Ce2Si2O7. Intense violet/blue electroluminescence was observed, with a turn-on voltage of about 13 V. The violet/blue emission is attributed to 4f–5d transitions of the Ce3+ ions in Ce2Si2O7, which are formed by interfacial reaction of CeO2 and Si. Electroluminescence and photoluminescence mechanisms of the Ce2Si2O7 light-emitting device are also discussed. PMID:26564241

  3. 1.4 μm band electroluminescence from organic light-emitting diodes based on thulium complexes

    NASA Astrophysics Data System (ADS)

    Zang, F. X.; Hong, Z. R.; Li, W. L.; Li, M. T.; Sun, X. Y.

    2004-04-01

    Near-infrared (NIR) electroluminescence (EL) devices have been fabricated employing thulium complexes as emitting materials. The EL emissions at 1.4 and 0.8 μm were observed from the devices of tris-(dibenzoylmethanato)-mono-(bathophenanthroline or 1,10-phenonthroline) thulium [Tm(DBM)3bath or Tm(DBM)3phen] at room temperature and assigned to 3F4-3H4 and 3F4-3H6 transitions of Tm3+ ions, respectively. By comparison with the NIR emissions of four Tm complexes with different ligands, it was found that the first ligand played a more important role for the Tm3+ ion emissions rather than the second one. In order to meet the requirement of optical communication, both Tm(DBM)3bath and erbium [Er] (DBM)3bath were incorporated into EL devices so that a broadened EL emission band ranging from 1.4 to 1.6 μm was obtained, showing the potential application of Tm complexes for optical communication systems.

  4. Multicolor and near-infrared electroluminescence from the light-emitting devices with rare-earth doped TiO{sub 2} films

    SciTech Connect

    Zhu, Chen; Gao, Zhifei; Wang, Canxing; Li, Dongsheng; Ma, Xiangyang Yang, Deren; Lv, Chunyan

    2015-09-28

    We report on multicolor and near-infrared electroluminescence (EL) from the devices using rare-earth doped TiO{sub 2} (TiO{sub 2}:RE) films as light-emitting layers, which are ascribed to the impact excitation of RE{sup 3+} ions, with the EL onset voltages below 10 V. The devices are in the structure of ITO/TiO{sub 2}:RE/SiO{sub 2}/Si, in which the SiO{sub 2} layer is ∼10 nm thick and RE includes Eu, Er, Tm, Nd, and so on. With sufficiently high positive voltage applied on the ITO electrode, the conduction electrons in Si can tunnel into the conduction band of SiO{sub 2} layer via the trap-assisted tunneling mechanism, gaining the potential energy ∼4 eV higher than the conduction band edge of TiO{sub 2}. Therefore, as the electrons in the SiO{sub 2} layer drift into the TiO{sub 2}:RE layer, they become hot electrons. Such hot electrons impact-excite the RE{sup 3+} ions incorporated into the TiO{sub 2} host, leading to the characteristic emissions.

  5. Polarization characteristics of electroluminescence and net modal gain in highly stacked InAs/GaAs quantum-dot laser devices

    NASA Astrophysics Data System (ADS)

    Suwa, Masaya; Andachi, Takaya; Kaizu, Toshiyuki; Harada, Yukihiro; Kita, Takashi

    2016-10-01

    We studied the polarization anisotropy of electroluminescence (EL) and net modal gain characteristics of laser device structures containing 40 stacked InAs/GaAs quantum dot (QD) layers. The electronic coupling between the closely stacked QDs enhanced the transverse-magnetic (TM) polarization component owing to the heavy- and light-hole mixing. Thereby, the [110]-waveguide devices exhibited a laser oscillation of not only the transverse-electric (TE) but also the TM component. Laser oscillation occurred at 1137 nm from the first excited state for the 300-μm-long cavity, while it occurred at 1167 nm from the ground state for the 1000-μm-long cavity. The polarization anisotropy of the EL intensity strongly depended on the injection current density. The polarized EL intensity was almost isotropic at low injection current density. As the injection current density was increased, the TE component was gradually enhanced, which resulted in a markedly TE-dominant anisotropy above the threshold current density for laser oscillation. The net modal gains evaluated using the Hakki-Paoli method also exhibited a TE-enhanced characteristic with increasing injection current density. As the EL spectra of the TE component have an inhomogeneous broadening narrower than that of the TM component, the TE-mode intensity is likely to be enhanced by the concentration of the injected carriers.

  6. Correlation between charge transport and electroluminescence properties of Si-rich oxide/nitride/oxide-based light emitting capacitors

    NASA Astrophysics Data System (ADS)

    Berencén, Y.; Ramírez, J. M.; Jambois, O.; Domínguez, C.; Rodríguez, J. A.; Garrido, B.

    2012-08-01

    The electrical and electroluminescence (EL) properties at room and high temperatures of oxide/nitride/oxide (ONO)-based light emitting capacitors are studied. The ONO multidielectric layer is enriched with silicon by means of ion implantation. The exceeding silicon distribution follows a Gaussian profile with a maximum of 19%, centered close to the lower oxide/nitride interface. The electrical measurements performed at room and high temperatures allowed to unambiguously identify variable range hopping (VRH) as the dominant electrical conduction mechanism at low voltages, whereas at moderate and high voltages, a hybrid conduction formed by means of variable range hopping and space charge-limited current enhanced by Poole-Frenkel effect predominates. The EL spectra at different temperatures are also recorded, and the correlation between charge transport mechanisms and EL properties is discussed.

  7. Synthesis, photophysical, electrochemical and electroluminescent properties of a novel iridium(III) complex based on 2-phenylbenzo[d]oxazole derivative.

    PubMed

    Li, Xiao; Yu, Xiao-Ting; Chi, Hai-Jun; Dong, Yan; Xiao, Guo-Yong; Lei, Peng; Zhang, Dong-Yu; Cui, Zheng

    2013-12-01

    A new phosphorescent iridium (III) complex based on 2-(4-tert-butylphenyl)-5-methylbenzo[d]oxazole as main ligand, i.e. bis(2-(4-tert-butylphenyl)-5-methylbenzo[d]oxazole-N,C(2'))iridium(acetylacetonate) [(tmbo)2Ir(acac)], was synthesized for organic light-emitting diodes (OLEDs), and its photophysical, electrochemical and electroluminescent properties were investigated. The complex displayed strong phosphorescence emission, high decomposition temperature, short phosphorescent lifetime and reversible redox electrochemical behavior. The OLEDs based on (tmbo)2Ir(acac) as dopant emitter exhibited maximum luminance efficiency of 26.1cdA(-1) and high luminance of 16,445 cd m(-2). Interestingly, highly doped device based on (tmbo)2Ir(acac) showed high efficiency with negligible roll-off under a wide range of driving current density, which was mainly attributed to the effect of bulky steric hindrance of multi-methyl groups on this complex and its short phosphorescent lifetime.

  8. Synthesis, photophysical, electrochemical and electroluminescent properties of a novel iridium(III) complex based on 2-phenylbenzo[d]oxazole derivative

    NASA Astrophysics Data System (ADS)

    Li, Xiao; Yu, Xiao-Ting; Chi, Hai-Jun; Dong, Yan; Xiao, Guo-Yong; Lei, Peng; Zhang, Dong-Yu; Cui, Zheng

    2013-12-01

    A new phosphorescent iridium (III) complex based on 2-(4-tert-butylphenyl)-5-methylbenzo[d]oxazole as main ligand, i.e. bis(2-(4-tert-butylphenyl)-5-methylbenzo[d]oxazole-N,C2‧)iridium(acetylacetonate) [(tmbo)2Ir(acac)], was synthesized for organic light-emitting diodes (OLEDs), and its photophysical, electrochemical and electroluminescent properties were investigated. The complex displayed strong phosphorescence emission, high decomposition temperature, short phosphorescent lifetime and reversible redox electrochemical behavior. The OLEDs based on (tmbo)2Ir(acac) as dopant emitter exhibited maximum luminance efficiency of 26.1 cd A-1 and high luminance of 16,445 cd m-2. Interestingly, highly doped device based on (tmbo)2Ir(acac) showed high efficiency with negligible roll-off under a wide range of driving current density, which was mainly attributed to the effect of bulky steric hindrance of multi-methyl groups on this complex and its short phosphorescent lifetime.

  9. Correlation between electroluminescence and charge trapping in multi-color Eu implanted Si-based light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Nazarov, A. N.; Tyagulskyy, I. P.; Tyagulskiy, S. I.; Rebohle, L.; Skorupa, W.; Biskupek, J.; Kaiser, U.

    2009-05-01

    Electroluminescence (EL) spectra, charge trapping during operation of EL devices and clustering of rare earth oxides in SiO 2 have been investigated in Eu implanted SiO 2-Si structures which demonstrate luminescence associated with the light-emitting transitions in Eu 2+ and Eu 3+. Strong electron trapping in all studied regions of the injected charge (from 1×10 14 to 1×10 18 e/cm 2) during operation of the light-emitting devices has been found that it considerably differed from the oxides implanted by other rare earth impurities (Ce, Tb, Gd, Er, Tm). It has been shown that the observed strong electron trapping and the low EL intensity in the Eu implanted structures were associated with enhanced clustering of the Eu oxides. The mechanism of electron trapping in the SiO 2 containing a large cluster concentration is discussed, and flash lamp annealing is proposed to decrease the nanocluster size and to enhance the EL intensity.

  10. Tervalent conducting polymers with tailor-made work functions: preparation, characterization, and applications as cathodes in electroluminescent devices.

    PubMed

    Bloom, C J; Elliott, C M; Schroeder, P G; France, C B; Parkinson, B A

    2001-09-26

    A series of conducting polymers have been prepared through thermal polymerization of transition-metal diimine complexes. The as-polymerized material is electrochemically converted into its formally zerovalent form. Due to the proximity of the half-wave potentials of the formal 1+/0 and 0/1- couples, there is substantial disproportionation of the redox sites at room temperature, resulting in a conductive tervalent mixed-valent material. The redox processes that give rise to this mixed-valent material are predominantly ligand-based, and therefore are highly sensitive to substitution on the ligand periphery. Solution redox chemistry of the monomer can be used to accurately predict the work function of the corresponding zerovalent conducting polymer, which has been verified by ultraviolet photoelectron spectroscopy. Many of these materials have especially low work functions (<3.6 eV) making them appropriate materials to use as cathode materials in organic light-emitting devices (OLEDs). Working examples of tris(8-hydroxyquinoline)aluminum(III)-based OLEDs have been fabricated using one of these polymers as a cathode.

  11. Efficient Deep-Blue Electroluminescence Based on Phenanthroimidazole-Dibenzothiophene Derivatives with Different Oxidation States of the Sulfur Atom.

    PubMed

    Tang, Xiangyang; Shan, Tong; Bai, Qing; Ma, Hongwei; He, Xin; Lu, Ping

    2017-03-02

    Developing efficient deep-blue materials is a long-term research focus in the field of organic light-emitting diodes (OLEDs). In this paper, we report two deep-blue molecules, PITO and PISF, which share similar chemical structures but exhibit different photophysical and device properties. These two molecules consist of phenanthroimidazole and dibenzothiophene analogs. The distinction of their chemical structures lies in the different oxidation states of the S atom. For PITO, the S atom is oxidized and the resulting structure dibenzothiophene S,S-dioxide becomes electron deficient. Therefore, PITO displays remarkable solvatochromism, implying a charge-transfer (CT) excited state formed between the donor (D) phenanthroimidazole and acceptor (A) dibenzothiophene S,S-dioxide. For PISF, it is constituted of phenanthroimidazole and dibenzothiophene in which the S atom is not oxidized. PISF displays locally excited (LE) emission with little solvatochromism. Compared with PISF, the D-A molecule PITO with an electron-deficient group shows a much lower LUMO energy level, which is in favor of electron injection in device. In addition, PITO exhibits more balanced carrier transport. However, PISF is capable of emitting in the shorter wavelength region, which is beneficial to obtain better color purity. The doped electroluminescence (EL) device of the D-A molecule PITO manifests deep-blue emission with CIE coordinates of (0.15, 0.08) and maximum external quantum efficiency (EQE) of 4.67 %. The doped EL device of the LE molecule PISF, however, reveals an even bluer emission with CIE coordinates of (0.15, 0.06) and a maximum EQE of 4.08 %.

  12. Electric-field-induced strong enhancement of electroluminescence in multilayer molybdenum disulfide

    PubMed Central

    Li, Dehui; Cheng, Rui; Zhou, Hailong; Wang, Chen; Yin, Anxiang; Chen, Yu; Weiss, Nathan O.; Huang, Yu; Duan, Xiangfeng

    2015-01-01

    The layered transition metal dichalcogenides have attracted considerable interest for their unique electronic and optical properties. While the monolayer MoS2 exhibits a direct bandgap, the multilayer MoS2 is an indirect bandgap semiconductor and generally optically inactive. Here we report electric-field-induced strong electroluminescence in multilayer MoS2. We show that GaN–Al2O3–MoS2 and GaN–Al2O3–MoS2–Al2O3-graphene vertical heterojunctions can be created with excellent rectification behaviour. Electroluminescence studies demonstrate prominent direct bandgap excitonic emission in multilayer MoS2 over the entire vertical junction area. Importantly, the electroluminescence efficiency observed in multilayer MoS2 is comparable to or higher than that in monolayers. This strong electroluminescence can be attributed to electric-field-induced carrier redistribution from the lowest energy points (indirect bandgap) to higher energy points (direct bandgap) in k-space. The electric-field-induced electroluminescence is general for other layered materials including WSe2 and can open up a new pathway towards transition metal dichalcogenide-based optoelectronic devices. PMID:26130491

  13. Electroluminescent Displays Made With Alternative Dopants

    NASA Technical Reports Server (NTRS)

    Robertson, James B.

    1993-01-01

    Metals and metal fluorides deposited in ZnS to form color phosphors. Single-layer, thin-film electroluminescent display device contains ZnS host layer doped to form green, red, and blue phosphors. Luminescence in chosen colors at chosen intersections between rows and columns produced by application of voltages to appropriate row-and-column pairs of conductors.

  14. Changes induced in a ZnS:Cr-based electroluminescent waveguide structure by intrinsic near-infrared laser radiation

    SciTech Connect

    Vlasenko, N. A. Oleksenko, P. F.; Mukhlyo, M. A.; Veligura, L. I.

    2013-08-15

    The causes of changes that occur in a thin-film electroluminescent metal-insulator-semiconductor-insulator-metal waveguide structure based on ZnS:Cr (Cr concentration of {approx}4 Multiplication-Sign 10{sup 20} cm{sup -3}) upon lasing ({lambda} Almost-Equal-To 2.6 {mu}m) and that induce lasing cessation are studied. It is established that lasing ceases because of light-scattering inhomogeneities formed in the structure and, hence, optical losses enhance. The origin of the inhomogeneities and the causes of their formation are clarified by studying the surface topology and the crystal structure of constituent layers of the samples before and after lasing. The studies are performed by means of atomic force microscopy and X-ray radiography. It is shown that a substantial increase in the sizes of grains on the surface of the structure is the manifestation of changes induced in the ZnS:Cr film by recrystallization. Recrystallization is initiated by local heating by absorbed laser radiation in existing Cr clusters and quickened by a strong electric field (>1 MV cm{sup -1}). The changes observed in the ZnS:Cr film are as follows: the textured growth of ZnS crystallites, an increase in the content of Cr clusters, and the appearance of some CrS and a rather high ZnO content. Some ways for improving the stability of lasing in the ZnS:Cr-based waveguide structures are proposed.

  15. Characterization of GaN-based metal-semiconductor field-effect transistors by comparing electroluminescence, photoionization, and cathodoluminescence spectroscopies

    NASA Astrophysics Data System (ADS)

    Armani, N.; Grillo, V.; Salviati, G.; Manfredi, M.; Pavesi, M.; Chini, A.; Meneghesso, G.; Zanoni, E.

    2002-09-01

    We report on a methodological comparison between photocurrent (PC), electroluminescence (EL), and cathodoluminescence (CL) investigations on GaN metal-semiconductor field-effect transistors. The purpose of this work is to show the effectiveness and the complementarity of these experimental techniques and to investigate the presence and nature of electron traps which limit the performances of the devices. PC measurements reveal four distinct energy levels, located at 1.75, 2.32, 2.67, and 3.15 eV, responsible for current collapse. The 1.75 eV level has also been observed in low temperature EL curves. The 2.32 and 2.67 eV levels, on the basis of the comparison with CL and EL results, can be correlated with the so-called "yellow band," located at 2.2 eV. The origin of 1.75 and 3.15 eV levels is at present unknown, however a nonradiative nature has been attributed to the 3.15 eV level, due to the absence of this signature in both CL and EL spectra. The luminescence measurements also reveal the presence of the donor-acceptor pair emission at 3.27 eV and the near-band-edge transition at 3.45 eV. EL measurements show a series of emission peaks in the energy range between 1 and 1.4 eV, while the CL spectra reveal a broadband at 2.8 eV, which arises mainly from the semi-insulating layer. This result has been obtained by increasing the energy of the CL electron beam, allowing us to investigate both the conduction channel and the layers underneath it.

  16. Magnetic field enhanced electroluminescence in organic light emitting diodes based on electron donor-acceptor exciplex blends

    NASA Astrophysics Data System (ADS)

    Baniya, Sangita; Basel, Tek; Sun, Dali; McLaughlin, Ryan; Vardeny, Zeev Valy

    2016-03-01

    A useful process for light harvesting from injected electron-hole pairs in organic light emitting diodes (OLED) is the transfer from triplet excitons (T) to singlet excitons (S) via reverse intersystem crossing (RISC). This process adds a delayed electro-luminescence (EL) emission component that is known as thermally activated delayed fluorescence (TADF). We have studied electron donor (D)/acceptor(A) blends that form an exciplex manifold in which the energy difference, ΔEST between the lowest singlet (S1) and triplet (T1) levels is relatively small (<100 meV), and thus allows RISC at ambient temperature. We found that the EL emission in OLED based on the exciplex blend is enhanced up to 40% by applying a relatively weak magnetic field of 50 mT at ambient. Moreover the MEL response is activated with activation energy similar that of the EL emission. This suggests that the large magneto-EL originates from an additional spin-mixing channel between singlet and triplet states of the generated exciplexes, which is due to TADF. We will report on the MEL dependencies on the temperature, bias voltage, and D-A materials for optimum OLED performance. Supported by SAMSUNG Global Research Outreach (GRO) program, and also by the NSF-Material Science & Engineering Center (MRSEC) program at the University of Utah (DMR-1121252).

  17. Highly efficient phosphorescent organic light-emitting devices based on Re(CO)3Cl-bathophenanthroline

    NASA Astrophysics Data System (ADS)

    Li, Jiang; Si, Zhenjun; Liu, Chunbo; Li, Chuannan; Zhao, Feifei; Duan, Yu; Chen, Ping; Liu, Shiyong; Li, Bin

    2007-05-01

    Highly efficient orange organic electroluminescent devices based on Re(CO)3Cl-bathophenanthroline have been fabricated. A device with 9 wt% shows the highest efficiencies of 13.8 cd A-1 (luminance efficiency), 8.69 lm W-1 (power efficiency) and 5.24% (external quantum efficiency). Maximum luminance over 4000 cd m-2 is obtained. By discussing the mechanisms, it is believed that trapping contributes mostly to these relatively much higher efficiencies.

  18. Field-effect electroluminescence in silicon nanocrystals.

    PubMed

    Walters, Robert J; Bourianoff, George I; Atwater, Harry A

    2005-02-01

    There is currently worldwide interest in developing silicon-based active optical components in order to leverage the infrastructure of silicon microelectronics technology for the fabrication of optoelectronic devices. Light emission in bulk silicon-based devices is constrained in wavelength to infrared emission, and in efficiency by the indirect bandgap of silicon. One promising strategy for overcoming these challenges is to make use of quantum-confined excitonic emission in silicon nanocrystals. A critical challenge for silicon nanocrystal devices based on nanocrystals embedded in silicon dioxide has been the development of a method for efficient electrical carrier injection. We report here a scheme for electrically pumping dense silicon nanocrystal arrays by a field-effect electroluminescence mechanism. In this excitation process, electrons and holes are both injected from the same semiconductor channel across a tunnelling barrier in a sequential programming process, in contrast to simultaneous carrier injection in conventional pn-junction light-emitting-diode structures. Light emission is strongly correlated with the injection of a second carrier into a nanocrystal that has been previously programmed with a charge of the opposite sign.

  19. Multicolor light-emitting devices with Tb2O3 on silicon

    PubMed Central

    Li, Ling; Wang, Shenwei; Mu, Guangyao; Yin, Xue; Yi, Lixin

    2017-01-01

    Great efforts have been devoted to achieving efficient Si-based light-emitting devices. Here we report new light-emitting devices fabricated with Tb2O3 on Si substrates. Intense green electroluminescence was observed, with a turn-on voltage of about 8 V. The green emission is attributed to the characteristic transitions of Tb3+ ions in Tb2O3. The electroluminescence mechanisms of the Tb2O3 light-emitting devices are discussed. In addition, visible and near infrared electroluminescence was observed in rare-earth (Eu3+, Sm3+ and Yb3+) doped Tb2O3 light-emitting devices. PMID:28220809

  20. Multicolor light-emitting devices with Tb2O3 on silicon

    NASA Astrophysics Data System (ADS)

    Li, Ling; Wang, Shenwei; Mu, Guangyao; Yin, Xue; Yi, Lixin

    2017-02-01

    Great efforts have been devoted to achieving efficient Si-based light-emitting devices. Here we report new light-emitting devices fabricated with Tb2O3 on Si substrates. Intense green electroluminescence was observed, with a turn-on voltage of about 8 V. The green emission is attributed to the characteristic transitions of Tb3+ ions in Tb2O3. The electroluminescence mechanisms of the Tb2O3 light-emitting devices are discussed. In addition, visible and near infrared electroluminescence was observed in rare-earth (Eu3+, Sm3+ and Yb3+) doped Tb2O3 light-emitting devices.

  1. Efficient electroluminescence from new lanthanide (Eu3+, Sm3+) complexes.

    PubMed

    Yu, Jiangbo; Zhou, Liang; Zhang, Hongjie; Zheng, Youxuan; Li, Huanrong; Deng, Ruiping; Peng, Zeping; Li, Zhefeng

    2005-03-07

    The syntheses, structures, and electroluminescent properties are described for two new lanthanide complexes Ln(HFNH)3phen [HFNH = 4,4,5,5,6,6,6-heptafluoro-1-(2-naphthyl)hexane-1,3-dione; phen = 1,10-phenanthroline; Ln = Eu3+ (1), Sm3+ (2)]. Both complexes exhibit bright photoluminescence at room temperature (RT) due to the characteristic emission of Eu3+ and Sm3+ ion. Several devices using the two complexes as emitters were fabricated. The performances of these devices are among the best reported for devices using europium complex and samarium complex as emitters. The device based on 1 with the structure ITO/TPD (50 nm)/1:CBP (10%, 40 nm)/BCP (20 nm)/AlQ (30 nm)/LiF (1 nm)/Al (200 nm) exhibits the maximum brightness of 957 cd/m2, current efficiency of 4.14 cd/A, and power efficiency of 2.28 lm/W with a pure red Eu3+ ion emission. Especially, at the high brightness of 200 cd/m2, the device of 1 still has a high current efficiency of 2.15 cd/A. The device of 2 with a three-layer structure of ITO/TPD (50 nm)/2 (50 nm)/BCP (20 nm)/LiF (1 nm)/Al (200 nm) gives the maximum brightness of 42 cd/m2, current efficiency of 0.18 cd/A. By the comparison of the electroluminescent properties of devices based on Eu(TTA3phen (TTA = 2-thenoyltrifluoroacteonate) and 1, we conclude that the polyfluoration on the alkyl group of the ligand and the introduction of the long conjugate naphthyl group into the ligand improve the efficiency of 1-doped devices, especially at high current densities.

  2. Electrodeposited, Transverse Nanowire Electroluminescent Junctions.

    PubMed

    Qiao, Shaopeng; Xu, Qiang; Dutta, Rajen K; Le Thai, Mya; Li, Xiaowei; Penner, Reginald M

    2016-09-27

    The preparation by electrodeposition of transverse nanowire electroluminescent junctions (tn-ELJs) is described, and the electroluminescence (EL) properties of these devices are characterized. The lithographically patterned nanowire electrodeposition process is first used to prepare long (millimeters), linear, nanocrystalline CdSe nanowires on glass. The thickness of these nanowires along the emission axis is 60 nm, and the width, wCdSe, along the electrical axis is adjustable from 100 to 450 nm. Ten pairs of nickel-gold electrical contacts are then positioned along the axis of this nanowire using lithographically directed electrodeposition. The resulting linear array of nickel-CdSe-gold junctions produces EL with an external quantum efficiency, EQE, and threshold voltage, Vth, that depend sensitively on wCdSe. EQE increases with increasing electric field and also with increasing wCdSe, and Vth also increases with wCdSe and, therefore, the electrical resistance of the tn-ELJs. Vth down to 1.8(±0.2) V (for wCdSe ≈ 100 nm) and EQE of 5.5(±0.5) × 10(-5) (for wCdSe ≈ 450 nm) are obtained. tn-ELJs produce a broad EL emission envelope, spanning the wavelength range from 600 to 960 nm.

  3. Enhancement of electroluminescence in zirconium poly carboxylic acid-based light emitting diodes by bathophenanthroline ligand.

    PubMed

    Shahroosvand, Hashem; Nasouti, Fahimeh; Sousaraei, Ahmad; Mohajerani, Ezeddin; Khabbazi, Amir

    2013-06-28

    The reactions of a zirconium salt with 1,2,4,5-benzenetetracarboxylate (btec), bathophenanthroline (Bphen) and thiocyanate ions were synthesized and studied by changing the mole ratio, the order of reactant and their pH. It is found that the coordination mode of btec acid depends on the control of reaction conditions. Monodentate, bidentate and bridging modes were investigated by FT-IR spectroscopy. The structures of Zr(btec) and Zr(btec)(Bphen) complexes were also characterized by UV-Vis, CHN, ICP-AES, (1)H NMR and cyclic voltammetry. The role of Bphen ligand in the photopysical properties of Zr(btec)(Bphen) complexes was investigated by DFT calculation. The photoluminescence (PL) emission of nine Zr(btec) complexes that have two peaks, a sharp and intense band for the first peak from 320 to 430 nm in comparison to the second peak with a less intensity and broadened in the regions of 650-780 nm. PL spectra of twelve Zr(btec)(Bphen) complexes also showed bands at 450, 550, 625 nm. LED devices with Zr complex as emitter layer and the structure ITO/PEDOT:PSS/PVK:PBD/zirconium complex/Al emitted a broad band centered at 550 and 650 originating from the Zr complexes. The EL spectra of Zr(btec) and Zr(btec)(Bphen) complexes indicated a long red shift rather than PVK:PBD blend. We believe that the electroplex occurring at PVK-Zr complexes interface is responsible for the green-red emission in the EL of the device. These observations suggest an important role for the Bphen ligand to improve EL performance.

  4. Visible electroluminescence in spark-processed silicon

    NASA Astrophysics Data System (ADS)

    Shepherd, Nigel Dexter

    Spark-processing is a novel technique that transforms silicon into a material with unique optical and magnetic properties. In this work, the electroluminescence (EL) from spark-processed silicon (sp-Si) has been studied and characterized. The devices studied have a MOS (metal-oxide-semiconductor) type structure. The EL spectrum is broad, and has a threshold wavelength that extends beyond 350 nm, and peaks at around 650 and 730 nm. The threshold voltage for the EL process is typically in the 5--8 V range. Irrespective of whether the base silicon is n or p-type, EL is observed only under the condition of electron injection into the spark-processed layer. The processing conditions that result in the highest EL intensity have been established. Specifically, the processing parameters that results in the highest device currents and EL intensity are 7--8 kV, 10 mA, 12--13 kHz, around 750 mbar and 10 seconds of spark voltage, current, frequency, pressure and time respectively. It has been also been found that processing in air results in higher EL intensities, compared to processing in ultra-high purity nitrogen or oxygen. These conditions are believed to result in the optimal composition and thickness of the near surface SiOx layers, thought to be the optically active region in sp-Si EL devices. These processing conditions are also believed to result in a surface morphology that facilitates the best coverage by the semitransparent metal film, through which the electroluminescence is emitted. When a tungsten wire is used as the anode for spark-processing, the pattern of emission is a circular band of light. This band consists of small light-emitting spots, separated by non-emitting regions. It is shown that by modifying the anode arrangement, significant improvements to the pattern of emission and EL intensity can be achieved. These improvements are proposed to be due to enhanced coverage by the semitransparent metal film. Based on the results of the EL characterization

  5. [Photoluminescent and electroluminescent properties of a new rare earth terbium complex].

    PubMed

    Wang, Li; Zhang, Xi-qing; Lin, Peng; Xiong, De-pin; Huang, Shi-hua; Yu, Tian-zhi

    2004-06-01

    Pure green and narrowbandwidth emission from an organic electroluminescent device was presented by using arare earth terbium (III) complex as the emissive layer. The structure of the device was ITO/PVK/Tb/PBD/LiF/Al. It was proved that this new kind of rare earth complex has excellent photoluminescent and electroluminescent properties. The electroluminescent spectrum of the device was very similar to that of the terbium (III) complex film. The electroluminescent mechanism of the device was proposed by measuring and analyzing the spectra and electroluminescent property of the device. It is proposed that the excited carriers of PVK and PBD were captured by Tb3+ and light was emitted when the electrons and holes recombined at Tb3+.

  6. Electroluminescence Imaging Of Space Solar Cells

    NASA Astrophysics Data System (ADS)

    Zimmermann, C. G.

    2011-10-01

    Space solar power is one of the few applications where large area III-V devices are used. Therefore there is great potential for a spatially resolved technique in the inspection, failure investigation and characterization of these devices. Mechanical defects can be identified by electroluminescence imaging unambiguously. The impact of a cell crack on the current distribution in the cell is modeled and the electroluminescence signature of a cell crack is derived. Another qualitative application is failure investigation of cells that suffer degradation, for example in environmental testing. Series resistance problems can be visualized and the location of an environmental attack can be pinpointed on a μm length scale. Finally under the appropriate simplifications, even a quantitative cell characterization can be attempted. Maps of the open circuit voltage and the current at the operating voltage identify shunts quantitatively.

  7. Silicon nanowire hot electron electroluminescence

    NASA Astrophysics Data System (ADS)

    du Plessis, Monuko; Joubert, Trudi-Heleen

    2016-02-01

    This paper investigates the avalanche electroluminescence characteristics of pn junctions formed in silicon nanowires fabricated in a silicon-on-insula*tor (SOI) technology. Since carriers are confined to the nanowires, it is possible to study the effect of electric field strength on device performance while the current density and carrier concentrations are kept constant. This is achieved by varying the nanowire length while keeping the bias current constant, eventually driving the pn junction into the reach-through bias condition. It is observed that photon emission for photon energies higher than 1.2 eV increases when the nanowire length is reduced, while photon emission with energies less than 1.2 eV decreases. The higher electric field in the nanowire at shorter nanowire lengths enhances the high-energy photon emission and attenuates the low energy photon emission.

  8. White-blue electroluminescence from a Si quantum dot hybrid light-emitting diode

    SciTech Connect

    Xin, Yunzi; Nishio, Kazuyuki; Saitow, Ken-ichi

    2015-05-18

    A silicon (Si) quantum dot (QD)-based hybrid inorganic/organic light-emitting diode (LED) was fabricated via solution processing. This device exhibited white-blue electroluminescence at a low applied voltage of 6 V, with 78% of the effective emission obtained from the Si QDs. This hybrid LED produced current and optical power densities 280 and 350 times greater than those previously reported for such device. The superior performance of this hybrid device was obtained by both the prepared Si QDs and the optimized layer structure and thereby improving carrier migration through the hybrid LED and carrier recombination in the homogeneous Si QD layer.

  9. ZnCdMgSe-Based Semiconductors for Intersubband Devices

    SciTech Connect

    Tamargo, Maria C.

    2008-11-13

    This paper presents a review of recent results on the application of ZnCdMgSe-based wide bandgap II-VI compounds to intersubband devices such as quantum cascade lasers and quantum well infrared photodetectors operating in the mid-infrared region. The conduction band offset of ZnCdSe/ZnCdMgSe quantum well structures was determined from contactless electroreflectance measurements to be as high as 1.12 eV. FT-IR was used to measure intersubband absorption in multi-quantum well structures in the mid-IR range. Electroluminescence at 4.8 {mu}m was observed from a quantum cascade emitter structure made from these materials. Preliminary results are also presented on self assembled quantum dots of CdSe on ZnCdMgSe, and novel quantum well structures with metastable binary MgSe barriers.

  10. [Progress of organometallic complexes and their application to organic electroluminescent materials].

    PubMed

    Zhou, Rui; An, Zhong-Wei; Chai, Sheng-Yong

    2004-08-01

    Organic electroluminescent (EL) material is one of most prospective display materials in flat panel display. Organometallic complexes, which have five or six member ring structures, with high stability, high melting point and high fluorescence quantum efficiency, are widely applied in organic EL devices. The recent progress in organometallic complexes is summarized in terms of the electroluminescence of ligands and metal atoms.

  11. Photoemission-based microelectronic devices

    PubMed Central

    Forati, Ebrahim; Dill, Tyler J.; Tao, Andrea R.; Sievenpiper, Dan

    2016-01-01

    The vast majority of modern microelectronic devices rely on carriers within semiconductors due to their integrability. Therefore, the performance of these devices is limited due to natural semiconductor properties such as band gap and electron velocity. Replacing the semiconductor channel in conventional microelectronic devices with a gas or vacuum channel may scale their speed, wavelength and power beyond what is available today. However, liberating electrons into gas/vacuum in a practical microelectronic device is quite challenging. It often requires heating, applying high voltages, or using lasers with short wavelengths or high powers. Here, we show that the interaction between an engineered resonant surface and a low-power infrared laser can cause enough photoemission via electron tunnelling to implement feasible microelectronic devices such as transistors, switches and modulators. The proposed photoemission-based devices benefit from the advantages of gas-plasma/vacuum electronic devices while preserving the integrability of semiconductor-based devices. PMID:27811946

  12. Photoemission-based microelectronic devices

    NASA Astrophysics Data System (ADS)

    Forati, Ebrahim; Dill, Tyler J.; Tao, Andrea R.; Sievenpiper, Dan

    2016-11-01

    The vast majority of modern microelectronic devices rely on carriers within semiconductors due to their integrability. Therefore, the performance of these devices is limited due to natural semiconductor properties such as band gap and electron velocity. Replacing the semiconductor channel in conventional microelectronic devices with a gas or vacuum channel may scale their speed, wavelength and power beyond what is available today. However, liberating electrons into gas/vacuum in a practical microelectronic device is quite challenging. It often requires heating, applying high voltages, or using lasers with short wavelengths or high powers. Here, we show that the interaction between an engineered resonant surface and a low-power infrared laser can cause enough photoemission via electron tunnelling to implement feasible microelectronic devices such as transistors, switches and modulators. The proposed photoemission-based devices benefit from the advantages of gas-plasma/vacuum electronic devices while preserving the integrability of semiconductor-based devices.

  13. Transistor and memory devices based on novel organic and biomaterials

    NASA Astrophysics Data System (ADS)

    Tseng, Jia-Hung

    Organic semiconductor devices have aroused considerable interest because of the enormous potential in many technological applications. Organic electroluminescent devices have been extensively applied in display technology. Rapid progress has also been made in transistor and memory devices. This thesis considers aspects of the transistor based on novel organic single crystals and memory devices using hybrid nanocomposites comprising polymeric/inorganic nanoparticles, and biomolecule/quantum dots. Organic single crystals represent highly ordered structures with much less imperfections compared to amorphous thin films for probing the intrinsic charge transport in transistor devices. We demonstrate that free-standing, thin organic single crystals with natural flexing ability can be fabricated as flexible transistors. We study the surface properties of the organic crystals to determine a nearly perfect surface leading to high performance transistors. The flexible transistors can maintain high performance under reversible bending conditions. Because of the high quality crystal technique, we further develop applications on organic complementary circuits and organic single crystal photovoltaics. In the second part, two aspects of memory devices are studied. We examine the charge transfer process between conjugated polymers and metal nanoparticles. This charge transfer process is essential for the conductance switching in nanoseconds to induce the memory effect. Under the reduction condition, the charge transfer process is eliminated as well as the memory effect, raising the importance of coupling between conjugated systems and nanoparticle accepters. The other aspect of memory devices focuses on the interaction of virus biomolecules with quantum dots or metal nanoparticles in the devices. We investigate the impact of memory function on the hybrid bio-inorganic system. We perform an experimental analysis of the charge storage activation energy in tobacco mosaic virus with

  14. Relaxation of parameters of thin-film electroluminescent ZnS:Mn-based structures when turned off

    SciTech Connect

    Gurin, N. T. Sabitov, O. Yu.

    2008-06-15

    Results of experimental study of decay of the current flowing through a thin-film electroluminescent MISIM structure indicate a bimolecular process of electron capture by the surface states of the anode interface. A two-stage model of the process is suggested. At the first stage, the impact Auger capture of hot electrons takes place. At the second stage, upon varying the field direction, the holes of the valence band generated due to tunnel emission from deep centers drift to this interface, where they recombine with electrons of deepest occupied surface states. The electron lifetime and rate of the surface capture of electrons as well as their dependences on excitation parameters are determined. The behavior of the time dependence of the instant internal quantum yield at the decay portion is interpreted.

  15. Current and Temperature Dependences of Electroluminescence of InGaN-Based UV/Blue/Green Light-Emitting Diodes

    NASA Astrophysics Data System (ADS)

    Mukai, Takashi; Yamada, Motokazu; Nakamura, Shuji

    1998-11-01

    Current and temperature dependences of the electroluminescence of InGaN UV/blue/green single-quantum-well (SQW)-structure light-emitting diodes (LEDs) were studied. The emission mechanism of InGaN SQW-structure LEDs with emission peak wavelengths longer than 375 nm is dominated by carrier recombination at large localized energy states caused by In composition fluctuation in the InGaN well layer. When the emission peak wavelength becomes shorter than 375 nm, the conventional band-to-band emission mechanism becomes dominant due to poor carrier localization resulting from small In composition fluctuations. In addition, the quantum-confined Stark effect due to the piezoelectric field becomes dominant, which causes a low output power of the UV LEDs.

  16. Mid-infrared electro-luminescence and absorption from AlGaN/GaN-based multi-quantum well inter-subband structures

    SciTech Connect

    Hofstetter, Daniel; Bour, David P.; Kirste, Lutz

    2014-06-16

    We present electro-modulated absorption and electro-luminescence measurements on chirped AlGaN/GaN-based multi-quantum well inter-subband structures grown by metal-organic vapour phase epitaxy. The absorption signal is a TM-polarized, 70 meV wide feature centred at 230 meV. At medium injection current, a 58 meV wide luminescence peak corresponding to an inter-subband transition at 1450 cm{sup −1} (180 meV) is observed. Under high injection current, we measured a 4 meV wide structure peaking at 92.5 meV in the luminescence spectrum. The energy location of this peak is exactly at the longitudinal optical phonon of GaN.

  17. Graphene-based conformal devices.

    PubMed

    Park, Yong Ju; Lee, Seoung-Ki; Kim, Min-Seok; Kim, Hyunmin; Ahn, Jong-Hyun

    2014-08-26

    Despite recent progress in bendable and stretchable thin-film transistors using novel designs and materials, the development of conformal devices remains limited by the insufficient flexibility of devices. Here, we demonstrate the fabrication of graphene-based conformal and stretchable devices such as transistor and tactile sensor on a substrate with a convoluted surface by scaling down the device thickness. The 70 nm thick graphene-based conformal devices displayed a much lower bending stiffness than reported previously. The demonstrated devices provided excellent conformal coverage over an uneven animal hide surface without the need for an adhesive. In addition, the ultrathin graphene devices formed on the three-dimensionally curved animal hide exhibited stable electrical characteristics, even under repetitive bending and twisting. The advanced performance and flexibility demonstrated here show promise for the development and adoption of wearable electronics in a wide range of future applications.

  18. Analysis of power supply circuits for electroluminescent panels

    NASA Astrophysics Data System (ADS)

    Drumea, Andrei; Dobre, Robert Alexandru

    2016-12-01

    The electroluminescent panel is a light emitting device that requires for normal operations alternative voltages with peak to peak amplitudes in 100V… 300V range and frequencies in 100Hz … 2 kHz range. Its advantages, when compared with standard light sources like incandescent lamps, gas-discharge lamps or light emitting diodes (LEDs), are lower power consumption, flexible substrate and uniform light without observable luminous points. One disadvantage of electroluminescent panels is the complex power supply required to drive them, but the continuous improvement in passive and active integrated devices for switched mode power supplies will eventually solve this issue. The present paper studies different topologies for these power supplies and the effect of the electric parameters like the amplitude, frequency, waveform of the supplying voltage on the light emission and on power consumption for electroluminescent panels with different size and colors.

  19. Organic electroluminescent structures for new generation of display systems

    NASA Astrophysics Data System (ADS)

    Ermakov, Oleg N.; Kaplunov, Michail G.; Efimov, Oleg N.; Stakharny, Sergey A.

    2007-05-01

    Brief history, modern state and development trends of organic electroluminescent structures technology (so-called OLED technology) are reviewed including research activities in this field in Russia. It's noted that OLED technology is one of the most promising newly emerging display technologies. Due to advantages of these devices (low power consumption, potential flexibility, wide color range) it is particularly well suited for small area display applications (micro displays) such as cell phones, virtual imaging systems, portable electronics. Experimental results for homemade blue light emitting OLED structures and hermetically sealed numeric displays are presented including photoluminescence (PL) and electroluminescence (EL ) current-voltage and brightness characteristics. It is noted that visible electroluminescence is observed at ultra low current level of nearly 1 μA, luminous efficiency exceeding 1 lm/W thus being nearly the same as for super bright inorganic inGaN/IGaN LEDs. Special attention is paid for destabilizing factors (temperature and degradation phenomena) influence on device characteristics.

  20. Asphaltene based photovoltaic devices

    DOEpatents

    Chianelli, Russell R.; Castillo, Karina; Gupta, Vipin; Qudah, Ali M.; Torres, Brenda; Abujnah, Rajib E.

    2016-03-22

    Photovoltaic devices and methods of making the same, are disclosed herein. The cell comprises a photovoltaic device that comprises a first electrically conductive layer comprising a photo-sensitized electrode; at least one photoelectrochemical layer comprising metal-oxide particles, an electrolyte solution comprising at least one asphaltene fraction, wherein the metal-oxide particles are optionally dispersed in a surfactant; and a second electrically conductive layer comprising a counter-electrode, wherein the second electrically conductive layer comprises one or more conductive elements comprising carbon, graphite, soot, carbon allotropes or any combinations thereof.

  1. Room-temperature electroluminescence from two-dimensional lead halide perovskites

    NASA Astrophysics Data System (ADS)

    Li, Renzhi; Yi, Chang; Ge, Rui; Zou, Wei; Cheng, Lu; Wang, Nana; Wang, Jianpu; Huang, Wei

    2016-10-01

    Room-temperature electroluminescence (EL) is demonstrated from a light-emitting diode (LED) based on two-dimensional lead halide perovskites, (C6H5NH3)2PbI4. The device has a multilayer structure of ITO/Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate)/(C6H5CH2NH3)2PbI4/Bathophenanthroline/Al. The EL emission peaks at 526 nm with a narrow full width at half maximum of 15 nm, which origins from perovskite exciton emission. The LED device exhibits a maximum luminance of ˜9 cd m-2 at a bias of 5 V.

  2. Double side electroluminescence from p-NiO/n-ZnO nanowire heterojunctions

    SciTech Connect

    Wang, J.-Y.; Chen, Y.-T.; Chen, C.-T.; Chen, Y.-L.; Chen, Y.-F.; Lee, C.-Y.; Lin, C.-F.

    2009-09-28

    Double side light emission devices based on p-NiO/n-ZnO nanowire heterojunctions have been fabricated on indium tin oxide substrate by radio frequency magnetron sputtering combined with hydrothermal process. According to the energy band alignment, the detected broad visible and narrow ultraviolet electroluminescence arise from defect and band edge transitions in ZnO nanowires, respectively. The unique property of the double side emission is due to the nature of the large band gap of NiO film. It provides a good opportunity for the emission of a light emitting device with different colors on the top and back sides, simultaneously.

  3. Carbon based prosthetic devices

    SciTech Connect

    Devlin, D.J.; Carroll, D.W.; Barbero, R.S.; Archuleta, T.; Klawitter, J.J.; Ogilvie, W.; Strzepa, P.; Cook, S.D.

    1998-12-31

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The project objective was to evaluate the use of carbon/carbon-fiber-reinforced composites for use in endoprosthetic devices. The application of these materials for the metacarpophalangeal (MP) joints of the hand was investigated. Issues concerning mechanical properties, bone fixation, biocompatibility, and wear are discussed. A system consisting of fiber reinforced materials with a pyrolytic carbon matrix and diamond-like, carbon-coated wear surfaces was developed. Processes were developed for the chemical vapor infiltration (CVI) of pyrolytic carbon into porous fiber preforms with the ability to tailor the outer porosity of the device to provide a surface for bone in-growth. A method for coating diamond-like carbon (DLC) on the articulating surface by plasma-assisted chemical vapor deposition (CVD) was developed. Preliminary results on mechanical properties of the composite system are discussed and initial biocompatibility studies were performed.

  4. Blue/pink/purple electroluminescence from metal-oxide-semiconductor devices fabricated by spin-coating of [tantalum:(gadolinium/praseodymium)] and (praseodymium:cerium) organic compounds on silicon

    NASA Astrophysics Data System (ADS)

    Ohzone, Takashi; Matsuda, Toshihiro; Fukuoka, Ryouhei; Hattori, Fumihiro; Iwata, Hideyuki

    2016-08-01

    Blue/pink/purple electroluminescence (EL) from metal-oxide-semiconductor (MOS) devices with an indium tin oxide (ITO)/[Gd/(Ta + Gd/Pr)/(Pr + Ce)-Si-O] insulator layer/n+-Si substrate surface is reported. The insulator layers were fabricated from organic liquid sources of Gd or (Ta + Gd/Pr)/(Pr + Ce) mixtures, which were spin-coated on the n+-Si substrate and annealed at 950 °C for 30 min in air. The EL emission could be observed by the naked eye in the dark in the Fowler-Nordheim (FN) tunnel current regions. Peak wavelengths in the measured EL spectra were independent of the positive current. The EL intensity ratio of ultraviolet (UV) to the visible range varied with the composition ratio of the (Ta + Gd) liquids, and an optimum Ta to Gd ratio existed for the strongest blue emission, which could be attributed to the Ta-related oxide/silicate. The pink EL of the device fabricated with the (\\text{Ta}:\\text{Pr} = 6:4) mixture ratio can be explained by EL emission peaks related to the Pr3+ ions. The purple EL observed from the (\\text{Pr}:\\text{Ce} = 6:4) device corresponds to the strong and broad emission profile near the 357 nm peak, which cannot be assigned to Ce3+ ions. The results suggest that the EL can be attributed to the double-layer oxides with different compositions in the MOS devices. The upper layer consists of various Ta-, Gd-, Pr-, and Ce-related oxides and their silicates, while the lower SiO x -rich layer contributes to the FN current due to the high electric field, and thus the various EL colors.

  5. 2-(2-Hydroxyphenyl)benzimidazole-based four-coordinate boron-containing materials with highly efficient deep-blue photoluminescence and electroluminescence.

    PubMed

    Zhang, Zhenyu; Zhang, Houyu; Jiao, Chuanjun; Ye, Kaiqi; Zhang, Hongyu; Zhang, Jingying; Wang, Yue

    2015-03-16

    Two novel four-coordinate boron-containing emitters 1 and 2 with deep-blue emissions were synthesized by refluxing a 2-(2-hydroxyphenyl)benzimidazole ligand with triphenylborane or bromodibenzoborole. The boron chelation produced a new π-conjugated skeleton, which rendered the synthesized boron materials with intense fluorescence, good thermal stability, and high carrier mobility. Both compounds displayed deep-blue emissions in solutions with very high fluorescence quantum yields (over 0.70). More importantly, the samples showed identical fluorescence in the solution and solid states, and the efficiency was maintained at a high level (approximately 0.50) because of the bulky substituents between the boron atom and the benzimidazole unit, which can effectively separate the flat luminescent units. In addition, neat thin films composed of 1 or 2 exhibited high electron and hole mobility in the same order of magnitude 10(-4), as determined by time-of-flight. The fabricated electroluminescent devices that employed 1 or 2 as emitting materials showed high-performance deep-blue emissions with Commission Internationale de L'Eclairage (CIE) coordinates of (X = 0.15, Y = 0.09) and (X = 0.16, Y = 0.08), respectively. Thus, the synthesized boron-containing materials are ideal candidates for fabricating high-performance deep-blue organic light-emitting diodes.

  6. Electroluminescence from ZnO-nanofilm/Si-micropillar heterostructure arrays.

    PubMed

    Chan, Yu Fei; Su, Wei; Zhang, Chang Xing; Wu, Zheng Long; Tang, Ying; Sun, Xiao Qi; Xu, Hai Jun

    2012-10-22

    ZnO-nanofilm/Si-micropillar p-n nanoheterostructure arrays were prepared by growing n-type ZnO onto a p-type nanoporous Si pillar array. Its current-voltage characteristics of nanoheterostructure showed good rectifying behavior with onset voltage of ~1.5 V, forward current density of ~28.7 mA/cm(2) at 2.5 V, leakage current density of ~0.15 mA/cm(2) and rectifying ratio of ~121 at ± 2.5 V. The electron transport across nanohetreostructure obeys the trap-charge-limit current model. Moreover, strong white light electroluminescence from ZnO-nanofilm/Si-micropillar light-emitting diode (LED) has been achieved, which could open up possibilities to build new ZnO/Si-based highly efficient solid-state lighting devices.

  7. Interfused semiconductor nanocrystals: brilliant blue photoluminescence and electroluminescence.

    PubMed

    Jun, Shinae; Jang, Eunjoo

    2005-09-28

    We describe a method for producing blue light-emitting interfused CdSe//ZnS (QE up to 60%) nanocrystals and report the good performance of an electroluminescent device which uses them (external quantum efficiency approximately 1.5 cd A(-1)).

  8. [Electroluminescence character of novel unsymmetry substituted phthalocyanines].

    PubMed

    Xia, Dao-cheng; Li, Wan-cheng; Han, Shuang; Cheng, Chuan-hui; Li, Quan-quan; Wang, Jin; Zhang, Wei; Li, Zhu

    2010-09-01

    The authors for the first time fabricated OLEDs employing novel phthalocynines: 2(3)-(p-tert-butylphenoxy) copper phthalocyanine(1), 2(3),16(17)-di(p-tert-butyl-phenoxy) copper phthalocyanine(2) and 2(3), 9(10), 16(17)-tri (p-tert-butylphenoxy) copper phthalocyanine(3) as light emitting layer, and their electroluminescence character was studied. The final structures of three-layer OLEDs based on copper 2(3)-(p-tert-butylphenoxy) copper phthalocyanine (1) and 2(3), 9(10), 16(17)-tri (p-tert-butylphenoxy) copper phthalocyanine(3) were ITO/NPB(40 nm)/Pc(30 nm)/AlQ(43.5 nm)/LiF (0.5 nm)/Al(120 nm). The structure of three-layer OLED based on 2(3), 9(10), 16(17)-tri (p-tert-butylphenoxy) copper phthalocyanine (3) was ITO/NPB(30 nm)/Pc(30 nm) /BCP(20 nm)/A1Q(30 nm)/LiF (0. 5 nm)/Al(120 nm). Room-temperature electroluminescence was observed at about 869 nmand 1 062 nm for 2(3)-(p-tert-butylphenoxy) copper phthalocyanine(1); room-temperature electroluminescence of 2(3),16(17) -di(p-tert-butyl-phenoxy) copper phthalocyanine(2) was found at about 1050 nm and 1110 nm; and room-temperature electroluminescence of 2(3), 9(10), 16( 17)-tri (p-tert-butylphenoxy) copper phthalocyanine(3) was studied at about 1095 and 1204 nm. The emission wavelengths and the half bandwidths were quite different for the phthalocyanine, which may be due to the differences in the number of substituted and the molecular aggregations in vacuum sublimed films. The difference in Stokes shift relaxation was also induced by the molecular aggregations.

  9. Photo- and electroluminescence properties of lanthanide tungstate-doped porous anodic aluminum oxide

    NASA Astrophysics Data System (ADS)

    Staninski, Krzysztof; Piskuła, Zbigniew; Kaczmarek, Małgorzata

    2017-02-01

    A new cathode material for the potential use in light-emitting devices, based on porous anodic alumina (PAA), aluminum and ITO layers has been synthesized. Porous alumina samples with ordered pore arrays were prepared electrochemically from high purity Al sheet in H2SO4 and H3PO4. To be able to apply the matrix obtained in the electroluminescence cell, the thickness of the barrier layer of aluminum oxide was decreased by slow reduction of the anodization voltage to zero. The luminescence and electroluminescence (EL) properties of the Al2O3 matrix admixtured with Eu3+ and Tb3+ ions as well as europium and terbium tungstates, were determined. The particles of inorganic luminophore were synthesized on the walls of the matrix cylindrical nanopores in the two-step process of immersion in solutions of TbCl3 or EuCl3 and Na2WO4. The effect of the nanopores diameter and the thickness of the porous Al2O3 layer on the intensity and relative yield of electroluminescence was analyzed, the best results were obtained for 80-90 μm PAA layers with 140 nm nanopores.

  10. Polyhedral Oligomeric Silsesquioxane Enhances the Brightness of Perovskite Nanocrystal-Based Green Light-Emitting Devices.

    PubMed

    Huang, He; Lin, Hong; Kershaw, Stephen V; Susha, Andrei S; Choy, Wallace C H; Rogach, Andrey L

    2016-11-03

    The beneficial role of the insulating material polyhedral oligomeric silsesquioxane (POSS) as a solution additive or an additional hole-blocking layer to enhance the performance of electroluminescent green light-emitting devices (LEDs) based on CsPbBr3 perovskite nanocrystals is demonstrated. POSS improves the surface coverage and the morphological features of the films deposited either from supernatant or suspension of perovskite nanocrystals. The external quantum efficiency and the luminance efficiency of LEDs with an additional POSS layer reach 0.35% and 1.20 cd/A, respectively, constituting a more than 17-fold enhancement to the reference devices without POSS; the LED peak luminance reaches 2983 cd/m(2), and the device stability is improved. The POSS acts as a hole-blocking layer between the perovskite nanocrystals and TPBi, keeping both electrons and holes located within the active layer for an efficient recombination.

  11. Streamline-based microfluidic device

    NASA Technical Reports Server (NTRS)

    Tai, Yu-Chong (Inventor); Zheng, Siyang (Inventor); Kasdan, Harvey (Inventor)

    2013-01-01

    The present invention provides a streamline-based device and a method for using the device for continuous separation of particles including cells in biological fluids. The device includes a main microchannel and an array of side microchannels disposed on a substrate. The main microchannel has a plurality of stagnation points with a predetermined geometric design, for example, each of the stagnation points has a predetermined distance from the upstream edge of each of the side microchannels. The particles are separated and collected in the side microchannels.

  12. Enhancing the electroluminescence efficiency of Si NC/SiO2 superlattice-based light-emitting diodes through hydrogen ion beam treatment

    NASA Astrophysics Data System (ADS)

    Fu, Sheng-Wen; Chen, Hui-Ju; Wu, Hsuan-Ta; Chen, Shao-Ping; Shih, Chuan-Feng

    2016-03-01

    This paper presents a novel method for enhancing the electroluminescence (EL) efficiency of ten-period silicon-rich oxide (SRO)/SiO2 superlattice-based light-emitting diodes (LEDs). A hydrogen ion beam (HIB) was used to irradiate each SRO layer of the superlattices to increase the interfacial roughness on the nanoscale and the density of the Si nanocrystals (Si NCs). Fowler-Nordheim (F-N) tunneling was the major mechanism for injecting the carriers into the Si NCs. The barrier height of the F-N tunneling was lowered by forming a nano-roughened interface and the nonradiative Pb centers were passivated through the HIB treatment. Additionally, the reflectance of the LEDs was lowered because of the nano-roughened interface. These factors considerably increased the slope efficiency of EL and the maximum output power of the LEDs. The lighting efficiency increased by an order of magnitude, and the turn-on voltage decreased considerably. This study established an efficient approach for obtaining bright Si NC/SiO2 superlattice-based LEDs.

  13. Enhancing the electroluminescence efficiency of Si NC/SiO2 superlattice-based light-emitting diodes through hydrogen ion beam treatment.

    PubMed

    Fu, Sheng-Wen; Chen, Hui-Ju; Wu, Hsuan-Ta; Chen, Shao-Ping; Shih, Chuan-Feng

    2016-04-07

    This paper presents a novel method for enhancing the electroluminescence (EL) efficiency of ten-period silicon-rich oxide (SRO)/SiO2 superlattice-based light-emitting diodes (LEDs). A hydrogen ion beam (HIB) was used to irradiate each SRO layer of the superlattices to increase the interfacial roughness on the nanoscale and the density of the Si nanocrystals (Si NCs). Fowler-Nordheim (F-N) tunneling was the major mechanism for injecting the carriers into the Si NCs. The barrier height of the F-N tunneling was lowered by forming a nano-roughened interface and the nonradiative Pb centers were passivated through the HIB treatment. Additionally, the reflectance of the LEDs was lowered because of the nano-roughened interface. These factors considerably increased the slope efficiency of EL and the maximum output power of the LEDs. The lighting efficiency increased by an order of magnitude, and the turn-on voltage decreased considerably. This study established an efficient approach for obtaining bright Si NC/SiO2 superlattice-based LEDs.

  14. Electrical and Optical Characterization of Nanowire based Semiconductor Devices

    NASA Astrophysics Data System (ADS)

    Ayvazian, Talin

    This research project is focused on a new strategy for the creation of nanowire based semiconductor devices. The main goal is to understand and optimize the electrical and optical properties of two types of nanoscale devices; in first type lithographically patterned nanowire electrodeposition (LPNE) method has been utilized to fabricate nanowire field effect transistors (NWFET) and second type involved the development of light emitting semiconductor nanowire arrays (NWLED). Field effect transistors (NWFETs) have been prepared from arrays of polycrystalline cadmium selenide (pc-CdSe) nanowires using a back gate configuration. pc-CdSe nanowires were fabricated using the lithographically patterned nanowire electrode- position (LPNE) process on SiO2 /Si substrates. After electrodeposition, pc-CdSe nanowires were thermally annealed at 300 °C x 4 h either with or without exposure to CdCl 2 in methanol a grain growth promoter. The influence of CdCl2 treatment was to increase the mean grain diameter as determined by X-ray diffraction pattern and to convert the crystal structure from cubic to wurtzite. Transfer characteristics showed an increase of the field effect mobility (mu eff) by an order of magnitude and increase of the Ion/I off ratio by a factor of 3-4. Light emitting devices (NW-LED) based on lithographically patterned pc-CdSe nanowire arrays have been investigated. Electroluminescence (EL) spectra of CdSe nanowires under various biases exhibited broad emission spectra centered at 750 nm close to the band gap of CdSe (1.7eV). To enhance the intensity of the emitted light and the external quantum efficiency (EQE), the distance between the contacts were reduced from 5 mum to less than 1 mum which increased the efficiency by an order of magnitude. Also, increasing the annealing temperature of nanowires from 300 °C x4 h to 450 This research project is focused on a new strategy for the creation of nanowire based semiconductor devices. The main goal is to understand

  15. FIrpic: archetypal blue phosphorescent emitter for electroluminescence.

    PubMed

    Baranoff, Etienne; Curchod, Basile F E

    2015-05-14

    FIrpic is the most investigated bis-cyclometallated iridium complex in particular in the context of organic light emitting diodes (OLEDs) because of its attractive sky-blue emission, high emission efficiency, and suitable energy levels. In this Perspective we review the synthesis, structural characterisations, and key properties of this emitter. We also survey the theoretical studies and summarise a series of selected monochromatic electroluminescent devices using FIrpic as the emitting dopant. Finally we highlight important shortcomings of FIrpic as an emitter for OLEDs. Despite the large body of work dedicated to this material, it is manifest that the understanding of photophysical and electrochemical processes are only broadly understood mainly because of the different environment in which these properties are measured, i.e., isolated molecules in solvent vs. device.

  16. Growth and characterization of silicon-based optoelectronic devices

    NASA Astrophysics Data System (ADS)

    Filios, Adam A.

    layers sandwiched between monolayers of oxygen. The key for its fabrication is that epitaxial growth of silicon may be continued beyond the interruption with exposure to oxygen. Prepared by an Ultra High Vacuum (UHV), Molecular Beam Epitaxial (MBE) technique, the multilayer device is extremely stable and robust, and can be readily integrated with conventional silicon VLSI processing. In addition, it exhibits bright, room temperature, visible photoluminescent and electroluminescent emission, at least as strong as that of porous silicon. With its efficient light emission, robustness and stability, the c-Si/O superlattice may hold the promise of a truly integrated silicon-based optoelectronic device.

  17. Zinc Oxide Based Photonics Devices

    DTIC Science & Technology

    2003-12-09

    project are to develop critical technlogies required for ZnO-based photonic device; high-quality ZnO film growth, p/n-doping processes, etching...measured hole mobility values in the range from 1 to 50 cm2/V-sec. These results are shown in a recent publication [Y.R. Ryu et al, Appl. Phys. Lett. 83...effect measurements showed such undoped ZnO films to be intrinsic n-type, with electron concentration values in the low 1017 cm-3 range, and mobility

  18. Wavelength-Tunable Electroluminescent Light Sources from Individual Ga-Doped ZnO Microwires.

    PubMed

    Jiang, Mingming; He, Gaohang; Chen, Hongyu; Zhang, Zhenzhong; Zheng, Lingxia; Shan, Chongxin; Shen, Dezhen; Fang, Xiaosheng

    2017-03-07

    Electrically driven wavelength-tunable light emission from biased individual Ga-doped ZnO microwires (ZnO:Ga MWs) is demonstrated. Single crystalline ZnO:Ga MWs with different Ga-doping concentrations have been synthesized using a one-step chemical vapor deposition method. Strong electrically driven light emission from individual ZnO:Ga MW based devices is realized with tunable colors, and the emission region is localized toward the center of the wires. Increasing Ga-doping concentration in the MWs can lead to the redshift of electroluminescent emissions in the visible range. Interestingly, owing to the lack of rectification characteristics, relevant electrical measurement results show that the alternating current-driven light emission functions excellently on the ZnO:Ga MWs. Consequently, individual ZnO:Ga MWs, which can be analogous to incandescent sources, offer unique possibilities for future electroluminescence light sources. This typical multicolor emitter can be used to rival and complement other conventional semiconductor devices in displays and lighting.

  19. Bolometric Device Based on Fluxoid Quantization

    NASA Technical Reports Server (NTRS)

    Bonetti, Joseph A.; Kenyon, Matthew E.; Leduc, Henry G.; Day, Peter K.

    2010-01-01

    The temperature dependence of fluxoid quantization in a superconducting loop. The sensitivity of the device is expected to surpass that of other superconducting- based bolometric devices, such as superconducting transition-edge sensors and superconducting nanowire devices. Just as important, the proposed device has advantages in sample fabrication.

  20. Blue-green emitting cationic iridium complexes with 1,3,4-oxadiazole cyclometallating ligands: synthesis, photophysical and electrochemical properties, theoretical investigation and electroluminescent devices.

    PubMed

    Wang, Zhen; He, Lei; Duan, Lian; Yan, Jun; Tang, Ruiren; Pan, Chunyue; Song, Xiangzhi

    2015-09-28

    Two cationic iridium complexes, namely [Ir(dph-oxd)2(bpy)]PF6 (1) and [Ir(dph-oxd)2(pzpy)]PF6 (2), using 2,5-diphenyl-1,3,4-oxadiazole (dph-oxd) as the cyclometallating ligand and 2,2'-bipyridine (bpy) or 2-(1H-pyrazol-1-yl)pyridine (pzpy) as the ancillary ligands, have been synthesized, and their photophysical and electrochemical properties have been comprehensively investigated. In solution, both complexes emit efficient blue-green light. For complex 1, the light emission in a neat film is remarkably red-shifted; in solid state, it gives an intriguing piezochromic phenomenon. Compared with archetype [Ir(ppy)2(bpy)]PF6 (ppy is 2-phenylpyridine), complex 1 shows a largely stabilized HOMO (highest occupied molecular orbital) level, induced by the electron-deficient 1,3,4-oxadiazole (oxd) heterocycle of dph-oxd, which results in an enlarged energy gap and blue-shifted emission. Compared with complex 1, complex 2 shows an enhanced LUMO (lowest unoccupied molecular orbital) level, caused by the electron-rich pzpy ancillary ligand, but they exhibit similar emission energy in solution. For both complexes, theoretical calculations reveal that their blue-green emission in solution arises primarily from the (3)π-π* states centered on dph-oxd; moreover, complex 1 bears close-lying (3)π-π* and (3)CT (charge-transfer) states, underlying its remarkably red-shifted emission in the neat film and unique piezochromic behavior in the solid state. Solid state light emitting electrochemical cells (LECs) based on complexes 1 and 2 give efficient yellow and green-blue light, with peak current efficiencies of 18.3 and 5.2 cd A(-1), respectively. It is demonstrated that oxd-type cyclometallating ligands are promising as an avenue to stabilize the HOMOs and tune emission properties of cationic iridium complexes to a large extent.

  1. Polymer and small molecule based hybrid light source

    DOEpatents

    Choong, Vi-En; Choulis, Stelios; Krummacher, Benjamin Claus; Mathai, Mathew; So, Franky

    2010-03-16

    An organic electroluminescent device, includes: a substrate; a hole-injecting electrode (anode) coated over the substrate; a hole injection layer coated over the anode; a hole transporting layer coated over the hole injection layer; a polymer based light emitting layer, coated over the hole transporting layer; a small molecule based light emitting layer, thermally evaporated over the polymer based light emitting layer; and an electron-injecting electrode (cathode) deposited over the electroluminescent polymer layer.

  2. Variably spaced superlattice energy filter, a new device design concept for high-energy electron injection

    NASA Technical Reports Server (NTRS)

    Summers, C. J.; Brennan, K. F.

    1986-01-01

    A new variably spaced superlattice energy filter is proposed which provides high-energy injection of electrons into a bulk semiconductor layer based on resonant tunneling between adjacent quantum well levels which are brought into alignment by an applied bias. Applications of this concept to a variety of optoelectronic devices and to thin-film electroluminescent devices and photodetectors are discussed.

  3. Cotton-based Diagnostic Devices

    PubMed Central

    Lin, Shang-Chi; Hsu, Min-Yen; Kuan, Chen-Meng; Wang, Hsi-Kai; Chang, Chia-Ling; Tseng, Fan-Gang; Cheng, Chao-Min

    2014-01-01

    A good diagnostic procedure avoids wasting medical resources, is easy to use, resists contamination, and provides accurate information quickly to allow for rapid follow-up therapies. We developed a novel diagnostic procedure using a “cotton-based diagnostic device” capable of real-time detection, i.e., in vitro diagnostics (IVD), which avoids reagent contamination problems common to existing biomedical devices and achieves the abovementioned goals of economy, efficiency, ease of use, and speed. Our research reinforces the advantages of an easy-to-use, highly accurate diagnostic device created from an inexpensive and readily available U.S. FDA-approved material (i.e., cotton as flow channel and chromatography paper as reaction zone) that adopts a standard calibration curve method in a buffer system (i.e., nitrite, BSA, urobilinogen and uric acid assays) to accurately obtain semi-quantitative information and limit the cross-contamination common to multiple-use tools. Our system, which specifically targets urinalysis diagnostics and employs a multiple biomarker approach, requires no electricity, no professional training, and is exceptionally portable for use in remote or home settings. This could be particularly useful in less industrialized areas. PMID:25393975

  4. Ag-Decorated Localized Surface Plasmon-Enhanced Ultraviolet Electroluminescence from ZnO Quantum Dot-Based/GaN Heterojunction Diodes by Optimizing MgO Interlayer Thickness

    NASA Astrophysics Data System (ADS)

    Chen, Cheng; Chen, Jingwen; Zhang, Jun; Wang, Shuai; Zhang, Wei; Liang, Renli; Dai, Jiangnan; Chen, Changqing

    2016-10-01

    We demonstrate the fabrication and characterization of localized surface plasmon (LSP)-enhanced n-ZnO quantum dot (QD)/MgO/p-GaN heterojunction light-emitting diodes (LEDs) by embedding Ag nanoparticles (Ag-NPs) into the ZnO/MgO interface. The maximum enhancement ration of the Ag-NP-decorated LEDs in electroluminescence (EL) is 4.3-fold by optimizing MgO electron-blocking layer thickness. The EL origination was investigated qualitatively in terms of photoluminescence (PL) results. Through analysis of the energy band structure of device and carrier transport mechanisms, it suggests that the EL enhancement is attributed to the increased rate of spontaneous emission and improved internal quantum efficiency induced by exciton-LSP coupling.

  5. High Contrast Electroluminescent Numeric Readout Device.

    DTIC Science & Technology

    1980-08-01

    Seal Design ... ............ .. 22 10 Package Component Parts ........... 24 11 Frit Sealed Subassembly .............. .... 25 12 Sealed Package...layer ceramic with vertically conducting vias can be tooled to provide two or three layer circuitry as well as the vertical interconnects and seal area...to the display. This method of laminating layers of unfired but screened ceramic tape to form a multi-layer composite is now routinely applied in

  6. Interband cascade light emitting devices based on type-II quantum wells

    SciTech Connect

    Yang, Rui Q.; Lin, C.H.; Murry, S.J.

    1997-06-01

    The authors discuss physical processes in the newly developed type-II interband cascade light emitting devices, and review their recent progress in the demonstration of the first type-II interband cascade lasers and the observation of interband cascade electroluminescence up to room temperature in a broad mid-infrared wavelength region (extended to 9 {mu}m).

  7. Organic solution-processible electroluminescent molecular glasses for non-doped standard red OLEDs with electrically stable chromaticity

    SciTech Connect

    Bi, Xiaoman; Zuo, Weiwei; Liu, Yingliang Zhang, Zhenru; Zeng, Cen; Xu, Shengang; Cao, Shaokui

    2015-10-15

    Highlights: • The D–A–D electroluminescent molecular glasses are synthesized. • Non-doped red electroluminescent film is fabricated by spin-coating. • Red OLED shows stable wavelength, luminous efficiency and chromaticity. • CIE1931 coordinate is in accord with standard red light in PAL system. - Abstract: Organic light-emitting molecular glasses (OEMGs) are synthesized through the introduction of nonplanar donor and branched aliphatic chain into electroluminescent emitters. The target OEMGs are characterized by {sup 1}H NMR, {sup 13}C NMR, IR, UV–vis and fluorescent spectra as well as elemental analysis, TG and DSC. The results indicated that the optical, electrochemical and electroluminescent properties of OEMGs are adjusted successfully by the replacement of electron-donating group. The non-doped OLED device with a standard red electroluminescent emission is achieved by spin-coating the THF solution of OEMG with a triphenylamine moiety. This non-doped red OLED device takes on an electrically stable electroluminescent performance, including the stable maximum electroluminescent wavelength of 640 nm, the stable luminous efficiency of 2.4 cd/A and the stable CIE1931 coordinate of (x, y) = (0.64, 0.35), which is basically in accord with the CIE1931 coordinate (x, y) = (0.64, 0.33) of standard red light in PAL system.

  8. Electroluminescent, polycrystalline cadmium selenide nanowire arrays.

    PubMed

    Ayvazian, Talin; van der Veer, Wytze E; Xing, Wendong; Yan, Wenbo; Penner, Reginald M

    2013-10-22

    Electroluminescence (EL) from nanocrystalline CdSe (nc-CdSe) nanowire arrays is reported. The n-type, nc-CdSe nanowires, 400-450 nm in width and 60 nm in thickness, were synthesized using lithographically patterned nanowire electrodeposition, and metal-semiconductor-metal (M-S-M) devices were prepared by the evaporation of two gold contacts spaced by either 0.6 or 5 μm. These M-S-M devices showed symmetrical current voltage curves characterized by currents that increased exponentially with applied voltage bias. As the applied biased was increased, an increasing number of nanowires within the array "turned on", culminating in EL emission from 30 to 50% of these nanowires at applied voltages of 25-30 V. The spectrum of the emitted light was broad and centered at 770 nm, close to the 1.74 eV (712 nm) band gap of CdSe. EL light emission occurred with an external quantum efficiency of 4 × 10(-6) for devices with a 0.60 μm gap between the gold contacts and 0.5 × 10(-6) for a 5 μm gap-values similar to those reported for M-S-M devices constructed from single-crystalline CdSe nanowires. Kelvin probe force microscopy of 5 μm nc-CdSe nanowire arrays showed pronounced electric fields at the gold electrical contacts, coinciding with the location of strongest EL light emission in these devices. This electric field is implicated in the Poole-Frenkel minority carrier emission and recombination mechanism proposed to account for EL light emission in most of the devices that were investigated.

  9. Semiconductor-based, large-area, flexible, electronic devices

    DOEpatents

    Goyal, Amit

    2011-03-15

    Novel articles and methods to fabricate the same resulting in flexible, large-area, triaxially textured, single-crystal or single-crystal-like, semiconductor-based, electronic devices are disclosed. Potential applications of resulting articles are in areas of photovoltaic devices, flat-panel displays, thermophotovoltaic devices, ferroelectric devices, light emitting diode devices, computer hard disc drive devices, magnetoresistance based devices, photoluminescence based devices, non-volatile memory devices, dielectric devices, thermoelectric devices and quantum dot laser devices.

  10. Current transport and electroluminescence mechanisms in thin SiO2 films containing Si nanocluster-sensitized erbium ions

    NASA Astrophysics Data System (ADS)

    Jambois, O.; Berencen, Y.; Hijazi, K.; Wojdak, M.; Kenyon, A. J.; Gourbilleau, F.; Rizk, R.; Garrido, B.

    2009-09-01

    We have studied the current transport and electroluminescence properties of metal oxide semiconductor (MOS) devices in which the oxide layer, which is codoped with silicon nanoclusters and erbium ions, is made by magnetron sputtering. Electrical measurements have allowed us to identify a Poole-Frenkel conduction mechanism. We observe an important contribution of the Si nanoclusters to the conduction in silicon oxide films, and no evidence of Fowler-Nordheim tunneling. The results suggest that the electroluminescence of the erbium ions in these layers is generated by energy transfer from the Si nanoparticles. Finally, we report an electroluminescence power efficiency above 10-3%.

  11. Resistive Switching Memory Devices Based on Proteins.

    PubMed

    Wang, Hong; Meng, Fanben; Zhu, Bowen; Leow, Wan Ru; Liu, Yaqing; Chen, Xiaodong

    2015-12-09

    Resistive switching memory constitutes a prospective candidate for next-generation data storage devices. Meanwhile, naturally occurring biomaterials are promising building blocks for a new generation of environmentally friendly, biocompatible, and biodegradable electronic devices. Recent progress in using proteins to construct resistive switching memory devices is highlighted. The protein materials selection, device engineering, and mechanism of such protein-based resistive switching memory are discussed in detail. Finally, the critical challenges associated with protein-based resistive switching memory devices are presented, as well as insights into the future development of resistive switching memory based on natural biomaterials.

  12. Bright Multicolor Bandgap Fluorescent Carbon Quantum Dots for Electroluminescent Light-Emitting Diodes.

    PubMed

    Yuan, Fanglong; Wang, Zhibin; Li, Xiaohong; Li, Yunchao; Tan, Zhan'ao; Fan, Louzhen; Yang, Shihe

    2017-01-01

    Multicolor bandgap fluorescent carbon quantum dots (MCBF-CQDs) from blue to red with quantum yield up to 75% are synthesized using a solvothermal method. For the first time, monochrome electroluminescent light-emitting diodes (LEDs) with MCBF-CQDs directly as an active emission layer are fabricated. The maximum luminance of blue LEDs reaches 136 cd m(-2) , which is the best performance for CQD-based monochrome electroluminescent LEDs.

  13. Blue-red electroluminescence from hybrid Eu:phosphors/ZnO-nanowires/p-GaN LED

    NASA Astrophysics Data System (ADS)

    Viana, B.; Pauporte, T.; Lupan, O.; Devis, L.; Gacoin, T.

    2014-03-01

    Nanowire (NW) based light emitting diodes (LEDs) have drawn great research interest due to many advantages compared to thin film based devices. Marked improved performances are expected from nanostructured active layers for light emission. Semiconducting oxide nanowires can act as direct waveguides and favor emitted light extraction without use of lens and reflectors in LEDs. Moreover, the use of ZnO wires avoids the presence of grain boundaries and then the emission efficiency is boosted by the absence of non-radiative recombinations at the joint defects. In this context, europium (Eu):Chelate/ZnO:Mg-nanowires/p-GaN light-emitting-diode (LED) structures have been fabricated showing near-UV/violet electroluminescence and red emission from trivalent europium. Fabricated LED structures exhibit UV-blue light at about 380 nm coming from the n-(ZnO:Mg)/p-GaN and a sharp red emission at ˜611 nm related to the intra-4f transition of Eu ions. It is found that in the case of the ZnO:Mg, the emission wavelength is slightly shifted to smaller wavelength to be well adapted to the trivalent europium excitation band. Radiative energy transfer is achieved through strong overlap between the emission wavelength from n-(ZnO:Mg)/p- GaN heterojunction and chelate ligand intensive absorption band. Indeed the Eu:chelate/(ZnO:Mg)-nanowires/p-GaN structure appears well adapted to UV/blue and red dual emission. Our results shows that the design of LEDs based on the chelate ligands are important issue to enhance the performance of electroluminescence devices based on ZnO nanowire arrays/p-GaN heterojunction and rare-earth metal complexes.

  14. Quantifying Solar Cell Cracks in Photovoltaic Modules by Electroluminescence Imaging

    SciTech Connect

    Spataru, Sergiu; Hacke, Peter; Sera, Dezso; Glick, Stephen; Kerekes, Tamas; Teodorescu, Remus

    2015-06-14

    This article proposes a method for quantifying the percentage of partially and totally disconnected solar cell cracks by analyzing electroluminescence images of the photovoltaic module taken under high- and low-current forward bias. The method is based on the analysis of the module's electroluminescence intensity distribution, applied at module and cell level. These concepts are demonstrated on a crystalline silicon photovoltaic module that was subjected to several rounds of mechanical loading and humidity-freeze cycling, causing increasing levels of solar cell cracks. The proposed method can be used as a diagnostic tool to rate cell damage or quality of modules after transportation. Moreover, the method can be automated and used in quality control for module manufacturers, installers, or as a diagnostic tool by plant operators and diagnostic service providers.

  15. RANDOM ACCESS CONTROL OF ELECTROLUMINESCENT ELEMENTS.

    DTIC Science & Technology

    Cadmium selenide (CdSe) switches were devised to control the luminous emittance of electroluminescent cells in a solid-state display. The technique...purpose of this contract was to establish the feasibility of utilizing the hysteretic effect in cadmium selenide to provide switching and storage to an...array of electroluminescent cells by investigating the cadmium selenide material, by studying panel structure, and by investigating the addressing of

  16. Visible and near infrared emitting thin film electroluminescent gallium nitride doped with rare earths

    NASA Astrophysics Data System (ADS)

    Kim, Joo Han

    Visible and near-infrared (NIR) light-emitting thin-film electroluminescent gallium nitride (GaN) doped with rare earth (RE) elements was studied. The rare-earth-doped GaN thin films were prepared by radio frequency (RF) planar magnetron co-sputtering of separate targets consisting of a GaN compound target and a metallic rare earth target in a pure nitrogen atmosphere. The luminescence of rare-earth-doped GaN was shown to be a strong function of its structure and properties, and growth parameters affected the structure and properties of the GaN host films. A phase transition from the thermodynamically stable wurtzite to the metastable zinc-blende structure at room temperature in GaN host films was observed upon increasing the impact energy of the bombarding species, thereby increasing the compressive stress in the GaN film. The switch from wurtzite to zinc-blende GaN occurred at a compressive internal stress of ˜1 GPa. The internal compressive stress above this threshold value apparently stabilizes the zinc-blende GaN phase at room temperature. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) showed that the impact by hyperthermal species yielded a highly condensed fibrous GaN microstructure with a smooth surface morphology due to annihilation of porosity by knock-on and bombardment-induced adatom mobility. X-ray diffraction and texture analyses showed that the GaN films deposited at a low pressure had a predominant cubic phase with a preferred crystallographic orientation of the [111] direction perpendicular to the surface of the film. X-ray rocking curve data revealed that cubic GaN films grown with a lower growth rate exhibited a more highly [111]-textured structure. Alternating-current thin-film electroluminescent (ACTFEL) devices were fabricated based on GaN doped with rare earth (RE) elements. Visible electroluminescent light emission peaks at 475 (blue), 530 (green), and 614 nm (red) were demonstrated at room temperature

  17. Thorough subcells diagnosis in a multi-junction solar cell via absolute electroluminescence-efficiency measurements.

    PubMed

    Chen, Shaoqiang; Zhu, Lin; Yoshita, Masahiro; Mochizuki, Toshimitsu; Kim, Changsu; Akiyama, Hidefumi; Imaizumi, Mitsuru; Kanemitsu, Yoshihiko

    2015-01-16

    World-wide studies on multi-junction (tandem) solar cells have led to record-breaking improvements in conversion efficiencies year after year. To obtain detailed and proper feedback for solar-cell design and fabrication, it is necessary to establish standard methods for diagnosing subcells in fabricated tandem devices. Here, we propose a potential standard method to quantify the detailed subcell properties of multi-junction solar cells based on absolute measurements of electroluminescence (EL) external quantum efficiency in addition to the conventional solar-cell external-quantum-efficiency measurements. We demonstrate that the absolute-EL-quantum-efficiency measurements provide I-V relations of individual subcells without the need for referencing measured I-V data, which is in stark contrast to previous works. Moreover, our measurements quantify the absolute rates of junction loss, non-radiative loss, radiative loss, and luminescence coupling in the subcells, which constitute the "balance sheets" of tandem solar cells.

  18. Photo- and electroluminescence of mixed-ligand Eu(III) complexes

    NASA Astrophysics Data System (ADS)

    Eremina, N. S.; Meshkova, S. B.; Degtyarenko, K. M.; Kopylova, T. N.; Topilova, Z. M.; Gadirov, R. M.; Samsonova, L. G.

    2012-05-01

    Spectral and luminescent properties of mixed-ligand Eu(III) complexes were studied in solutions and in polyvinylcarbazole (PVC) thin films. Trends in their variations were found depending on the complex structure and excitation mode. The electroluminescence was observed in ITO/PEDOT/Eu complex:PVC/CaMg/Al devices. Their current-voltage and voltage-brightness characteristics were investigated.

  19. Carbon Nanotubes Based Quantum Devices

    NASA Technical Reports Server (NTRS)

    Lu, Jian-Ping

    1999-01-01

    This document represents the final report for the NASA cooperative agreement which studied the application of carbon nanotubes. The accomplishments are reviewed: (1) Wrote a review article on carbon nanotubes and its potentials for applications in nanoscale quantum devices. (2) Extensive studies on the effects of structure deformation on nanotube electronic structure and energy band gaps. (3) Calculated the vibrational spectrum of nanotube rope and the effect of pressure. and (4) Investigate the properties of Li intercalated nanotube ropes and explore their potential for energy storage materials and battery applications. These studies have lead to four publications and seven abstracts in international conferences.

  20. Adaptive Device Context Based Mobile Learning Systems

    ERIC Educational Resources Information Center

    Pu, Haitao; Lin, Jinjiao; Song, Yanwei; Liu, Fasheng

    2011-01-01

    Mobile learning is e-learning delivered through mobile computing devices, which represents the next stage of computer-aided, multi-media based learning. Therefore, mobile learning is transforming the way of traditional education. However, as most current e-learning systems and their contents are not suitable for mobile devices, an approach for…

  1. White light from an electroluminescent diode made from poly(3(4-octylphenyl)-2,2min -bithiophene) and an oxadiazole derivative

    NASA Astrophysics Data System (ADS)

    Berggren, M.; Gustafsson, G.; Inganas, O.; Andersson, M. R.; Hjertberg, T.; Wennerstrom, O.

    1994-12-01

    We report on an electroluminescent diode emitting red, green, and blue light simultaneously. The device is based on a thin polymer layer, poly(3-(4-octylphenyl)-2,2 min-bithiophene) and a thick molecular layer, 2-(4-biphenylyl)-5-(4-tertbutyl-phenyl)1,3,5-oxadiazole. The quantum efficiency for light conversion is 0.3% and the turn-on voltage for light emission is 7 V. In this arcitcle we present electric and spectroscopic characterizations. A mechanism for the light emission, based on electron and hole recombination between the two organic layers, is proposed.

  2. Polymer-based electrocaloric cooling devices

    DOEpatents

    Zhang, Qiming; Lu, Sheng-Guo; Li, Xinyu; Gorny, Lee; Cheng, Jiping; Neese, Bret P; Chu, Baojin

    2014-10-28

    Cooling devices (i.e., refrigerators or heat pumps) based on polymers which exhibit a temperature change upon application or removal of an electrical field or voltage, (e.g., fluoropolymers or crosslinked fluoropolymers that exhibit electrocaloric effect).

  3. Estimation of exciton reverse transfer for variable spectra and high efficiency in interlayer-based organic light-emitting devices

    NASA Astrophysics Data System (ADS)

    Liu, Shengqiang; Zhao, Juan; Huang, Jiang; Yu, Junsheng

    2016-12-01

    Organic light-emitting devices (OLEDs) with three different exciton adjusting interlayers (EALs), which are inserted between two complementary blue and yellow emitting layers, are fabricated to demonstrate the relationship between the EAL and device performance. The results show that the variations of type and thickness of EAL have different adjusting capability and distribution control on excitons. However, we also find that the reverse Dexter transfer of triplet exciton from the light-emitting layer to the EAL is an energy loss path, which detrimentally affects electroluminescent (EL) spectral performance and device efficiency in different EAL-based devices. Based on exciton distribution and integration, an estimation of exciton reverse transfer is developed through a triplet energy level barrier to simulate the exciton behavior. Meanwhile, the estimation results also demonstrate the relationship between the EAL and device efficiency by a parameter of exciton reverse transfer probability. The estimation of exciton reverse transfer discloses a crucial role of the EALs in the interlayer-based OLEDs to achieve variable EL spectra and high efficiency.

  4. Red electroluminescence of ruthenium sensitizer functionalized by sulfonate anchoring groups.

    PubMed

    Shahroosvand, Hashem; Abbasi, Parisa; Mohajerani, Ezeddin; Janghouri, Mohammad

    2014-06-28

    We have synthesized five novel Ru(ii) phenanthroline complexes with an additional aryl sulfonate ligating substituent at the 5-position [Ru(L)(bpy)2](BF4)2 (1), [Ru(L)(bpy)(SCN)2] (2), [Ru(L)3](BF4)2 (3), [Ru(L)2(bpy)](BF4)2 (4) and [Ru(L)(BPhen)(SCN)2] (5) (where L = 6-one-[1,10]phenanthroline-5-ylamino)-3-hydroxynaphthalene 1-sulfonic, bpy = 2,2'-bipyridine, BPhen = 4,7-diphenyl-1,10-phenanthroline), as both photosensitizers for oxide semiconductor solar cells (DSSCs) and light emitting diodes (LEDs). The absorption and emission maxima of these complexes red shifted upon extending the conjugation of the phenanthroline ligand. Ru phenanthroline complexes exhibit broad metal to ligand charge transfer-centered electroluminescence (EL) with a maximum near 580 nm. Our results indicated that a particular structure (2) can be considered as both DSSC and OLED devices. The efficiency of the LED performance can be tuned by using a range of ligands. Device (2) has a luminance of 550 cd m(-2) and maximum efficiency of 0.9 cd A(-1) at 18 V, which are the highest values among the five devices. The turn-on voltage of this device is approximately 5 V. The role of auxiliary ligands in the photophysical properties of Ru complexes was investigated by DFT calculation. We have also studied photovoltaic properties of dye-sensitized nanocrystalline semiconductor solar cells based on Ru phenanthroline complexes and an iodine redox electrolyte. A solar energy to electricity conversion efficiency (η) of 0.67% was obtained for Ru complex (2) under standard AM 1.5 irradiation with a short-circuit photocurrent density (Jsc) of 2.46 mA cm(-2), an open-circuit photovoltage (Voc) of 0.6 V, and a fill factor (ff) of 40%, which are all among the highest values for ruthenium sulfonated anchoring groups reported so far. Monochromatic incident photon to current conversion efficiency was 23% at 475 nm. Photovoltaic studies clearly indicated dyes with two SCN substituents yielded a higher Jsc for the

  5. Magnetic skyrmion-based synaptic devices.

    PubMed

    Huang, Yangqi; Kang, Wang; Zhang, Xichao; Zhou, Yan; Zhao, Weisheng

    2017-02-24

    Magnetic skyrmions are promising candidates for next-generation information carriers, owing to their small size, topological stability, and ultralow depinning current density. A wide variety of skyrmionic device concepts and prototypes have recently been proposed, highlighting their potential applications. Furthermore, the intrinsic properties of skyrmions enable new functionalities that may be inaccessible to conventional electronic devices. Here, we report on a skyrmion-based artificial synapse device for neuromorphic systems. The synaptic weight of the proposed device can be strengthened/weakened by positive/negative stimuli, mimicking the potentiation/depression process of a biological synapse. Both short-term plasticity and long-term potentiation functionalities have been demonstrated with micromagnetic simulations. This proposal suggests new possibilities for synaptic devices in neuromorphic systems with adaptive learning function.

  6. Magnetic skyrmion-based synaptic devices

    NASA Astrophysics Data System (ADS)

    Huang, Yangqi; Kang, Wang; Zhang, Xichao; Zhou, Yan; Zhao, Weisheng

    2017-02-01

    Magnetic skyrmions are promising candidates for next-generation information carriers, owing to their small size, topological stability, and ultralow depinning current density. A wide variety of skyrmionic device concepts and prototypes have recently been proposed, highlighting their potential applications. Furthermore, the intrinsic properties of skyrmions enable new functionalities that may be inaccessible to conventional electronic devices. Here, we report on a skyrmion-based artificial synapse device for neuromorphic systems. The synaptic weight of the proposed device can be strengthened/weakened by positive/negative stimuli, mimicking the potentiation/depression process of a biological synapse. Both short-term plasticity and long-term potentiation functionalities have been demonstrated with micromagnetic simulations. This proposal suggests new possibilities for synaptic devices in neuromorphic systems with adaptive learning function.

  7. Analysis of the electroluminescence features of silicon metal-insulator-semiconductor structures as a tool for diagnostics of the injection properties of a dielectric layer

    NASA Astrophysics Data System (ADS)

    Illarionov, Yu. Yu.; Vexler, M. I.; Isakov, D.; Fedorov, V. V.; Sing, Yew Kwang

    2013-10-01

    A technique for diagnostics of the injection properties of thin dielectric layers based on analysis of the data on silicon electroluminescence in a metal-insulator-semiconductor structure is proposed. The possibility of applying this technique to control the electron injection energy (in particular, when the barrier parameters are poorly known) is demonstrated by the example of samples with CaF2 and HfO2/SiO2. The results obtained are important for application of the insulators under study in microelectronic devices.

  8. Devices based on surface plasmon interference filters

    NASA Technical Reports Server (NTRS)

    Wang, Yu (Inventor)

    2001-01-01

    Devices based on surface plasmon filters having at least one metal-dielectric interface to support surface plasmon waves. A multi-layer-coupled surface plasmon notch filter is provided to have more than two symmetric metal-dielectric interfaces coupled with one another to produce a transmission spectral window with desired spectral profile and bandwidth. Such notch filters can form various color filtering devices for color flat panel displays.

  9. Organic Nonlinear Optical Materials and Devices Symposium Held in San Francisco, California on 6-9 April 1999. Volume 561

    DTIC Science & Technology

    electroluminescent materials and devices for displays. The symposium highlighted developments in materials chemistry and physics relevant to such devices and struck a balance between basic science and technology.

  10. Paper-based CRP Monitoring Devices

    PubMed Central

    Lin, Shang-Chi; Tseng, Chung-Yuh; Lai, Po-Liang; Hsu, Min-Yen; Chu, Shueh-Yao; Tseng, Fan-Gang; Cheng, Chao-Min

    2016-01-01

    Here, we discuss the development of a paper-based diagnostic device that is inexpensive, portable, easy-to-use, robust, and capable of running simultaneous tests to monitor a relevant inflammatory protein for clinical diagnoses i.e. C-reactive protein (CRP). In this study, we first attempted to make a paper-based diagnostic device via the wax printing method, a process that was used in previous studies. This device has two distinct advantages: 1) reduced manufacturing and assay costs and operation duration via using wax printing method to define hydrophobic boundaries (for fluidic devices or general POC devices); and, 2) the hydrophilicity of filter paper, which is used to purify and chromatographically correct interference caused by whole blood components with a tiny amount of blood sample (only 5 μL). Diagnosis was based on serum stain length retained inside the paper channels of our device. This is a balanced function between surface tension and chromatographic force following immune reactions (CRP assays) with a paper-embedded biomarker. PMID:27910861

  11. Paper-based CRP Monitoring Devices

    NASA Astrophysics Data System (ADS)

    Lin, Shang-Chi; Tseng, Chung-Yuh; Lai, Po-Liang; Hsu, Min-Yen; Chu, Shueh-Yao; Tseng, Fan-Gang; Cheng, Chao-Min

    2016-12-01

    Here, we discuss the development of a paper-based diagnostic device that is inexpensive, portable, easy-to-use, robust, and capable of running simultaneous tests to monitor a relevant inflammatory protein for clinical diagnoses i.e. C-reactive protein (CRP). In this study, we first attempted to make a paper-based diagnostic device via the wax printing method, a process that was used in previous studies. This device has two distinct advantages: 1) reduced manufacturing and assay costs and operation duration via using wax printing method to define hydrophobic boundaries (for fluidic devices or general POC devices); and, 2) the hydrophilicity of filter paper, which is used to purify and chromatographically correct interference caused by whole blood components with a tiny amount of blood sample (only 5 μL). Diagnosis was based on serum stain length retained inside the paper channels of our device. This is a balanced function between surface tension and chromatographic force following immune reactions (CRP assays) with a paper-embedded biomarker.

  12. Fabrication and Characterization of ZnO:Al/Sr0.8Bi2.2Ta2O9/Y2O3:Eu Structures for Ferroelectric-Electroluminescent Devices

    NASA Astrophysics Data System (ADS)

    Aizawa, Koji; Inagaki, Hiroyuki; Takatsuka, Yushi; Hoko, Koichi; Otani, Yusuke; Tokunaga, Yoshiaki

    2009-09-01

    ZnO:Al (AZO)/Sr0.8Bi2.2Ta2O9 (SBT)/Pt and AZO/SBT/Y2O3:Eu/Pt structures were fabricated, and their crystallinity, ferroelectric, and electroluminescent (EL) properties were investigated for the first time. The AZO/SBT/Pt structures showed a typical hysteresis loop, in which their double remnant polarization was approximately 5.3 µC/cm2. The polycrystalline SBT/Y2O3:Eu structures were grown on a Pt-coated substrate, in which ferroelectric phases were formed on an Y2O3:Eu film with cubic crystals. The electrical and EL properties of the AZO/SBT/Y2O3:Eu/Pt structures were measured, and then EL emission peaks associated with the 5D0-7F1 (λ=601 nm) and 5D0-7F2 (λ=617 nm) transitions of Eu3+ were observed. The EL emission pattern of the AZO/SBT/Y2O3:Eu/Pt structure was different from the PL emission pattern of the Y2O3:Eu film. Furthermore, polarization-voltage characteristics with counterclockwise hysteresis loops and an asymmetric behavior of current-voltage characteristics were observed in the fabricated AZO/SBT/Y2O3/Pt:Eu structures.

  13. Quasi-Fermi level splitting evaluation based on electroluminescence analysis in multiple quantum-well solar cells for investigating cell performance under concentrated light

    NASA Astrophysics Data System (ADS)

    Inoue, Tomoyuki; Toprasertpong, Kasidit; Delamarre, Amaury; Watanabe, Kentaroh; Paire, Myriam; Lombez, Laurent; Guillemoles, Jean-François; Sugiyama, Masakazu; Nakano, Yoshiaki

    2016-03-01

    Insertion of InGaAs/GaAsP strain-balanced multiple quantum wells (MQWs) into i-regions of GaAs p-i-n solar cells show several advantages against GaAs bulk p-i-n solar cells. Particularly under high-concentration sunlight condition, enhancement of the open-circuit voltage with increasing concentration ratio in thin-barrier MQW cells has been reported to be more apparent than that in GaAs bulk cells. However, investigation of the MQW cell mechanisms in terms of I-V characteristics under high-concentration sunlight suffers from the increase in cell temperature and series resistance. In order to investigate the mechanism of the steep enhancement of open-circuit voltage in MQW cells under high-concentration sunlight without affected by temperature, the quasi-Fermi level splitting was evaluated by analyzing electroluminescence (EL) from a cell. Since a cell under current injection with a density Jinjhas similar excess carrier density to a cell under concentrated sunlight with an equivalent short-circuit current Jsc = Jinj, EL measurement with varied Jinj can approximately evaluate a cell performance under a variety of concentration ratio. In addition to the evaluation of quasi-Fermi level splitting, the external luminescence efficiency was also investigated with the EL measurement. The MQW cells showed higher external luminescence efficiency than the GaAs reference cells especially under high-concentration condition. The results suggest that since the MQW region can trap and confine carriers, the localized excess carriers inside the cells make radiative recombination more dominant.

  14. Phonon-assisted transient electroluminescence in Si

    SciTech Connect

    Cheng, Tzu-Huan; Chu-Su, Yu; Liu, Chien-Sheng; Lin, Chii-Wann

    2014-06-30

    The phonon-replica infrared emission is observed at room temperature from indirect band gap Si light-emitting diode under forward bias. With increasing injection current density, the broadened electroluminescence spectrum and band gap reduction are observed due to joule heating. The spectral-resolved temporal response of electroluminescence reveals the competitiveness between single (TO) and dual (TO + TA) phonon-assisted indirect band gap transitions. As compared to infrared emission with TO phonon-replica, the retarder of radiative recombination at long wavelength region (∼1.2 μm) indicates lower transition probability of dual phonon-replica before thermal equivalent.

  15. Strongly enhanced field-dependent single-molecule electroluminescence

    NASA Astrophysics Data System (ADS)

    Lee, Tae-Hee; Gonzalez, Jose I.; Dickson, Robert M.

    2002-08-01

    Individual, strongly electroluminescent Agn molecules (n = 28 atoms) have been electrically written within otherwise nonemissive silver oxide films. Exhibiting characteristic single-molecule behavior, these individual room-temperature molecules exhibit extreme electroluminescence enhancements (>104 vs. bulk and dc excitation on a per molecule basis) when excited with specific ac frequencies. Occurring through field extraction of electrons with subsequent reinjection and radiative recombination, single-molecule electroluminescence is enhanced by a general mechanism that avoids slow bulk material response. Thus, while we detail strong electroluminescence from single, highly fluorescent Agn molecules, this mechanism also yields strong ac-excited electroluminescence from similarly prepared, but otherwise nonemissive, individual Cu nanoclusters.

  16. III-antimonide/nitride based semiconductors for optoelectronic materials and device studies : LDRD 26518 final report.

    SciTech Connect

    Kurtz, Steven Ross; Hargett, Terry W.; Serkland, Darwin Keith; Waldrip, Karen Elizabeth; Modine, Normand Arthur; Klem, John Frederick; Jones, Eric Daniel; Cich, Michael Joseph; Allerman, Andrew Alan; Peake, Gregory Merwin

    2003-12-01

    The goal of this LDRD was to investigate III-antimonide/nitride based materials for unique semiconductor properties and applications. Previous to this study, lack of basic information concerning these alloys restricted their use in semiconductor devices. Long wavelength emission on GaAs substrates is of critical importance to telecommunication applications for cost reduction and integration into microsystems. Currently InGaAsN, on a GaAs substrate, is being commercially pursued for the important 1.3 micrometer dispersion minima of silica-glass optical fiber; due, in large part, to previous research at Sandia National Laboratories. However, InGaAsN has not shown great promise for 1.55 micrometer emission which is the low-loss window of single mode optical fiber used in transatlantic fiber. Other important applications for the antimonide/nitride based materials include the base junction of an HBT to reduce the operating voltage which is important for wireless communication links, and for improving the efficiency of a multijunction solar cell. We have undertaken the first comprehensive theoretical, experimental and device study of this material with promising results. Theoretical modeling has identified GaAsSbN to be a similar or potentially superior candidate to InGaAsN for long wavelength emission on GaAs. We have confirmed these predictions by producing emission out to 1.66 micrometers and have achieved edge emitting and VCSEL electroluminescence at 1.3 micrometers. We have also done the first study of the transport properties of this material including mobility, electron/hole mass, and exciton reduced mass. This study has increased the understanding of the III-antimonide/nitride materials enough to warrant consideration for all of the target device applications.

  17. Legibility of electroluminescent instrument panels investigated

    NASA Technical Reports Server (NTRS)

    Mc Lean, M. V.; Miller, G. E.

    1966-01-01

    Legibility studies of several EL /electroluminescent/ displays correlate reading time and accuracy with number size, stroke/width ratio, indicia size, pointer width, contrast, ambient illumination, and color background and and contrast. Human factor criteria established on non-EL displays may not apply to EL displays.

  18. Development of gallium aluminum phosphide electroluminescent diodes

    NASA Technical Reports Server (NTRS)

    Chicotka, R. J.; Lorenz, M. R.; Nethercot, A. H.; Pettit, G. D.

    1972-01-01

    Work done on the development of gallium aluminum phosphide alloys for electroluminescent light sources is described. The preparation of this wide band gap semiconductor alloy, its physical properties (particularly the band structure, the electrical characteristics, and the light emitting properties) and work done on the fabrication of diode structures from these alloys are broadly covered.

  19. Electroluminescence from GeSn heterostructure pin diodes at the indirect to direct transition

    SciTech Connect

    Gallagher, J. D.; Menéndez, J.; Senaratne, C. L.; Sims, P.; Kouvetakis, J.; Aoki, T.

    2015-03-02

    The emission properties of GeSn heterostructure pin diodes have been investigated. The devices contain thick (400–600 nm) Ge{sub 1−y}Sn{sub y} i-layers spanning a broad compositional range below and above the crossover Sn concentration y{sub c} where the Ge{sub 1−y}Sn{sub y} alloy becomes a direct-gap material. These results are made possible by an optimized device architecture containing a single defected interface thereby mitigating the deleterious effects of mismatch-induced defects. The observed emission intensities as a function of composition show the contributions from two separate trends: an increase in direct gap emission as the Sn concentration is increased, as expected from the reduction and eventual reversal of the separation between the direct and indirect edges, and a parallel increase in non-radiative recombination when the mismatch strains between the structure components is partially relaxed by the generation of misfit dislocations. An estimation of recombination times based on the observed electroluminescence intensities is found to be strongly correlated with the reverse-bias dark current measured in the same devices.

  20. Electroluminescence et radiation thermique dans les nanotubes de carbone

    NASA Astrophysics Data System (ADS)

    Adam, Elyse

    We present here a spectroscopic study of the light emission properties of different nanotube devices with the aim to clarify the different mechanisms leading to the light emission. The first study consists of taking measurements from a thick (˜ 450 nm) macroscopic suspended carbon nanotube film connected between two electrodes. A significant increase of the temperature is expected when voltage is applied since thermal dissipation by the substrate is suppressed for this configuration. In imaging mode, we observed that infrared light is emitted from the entire area of the film instead of being localized. This observation demonstrates that the light emission arise from thermal emission. Spectra measured on this device all present a smooth response, characteristic of that of a blackbody. As expected for a pure thermal source, the results fit well the Planck formula. Because the Planck formula is temperature dependant, it became possible to extract a lower limit of the temperature of the film as a function of voltage. The temperature increases more or less from 350K to 600K when the voltage increases from 0.1V to 1.6V. The second study is made using a sub-monolayer network of carbon nanotubes interconnected together to form a semiconducting layer. The large number of tube-tube junctions in the networks limits the current and prevents the temperature to rise significantly at higher bias. The intimate contact between the network and the substrate also prevent the temperature of the film to increase significantly due to a good thermalizaton. Hence, electroluminescence from excitonic recombination is expected to be dominant over heat radiation for this type of devices. First, spatial resolution measurements on long channel network devices shows that the light-emitting zone is always located near the minority charge injector contact. This result demonstrates that light emission arises from electroluminescence in network from a bipolar current. Thermal emission can therefore

  1. OLED devices with internal outcoupling

    DOEpatents

    Liu, Jr., Jie Jerry; Sista, Srinivas Prasad; Shi, Xiaolei; Zhao, Ri-An; Chichak, Kelly Scott; Youmans, Jeffrey Michael; Janora, Kevin Henry; Turner, Larry Gene

    2016-12-06

    Optoelectronic devices with enhanced internal outcoupling include a substrate, an anode, a cathode, an electroluminescent layer, and an electron transporting layer comprising inorganic nanoparticles dispersed in an organic matrix.

  2. Force based displacement measurement in micromechanical devices

    SciTech Connect

    O {close_quote}Shea, S. J.; Ng, C. K.; Tan, Y. Y.; Xu, Y.; Tay, E. H.; Chua, B. L.; Tien, N. C.; Tang, X. S.; Chen, W. T.

    2001-06-18

    We demonstrate how force detection methods based on atomic force microscopy can be used to measure displacement in micromechanical devices. We show the operation of a simple microfabricated accelerometer, the proof mass of which incorporates a tip which can be moved towards an opposing surface. Both noncontact operation using long range electrostatic forces and tapping mode operation are demonstrated. The displacement sensitivity of the present device using feedback to control the tip-surface separation is approximately 1 nm. {copyright} 2001 American Institute of Physics.

  3. Neuroelectronic device based on nanocoax arrays

    NASA Astrophysics Data System (ADS)

    Naughton, Jeffrey R.; Lundberg, Jaclyn N.; Varela, Juan A.; Burns, Michael J.; Chiles, Thomas C.; Christianson, John P.; Naughton, Michael J.

    2015-03-01

    We report on development of a nanocoax-based neuroelectronic array. The device has been used in real time to noninvasively couple to a ganglion sac located along the main nerve cord of the leech Hirudo medicinalis. This allowed for extracellular recording of synaptic activity in the form of spontaneous synapse firing in pre- and post-synaptic somata, with the next target being recording of local field potentials from rat hippocampal cells. We also discuss an alteration of the architecture to facilitate optical integration of the nanoarray, toward utilizing the so-modified device to elicit / inhibit action potentials in optogenetically-modified cells.

  4. Cellphone-based devices for bioanalytical sciences.

    PubMed

    Vashist, Sandeep Kumar; Mudanyali, Onur; Schneider, E Marion; Zengerle, Roland; Ozcan, Aydogan

    2014-05-01

    During the last decade, there has been a rapidly growing trend toward the use of cellphone-based devices (CBDs) in bioanalytical sciences. For example, they have been used for digital microscopy, cytometry, read-out of immunoassays and lateral flow tests, electrochemical and surface plasmon resonance based bio-sensing, colorimetric detection and healthcare monitoring, among others. Cellphone can be considered as one of the most prospective devices for the development of next-generation point-of-care (POC) diagnostics platforms, enabling mobile healthcare delivery and personalized medicine. With more than 6.5 billion cellphone subscribers worldwide and approximately 1.6 billion new devices being sold each year, cellphone technology is also creating new business and research opportunities. Many cellphone-based devices, such as those targeted for diabetic management, weight management, monitoring of blood pressure and pulse rate, have already become commercially-available in recent years. In addition to such monitoring platforms, several other CBDs are also being introduced, targeting e.g., microscopic imaging and sensing applications for medical diagnostics using novel computational algorithms and components already embedded on cellphones. This report aims to review these recent developments in CBDs for bioanalytical sciences along with some of the challenges involved and the future opportunities.

  5. Cellphone-based devices for bioanalytical sciences

    PubMed Central

    Vashist, Sandeep Kumar; Mudanyali, Onur; Schneider, E.Marion; Zengerle, Roland; Ozcan, Aydogan

    2014-01-01

    During the last decade, there has been a rapidly growing trend toward the use of cellphone-based devices (CBDs) in bioanalytical sciences. For example, they have been used for digital microscopy, cytometry, read-out of immunoassays and lateral flow tests, electrochemical and surface plasmon resonance based bio-sensing, colorimetric detection and healthcare monitoring, among others. Cellphone can be considered as one of the most prospective devices for the development of next-generation point-of-care (POC) diagnostics platforms, enabling mobile healthcare delivery and personalized medicine. With more than 6.5 billion cellphone subscribers worldwide and approximately 1.6 billion new devices being sold each year, cellphone technology is also creating new business and research opportunities. Many cellphone-based devices, such as those targeted for diabetic management, weight management, monitoring of blood pressure and pulse rate, have already become commercially-available in recent years. In addition to such monitoring platforms, several other CBDs are also being introduced, targeting e.g., microscopic imaging and sensing applications for medical diagnostics using novel computational algorithms and components already embedded on cellphones. This manuscript aims to review these recent developments in CBDs for bioanalytical sciences along with some of the challenges involved and the future opportunities. PMID:24287630

  6. Analysis of degradation mechanisms in AlInN/GaN HEMTs by electroluminescence technique

    NASA Astrophysics Data System (ADS)

    Berthet, F.; Petitdidier, S.; Guhel, Y.; Trolet, J. L.; Mary, P.; Vivier, A.; Gaquière, C.; Boudart, B.

    2017-01-01

    In this paper, the impact of a severe on-state stress on the IDS (VDS, VGS) characteristics of AlInN/GaN devices is analyzed by electroluminescence technique performed at room temperature. In fact, the devices operate in bias conditions that allow measuring the bell- shaped gate current. To our knowledge, it is the first time that a bell-shaped gate current centered at a positive VGS and measured at room temperature has been shown for an AlInN/GaN transistor. We have also highlighted that electroluminescence spectra are related to the superposition of intraband radiative electron transitions, Fabry-Perot oscillations, and emission bands induced by recombination of electrons due to electron traps. In these conditions, it is not so easy to extract energies levels of electron traps existing in unstressed and stressed AlInN/GaN HEMTs from electroluminescence spectra. Thus, we have also shown that the electrical degradations induced by on-state stress are mainly related to the trapping of hot electron by deep pre-existing electron traps in the devices. Moreover, we have highlighted the existence of two electron traps activated at 1.6 and 1.8 eV in the devices.

  7. AC field-induced polymer electroluminescence with single wall carbon nanotubes.

    PubMed

    Sung, Jinwoo; Choi, Yeon Sik; Kang, Seok Ju; Cho, Sung Hwan; Lee, Tae-Woo; Park, Cheolmin

    2011-03-09

    We developed a high-performance field-induced polymer electroluminescence (FPEL) device consisting of four stacked layers: a top metal electrode/thin solution-processed nanocomposite film of single wall carbon nanotubes (SWNTs) and a fluorescent polymer/insulator/transparent bottom electrode working under an alternating current (AC) electric field. A small amount of SWNTs that were highly dispersed in the fluorescent polymer matrix by a conjugate block copolymer dispersant significantly enhanced EL, and we were able to realize an SWNT-FPEL device with a light emission of approximately 350 cd/m(2) at an applied voltage of ±25 V and an AC frequency of 300 kHz. The brightness of the SWNT-FPEL device is much greater than those of other AC-based organic or even inorganic ELs that generally require at least a few hundred volts. Light is emitted from our SWNT-FPEL device because of the sequential injection of field-induced holes and then electron carriers through ambipolar carbon nanotubes under an AC field, followed by exciton formation in the conjugated organic layer. Field-induced bipolar charge injection provides great material design freedom for our devices; the energy level does not have to be aligned between the electrode and the emission layer, and the balance of the carrier injected and transported can be altered in contrast to that in conventional organic light-emitting diodes, leading to an extremely cost-effective and unified device architecture that is applicable to all red-green-blue fluorescent polymers.

  8. Carbon Based Transistors and Nanoelectronic Devices

    NASA Astrophysics Data System (ADS)

    Rouhi, Nima

    Carbon based materials (carbon nanotube and graphene) has been extensively researched during the past decade as one of the promising materials to be used in high performance device technology. In long term it is thought that they may replace digital and/or analog electronic devices, due to their size, near-ballistic transport, and high stability. However, a more realistic point of insertion into market may be the printed nanoelectronic circuits and sensors. These applications include printed circuits for flexible electronics and displays, large-scale bendable electrical contacts, bio-membranes and bio sensors, RFID tags, etc. In order to obtain high performance thin film transistors (as the basic building block of electronic circuits) one should be able to manufacture dense arrays of all semiconducting nanotubes. Besides, graphene synthesize and transfer technology is in its infancy and there is plenty of room to improve the current techniques. To realize the performance of nanotube and graphene films in such systems, we need to economically fabricate large-scale devices based on these materials. Following that the performance control over such devices should also be considered for future design variations for broad range of applications. Here we have first investigated carbon nanotube ink as the base material for our devices. The primary ink used consisted of both metallic and semiconducting nanotubes which resulted in networks suitable for moderate-resistivity electrical connections (such as interconnects) and rfmatching circuits. Next, purified all-semiconducting nanotube ink was used to fabricate waferscale, high performance (high mobility, and high on/off ratio) thin film transistors for printed electronic applications. The parameters affecting device performance were studied in detail to establish a roadmap for the future of purified nanotube ink printed thin film transistors. The trade of between mobility and on/off ratio of such devices was studied and the

  9. Improving the diversity of manufacturing electroluminescent flat panel displays

    SciTech Connect

    Moss, T.S.; Samuels, J.A.; Smith, D.C.

    1995-09-01

    Crystalline calcium thiogallate with a cerium dopant has been deposited by metal-organic chemical vapor deposition (MOCVD) at temperatures below 600{degrees}C on a low cost glass substrate. An EL luminance of 1.05 fL was observed 40 volts above threshold at 60 Hz. This is more than an order of magnitude improvement over earlier crystalline-as-deposited thiogallate materials. These results pave the way for the use of MOCVD as a potential method for processing full color thin-film electroluminescent (TFEL) flat panel displays. The formation of the CaGa{sub 2}S{sub 4}:Ce phosphor requires precise control over a number of deposition parameters including flow rates, substrate temperature, and reactor pressure. The influence of these parameters will be discussed in terms of structure, uniformity, and TFEL device performance.

  10. Quantum Dots for Wide Color Gamut Displays from Photoluminescence to Electroluminescence

    NASA Astrophysics Data System (ADS)

    Kang, Yongyin; Song, Zhicheng; Jiang, Xiaofang; Yin, Xia; Fang, Long; Gao, Jing; Su, Yehua; Zhao, Fei

    2017-02-01

    Monodisperse quantum dots (QDs) were prepared by low-temperature process. The remarkable narrow emission peak of the QDs helps the liquid crystal displays (LCD) and electroluminescence displays (QD light-emitting diode, QLED) to generate wide color gamut performance. The range of the color gamut for QD light-converting device (QLCD) is controlled by both the QDs and color filters (CFs) in LCD, and for QLED, the optimized color gamut is dominated by QD materials.

  11. Quantum Dots for Wide Color Gamut Displays from Photoluminescence to Electroluminescence.

    PubMed

    Kang, Yongyin; Song, Zhicheng; Jiang, Xiaofang; Yin, Xia; Fang, Long; Gao, Jing; Su, Yehua; Zhao, Fei

    2017-12-01

    Monodisperse quantum dots (QDs) were prepared by low-temperature process. The remarkable narrow emission peak of the QDs helps the liquid crystal displays (LCD) and electroluminescence displays (QD light-emitting diode, QLED) to generate wide color gamut performance. The range of the color gamut for QD light-converting device (QLCD) is controlled by both the QDs and color filters (CFs) in LCD, and for QLED, the optimized color gamut is dominated by QD materials.

  12. Electroluminescence and Spectral Shift of CdS Nanoparticles on Si Wafer

    DTIC Science & Technology

    2002-01-01

    emitting active layer is simply fabricated by the spin - coating technique. Electroluminescence (EL) can be easily achieved by quantum tunneling of...percolatior, solutions for spin - coating purpose were produced by dissolving the nanoparicles in ethanol with a concentration of 1% (w/v). Fabrication of...diffusing easier. Conclusions The CdS nanoparticles prepared by chemical method are ready for spin - coating and EL device fabrication. The observed a

  13. Multicolor Electrochromic Devices Based on Molecular Plasmonics.

    PubMed

    Stec, Grant J; Lauchner, Adam; Cui, Yao; Nordlander, Peter; Halas, Naomi J

    2017-03-28

    Polycyclic aromatic hydrocarbon (PAH) molecules, the hydrogen-terminated, sub-nanometer-scale version of graphene, support plasmon resonances with the addition or removal of a single electron. Typically colorless when neutral, they are transformed into vivid optical absorbers in either their positively or negatively charged states. Here, we demonstrate a low-voltage, multistate electrochromic device based on PAH plasmon resonances that can be reversibly switched between nearly colorless (0 V), olive (+4 V), and royal blue (-3.5 V). The device exhibits highly efficient color change compared to electrochromic polymers and metal oxides, lower power consumption than liquid crystals, and is shown to reversibly switch for at least 100 cycles. We also demonstrate the additive property of molecular plasmon resonances in a single-layer device to display a reversible, transmissive-to-black device. This work illuminates the potential of PAH molecular plasmonics for the development of color displays and large-area color-changing applications due to their processability and ultralow power consumption.

  14. An observation of direct-gap electroluminescence in GaAs structures with Ge quantum wells

    SciTech Connect

    Aleshkin, V. Ya.; Dikareva, N. V.; Dubinov, A. A.; Zvonkov, B. N.; Kudryavtsev, K. E.; Nekorkin, S. M.

    2015-02-15

    A light-emitting diode structure based on GaAs with eight narrow Ge quantum wells is grown by laser sputtering. An electroluminescence line polarized predominately in the plane parallel to the constituent layers of the structure is revealed. The line corresponds to the direct optical transitions in momentum space in the Ge quantum wells.

  15. Synthesis and electroluminescent properties of anthracene derivatives containing electron-withdrawing oxide moieties

    SciTech Connect

    Yoon, Jhin-yeong; Na, Eun Jae; Park, Soo Na; Lee, Seok Jae; Kim, Young Kwan; Yoon, Seung Soo

    2014-10-15

    Highlights: • Blue fluorescent material is important for application in full-color displays. • We have synthesized emitters based on anthracene connected with oxide moieties. • 1C shows a highly efficient blue EL emission due to electron-injection property. - Abstract: A series of new blue-emitting materials: (4-(10-(naphthalen-2-yl)anthracen-9-yl)phenyl)(phenyl)methanone (1); 9-(naphthalen-2-yl)-10-(4-((diphenyl)phosphine oxide)phenyl)anthracene (2); 9-(naphthalen-2-yl)-10-(4-(phenylsulfonyl)phenyl)anthracene (3) were designed and synthesized via Suzuki cross-coupling reaction. Multilayer OLEDs were fabricated in the following sequence: ITO (180 nm)/NPB (50 nm)/blue materials 1–3 (30 nm)/TPBi (15 nm)/Liq (2 nm)/Al (100 nm). All devices showed the efficient blue EL emissions. In particular, the device using 1 as an emitter exhibited efficient blue electroluminescent properties with a maximum luminous, power, external quantum efficiency and CIE coordinates of 0.36 cd/A, 0.90 lm/W, 0.55% at 20 mA/cm{sup 2} and (x = 0.16, y = 0.20) at 10.0 V, respectively.

  16. Pure circular polarization electroluminescence at room temperature with spin-polarized light-emitting diodes.

    PubMed

    Nishizawa, Nozomi; Nishibayashi, Kazuhiro; Munekata, Hiro

    2017-02-21

    We report the room-temperature electroluminescence (EL) with nearly pure circular polarization (CP) from GaAs-based spin-polarized light-emitting diodes (spin-LEDs). External magnetic fields are not used during device operation. There are two small schemes in the tested spin-LEDs: first, the stripe-laser-like structure that helps intensify the EL light at the cleaved side walls below the spin injector Fe slab, and second, the crystalline AlO x spin-tunnel barrier that ensures electrically stable device operation. The purity of CP is depressively low in the low current density (J) region, whereas it increases steeply and reaches close to the pure CP when J > 100 A/cm(2) There, either right- or left-handed CP component is significantly suppressed depending on the direction of magnetization of the spin injector. Spin-dependent reabsorption, spin-induced birefringence, and optical spin-axis conversion are suggested to account for the observed experimental results.

  17. Electrorheological Fluid Based Force Feedback Device

    NASA Technical Reports Server (NTRS)

    Pfeiffer, Charles; Bar-Cohen, Yoseph; Mavroidis, Constantinos; Dolgin, Benjamin

    1999-01-01

    Parallel to the efforts to develop fully autonomous robots, it is increasingly being realized that there are applications where it is essential to have a fully controlled robot and "feel" its operating conditions, i.e. telepresence. This trend is a result of the increasing efforts to address tasks where humans can perform significantly better but, due to associated hazards, distance, physical limitations and other causes, only robots can be employed to perform these tasks. Such robots need to be assisted by a human that remotely controls the operation. To address the goal of operating robots as human surrogates, the authors launched a study of mechanisms that provide mechanical feedback. For this purpose, electrorheological fluids (ERF) are being investigated for the potential application as miniature haptic devices. This family of electroactive fluids has the property of changing the viscosity during electrical stimulation. Consequently, ERF can be used to produce force feedback haptic devices for tele-operated control of medical and space robotic systems. Forces applied at the robot end-effector due to a compliant environment are reflected to the user using an ERF device where a change in the system viscosity will occur proportionally to the transmitted force. Analytical model and control algorithms are being developed taking into account the non-linearities of these type of devices. This paper will describe the concept and the developed mechanism of ERF based force feedback. The test process and the physical properties of this device will be described and the results of preliminary tests will be presented.

  18. Highly efficient non-doped orange-red phosphorescent organic light-emitting devices based on a novel iridium complex

    NASA Astrophysics Data System (ADS)

    Qi, Yige; Wang, Xu; Li, Ming; Yu, Junsheng; Lu, Zhiyun

    2014-09-01

    The non-doped orange-red phosphorescent organic light-emitting device (PHOLED) based on a newly synthesized iridium complex, bis[2-(biphenyl-4-yl)benzothiazole-N,C2']iridium(III)(acetylacetonate) [(4Phbt)2Ir(acac)] has been demonstrated. The non-doped device with (4Phbt)2Ir(acac) as the emissive layer achieved ideal turn-on voltage (<4 V) and superior power efficiency (5 lm/W) as well as luminance efficiency (6 cd/A), respectively. Our device performance indicates that (4Phbt)2Ir(acac) possesses excellent self-quenching-resistant property. The potential of this property is originated from the introduction of bulky and twisted aromatic substituents in ligands, which break the molecular planarity and obstruct the molecular packing. Besides, the high electroluminescence efficiency is also attributed to that the energy level alignment between (4Phbt)2Ir(acac) and adjacent charge-transporting materials forms a well-like structure, which confines exciton effectively in emissive layer.

  19. Stretchable polymer-based electronic device

    DOEpatents

    Maghribi, Mariam N.; Krulevitch, Peter A.; Davidson, James Courtney; Wilson, Thomas S.; Hamilton, Julie K.; Benett, William J.; Tovar, Armando R.

    2008-02-26

    A stretchable electronic circuit or electronic device and a polymer-based process to produce a circuit or electronic device containing a stretchable conducting circuit. The stretchable electronic apparatus has a central longitudinal axis and the apparatus is stretchable in a longitudinal direction generally aligned with the central longitudinal axis. The apparatus comprises a stretchable polymer body and at least one circuit line operatively connected to the stretchable polymer body. The circuit line extends in the longitudinal direction and has a longitudinal component that extends in the longitudinal direction and has an offset component that is at an angle to the longitudinal direction. The longitudinal component and the offset component allow the apparatus to stretch in the longitudinal direction while maintaining the integrity of the circuit line.

  20. Glow discharge based device for solving mazes

    SciTech Connect

    Dubinov, Alexander E. Mironenko, Maxim S.; Selemir, Victor D.; Maksimov, Artem N.; Pylayev, Nikolay A.

    2014-09-15

    A glow discharge based device for solving mazes has been designed and tested. The device consists of a gas discharge chamber and maze-transformer of radial-azimuth type. It allows changing of the maze pattern in a short period of time (within several minutes). The device has been tested with low pressure air. Once switched on, a glow discharge has been shown to find the shortest way through the maze from the very first attempt, even if there is a section with potential barrier for electrons on the way. It has been found that ionization waves (striations) can be excited in the maze along the length of the plasma channel. The dependancy of discharge voltage on the length of the optimal path through the maze has been measured. A reduction in discharge voltage with one or two potential barriers present has been found and explained. The dependency of the magnitude of discharge ignition voltage on the length of the optimal path through the maze has been measured. The reduction of the ignition voltage with the presence of one or two potential barriers has been observed and explained.

  1. Growth and characterization of nonpolar and semipolar group-III nitrides-based heterostructures and devices

    NASA Astrophysics Data System (ADS)

    Chakraborty, Arpan

    Conventional state-of-the-art wurtzite nitrides based light-emitters, grown along the polar c-direction, are characterized by the presence of polarization-induced electrostatic fields in the quantum wells. These built-in fields are detrimental to the performance of optoelectronic devices. Growth of light-emitters along nonpolar and semipolar directions is an effective means to circumvent the adverse effects of polarization. This dissertation focuses on the growth and characterization of nonpolar and semipolar (Al, Ga, In)N based heterostructures and devices. Two nonpolar planes, a- and m-, and two semipolar planes, (10 11) and (1013), have been investigated in this thesis. Initially, the growth of n-type and p-type nonpolar a-plane GaN was optimized to yield cladding layers of the highest possible conductivity in the devices. Various interesting observations, e.g. low acceptor activation energy, anisotropic conductivity, etc, were made during the course of this study. In order to achieve defect reduction in planar a-plane GaN films, in-situ SiNx interlayers were used as nano-mask. The effect of SiNx interlayer on the structural and optical properties of the overgrown GaN layer was investigated. Growth of InGaN/GaN multiple-quantum wells (MQWs) along nonpolar and semipolar planes was investigated and their structural and optical properties were studied. The effect of defects on the emission properties of the MQWs has been addressed. Optical measurements revealed the absence of polarization in the MQWs. Based on the MQW optimization, light-emitting diodes were grown on nonpolar and semipolar templates and their electrical and optical properties were studied. Electroluminescence measurement confirmed the absence of built-in electric fields in the quantum well. We demonstrated the first nonpolar and semipolar light-emitting diodes with milliwatt-range output power. DC output power as high as 0.6 mW at 20 mA and pulsed output power as high as 23.5 mW at 1 A were

  2. Nanodot-based organic memory devices

    NASA Astrophysics Data System (ADS)

    Liu, Zhengchun

    2006-04-01

    In this study, resistor-type, diode-type, and transistor-type organic memory devices were investigated, aiming at the low-cost plastic integrated circuit applications. A series of solution-processing techniques including spin-coating, inkjet printing, and self-assembly were employed to fabricate these devices. The organic resistive memory device is based on a novel molecular complex film composed of tetracyanoquinodimethane (TCNQ) and a soluble methanofullerene derivative [6,6]-phenyl C61-butyric acid methyl ester (PCBM). It has an Al/molecules/Al sandwich structure. The molecular layer was formed by spin-coating technique instead of expensive vacuum deposition method. The current-voltage characteristics show that the device switches from the initial 'low' conduction state to 'high' conduction state upon application of external electric field at room temperature and return to 'low' conduction state when a high current pulse is applied. The on/off ratio is over 106. Each state has been found to remain stable for more than five months, even after the external electric field is removed. The PCBM nanodots wrapped by TCNQ molecules can form potential wells for charge trapping, and are believed to be responsible for the memory effects. A rewritable diode memory device was achieved in an improved configuration, i.e., ITO-PEDOT:PSS-PCBM/TCNQ-Al, where a semiconductor polymer PEDOT:PSS is used to form p+-N heterojunction with PCBM/TCNQ. It exhibits a diode characteristic (low conductive) before switching to a high-conductive Poole-Frenkel regime upon applying a positive external bias to ITO. The on/off ratio at +1.0 V is up to 105. Simulation results from Taurus-Medici are in qualitative agreement with the experimental results and the proposed charge storage model. The transistor-type memory device is fabricated on a heavily doped n-type silicon (n+-Si) substrate with a 100 nm thick thermally-grown oxide layer. The n+-Si serves as the gate electrode, while the oxide layer

  3. EDITORIAL: Frontiers in semiconductor-based devices Frontiers in semiconductor-based devices

    NASA Astrophysics Data System (ADS)

    Krishna, Sanjay; Phillips, Jamie; Ghosh, Siddhartha; Ma, Jack; Sabarinanthan, Jayshri; Stiff-Roberts, Adrienne; Xu, Jian; Zhou, Weidong

    2009-12-01

    This special cluster of Journal of Physics D: Applied Physics reports proceedings from the Frontiers in Semiconductor-Based Devices Symposium, held in honor of the 60th birthday of Professor Pallab Bhattacharya by his former doctoral students. The symposium took place at the University of Michigan, Ann Arbor on 6-7 December 2009. Pallab Bhattacharya has served on the faculty of the Electrical Engineering and Computer Science Department at the University of Michigan, Ann Arbor for 25 years. During this time, he has made pioneering contributions to semiconductor epitaxy, characterization of strained heterostructures, self-organized quantum dots, quantum-dot optoelectronic devices, and integrated optoelectronics. Professor Bhattacharya has been recognized for his accomplishments by membership of the National Academy of Engineering, by chaired professorships (Charles M Vest Distinguished University Professor and James R Mellor Professor of Engineering), and by selection as a Fellow of the IEEE, among numerous other honors and awards. Professor Bhattacharya has also made remarkable contributions in education, including authorship of the textbook Semiconductor Optoelectronic Devices (Prentice Hall, 2nd edition) and the production of 60 PhD students (and counting). In fact, this development of critical human resources is one of the biggest impacts of Professor Bhattacharya's career. His guidance and dedication have shaped the varied professional paths of his students, many of whom currently enjoy successful careers in academia, industry, and government around the world. This special cluster acknowledges the importance of Professor Bhattacharya's influence as all of the contributions are from his former doctoral students. The symposium reflects the significant impact of Professor Bhattacharya's research in that the topics span diverse, critical research areas, including: semiconductor lasers and modulators, nanoscale quantum structure-based devices, flexible CMOS-based

  4. Evaluation of the absolute photoluminescence quantum yields of molecularly doped organic composite films and the electroluminescence efficiencies of molecular light-emitting devices containing oligoheterocycles as efficient emission centers

    NASA Astrophysics Data System (ADS)

    Kushto, Gary P.; Hill, Ian G.; Mitschke, Ullrich; Baeuerle, Peter; Kafafi, Zakya H.

    2001-02-01

    The absolute photoluminescence quantum yields ((Phi) PL) of three end-capped oligothiophene derivatives dispersed in N,N'-((alpha) -naphthyl)-N,N'-diphenyl-1,1'-biphenyl ((alpha) -NPD) have been evaluated and the most efficient of the emitters was used as a dopant in molecular organic LEDs. Composite films of 2,5-bis [5-(4,5,6,7- tetrahydrobenzo[b]thien-2-yl) thien-2-yl]-furan (EC5FUR); 2,5-bis [5-(4,5,6,7- tetrahydrobenzo[b]thien-2-yl) thien-2-yl]-oxazole (EC5OXZ) and 2,5-bis [5-(4,5,6,7- tetrahydrobenzo[b]thien-2-yl)thien-2-yl]-1,3,4- oxadiazole (EC5OXD) doped into (alpha) -NPD were found to have (Phi) PL values of 78, 62 and 28%, respectively. MOLED devices were fabricated using an EC5FUR/(alpha) -NPD composite as the emitting layer and the external quantum efficiencies ((eta) EL) of these devices were evaluated. The results of the device characterization show that the inclusion of EC5FUR in the NPD hole transport layer increases the device (eta) EL to 1.45% at a current density of 10 mA/cm2. In addition, the concentration dependence of the (eta) EL on the EC5FUR dopant in certain device structures when considered in conjunction with the current results of ultraviolet photoemission spectroscopic experiments suggests that this dopant species may be acting as both a hole and electron trap in the (alpha) -NPD host.

  5. Self-Host Blue Dendrimer Comprised of Thermally Activated Delayed Fluorescence Core and Bipolar Dendrons for Efficient Solution-Processable Nondoped Electroluminescence.

    PubMed

    Ban, Xinxin; Jiang, Wei; Sun, Kaiyong; Lin, Baoping; Sun, Yueming

    2017-03-01

    A self-host thermally activated delayed fluorescence (TADF) dendrimer POCz-DPS for solution-processed nondoped blue organic light-emitting diodes (OLEDs) was designed and synthesized, in which the bipolar phosphine oxide carbazole moiety was introduced by alkyl chain to ensure balanced charge transfer. The investigation of physical properties showed that the bipolar dendrons not only improve the morphological stability but also restrain the concentration quenching effect of the TADF emissive core. The spin-coated OLEDs featuring POCz-DPS as the host-free blue emitter achieved the highest external quantum efficiency (7.3%) and color purity compared with those of doped or nondoped devices based on the parent molecule DMOC-DPS, which indicates that incorporating the merits of encapsulation and bipolar dendron is an effective way to improve the electroluminescent performance of the TADF emitter used for a solution-processed nondoped device.

  6. Optoelectronic characteristics of inorganic/organic hybrid device based on poly(N-vinylcarbazole)/ cadmium selenide thin films.

    PubMed

    Tang, Aiwei; Teng, Feng; Hou, Yanbing; Xiong, Sha; Feng, Bin; Qian, Lei; Wang, Yongsheng

    2008-03-01

    Inorganic/organic hybrid light-emitting diodes were easily fabricated with a thin film containing water-soluble cadmium selenide nanocrystals and poly(N-vinylcarbazole) as an emitting layer by a spin-coating method. The cadmium selenide nanocrystals were synthesized in aqueous solution with L-cysteine hydrochloride as the stabilizer and were transferred from the aqueous solution into chloroform by a cationic surfactant cetyltrimethyl ammonium bromide. A broad emission spanning the whole visible wavelength range was obtained from the inorganic/organic hybrid devices whether poly(N-vinylcarbazole) was present in the devices or not, and the electroluminescence intensity of the devices increased as the applied voltages increased. However, an obvious blue-shift of the wavelength was observed with the increasing applied voltages in the device with poly(N-vinylcarbazole). Accordingly, the emission color of the device made with poly(N-vinylcarbazole) could be tuned from white to blue by varying the applied voltages, but the emission color of the device made without poly(N-vinylcarbazole) was almost constrained in the white region. This can be attributed to a limited contribution of poly(N-vinylcarbazole) emission to the electroluminescence spectra under the higher applied voltage. By comparing the electroluminescence intensity and the current-voltage characteristics of the devices made with and without poly(N-vinylcarbazole), the performance of the device with poly(N-vinylcarbazole) was improved greatly, which indicated that poly(N-vinylcarbazole) played an important role in the carrier injection and transportation in the device with poly(N-vinylcarbazole).

  7. Terahertz polarimetry based on metamaterial devices

    NASA Astrophysics Data System (ADS)

    Metcalfe, Grace D.; Wraback, Michael; Strikwerda, Andrew; Fan, Kebin; Zhang, Xin; Averitt, Richard

    2012-05-01

    Polarimetry is a well-developed technique in radar based applications and stand-off spectroscopic analysis at optical frequencies. Extension to terahertz (THz) frequencies could provide a breakthrough in spectroscopic methods since the THz portion of the electromagnetic spectrum provides unique spectral signatures of chemicals and biological molecules, useful for filling gaps in detection and identification. Distinct advantages to a THz polarimeter include enhanced image-contrast based on differences in scattering of horizontally and vertically polarized radiation, and measurements of the dielectric response, and thereby absorption, of materials in reflection in real-time without the need of a reference measurement. To implement a prototype THz polarimeter, we have developed low profile, high efficiency metamaterial-based polarization control components at THz frequencies. Static metamaterial-based half- and quarter-wave plates operating at 0.35 THz frequencies were modeled and fabricated, and characterized using a MHz resolution, continuous-wave spectrometer operating in the 0.09 to 1.2 THz range to verify the design parameters such as operational frequency and bandwidth, insertion loss, and phase shift. The operation frequency was chosen to be in an atmospheric window (between water absorption lines) but can be designed to function at any frequency. Additional advantages of metamaterial devices include their compact size, flexibility, and fabrication ease over large areas using standard microfabrication processing. Wave plates in both the transmission and reflection mode were modeled, tested, and compared. Data analysis using Jones matrix theory showed good agreement between experimental data and simulation.

  8. Electroluminescence from nonpolar n-ZnO/p-AlGaN heterojunction light-emitting diode on r-sapphire

    NASA Astrophysics Data System (ADS)

    Chen, Jingwen; Zhang, Jun; Dai, Jiangnan; Wu, Feng; Wang, Shuai; Chen, Cheng; Long, Hanling; Liang, Renli; Zhao, Chong; Chen, Changqing; Tang, Zhiwu; Cheng, Hailing; He, Yunbin; Li, Mingkai

    2017-03-01

    Nonpolar a-plane n-ZnO/p-AlGaN heterojunction light-emitting diodes (LEDs) have been prepared on r-sapphire substrate using metal organic chemical vapor deposition and a pulsed laser deposition method. The dominant electroluminescence emission at 390 nm from the interband transition in n-ZnO layer under a forward bias was observed. Interestingly, electroluminescence with emission at 385 nm based on an avalanche mechanism was also achieved under reverse bias. The mechanisms of both the electroluminescence and I–V characteristics are discussed in detail by considering the avalanche effect. It is demonstrated that the crystalline quality of n-ZnO, not the p-AlGaN, is what affects the performance of the nonpolar ZnO based avalanche LED.

  9. Near-infrared roll-off-free electroluminescence from highly stable diketopyrrolopyrrole light emitting diodes

    NASA Astrophysics Data System (ADS)

    Sassi, Mauro; Buccheri, Nunzio; Rooney, Myles; Botta, Chiara; Bruni, Francesco; Giovanella, Umberto; Brovelli, Sergio; Beverina, Luca

    2016-09-01

    Organic light emitting diodes (OLEDs) operating in the near-infrared spectral region are gaining growing relevance for emerging photonic technologies, such as lab-on-chip platforms for medical diagnostics, flexible self-medicated pads for photodynamic therapy, night vision and plastic-based telecommunications. The achievement of efficient near-infrared electroluminescence from solution-processed OLEDs is, however, an open challenge due to the low photoluminescence efficiency of most narrow-energy-gap organic emitters. Diketopyrrolopyrrole-boron complexes are promising candidates to overcome this limitation as they feature extremely high photoluminescence quantum yield in the near-infrared region and high chemical stability. Here, by incorporating suitably functionalized diketopyrrolopyrrole derivatives emitting at ~760 nm in an active matrix of poly(9,9-dioctylfluorene-alt-benzothiadiazole) and without using complex light out-coupling or encapsulation strategies, we obtain all-solution-processed NIR-OLEDs with external quantum efficiency as high as 0.5%. Importantly, our test-bed devices show no efficiency roll-off even for high current densities and high operational stability, retaining over 50% of the initial radiant emittance for over 50 hours of continuous operation at 10 mA/cm2, which emphasizes the great applicative potential of the proposed strategy.

  10. Size-dependent electroluminescence from Si quantum dots embedded in amorphous SiC matrix

    NASA Astrophysics Data System (ADS)

    Rui, Yunjun; Li, Shuxin; Xu, Jun; Song, Chao; Jiang, Xiaofan; Li, Wei; Chen, Kunji; Wang, Qimin; Zuo, Yuhua

    2011-09-01

    Si quantum dots (QDs) were formed by thermal annealing the hydrogenated amorphous silicon carbide films (a-SiCx:H) with different C/Si ratio x, which were controlled by using a different gas ratio R of methane to silane during the deposition process. By adjusting x and post annealing temperature, the QD size can be changed from 1.4 to 4.2 nm accordingly, which was verified by the Raman spectra and transmission electron microscopy images. Size-dependent electroluminescence (EL) was observed, and the EL intensity was higher for the sample containing small-sized Si QDs due to the quantum confinement effect (QCE). The EL peak energy as a function of the Si QDs size was in good agreement with a modified effective mass approximation (EMA) model. The calculated finite barrier potential of the Si QDs embedded in SiC matrix is 0.4 and 0.8 eV for conduction and valence band, respectively. Moreover, the current-voltage properties and the linear relationship between the integrated EL intensity and injection current indicate that the carrier transport is dominated by Fowler-Nordheim tunneling and the EL mechanism is originated from the bipolar recombination of electron-hole pairs at Si QDs. Our results demonstrate Si QDs embedded in amorphous SiC matrix has the potential application in Si-based light emitting devices and the third-generation solar cells.

  11. Thorough subcells diagnosis in a multi-junction solar cell via absolute electroluminescence-efficiency measurements

    PubMed Central

    Chen, Shaoqiang; Zhu, Lin; Yoshita, Masahiro; Mochizuki, Toshimitsu; Kim, Changsu; Akiyama, Hidefumi; Imaizumi, Mitsuru; Kanemitsu, Yoshihiko

    2015-01-01

    World-wide studies on multi-junction (tandem) solar cells have led to record-breaking improvements in conversion efficiencies year after year. To obtain detailed and proper feedback for solar-cell design and fabrication, it is necessary to establish standard methods for diagnosing subcells in fabricated tandem devices. Here, we propose a potential standard method to quantify the detailed subcell properties of multi-junction solar cells based on absolute measurements of electroluminescence (EL) external quantum efficiency in addition to the conventional solar-cell external-quantum-efficiency measurements. We demonstrate that the absolute-EL-quantum-efficiency measurements provide I–V relations of individual subcells without the need for referencing measured I–V data, which is in stark contrast to previous works. Moreover, our measurements quantify the absolute rates of junction loss, non-radiative loss, radiative loss, and luminescence coupling in the subcells, which constitute the “balance sheets” of tandem solar cells. PMID:25592484

  12. Near-infrared roll-off-free electroluminescence from highly stable diketopyrrolopyrrole light emitting diodes

    PubMed Central

    Sassi, Mauro; Buccheri, Nunzio; Rooney, Myles; Botta, Chiara; Bruni, Francesco; Giovanella, Umberto; Brovelli, Sergio; Beverina, Luca

    2016-01-01

    Organic light emitting diodes (OLEDs) operating in the near-infrared spectral region are gaining growing relevance for emerging photonic technologies, such as lab-on-chip platforms for medical diagnostics, flexible self-medicated pads for photodynamic therapy, night vision and plastic-based telecommunications. The achievement of efficient near-infrared electroluminescence from solution-processed OLEDs is, however, an open challenge due to the low photoluminescence efficiency of most narrow-energy-gap organic emitters. Diketopyrrolopyrrole-boron complexes are promising candidates to overcome this limitation as they feature extremely high photoluminescence quantum yield in the near-infrared region and high chemical stability. Here, by incorporating suitably functionalized diketopyrrolopyrrole derivatives emitting at ~760 nm in an active matrix of poly(9,9-dioctylfluorene-alt-benzothiadiazole) and without using complex light out-coupling or encapsulation strategies, we obtain all-solution-processed NIR-OLEDs with external quantum efficiency as high as 0.5%. Importantly, our test-bed devices show no efficiency roll-off even for high current densities and high operational stability, retaining over 50% of the initial radiant emittance for over 50 hours of continuous operation at 10 mA/cm2, which emphasizes the great applicative potential of the proposed strategy. PMID:27677240

  13. Electroluminescence from single-wall carbon nanotube network transistors.

    PubMed

    Adam, E; Aguirre, C M; Marty, L; St-Antoine, B C; Meunier, F; Desjardins, P; Ménard, D; Martel, R

    2008-08-01

    The electroluminescence (EL) properties from single-wall carbon nanotube network field-effect transistors (NNFETs) and small bundle carbon nanotube field effect transistors (CNFETs) are studied using spectroscopy and imaging in the near-infrared (NIR). At room temperature, NNFETs produce broad (approximately 180 meV) and structured NIR spectra, while they are narrower (approximately 80 meV) for CNFETs. EL emission from NNFETs is located in the vicinity of the minority carrier injecting contact (drain) and the spectrum of the emission is red shifted with respect to the corresponding absorption spectrum. A phenomenological model based on a Fermi-Dirac distribution of carriers in the nanotube network reproduces the spectral features observed. This work supports bipolar (electron-hole) current recombination as the main mechanism of emission and highlights the drastic influence of carrier distribution on the optoelectronic properties of carbon nanotube films.

  14. Nanosized optoelectronic devices based on photoactivated proteins.

    PubMed

    Dimonte, Alice; Frache, Stefano; Erokhin, Victor; Piccinini, Gianluca; Demarchi, Danilo; Milano, Francesco; Micheli, Giovanni De; Carrara, Sandro

    2012-11-12

    Molecular nanoelectronics is attracting much attention, because of the possibility to add functionalities to silicon-based electronics by means of intrinsically nanoscale biological or organic materials. The contact point between active molecules and electrodes must present, besides nanoscale size, a very low resistance. To realize Metal-Molecule-Metal junctions it is, thus, mandatory to be able to control the formation of useful nanometric contacts. The distance between the electrodes has to be of the same size of the molecule being put in between. Nanogaps technology is a perfect fit to fulfill this requirement. In this work, nanogaps between gold electrodes have been used to develop optoelectronic devices based on photoactive proteins. Reaction Centers (RC) and Bacteriorhodopsin (BR) have been inserted in nanogaps by drop casting. Electrical characterizations of the obtained structures were performed. It has been demonstrated that these nanodevices working principle is based on charge separation and photovoltage response. The former is induced by the application of a proper voltage on the RC, while the latter comes from the activation of BR by light of appropriate wavelengths.

  15. Enhancement of electroluminescence from embedded Si quantum dots/SiO2multilayers film by localized-surface-plasmon and surface roughening

    PubMed Central

    Li, Wei; Wang, Shaolei; Hu, Mingyue; He, Sufeng; Ge, Pengpeng; Wang, Jing; Guo, Yan Yan; Zhaowei, Liu

    2015-01-01

    In this paper, we prepared a novel structure to enhance the electroluminescence intensity from Si quantum dots/SiO2multilayers. An amorphous Si/SiO2 multilayer film was fabricated by plasma-enhanced chemical vapor deposition on a Pt nanoparticle (NP)-coated Si nanopillar array substrate. By thermal annealing, an embedded Si quantum dot (QDs)/SiO2 multilayer film was obtained. The result shows that electroluminescence intensity was significantly enhanced. And, the turn-on voltage of the luminescent device was reduced to 3 V. The enhancement of the light emission is due to the resonance coupling between the localized-surface-plasmon (LSP) of Pt NPs and the band-gap emission of Si QDs/SiO2 multilayers. The other factors were the improved absorption of excitation light and the increase of light extraction ratio by surface roughening structures. These excellent characteristics are promising for silicon-based light-emitting applications. PMID:26138830

  16. A Laboratory-Based Course in Display Technology

    ERIC Educational Resources Information Center

    Sarik, J.; Akinwande, A. I.; Kymissis, I.

    2011-01-01

    A laboratory-based class in flat-panel display technology is presented. The course introduces fundamental concepts of display systems and reinforces these concepts through the fabrication of three display devices--an inorganic electroluminescent seven-segment display, a dot-matrix organic light-emitting diode (OLED) display, and a dot-matrix…

  17. Semiconductor-based, large-area, flexible, electronic devices on {110}<100> oriented substrates

    SciTech Connect

    Goyal, Amit

    2014-08-05

    Novel articles and methods to fabricate the same resulting in flexible, oriented, semiconductor-based, electronic devices on {110}<100> textured substrates are disclosed. Potential applications of resulting articles are in areas of photovoltaic devices, flat-panel displays, thermophotovoltaic devices, ferroelectric devices, light emitting diode devices, computer hard disc drive devices, magnetoresistance based devices, photoluminescence based devices, non-volatile memory devices, dielectric devices, thermoelectric devices and quantum dot laser devices.

  18. [100] or [110] aligned, semiconductor-based, large-area, flexible, electronic devices

    DOEpatents

    Goyal, Amit

    2015-03-24

    Novel articles and methods to fabricate the same resulting in flexible, large-area, [100] or [110] textured, semiconductor-based, electronic devices are disclosed. Potential applications of resulting articles are in areas of photovoltaic devices, flat-panel displays, thermophotovoltaic devices, ferroelectric devices, light emitting diode devices, computer hard disc drive devices, magnetoresistance based devices, photoluminescence based devices, non-volatile memory devices, dielectric devices, thermoelectric devices and quantum dot laser devices.

  19. Light emitting ceramic device

    DOEpatents

    Valentine, Paul; Edwards, Doreen D.; Walker, Jr., William John; Slack, Lyle H.; Brown, Wayne Douglas; Osborne, Cathy; Norton, Michael; Begley, Richard

    2010-05-18

    A light-emitting ceramic based panel, hereafter termed "electroceramescent" panel, is herein claimed. The electroceramescent panel is formed on a substrate providing mechanical support as well as serving as the base electrode for the device. One or more semiconductive ceramic layers directly overlay the substrate, and electrical conductivity and ionic diffusion are controlled. Light emitting regions overlay the semiconductive ceramic layers, and said regions consist sequentially of a layer of a ceramic insulation layer and an electroluminescent layer, comprised of doped phosphors or the equivalent. One or more conductive top electrode layers having optically transmissive areas overlay the light emitting regions, and a multi-layered top barrier cover comprising one or more optically transmissive non-combustible insulation layers overlay said top electrode regions.

  20. Diode-laser-based therapy device

    NASA Astrophysics Data System (ADS)

    Udrea, Mircea V.; Nica, Adriana S.; Florian, Mariana; Poenaru, Daniela; Udrea, Gabriela; Lungeanu, Mihaela; Sporea, Dan G.; Vasiliu, Virgil V.; Vieru, Roxana

    2004-10-01

    A new therapy laser device is presented. The device consists of a central unit and different types of laser probes. The laser probe model SL7-650 delivers seven red (650 nm), 5 mW diode lasers convergent beams. The beams converge at about 30 cm in front of the laser probe and the irradiated area might be varied by simple displacement of the laser probe with respect to the target. The laser probe SL1-808 emits single infrared laser beam up to 500 mW. The efficiency of the use of this device in physiotherapy, and rheumatology, has been put into evidence after years of testing. Dermatology and microsurgery are users of infrared powerful laser probes. The device has successfully passed technical and clinical tests in order to be certified. The laser device design and some medical results are given.

  1. Synthesis and electroluminescent properties of a novel electroluminescence material of bis-2-(4-(diphenylphosphino)phenyl)benzo[d]oxazole (DPB).

    PubMed

    Hoanh, Trinh Dac; Kim, Ik-Hwan; Kim, Dong-Eun; Shin, Hoon-Kyu; Kwon, Young-Soo; Chang, Sang-Mok; Lee, Burm-Jong

    2014-08-01

    A new light-emissive material, bis-2-(4-(diphenylphosphino)phenyl)benzo[d]oxazole (DPB), has been synthesized and characterized by FT-NMR, FT-IR, UV-Vis and elemental analysis. DPB has the band gap of 4.3 eV between HOMO and LUMO levels. The photoluminescence (PL) of DPB was measured at 410 nm from the chloroform solution. The electroluminescent (EL) devices with structures of ITO/NPB/DPB/LiF/Al and ITO/NPB/DPB/Alq3/LiF/Al were constructed and showed maximum emission at 540 nm. The device using DPB as emitting material showed the luminance of 1000 cd/m2 at 11 V. The CIE chromaticity of the device showed near the region of white color emission.

  2. Intense deep blue exciplex electroluminescence from NPB/TPBi:PPh3O-based OLEDs and their intrinsic degradation mechanisms (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Shinar, Joseph; Hippola, Chamika; Danilovic, Dusan; Bhattacharjee, Ujjal; Petrich, Jacob W.; Shinar, Ruth

    2016-09-01

    We describe intense and efficient deep blue (430 - 440 nm) exciplex emission from NPB/TPBi:PPh3O OLEDs where the luminous efficiency approaches 4 Cd/A and the maximal brightness exceeds 22,000 Cd/m2. Time resolved PL measurements confirm the exciplex emission from NPB:TPBi, as studied earlier by Monkman and coworkers [Adv. Mater. 25, 1455 (2013)]. However, the inclusion of PPh3O improves the OLED performance significantly. The effect of PPh3O on the EL and PL will be discussed. The NPB/TPBi:PPh3O-based OLEDs were also studied by optically and electrically detected magnetic resonance (ODMR and EDMR, respectively). In particular, the amplitude of the negative (EL- and current-quenching) spin 1/2 resonance, previously attributed to enhanced formation of strongly EL-quenching positive bipolarons, increases as the OLEDs degrade in a dry nitrogen atmosphere. This degradation mechanism is discussed in relation to degradation induced by hot polarons that are energized by exciton annihilation.

  3. Antimony Based III-V Thermophotovoltaic Devices

    SciTech Connect

    CA Wang

    2004-06-09

    Antimony-based III-V thermophotovoltaic (TPV) cells are attractive converters for systems with low radiator temperature around 1100 to 1700 K, since these cells potentially can be spectrally matched to the thermal source. Cells under development include GaSb and the lattice-matched GaInAsSb/GaSb and InPAsSb/InAs quaternary systems. GaSb cell technology is the most mature, owing in part to the relative ease in preparation of the binary alloy compared to quaternary GaInAsSb and InPAsSb alloys. Device performance of 0.7-eV GaSb cells exceeds 90% of the practical limit. GaInAsSb TPV cells have been the primary focus of recent research, and cells with energy gap E{sub g} ranging from {approx}0.6 to 0.49 eV have been demonstrated. Quantum efficiency and fill factor approach theoretical limits. Open-circuit voltage factor is as high as 87% of the practical limit for the higher-E{sub g} cells, but degrades to below 80% with decreasing E{sub g} of the alloy, which might be due to Auger recombination. InPAsSb cells are the least studied, and a cell with E{sub g} = 0.45-eV has extended spectral response out to 4.3 {micro}m. This paper briefly reviews the main contributions that have been made for antimonide-based TPV cells, and suggests additional studies for further performance enhancements.

  4. Synaptic devices based on purely electronic memristors

    SciTech Connect

    Pan, Ruobing; Li, Jun; Zhuge, Fei E-mail: h-cao@nimte.ac.cn; Zhu, Liqiang; Liang, Lingyan; Zhang, Hongliang; Gao, Junhua; Cao, Hongtao E-mail: h-cao@nimte.ac.cn; Fu, Bing; Li, Kang

    2016-01-04

    Memristive devices have been widely employed to emulate biological synaptic behavior. In these cases, the memristive switching generally originates from electrical field induced ion migration or Joule heating induced phase change. In this letter, the Ti/ZnO/Pt structure was found to show memristive switching ascribed to a carrier trapping/detrapping of the trap sites (e.g., oxygen vacancies or zinc interstitials) in ZnO. The carrier trapping/detrapping level can be controllably adjusted by regulating the current compliance level or voltage amplitude. Multi-level conductance states can, therefore, be realized in such memristive device. The spike-timing-dependent plasticity, an important Hebbian learning rule, has been implemented in this type of synaptic device. Compared with filamentary-type memristive devices, purely electronic memristors have potential to reduce their energy consumption and work more stably and reliably, since no structural distortion occurs.

  5. Toward biomaterial-based implantable photonic devices

    NASA Astrophysics Data System (ADS)

    Humar, Matjaž; Kwok, Sheldon J. J.; Choi, Myunghwan; Yetisen, Ali K.; Cho, Sangyeon; Yun, Seok-Hyun

    2017-03-01

    Optical technologies are essential for the rapid and efficient delivery of health care to patients. Efforts have begun to implement these technologies in miniature devices that are implantable in patients for continuous or chronic uses. In this review, we discuss guidelines for biomaterials suitable for use in vivo. Basic optical functions such as focusing, reflection, and diffraction have been realized with biopolymers. Biocompatible optical fibers can deliver sensing or therapeutic-inducing light into tissues and enable optical communications with implanted photonic devices. Wirelessly powered, light-emitting diodes (LEDs) and miniature lasers made of biocompatible materials may offer new approaches in optical sensing and therapy. Advances in biotechnologies, such as optogenetics, enable more sophisticated photonic devices with a high level of integration with neurological or physiological circuits. With further innovations and translational development, implantable photonic devices offer a pathway to improve health monitoring, diagnostics, and light-activated therapies.

  6. Toward flexible polymer and paper-based energy storage devices.

    PubMed

    Nyholm, Leif; Nyström, Gustav; Mihranyan, Albert; Strømme, Maria

    2011-09-01

    All-polymer and paper-based energy storage devices have significant inherent advantages in comparison with many currently employed batteries and supercapacitors regarding environmental friendliness, flexibility, cost and versatility. The research within this field is currently undergoing an exciting development as new polymers, composites and paper-based devices are being developed. In this report, we review recent progress concerning the development of flexible energy storage devices based on electronically conducting polymers and cellulose containing composites with particular emphasis on paper-based batteries and supercapacitors. We discuss recent progress in the development of the most commonly used electronically conducting polymers used in flexible device prototypes, the advantages and disadvantages of this type of energy storage devices, as well as the two main approaches used in the manufacturing of paper-based charge storage devices.

  7. Synthesis, crystal structures and photo- and electro-luminescence of copper(I) complexes containing electron-transporting diaryl-1,3,4-oxadiazole.

    PubMed

    Yu, Tianzhi; Liu, Peng; Chai, Haifang; Kang, Jundan; Zhao, Yuling; Zhang, Hui; Fan, Duowang

    2014-05-01

    Two mononuclear Cu(I) complexes based on 2-(2-pyridyl)benzimidazolyl derivative ligand containing electron-transporting 1,3,4-oxadiazole group (L), [Cu(L)(PPh(3))2](BF(4)) and [Cu(L)(DPEphos)](BF(4)), where L = 1-(4-(5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl)benzyl)-2-(pyridin-2-yl)benzimidazole and DPEphos = bis[2-(diphenylphosphino)phenyl]ether, have been successfully synthesized and characterized. The X-ray crystal structure analyses of the ligand L and the complex [Cu(L)(PPh(3))2](BF(4)) were described. The photophysical properties of the complexes were examined by using UV-vis, photoluminescence spectroscopic analysis. The doped light-emitting devices using the Cu(I) complexes as dopants were fabricated. With no electron transporting layers employed in the devices, yellow electroluminescence from Cu(I) complexes were observed. The devices based on the complex [Cu(L)(DPEphos)](BF4) possess better performance as compared with the devices fabricated by the complex [Cu(L)(PPh(3))2](BF(4)). The devices with the structure of ITO/MoO(3) (2 nm)/NPB (40 nm)/CBP:[Cu(L)(DPEphos)](BF(4)) (8 wt%, 30 nm)/BCP (30 nm)/LiF (1 nm)/Al (150 nm) exhibit a maximum efficiency of 3.04 cd/A and a maximum brightness of 4,758 cd/m(2).

  8. Photomechanical modification of ZnS microcrystal to enhance electroluminescence by ultrashort-pulse laser processing

    NASA Astrophysics Data System (ADS)

    Nabesaka, Kyohei; Ishikawa, Yasuaki; Hosokawa, Yoichiroh; Uraoka, Yukiharu

    2017-02-01

    A ZnS microcrystal was treated with an ultrashort-pulse laser and applied to an inorganic electroluminescence (EL) phosphor. We found that the emission intensity of the EL phosphor was increased by laser-induced photomechanical modification. The pulse duration dependence of the emission enhancement and structural analysis by scanning electron microscopy indicated that the structural modification was induced inside the ZnS microcrystal, although a mechanical grinding would induce the structural modification mainly on the crystal surface. The results suggested a new way of enhancing the emission of inorganic EL devices.

  9. Improvement of electroluminescence performance by integration of ZnO nanowires and single-crystalline films on ZnO/GaN heterojunction

    SciTech Connect

    Shi, Zhifeng; Zhang, Yuantao Cui, Xijun; Wu, Bin; Zhuang, Shiwei; Yang, Fan; Zhang, Baolin; Du, Guotong; Yang, Xiaotian

    2014-03-31

    Heterojunction light-emitting diodes based on n-ZnO nanowires/ZnO single-crystalline films/p-GaN structure have been demonstrated for an improved electroluminescence performance. A highly efficient ultraviolet emission was observed under forward bias. Compared with conventional n-ZnO/p-GaN structure, high internal quantum efficiency and light extraction efficiency were simultaneously considered in the proposed diode. In addition, the diode can work continuously for ∼10 h with only a slight degradation in harsh environments, indicating its good reliability and application prospect in the future. This route opens possibilities for the development of advanced nanoscale devices in which the advantages of ZnO single-crystalline films and nanostructures can be integrated together.

  10. Printable Graphene-based Thermoelectric Device with High Temperature Capability

    NASA Astrophysics Data System (ADS)

    Li, Tian; Chen, Yanan; Drew, Dennis; Hu, Liangbing; NanomaterialsEmerging Devices Collaboration

    Thermoelectric devices are of particular interest due to their capability to convert heat into electrical power. We demonstrate the use of a Graphene-based thermoelectric device that can generate output voltages of hundreds of millivolts with an illuminating Graphene strip as the blackbody source. Our proposed device is superior for thermoelectric conversion mainly due to its high temperature capability that yields a maximum Carnot efficiency limit of 90% (referenced to room temperature) and a high Seebeck coefficient. Our device is also macroscopic with good mechanical strength and stabilized performance, making it attractive for large scale and reliable thermoelectric devices.

  11. Model-based engineering for medical-device software.

    PubMed

    Ray, Arnab; Jetley, Raoul; Jones, Paul L; Zhang, Yi

    2010-01-01

    This paper demonstrates the benefits of adopting model-based design techniques for engineering medical device software. By using a patient-controlled analgesic (PCA) infusion pump as a candidate medical device, the authors show how using models to capture design information allows for i) fast and efficient construction of executable device prototypes ii) creation of a standard, reusable baseline software architecture for a particular device family, iii) formal verification of the design against safety requirements, and iv) creation of a safety framework that reduces verification costs for future versions of the device software. 1.

  12. Device considerations for development of conductance-based biosensors

    PubMed Central

    Lee, Kangho; Nair, Pradeep R.; Scott, Adina; Alam, Muhammad A.; Janes, David B.

    2009-01-01

    Design and fabrication of electronic biosensors based on field-effect-transistor (FET) devices require understanding of interactions between semiconductor surfaces and organic biomolecules. From this perspective, we review practical considerations for electronic biosensors with emphasis on molecular passivation effects on FET device characteristics upon immobilization of organic molecules and an electrostatic model for FET-based biosensors. PMID:24753627

  13. Electrochromic devices based on lithium insertion

    DOEpatents

    Richardson, Thomas J.

    2006-05-09

    Electrochromic devices having as an active electrode materials comprising Sb, Bi, Si, Ge, Sn, Te, N, P, As, Ga, In, Al, C, Pb, I and chalcogenides are disclosed. The addition of other metals, i.e. Ag and Cu to the active electrode further enhances performance.

  14. Animation Based Learning of Electronic Devices

    ERIC Educational Resources Information Center

    Gero, Aharon; Zoabi, Wishah; Sabag, Nissim

    2014-01-01

    Two-year college teachers face great difficulty when they teach the principle of operation of the bipolar junction transistor--a subject which forms the basis for electronics studies. The difficulty arises from both the complexity of the device and by the lack of adequate scientific background among the students. We, therefore, developed a unique…

  15. OLED devices with internal outcoupling

    DOEpatents

    Liu, Jie Jerry; Sista, Srinivas Prasad; Shi, Xiaolei; Zhao, Ri-An; Chichak, Kelly Scott; Youmans, Jeffrey Michael; Janora, Kevin Henry; Turner, Larry Gene

    2015-03-03

    Optoelectronic devices that have enhanced internal outcoupling are disclosed. The devices include a substrate, an anode, a cathode, an electroluminescent layer, and a hole injecting layer. The hole injecting layer includes inorganic nanoparticles that have a bimodal particle size distribution and which are dispersed in an organic matrix.

  16. Electron Devices Based on Transition Metal Dichalcogenides

    NASA Astrophysics Data System (ADS)

    Tosun, Mahmut

    Integrated circuits consists of building blocks called transistors. A transistor is a switch that enables logic operations to perform computing. Since the invention of the first integrated circuit, transistors have been scaled down in their dimensions to increase the density of transistors per unit area to enable more functionality. Transistor scaling is continued by introducing novel device structures and materials at each technology node. Due to the challenges such as short channel effects and the power consumption issues, novel materials are investigated as a candidate for next generation transistors. In this thesis, 2-dimensinal layered semiconductors, namely transition metal dichalcogenides (TMDCs) are studied to assess their electronic material properties as a candidate channel material for next generation electronic devices. Chapter one, introduces the challenges in the state of the art MOSFET devices. Then the motivation for the use of TMDCs in MOSFETs is explained. In chapter two, doping of the TMDCs is studied to be able to probe the intrinsic electronic properties of the devices fabricated using these materials. Contact resistance can be decreased by doping and TMDC MOSFETs with near-ideal performance metrics are demonstrated. In chapter three the CMOS integration of the devices using TMDCs are examined. Logic operations are conducted by fabricating WSe 2 n-FETs and p-FETs on the same flake. Then vertical 3-dimensional integration of n-FETs and p-FETs are demonstrated using the same gate. These transistors are connected as a CMOS inverter and logic operations are performed. Chapter four presents the band structure engineering study using TMDCs. Mono-multilayer MoS2 junctions are found to have a type-I heterojunction. Optoelectronic properties of this junction are investigated and the junction is shown to have a photoresponse that dominates the photoresponse coming from the contacts. In chapter five, the tunneling devices using TMDCs are studied. Dual

  17. Theoretical and material studies on thin-film electroluminescent devices

    NASA Technical Reports Server (NTRS)

    Summers, C. J.; Goldman, J. A.; Brennan, K.

    1988-01-01

    During this report period work was performed on the modeling of High Field Electronic Transport in Bulk ZnS and ZnSe, and also on the surface cleaning of Si for MBE growth. Some MBE growth runs have also been performed in the Varian GEN II System. A brief outline of the experimental work is given. A complete summary will be done at the end of the next reporting period at the completion of the investigation. The theoretical studies are included.

  18. Theoretical and material studies on thin-film electroluminescent devices

    NASA Technical Reports Server (NTRS)

    Summers, C. J.; Benz, R., II

    1987-01-01

    The effect of surface nucleation processes on the quality of ZnS layers grown on (001) GaAs substrates by molecular beam epitaxy is reported. Reflection high energy electron diffraction indicated that nucleation at high temperatures produced more planar surfaces than nucleation at low temperatures, but the crystalline quality as accessed by x ray double crystal diffractometry is relatively independent of nucleation temperature. A critical factor in layer quality was the initial roughness of the GaAs surfaces.

  19. Device- and semi-device-independent random numbers based on noninequality paradox

    NASA Astrophysics Data System (ADS)

    Li, Hong-Wei; Pawłowski, Marcin; Rahaman, Ramij; Guo, Guang-Can; Han, Zheng-Fu

    2015-08-01

    In this work, we propose device-independent true random number expansion protocols based on noninequality paradoxes such as Hardy's and Cabello's nonlocality arguments, thus highlighting the noninequality paradox as an important resource for device-independent quantum-information processing, in particular for generating true randomness. As a byproduct, we find that the nonlocal bound of the Cabello argument with arbitrary dimension is the same as the one achieved in the qubits system. More interestingly, we propose a dimension witness paradox based on the Cabello argument which can be used for constructing a semi-device-independent true random number expansion protocol.

  20. Electroluminescence from indirect band gap semiconductor ReS2

    NASA Astrophysics Data System (ADS)

    Gutiérrez-Lezama, Ignacio; Aditya Reddy, Bojja; Ubrig, Nicolas; Morpurgo, Alberto F.

    2016-12-01

    It has been recently claimed that bulk crystals of transition metal dichalcogenide (TMD) ReS2 are direct band gap semiconductors, which would make this material an ideal candidate, among all TMDs, for the realization of efficient opto-electronic devices. The situation is however unclear, because even more recently an indirect transition in the PL spectra of this material has been detected, whose energy is smaller than the supposed direct gap. To address this issue we exploit the properties of ionic liquid gated field-effect transistors (FETs) to investigate the gap structure of bulk ReS2. Using these devices, whose high quality is demonstrated by a record high electron FET mobility of 1100 cm2 V-1 s-1 at 4 K, we can induce hole transport at the surface of the material and determine quantitatively the smallest band gap present in the material, irrespective of its direct or indirect nature. The value of the band gap is found to be 1.41 eV, smaller than the 1.5 eV direct optical transition but in good agreement with the energy of the indirect optical transition, providing an independent confirmation that bulk ReS2 is an indirect band gap semiconductor. Nevertheless, contrary to the case of more commonly studied semiconducting TMDs (e.g., MoS2, WS2, etc) in their bulk form, we also find that ReS2 FETs fabricated on bulk crystals do exhibit electroluminescence when driven in the ambipolar injection regime, likely because the difference between direct and indirect gap is only 100 meV. We conclude that ReS2 does deserve more in-depth investigations in relation to possible opto-electronic applications.

  1. Developing resonant tunneling devices based on graphene

    NASA Astrophysics Data System (ADS)

    Yu, Eric; Tiwari, Sandip; Stewart, Derek

    2009-03-01

    We present an ab-initio study of the electronic properties of patterned graphene structures as candidate resonant tunneling devices. We consider graphene nanoribbons that have been modified with one or more narrow constrictions or patterned with periodic nanoscale antidotes[1]. Specifically, we focus on semi-metallic armchair nanoribbons with narrow semiconducting regions and semi-metallic zigzag nanoribbons patterned with antidots. Using a first-principles density functional theory (DFT) approach, we investigate the induced band-gap opening and transmission coefficients. We examine how varying the lengths of the constrictions, changing the separation between dots and their sizes affect transport properties. We will also discuss I-V characteristics of these graphene structures and evaluate the possibility of a negative differential resistance in these devices. [1] T. G. Pedersen et al., Physical Review Letters, 100 136804 (2008)

  2. Optoelectronic Devices Based on Novel Semiconductor Structures

    DTIC Science & Technology

    2006-06-14

    Force. 15. SUBJECT TERMS Terahertz devices, spectrometers, and systems; nanostructures and nanodevices 16. SECURITY CLASSIFICATION OF: 17. LIMITATION...Y. J. Ding and I. B. Zotova, "Coherent and tunable terahertz oscillators, generators, and amplifiers," J. Nonlinear Opt. Phys. & Mats. 11, 75-97...GaSe crystal," Opt. Left. 27, 1454-1456 (2002). 2. W. Shi and Y. J. Ding, "Continuously tunable and coherent terahertz radiation by means of phase

  3. Photoluminescence and electroluminescence characteristics of CaSiN2:Eu phosphor

    NASA Astrophysics Data System (ADS)

    Lee, Soon S.; Lim, Sungkyoo; Sun, Sey-Shing; Wager, John F.

    1997-11-01

    Photoluminescenc eand electroluminescence of CaSiN2:Eu materials were investigted to develop a new phosphor for thin film electroluminescence (TFEL) device applications. Ca3N2 and Si3N4 powders were mixed to form CaSiN2 hostmaterials and Eu was added as the luminescent center. The mixed powermatrials were cold pressed under the pressure of 1 Kg/cm2 to make pellets, and fired at 1400 degrees Celsius for 2 hours under N2H2 envrionemtn. Th ex-ry diffraction(CRD) patterns of synthesizd materals wer well matched with CaSiN2 of joint committee for powder diffraction standards (JCPDS) csrad. When illuminated by ultravilet rays, th enew phosphors emitted very bright red ligh of peak wav lenegth centered at 620 nm. Th TFEL devices with CaSiN2:Eu phosphor layser swre grown by sputter depositonof CaSiN2:Eu target. Red light emission was observed when the peak amplitude of the applied voltge exceeded 116 V.l The luminance was shown to increase sharply withth increase of the applied voltage. The maximum luminance was 1.62 Cd/m2 at the applied peak voltage of 276 V. The red emission from CaSiN2:Eu TFEL device seems to result from electronic transition of Eu3+ ions.The emission spectra of TFEl devices matchwell withth ephotoluminescence spectra of CaSiN2:Ey powders. The new devices structure and fabrication processes for the iimprovement of emission intenityof CaSiN2:Eu TFEl devices ar under investigation.

  4. Photoluminescence and electroluminescence of a tripodal compound containing 7-diethylamino-coumarin moiety

    NASA Astrophysics Data System (ADS)

    Yu, Tianzhi; Zhang, Peng; Zhao, Yuling; Zhang, Hui; Meng, Jing; Fan, Duowang; Dong, Wenkui

    2008-12-01

    A novel tripodal compound, tris[2-(7-diethylamino-coumarin-3-carboxamide)ethyl]amine (Tren-C), was synthesized and characterized by elemental analysis, infrared and 1H-NMR spectra. The photoluminescent (PL) and electroluminescent properties of Tren-C were investigated. Tren-C exhibits different colour emissions in solid states and solutions. The electroluminescence devices comprising vacuum vapour-deposited films using the compound as a dopant were fabricated, showing blue emissions that are identical to its PL spectrum in chloroform solutions. With the device structure of indium tin oxide (ITO)/4, 4', 4''-tris-N-naphthyl-N-phenylamino-triphenylamine (2-TNATA) (5 nm)/N, N'-bis-(naphthyl)-N, N'-diphenyl-1, 1'-biphenyl-4, 4'-diamine (NPB) (40 nm)/4, 4'-bis(9-carbazolyl) biphenyl (CBP) : Tren-C (0.5 wt%, 30 nm)/2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1, 3, 4-oxadiazole (Bu-PBD) (30 nm)/LiF (1 nm)/Al (100 nm), a maximum external quantum efficiency of 2.85%, a maximum luminous efficiency of 3.85 cd A-1 and a maximum luminance of 1450 cd m-2 are realized.

  5. Product-based Safety Certification for Medical Devices Embedded Software.

    PubMed

    Neto, José Augusto; Figueiredo Damásio, Jemerson; Monthaler, Paul; Morais, Misael

    2015-01-01

    Worldwide medical device embedded software certification practices are currently focused on manufacturing best practices. In Brazil, the national regulatory agency does not hold a local certification process for software-intensive medical devices and admits international certification (e.g. FDA and CE) from local and international industry to operate in the Brazilian health care market. We present here a product-based certification process as a candidate process to support the Brazilian regulatory agency ANVISA in medical device software regulation. Center of Strategic Technology for Healthcare (NUTES) medical device embedded software certification is based on a solid safety quality model and has been tested with reasonable success against the Class I risk device Generic Infusion Pump (GIP).

  6. Empirically based device modeling of bulk heterojunction organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Pierre, Adrien; Lu, Shaofeng; Howard, Ian A.; Facchetti, Antonio; Arias, Ana Claudia

    2013-10-01

    An empirically based, open source, optoelectronic model is constructed to accurately simulate organic photovoltaic (OPV) devices. Bulk heterojunction OPV devices based on a new low band gap dithienothiophene- diketopyrrolopyrrole donor polymer (P(TBT-DPP)) are blended with PC70BM and processed under various conditions, with efficiencies up to 4.7%. The mobilities of electrons and holes, bimolecular recombination coefficients, exciton quenching efficiencies in donor and acceptor domains and optical constants of these devices are measured and input into the simulator to yield photocurrent with less than 7% error. The results from this model not only show carrier activity in the active layer but also elucidate new routes of device optimization by varying donor-acceptor composition as a function of position. Sets of high and low performance devices are investigated and compared side-by-side.

  7. Electroluminescence Studies on Longwavelength Indium Arsenide Quantum Dot Microcavities Grown on Gallium Arsenide

    DTIC Science & Technology

    2011-12-01

    ELECTROLUMINESCENCE STUDIES ON LONG WAVELENGTH INDIUM ARSENIDE QUANTUM DOT MICROCAVITIES GROWN ON GALLIUM ARSENIDE THESIS John C...11-46 ELECTROLUMINESCENCE STUDIES ON LONGWAVELENGTH INDIUM ARSENIDE QUANTUM DOT MICROCAVITIES GROWN ON GALLIUM ARSENIDE THESIS...58 1 ELECTROLUMINESCENCE STUDIES ON LONGWAVELENGTH INDIUM ARSENIDE QUANTUM DOT MICROCAVITIES GROWN ON GALLIUM ARSENIDE I

  8. Reduced graphene oxide based flexible organic charge trap memory devices

    NASA Astrophysics Data System (ADS)

    Rani, Adila; Song, Ji-Min; Jung Lee, Mi; Lee, Jang-Sik

    2012-12-01

    A nonvolatile organic transistor memory device was developed using layer-by-layer assembly of 3-aminopropyltriethoxysilane (APTES) and solution-processed, reduced graphene oxide (rGO) as the charge trapping layer on flexible substrates. Reduction of graphene oxide and successful adsorption of the rGO on APTES-covered substrates were confirmed. The organic memory devices based on rGO exhibited reliable programmable memory operations, confirmed by program/erase operations, data retention, and endurance properties. These methods can potentially play a significant role in the fabrication of next-generation flexible nonvolatile memory devices based on graphene materials.

  9. Silicon photonic devices based on binary blazed gratings

    NASA Astrophysics Data System (ADS)

    Zhou, Zhiping; Yu, Li

    2013-09-01

    Optical technology is poised to revolutionize short-reach communication systems, and the leading technology is silicon photonics. Silicon photonic devices have attracted more and more attention and have been increasingly studied in recent years. Grating, which functions as a building block for many passive and active devices, is widely used in silicon photonics. This review presents some silicon photonic devices based on binary blazed gratings, such as grating couplers, beam splitters, polarization beam splitters, broadband reflectors, and narrow filters, that demonstrate much better performance than those based on uniform gratings, owing to the novel characteristics of binary blazed gratings.

  10. A Flexible Microcontroller-Based Data Acquisition Device

    PubMed Central

    Hercog, Darko; Gergič, Bojan

    2014-01-01

    This paper presents a low-cost microcontroller-based data acquisition device. The key component of the presented solution is a configurable microcontroller-based device with an integrated USB transceiver and a 12-bit analogue-to-digital converter (ADC). The presented embedded DAQ device contains a preloaded program (firmware) that enables easy acquisition and generation of analogue and digital signals and data transfer between the device and the application running on a PC via USB bus. This device has been developed as a USB human interface device (HID). This USB class is natively supported by most of the operating systems and therefore any installation of additional USB drivers is unnecessary. The input/output peripheral of the presented device is not static but rather flexible, and could be easily configured to customised needs without changing the firmware. When using the developed configuration utility, a majority of chip pins can be configured as analogue input, digital input/output, PWM output or one of the SPI lines. In addition, LabVIEW drivers have been developed for this device. When using the developed drivers, data acquisition and signal processing algorithms as well as graphical user interface (GUI), can easily be developed using a well-known, industry proven, block oriented LabVIEW programming environment. PMID:24892494

  11. A flexible microcontroller-based data acquisition device.

    PubMed

    Hercog, Darko; Gergič, Bojan

    2014-06-02

    This paper presents a low-cost microcontroller-based data acquisition device. The key component of the presented solution is a configurable microcontroller-based device with an integrated USB transceiver and a 12-bit analogue-to-digital converter (ADC). The presented embedded DAQ device contains a preloaded program (firmware) that enables easy acquisition and generation of analogue and digital signals and data transfer between the device and the application running on a PC via USB bus. This device has been developed as a USB human interface device (HID). This USB class is natively supported by most of the operating systems and therefore any installation of additional USB drivers is unnecessary. The input/output peripheral of the presented device is not static but rather flexible, and could be easily configured to customised needs without changing the firmware. When using the developed configuration utility, a majority of chip pins can be configured as analogue input, digital input/output, PWM output or one of the SPI lines. In addition, LabVIEW drivers have been developed for this device. When using the developed drivers, data acquisition and signal processing algorithms as well as graphical user interface (GUI), can easily be developed using a well-known, industry proven, block oriented LabVIEW programming environment.

  12. Hybrid device based on GaN nanoneedles and MEH-PPV/PEDOT:PSS polymer

    SciTech Connect

    Shin, Min Jeong; Gwon, Dong-Oh; Lee, Chan-Mi; Lee, Gang Seok; Jeon, In-Jun; Ahn, Hyung Soo; Yi, Sam Nyung; Ha, Dong Han

    2015-08-15

    Highlights: • A hybrid device was demonstrated by using MEH-PPV, PEDOT:PSS, and GaN nanoneedles. • I–V curve of the hybrid device showed its rectification behaviour, similar to a diode. • EL peak originated by the different potential barriers at MEH-PPV and GaN interface. - Abstract: A hybrid device that combines the properties of organic and inorganic semiconductors was fabricated and studied. It incorporated poly[2-methoxy-5-(2-ethylhexyloxy)- 1,4-phenylenevinylene] (MEH-PPV) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as organic polymers and GaN nanoneedles as an inorganic semiconductor. Layers of the two polymers were spin coated on to the GaN nanoneedles. The one peak in the electroluminescence spectrum originated from the MEH-PPV layer owing to the different potential barriers of electrons and holes at its interface with the GaN nanoneedles. However, the photoluminescence spectrum showed peaks due to both GaN nanoneedles and MEH-PPV. Such hybrid structures, suitably developed, might be able to improve the efficiency of optoelectronic devices.

  13. Tunable Near-Infrared Luminescence in Tin Halide Perovskite Devices.

    PubMed

    Lai, May L; Tay, Timothy Y S; Sadhanala, Aditya; Dutton, Siân E; Li, Guangru; Friend, Richard H; Tan, Zhi-Kuang

    2016-07-21

    Infrared emitters are reasonably rare in solution-processed materials. Recently, research into hybrid organo-lead halide perovskite, originally popular in photovoltaics,1-3 has gained traction in light-emitting diodes (LED) due to their low-cost solution processing and good performance.4-9 The lead-based electroluminescent materials show strong colorful emission in the visible region, but lack emissive variants further in the infrared. The concerns with the toxicity of lead may, additionally, limit their wide-scale applications. Here, we demonstrate tunable near-infrared electroluminescence from a lead-free organo-tin halide perovskite, using an ITO/PEDOT:PSS/CH3NH3Sn(Br1-xIx)3/F8/Ca/Ag device architecture. In our tin iodide (CH3NH3SnI3) LEDs, we achieved a 945 nm near-infrared emission with a radiance of 3.4 W sr(-1) m(-2) and a maximum external quantum efficiency of 0.72%, comparable with earlier lead-based devices. Increasing the bromide content in these tin perovskite devices widens the semiconductor bandgap and leads to shorter wavelength emissions, tunable down to 667 nm. These near-infrared LEDs could find useful applications in a range of optical communication, sensing and medical device applications.

  14. Substrate structures for InP-based devices

    DOEpatents

    Wanlass, Mark W.; Sheldon, Peter

    1990-01-01

    A substrate structure for an InP-based semiconductor device having an InP based film is disclosed. The substrate structure includes a substrate region having a lightweight bulk substrate and an upper GaAs layer. An interconnecting region is disposed between the substrate region and the InP-based device. The interconnecting region includes a compositionally graded intermediate layer substantially lattice-matched at one end to the GaAs layer and substantially lattice-matched at the opposite end to the InP-based film. The interconnecting region further includes a dislocation mechanism disposed between the GaAs layer and the InP-based film in cooperation with the graded intermediate layer, the buffer mechanism blocking and inhibiting propagation of threading dislocations between the substrate region, and the InP-based device.

  15. Medical Device Integration Model Based on the Internet of Things

    PubMed Central

    Hao, Aiyu; Wang, Ling

    2015-01-01

    At present, hospitals in our country have basically established the HIS system, which manages registration, treatment, and charge, among many others, of patients. During treatment, patients need to use medical devices repeatedly to acquire all sorts of inspection data. Currently, the output data of the medical devices are often manually input into information system, which is easy to get wrong or easy to cause mismatches between inspection reports and patients. For some small hospitals of which information construction is still relatively weak, the information generated by the devices is still presented in the form of paper reports. When doctors or patients want to have access to the data at a given time again, they can only look at the paper files. Data integration between medical devices has long been a difficult problem for the medical information system, because the data from medical devices are lack of mandatory unified global standards and have outstanding heterogeneity of devices. In order to protect their own interests, manufacturers use special protocols, etc., thus causing medical decices to still be the "lonely island" of hospital information system. Besides, unfocused application of the data will lead to failure to achieve a reasonable distribution of medical resources. With the deepening of IT construction in hospitals, medical information systems will be bound to develop towards mobile applications, intelligent analysis, and interconnection and interworking, on the premise that there is an effective medical device integration (MDI) technology. To this end, this paper presents a MDI model based on the Internet of Things (IoT). Through abstract classification, this model is able to extract the common characteristics of the devices, resolve the heterogeneous differences between them, and employ a unified protocol to integrate data between devices. And by the IoT technology, it realizes interconnection network of devices and conducts associate matching

  16. Medical Device Integration Model Based on the Internet of Things.

    PubMed

    Hao, Aiyu; Wang, Ling

    2015-01-01

    At present, hospitals in our country have basically established the HIS system, which manages registration, treatment, and charge, among many others, of patients. During treatment, patients need to use medical devices repeatedly to acquire all sorts of inspection data. Currently, the output data of the medical devices are often manually input into information system, which is easy to get wrong or easy to cause mismatches between inspection reports and patients. For some small hospitals of which information construction is still relatively weak, the information generated by the devices is still presented in the form of paper reports. When doctors or patients want to have access to the data at a given time again, they can only look at the paper files. Data integration between medical devices has long been a difficult problem for the medical information system, because the data from medical devices are lack of mandatory unified global standards and have outstanding heterogeneity of devices. In order to protect their own interests, manufacturers use special protocols, etc., thus causing medical decices to still be the "lonely island" of hospital information system. Besides, unfocused application of the data will lead to failure to achieve a reasonable distribution of medical resources. With the deepening of IT construction in hospitals, medical information systems will be bound to develop towards mobile applications, intelligent analysis, and interconnection and interworking, on the premise that there is an effective medical device integration (MDI) technology. To this end, this paper presents a MDI model based on the Internet of Things (IoT). Through abstract classification, this model is able to extract the common characteristics of the devices, resolve the heterogeneous differences between them, and employ a unified protocol to integrate data between devices. And by the IoT technology, it realizes interconnection network of devices and conducts associate matching

  17. A point acoustic device based on aluminum nanowires.

    PubMed

    Xie, Qian-Yi; Ju, Zhen-Yi; Tian, He; Xue, Qing-Tang; Chen, Yuan-Quan; Tao, Lu-Qi; Mohammad, Mohammad Ali; Zhang, Xue-Yue; Yang, Yi; Ren, Tian-Ling

    2016-03-14

    A point Electrical Thermal Acoustic (ETA) device based on aluminum nanowire contacts is designed and fabricated. Interdigitated structural aluminum nanowires are released from the substrate by Inductively Coupled Plasma Reactive Ion Etching (ICP-RIE). By releasing the interdigitated structure, the nanowires contact each other at approximately 1 mm above the wafer, forming a Point Contact Structure (PCS). It is found that the PCS acoustic device realizes high efficiency when a biased AC signal is applied. The PCS acoustic device reaches a sound pressure level as high as 67 dB at a distance of 1 cm with 74 mW AC input. The power spectrum is flat, ranging from 2 kHz to 20 kHz with a less than ±3 dB fluctuation. The highest normalized Sound Pressure Level (SPL) of the point contact structure acoustic device is 18 dB higher than the suspended aluminum wire acoustic device. Comparisons between the PCS acoustic device and the Suspended Aluminum Nanowire (SAN) acoustic device illustrate that the PCS acoustic device has a flatter power spectrum within the 20 kHz range, and enhances the SPL at a lower frequency. Enhancing the response at lower frequencies is extremely useful, which may enable earphone and loudspeaker applications within the frequency range of the human ear with the help of pulse density modulation.

  18. A rhythm-based authentication scheme for smart media devices.

    PubMed

    Lee, Jae Dong; Jeong, Young-Sik; Park, Jong Hyuk

    2014-01-01

    In recent years, ubiquitous computing has been rapidly emerged in our lives and extensive studies have been conducted in a variety of areas related to smart devices, such as tablets, smartphones, smart TVs, smart refrigerators, and smart media devices, as a measure for realizing the ubiquitous computing. In particular, smartphones have significantly evolved from the traditional feature phones. Increasingly higher-end smartphone models that can perform a range of functions are now available. Smart devices have become widely popular since they provide high efficiency and great convenience for not only private daily activities but also business endeavors. Rapid advancements have been achieved in smart device technologies to improve the end users' convenience. Consequently, many people increasingly rely on smart devices to store their valuable and important data. With this increasing dependence, an important aspect that must be addressed is security issues. Leaking of private information or sensitive business data due to loss or theft of smart devices could result in exorbitant damage. To mitigate these security threats, basic embedded locking features are provided in smart devices. However, these locking features are vulnerable. In this paper, an original security-locking scheme using a rhythm-based locking system (RLS) is proposed to overcome the existing security problems of smart devices. RLS is a user-authenticated system that addresses vulnerability issues in the existing locking features and provides secure confidentiality in addition to convenience.

  19. A Rhythm-Based Authentication Scheme for Smart Media Devices

    PubMed Central

    Lee, Jae Dong; Park, Jong Hyuk

    2014-01-01

    In recent years, ubiquitous computing has been rapidly emerged in our lives and extensive studies have been conducted in a variety of areas related to smart devices, such as tablets, smartphones, smart TVs, smart refrigerators, and smart media devices, as a measure for realizing the ubiquitous computing. In particular, smartphones have significantly evolved from the traditional feature phones. Increasingly higher-end smartphone models that can perform a range of functions are now available. Smart devices have become widely popular since they provide high efficiency and great convenience for not only private daily activities but also business endeavors. Rapid advancements have been achieved in smart device technologies to improve the end users' convenience. Consequently, many people increasingly rely on smart devices to store their valuable and important data. With this increasing dependence, an important aspect that must be addressed is security issues. Leaking of private information or sensitive business data due to loss or theft of smart devices could result in exorbitant damage. To mitigate these security threats, basic embedded locking features are provided in smart devices. However, these locking features are vulnerable. In this paper, an original security-locking scheme using a rhythm-based locking system (RLS) is proposed to overcome the existing security problems of smart devices. RLS is a user-authenticated system that addresses vulnerability issues in the existing locking features and provides secure confidentiality in addition to convenience. PMID:25110743

  20. Transient electroluminescence dynamics in small molecular organic light-emitting diodes

    SciTech Connect

    Gan, Z; Liu, R; Shinar, R; Shinar, J

    2010-09-14

    Intriguing electroluminescence (EL) spikes, following a voltage pulse applied to small molecular OLEDs, are discussed, elucidating carrier and exciton quenching dynamics and their relation to device structure. At low temperatures, all devices exhibit spikes at {approx} 70-300 ns and {mu}s-long tails. At 295 K only those with a hole injection barrier, carrier-trapping guest-host emitting layer, and no strong hole-blocking layer exhibit the spikes. They narrow and appear earlier under post-pulse reverse bias. The spikes and tails are in agreement with a revised model of recombination of correlated charge pairs (CCPs) and initially unpaired charges. Decreased post-pulse field-induced dissociative quenching of singlet excitons and CCPs, and possibly increased post-pulse current of holes that 'turn back' toward the recombination zone after having drifted beyond it are suspected to cause the spikes amplitude, which exceeds the dc EL.

  1. Strong yellow electroluminescence from manganese-silicon-implanted silicon-dioxide layers

    NASA Astrophysics Data System (ADS)

    Novikov, Sergey; Ovchinnikov, Victor F.; Haerkoenen, Jaakko; Sinkkonen, Juha A.

    2001-05-01

    Room temperature (RT) electroluminescence (EL) was obtained for the first time from Mn enriched Si/SiO2 structure. Si+ or Ar+ stimulated knock-on implantation through 20 nm Mn film with the subsequent annealing was used for EL device fabrication. Devices exhibit bright emission band at the 2.06 eV. The position does neither depend on implanted ion dose nor annealing procedure. EL is visible by naked eye even at current density as low as 1.5x10-6 Acm-2. Continuous wave external quantum efficiency 1.1x10-3 and power efficiency 1.5x10-5 have been achieved.

  2. Improved color purity and electroluminescent efficiency obtained by modulating thicknesses and evaporation rates of hole block and electron transport layers

    NASA Astrophysics Data System (ADS)

    Zhou, Liang; Deng, Ruiping; Feng, Jing; Li, Xiaona; Li, Xiyan; Zhang, Hongjie

    2011-01-01

    In this work, a series of electroluminescent (EL) devices based on trivalent europium (Eu3+) complex Eu(TTA)3phen (TTA = thenoyltrifluoroacetone, phen = 1,10-phenanthroline) were fabricated by selecting 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) and tris(8-hydroxyquinoline) aluminum (Alq3) as hole block and electron transport materials, respectively. Interestingly, we found the transport of electrons decreases gradually with increasing thicknesses and evaporation rates of BCP and Alq3 layers. Analyzing carrier distribution and EL spectra, we conclude that appropriately modulating the thicknesses and evaporation rates is an efficient way to decrease the accumulation of electrons in HBL, thus suppressing the EL of hole block material. On the other hand, decreasing the transport of electrons can also facilitate the balance of holes and electrons on Eu(TTA)3phen molecules, thus further enhancing the EL efficiency. As a result, pure Eu3+ emission with the efficiency as high as 8.49 cd/A was realized by controlling the thicknesses and evaporation rates of BCP and Alq3 layers to be 30 nm and 0.10 nm/s, 40 nm and 0.10 nm/s, respectively.

  3. Electrocaloric devices based on thin-film heat switches

    NASA Astrophysics Data System (ADS)

    Epstein, Richard I.; Malloy, Kevin J.

    2009-09-01

    We describe a new approach to refrigeration, heat pumping, and electrical generation that allows one to exploit the attractive properties of thin films of electrocaloric materials. Layers of electrocaloric material coupled with thin-film heat switches can work as either refrigerators and heat pumps or electrical generators, depending on the phasing of the applied voltages and heat switching. With heat switches based on thin layers of liquid crystals, the efficiency of electrocaloric thin-film devices can be at least as high as that of current thermoelectric devices. Advanced heat switches that may use carbon nanotubes would enable thin-film refrigerators and generators to outperform conventional vapor-compression devices.

  4. Diffractive devices based on blue phase liquid crystals

    NASA Astrophysics Data System (ADS)

    Li, Yan; Huang, Shuaijia; Su, Yikai

    2016-09-01

    Blue phase liquid crystal (BPLC) has been attractive for display and photonic applications for its sub-millisecond response time, no need for surface alignment, and an optically isotropic dark state. Because of these advantages, diffractive devices based on blue phase liquid crystals have great potential for wide applications. In this work, we present several BPLC diffractive devices. The operation principles, fabrication and experimental measurements will be discussed in details for two BPLC gratings realized by holographic method and a BPLC Fresnel lens using a spatial light modulator projector. All of these devices exhibit several attractive features such as sub-millisecond response, relatively high spatial resolution and polarization-independence.

  5. Evaluation of Vacuum-based Sampling Devices for Collection ...

    EPA Pesticide Factsheets

    Report The existing surface sampling strategy for a biological incident involving B. anthracis spores requires the use of various methods depending on the surface type. This project comparatively evaluated the vacuum sock and two additional vacuum-based collection devices (37 mm filter cassette and 3M™ Trace Evidence Filter) for their sampling efficacy. The 37 mm filter cassette was evaluated with mixed cellulose ester (MCE) filters or polytetrafluoroethylene (PTFE) filters installed, each was considered a unique device. These data were generated so appropriate sampling devices could be selected following a B. anthracis incident. Bacillus atrophaeus was used a surrogate.

  6. Absorbance Based Light Emitting Diode Optical Sensors and Sensing Devices

    PubMed Central

    O'Toole, Martina; Diamond, Dermot

    2008-01-01

    The ever increasing demand for in situ monitoring of health, environment and security has created a need for reliable, miniaturised sensing devices. To achieve this, appropriate analytical devices are required that possess operating characteristics of reliability, low power consumption, low cost, autonomous operation capability and compatibility with wireless communications systems. The use of light emitting diodes (LEDs) as light sources is one strategy, which has been successfully applied in chemical sensing. This paper summarises the development and advancement of LED based chemical sensors and sensing devices in terms of their configuration and application, with the focus on transmittance and reflectance absorptiometric measurements. PMID:27879829

  7. Electrochemical model of the polyaniline based organic memristive device

    SciTech Connect

    Demin, V. A. E-mail: victor.erokhin@fis.unipr.it; Erokhin, V. V. E-mail: victor.erokhin@fis.unipr.it; Kashkarov, P. K.; Kovalchuk, M. V.

    2014-08-14

    The electrochemical organic memristive device with polyaniline active layer is a stand-alone device designed and realized for reproduction of some synapse properties in the innovative electronic circuits, including the neuromorphic networks capable for learning. In this work, a new theoretical model of the polyaniline memristive is presented. The developed model of organic memristive functioning was based on the detailed consideration of possible electrochemical processes occuring in the active zone of this device. Results of the calculation have demonstrated not only the qualitative explanation of the characteristics observed in the experiment but also the quantitative similarities of the resultant current values. It is shown how the memristive could behave at zero potential difference relative to the reference electrode. This improved model can establish a basis for the design and prediction of properties of more complicated circuits and systems (including stochastic ones) based on the organic memristive devices.

  8. Integrated fuses for OLED lighting device

    DOEpatents

    Pschenitzka, Florian

    2007-07-10

    An embodiment of the present invention pertains to an electroluminescent lighting device for area illumination. The lighting device is fault tolerant due, in part, to the patterning of one or both of the electrodes into strips, and each of one or more of these strips has a fuse formed on it. The fuses are integrated on the substrate. By using the integrated fuses, the number of external contacts that are used is minimized. The fuse material is deposited using one of the deposition techniques that is used to deposit the thin layers of the electroluminescent lighting device.

  9. Green Phosphorescence and Electroluminescence of Sulfur Pentafluoride-Functionalized Cationic Iridium(III) Complexes.

    PubMed

    Shavaleev, Nail M; Xie, Guohua; Varghese, Shinto; Cordes, David B; Slawin, Alexandra M Z; Momblona, Cristina; Ortí, Enrique; Bolink, Henk J; Samuel, Ifor D W; Zysman-Colman, Eli

    2015-06-15

    We report on four cationic iridium(III) complexes [Ir(C^N)2(dtBubpy)](PF6) that have sulfur pentafluoride-modified 1-phenylpyrazole and 2-phenylpyridine cyclometalating (C^N) ligands (dtBubpy = 4,4'-di-tert-butyl-2,2'-bipyridyl). Three of the complexes were characterized by single-crystal X-ray structure analysis. In cyclic voltammetry, the complexes undergo reversible oxidation of iridium(III) and irreversible reduction of the SF5 group. They emit bright green phosphorescence in acetonitrile solution and in thin films at room temperature, with emission maxima in the range of 482-519 nm and photoluminescence quantum yields of up to 79%. The electron-withdrawing sulfur pentafluoride group on the cyclometalating ligands increases the oxidation potential and the redox gap and blue-shifts the phosphorescence of the iridium complexes more so than the commonly employed fluoro and trifluoromethyl groups. The irreversible reduction of the SF5 group may be a problem in organic electronics; for example, the complexes do not exhibit electroluminescence in light-emitting electrochemical cells (LEECs). Nevertheless, the complexes exhibit green to yellow-green electroluminescence in doped multilayer organic light-emitting diodes (OLEDs) with emission maxima ranging from 501 nm to 520 nm and with an external quantum efficiency (EQE) of up to 1.7% in solution-processed devices.

  10. Molecular-Based Devices and Circuits

    DTIC Science & Technology

    2008-09-23

    nano-cavities (50nm x 50nm) etched into the Si3N4 layer at the center of the electrode. Subsequently, molecules are self - assembled onto the bottom...various types of self assembled monolayers (SAMs) arranged in vertical configuration (Fig 2) . Each floor consists of different type of molecular layer...modified ferrocene film (Figure 2 compound 1) , and a the protein Azurin (Az). The Fc-based SAM can be used as a candidate for the bottom layer as we have

  11. Microwave based civil structure inspection device

    SciTech Connect

    Sohns, C.W.; Bible, D.W.

    1994-06-01

    A microwave based ``wall probe`` has been developed which is capable of nondestructive evaluation of architectural structures. By using microwaves in the 8 to 12 GHz range this probing instrument can detect subsurface characteristics through concrete, brick, wood or other building materials to depths in excess of 12 inches. The instrument interrogates a structure from a single side by transmitting a microwave signal into the surface at some angle of incidence and receiving the reflected signal some distance away on the same side of the structure. The transmitted signal is partially reflected at each internal boundary of different dielectric constant, giving a composite reflection which contains information from each internal layer. The reflected composite signal is compared in phase and amplitude to the transmitted signal and that reading is considered the ``signature`` of the structure under test. Computer algorithms analyze the signature for recognizable features and nonstandard construction.

  12. Ambient Sound-Based Collaborative Localization of Indeterministic Devices

    PubMed Central

    Kamminga, Jacob; Le, Duc; Havinga, Paul

    2016-01-01

    Localization is essential in wireless sensor networks. To our knowledge, no prior work has utilized low-cost devices for collaborative localization based on only ambient sound, without the support of local infrastructure. The reason may be the fact that most low-cost devices are indeterministic and suffer from uncertain input latencies. This uncertainty makes accurate localization challenging. Therefore, we present a collaborative localization algorithm (Cooperative Localization on Android with ambient Sound Sources (CLASS)) that simultaneously localizes the position of indeterministic devices and ambient sound sources without local infrastructure. The CLASS algorithm deals with the uncertainty by splitting the devices into subsets so that outliers can be removed from the time difference of arrival values and localization results. Since Android is indeterministic, we select Android devices to evaluate our approach. The algorithm is evaluated with an outdoor experiment and achieves a mean Root Mean Square Error (RMSE) of 2.18 m with a standard deviation of 0.22 m. Estimated directions towards the sound sources have a mean RMSE of 17.5° and a standard deviation of 2.3°. These results show that it is feasible to simultaneously achieve a relative positioning of both devices and sound sources with sufficient accuracy, even when using non-deterministic devices and platforms, such as Android. PMID:27649176

  13. MOF-based electronic and opto-electronic devices.

    PubMed

    Stavila, V; Talin, A A; Allendorf, M D

    2014-08-21

    Metal-organic frameworks (MOFs) are a class of hybrid materials with unique optical and electronic properties arising from rational self-assembly of the organic linkers and metal ions/clusters, yielding myriads of possible structural motifs. The combination of order and chemical tunability, coupled with good environmental stability of MOFs, are prompting many research groups to explore the possibility of incorporating these materials as active components in devices such as solar cells, photodetectors, radiation detectors, and chemical sensors. Although this field is only in its incipiency, many new fundamental insights relevant to integrating MOFs with such devices have already been gained. In this review, we focus our attention on the basic requirements and structural elements needed to fabricate MOF-based devices and summarize the current state of MOF research in the area of electronic, opto-electronic and sensor devices. We summarize various approaches to designing active MOFs, creation of hybrid material systems combining MOFs with other materials, and assembly and integration of MOFs with device hardware. Critical directions of future research are identified, with emphasis on achieving the desired MOF functionality in a device and establishing the structure-property relationships to identify and rationalize the factors that impact device performance.

  14. Terahertz biochip based on optoelectronic devices

    NASA Astrophysics Data System (ADS)

    Lu, Ja-Yu; Chen, Li-Jin; Kao, Tzeng-Fu; Chang, Hsu-Hao; Liu, An-Shyi; Yu, Yi-Chun; Wu, Ruey-Beei; Liu, Wei-Sheng; Chyi, Jen-Inn; Pan, Ci-Ling; Tsai, Ming-Cheng; Sun, Chi-Kuang

    2005-10-01

    The accurate detection of minute amounts of chemical and biological substances has been a major goal in bioanalytical technology throughout the twentieth century. Fluorescence dye labeling detection remains the effective analysis method, but it modifies the surroundings of molecules and lowering the precision of detection. An alternative label free detecting tool with little disturbance of target molecules is highly desired. Theoretical calculations and experiments have demonstrated that many biomolecules have intrinsic resonance due to vibration or rotation level transitions, allowing terahertz (THz)-probing technique as a potential tool for the label-free and noninvasive detection of biomolecules. In this paper, we first ever combined the THz optoelectronic technique with biochip technology to realize THz biosensing. By transferring the edge-coupled photonic transmitter into a thin glass substrate and by integrating with a polyethylene based biochip channel, near field THz detection of the biomolecules is demonstrated. By directly acquiring the absorption micro-spectrum in the THz range, different boiomecules can then be identified according to their THz fingerprints. For preliminary studies, the capability to identity different illicit drug powders is successfully demonstrated. This novel biochip sensing system has the advantages including label-free detection, high selectivity, high sensitivity, ease for sample preparation, and ease to parallel integrate with other biochip functionality modules. Our demonstrated detection capability allows specifying various illicit drug powders with weight of nano-gram, which also enables rapid identification with minute amounts of other important molecules including DNA, biochemical agents in terrorism warfare, explosives, viruses, and toxics.

  15. Fiber-based devices for DWDM optical communication systems

    NASA Astrophysics Data System (ADS)

    Gu, Claire; Xu, Yuan; Liu, Yisi; Pan, Jing-Jong; Zhou, Fengqing; Dong, Liang; He, Henry

    2005-01-01

    Photonic devices with low insertion loss are important in dense wavelength division multiplexing (DWDM) systems. Currently most of these devices, such as variable optical attenuators (VOA), switches, filters, and dispersion compensators, etc., involve bulk (or micro-optic) components that require conversions between fibers and free-space optical elements leading to high insertion loss. Recently, we have proposed, analyzed, and demonstrated several fiber based devices for DWDM optical communication systems. Here we present an in-line fiber VOA, a 2x2 switchable wavelength add/drop filter, and high performance dispersion compensators. The VOA is built with a side-polished fiber covered with a liquid crystal overlay. By varying the orientation of the liquid crystal molecules using an applied electric field, the loss of the device can be controlled. The 2x2 wavelength switch is designed by recording electrically switchable holographic gratings in a layer of holographic polymer dispersed liquid crystal (H-PDLC) sandwiched between two side-polished fibers. The dispersion compensators are based on high precision fiber Bragg gratings (FBG). A unique method for writing FBGs with arbitrary phase and amplitude distributions is demonstrated. All of these devices are analyzed theoretically and demonstrated experimentally. Both theoretical and experimental results will be presented and discussed. These devices are suitable for DWDM optical information transmission and network management.

  16. Noise and its reduction in graphene based nanopore devices.

    PubMed

    Kumar, Ashvani; Park, Kyeong-Beom; Kim, Hyun-Mi; Kim, Ki-Bum

    2013-12-13

    Ionic current fluctuations in graphene nanopore devices are a ubiquitous phenomenon and are responsible for degraded spatial and temporal resolution. Here, we descriptively investigate the impact of different substrate materials (Si and quartz) and membrane thicknesses on noise characteristics of graphene nanopore devices. To mitigate the membrane fluctuations and pin-hole defects, a SiNx membrane is transferred onto the substrate and a pore of approximately 70 nm in diameter is perforated prior to the graphene transfer. Comprehensive noise study reveals that the few layer graphene transferred onto the quartz substrate possesses low noise level and higher signal to noise ratio as compared to single layer graphene, without deteriorating the spatial resolution. The findings here point to improvement of graphene based nanopore devices for exciting opportunities in future single-molecule genomic screening devices.

  17. High Density Memory Based on Quantum Device Technology

    NASA Technical Reports Server (NTRS)

    vanderWagt, Paul; Frazier, Gary; Tang, Hao

    1995-01-01

    We explore the feasibility of ultra-high density memory based on quantum devices. Starting from overall constraints on chip area, power consumption, access speed, and noise margin, we deduce boundaries on single cell parameters such as required operating voltage and standby current. Next, the possible role of quantum devices is examined. Since the most mature quantum device, the resonant tunneling diode (RTD) can easily be integrated vertically, it naturally leads to the issue of 3D integrated memory. We propose a novel method of addressing vertically integrated bistable two-terminal devices, such as resonant tunneling diodes (RTD) and Esaki diodes, that avoids individual physical contacts. The new concept has been demonstrated experimentally in memory cells of field effect transistors (FET's) and stacked RTD's.

  18. Magnetophoretic-based microfluidic device for DNA Concentration.

    PubMed

    Shim, Sangjo; Shim, Jiwook; Taylor, William R; Kosari, Farhad; Vasmatzis, George; Ahlquist, David A; Bashir, Rashid

    2016-04-01

    Nucleic acids serve as biomarkers of disease and it is highly desirable to develop approaches to extract small number of such genomic extracts from human bodily fluids. Magnetic particles-based nucleic acid extraction is widely used for concentration of small amount of samples and is followed by DNA amplification in specific assays. However, approaches to integrate such magnetic particles based capture with micro and nanofluidic based assays are still lacking. In this report, we demonstrate a magnetophoretic-based approach for target-specific DNA extraction and concentration within a microfluidic device. This device features a large chamber for reducing flow velocity and an array of μ-magnets for enhancing magnetic flux density. With this strategy, the device is able to collect up to 95 % of the magnetic particles from the fluidic flow and to concentrate these magnetic particles in a collection region. Then an enzymatic reaction is used to detach the DNA from the magnetic particles within the microfluidic device, making the DNA available for subsequent analysis. Concentrations of over 1000-fold for 90 bp dsDNA molecules is demonstrated. This strategy can bridge the gap between detection of low concentration analytes from clinical samples and a range of micro and nanofluidic sensors and devices including nanopores, nano-cantilevers, and nanowires.

  19. Quantum-chemical investigation of the structure and electronic absorption spectra of electroluminescent zinc complexes

    NASA Astrophysics Data System (ADS)

    Minaev, B. F.; Baryshnikov, G. V.; Korop, A. A.; Minaeva, V. A.; Kaplunov, M. G.

    2013-01-01

    Using the quantum chemical methods of the density functional theory and of the electron density topological analysis, we have studied the structure of two recently synthesized electroluminescent zinc complexes, one with aminoquinoline ligands and the other with a Schiff base (N,O-donor). The energies and intensities of vertical excitations for the molecules under study have been calculated in terms of the PM3 semiempirical approximation taking into account the configurational interaction between singly excited singlet excited states. Good agreement between calculation results and experimental data on the electron density topological characteristics and on the visible and UV absorption spectra has been obtained.

  20. {100}<100> or 45.degree.-rotated {100}<100>, semiconductor-based, large-area, flexible, electronic devices

    SciTech Connect

    Goyal, Amit

    2012-05-15

    Novel articles and methods to fabricate the same resulting in flexible, {100}<100> or 45.degree.-rotated {100}<100> oriented, semiconductor-based, electronic devices are disclosed. Potential applications of resulting articles are in areas of photovoltaic devices, flat-panel displays, thermophotovoltaic devices, ferroelectric devices, light emitting diode devices, computer hard disc drive devices, magnetoresistance based devices, photoluminescence based devices, non-volatile memory devices, dielectric devices, thermoelectric devices and quantum dot laser devices.

  1. Flexible non-volatile memory devices based on organic semiconductors

    NASA Astrophysics Data System (ADS)

    Cosseddu, Piero; Casula, Giulia; Lai, Stefano; Bonfiglio, Annalisa

    2015-09-01

    The possibility of developing fully organic electronic circuits is critically dependent on the ability to realize a full set of electronic functionalities based on organic devices. In order to complete the scene, a fundamental element is still missing, i.e. reliable data storage. Over the past few years, a considerable effort has been spent on the development and optimization of organic polymer based memory elements. Among several possible solutions, transistor-based memories and resistive switching-based memories are attracting a great interest in the scientific community. In this paper, a route for the fabrication of organic semiconductor-based memory devices with performances beyond the state of the art is reported. Both the families of organic memories will be considered. A flexible resistive memory based on a novel combination of materials is presented. In particular, high retention time in ambient conditions are reported. Complementary, a low voltage transistor-based memory is presented. Low voltage operation is allowed by an hybrid, nano-sized dielectric, which is also responsible for the memory effect in the device. Thanks to the possibility of reproducibly fabricating such device on ultra-thin substrates, high mechanical stability is reported.

  2. Silicon Nanowire-Based Devices for Gas-Phase Sensing

    PubMed Central

    Cao, Anping; Sudhölter, Ernst J.R.; de Smet, Louis C.P.M.

    2014-01-01

    Since their introduction in 2001, SiNW-based sensor devices have attracted considerable interest as a general platform for ultra-sensitive, electrical detection of biological and chemical species. Most studies focus on detecting, sensing and monitoring analytes in aqueous solution, but the number of studies on sensing gases and vapors using SiNW-based devices is increasing. This review gives an overview of selected research papers related to the application of electrical SiNW-based devices in the gas phase that have been reported over the past 10 years. Special attention is given to surface modification strategies and the sensing principles involved. In addition, future steps and technological challenges in this field are addressed. PMID:24368699

  3. Encapsulation methods for organic electrical devices

    DOEpatents

    Blum, Yigal D.; Chu, William Siu-Keung; MacQueen, David Brent; Shi, Yijian

    2013-06-18

    The disclosure provides methods and materials suitable for use as encapsulation barriers in electronic devices. In one embodiment, for example, there is provided an electroluminescent device or other electronic device encapsulated by alternating layers of a silicon-containing bonding material and a ceramic material. The encapsulation methods provide, for example, electronic devices with increased stability and shelf-life. The invention is useful, for example, in the field of microelectronic devices.

  4. Acoustic wave based MEMS devices for biosensing applications.

    PubMed

    Voiculescu, Ioana; Nordin, Anis Nurashikin

    2012-03-15

    This paper presents a review of acoustic-wave based MEMS devices that offer a promising technology platform for the development of sensitive, portable, real-time biosensors. MEMS fabrication of acoustic wave based biosensors enables device miniaturization, power consumption reduction and integration with electronic circuits. For biological applications, the biosensors are integrated in a microfluidic system and the sensing area is coated with a biospecific layer. When a bioanalyte interacts with the sensing layer, mass and viscosity variations of the biospecific layer can be detected by monitoring changes in the acoustic wave properties such as velocity, attenuation, resonant frequency and delay time. Few types of acoustic wave devices could be integrated in microfluidic systems without significant degradation of the quality factor. The acoustic wave based MEMS devices reported in the literature as biosensors and presented in this review are film bulk acoustic wave resonators (FBAR), surface acoustic waves (SAW) resonators and SAW delay lines. Different approaches to the realization of FBARs, SAW resonators and SAW delay lines for various biochemical applications are presented. Methods of integration of the acoustic wave MEMS devices in the microfluidic systems and functionalization strategies will be also discussed.

  5. Improved electroluminescence with reversed bilayers of thiophene/phenylene co-oligomer derivatives

    NASA Astrophysics Data System (ADS)

    Dokiya, Shohei; Sasaki, Fumio; Hotta, Shu; Yanagi, Hisao

    2016-03-01

    Organic electroluminescence (EL) devices were fabricated with bilayered thiophene/phenylene co-oligomer (TPCO) derivatives: p-type 5,5‧-bis(4-biphenylyl)-2,2‧-bithiophene (BP2T) and n-type 5,5‧-bis(4‧-cyanobiphenyl-4-yl)-2,2‧-bithiophene (BP2T-CN). Two types of EL device, Al:Li/BP2T-CN/BP2T/ITO (device A) and Au/BP2T/BP2T-CN/ITO (device B), were investigated using vapor-deposited films of BP2T and BP2T-CN by changing the order of deposition onto the indium-tin-oxide (ITO)/glass substrate. The EL performance was significantly improved for device B in which the two molecules had a lying orientation suitable for efficient carrier injection and transport as well as surface emission. In device A, on the other hand, the standing BP2T orientation resulted in much lower current density and EL intensity.

  6. A point acoustic device based on aluminum nanowires

    NASA Astrophysics Data System (ADS)

    Xie, Qian-Yi; Ju, Zhen-Yi; Tian, He; Xue, Qing-Tang; Chen, Yuan-Quan; Tao, Lu-Qi; Mohammad, Mohammad Ali; Zhang, Xue-Yue; Yang, Yi; Ren, Tian-Ling

    2016-03-01

    A point Electrical Thermal Acoustic (ETA) device based on aluminum nanowire contacts is designed and fabricated. Interdigitated structural aluminum nanowires are released from the substrate by Inductively Coupled Plasma Reactive Ion Etching (ICP-RIE). By releasing the interdigitated structure, the nanowires contact each other at approximately 1 mm above the wafer, forming a Point Contact Structure (PCS). It is found that the PCS acoustic device realizes high efficiency when a biased AC signal is applied. The PCS acoustic device reaches a sound pressure level as high as 67 dB at a distance of 1 cm with 74 mW AC input. The power spectrum is flat, ranging from 2 kHz to 20 kHz with a less than +/-3 dB fluctuation. The highest normalized Sound Pressure Level (SPL) of the point contact structure acoustic device is 18 dB higher than the suspended aluminum wire acoustic device. Comparisons between the PCS acoustic device and the Suspended Aluminum Nanowire (SAN) acoustic device illustrate that the PCS acoustic device has a flatter power spectrum within the 20 kHz range, and enhances the SPL at a lower frequency. Enhancing the response at lower frequencies is extremely useful, which may enable earphone and loudspeaker applications within the frequency range of the human ear with the help of pulse density modulation.A point Electrical Thermal Acoustic (ETA) device based on aluminum nanowire contacts is designed and fabricated. Interdigitated structural aluminum nanowires are released from the substrate by Inductively Coupled Plasma Reactive Ion Etching (ICP-RIE). By releasing the interdigitated structure, the nanowires contact each other at approximately 1 mm above the wafer, forming a Point Contact Structure (PCS). It is found that the PCS acoustic device realizes high efficiency when a biased AC signal is applied. The PCS acoustic device reaches a sound pressure level as high as 67 dB at a distance of 1 cm with 74 mW AC input. The power spectrum is flat, ranging from 2 k

  7. Fixed Junction Photovoltaic Devices Based On Polymerizable Ionic Liquids

    NASA Astrophysics Data System (ADS)

    Limanek, Austin; Leger, Janelle, , Dr.

    Recently, polymer-based photovoltaic devices (PPVs) have received significant attention as a possible affordable, large area and flexible solar energy technology. In particular, research on chemically fixed p-i-n junctions in polymer photovoltaic devices has shown promising results. These devices are composed of ionic monomers in a polymer matrix sandwiched between two electrodes. When a potential is applied, the ionic monomers migrate towards their corresponding electrodes, enabling electrochemical doping of the polymer. This leads to the formation of bonds between the polymer and ionic monomers, resulting in the formation of a chemically fixed p-i-n junction. However, early devices suffered from long charging times and low overall response. This has been attributed to the low phase compatibility between the ionic monomers and the polymer. It has been shown for light-emitting electrochemical cells, replacing the ionic monomers with polymerizable ionic liquids (PILs) mitigates these challenges. We will present the use of PILs as the dopant in fixed junction PPV devices. Preliminary devices demonstrate significantly improved performance, decreased charging times, and high open circuit voltages. This research supported by the National Science Foundation DMR-1057209.

  8. Switchable Solar Window Devices Based on Polymer Dispersed Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Murray, Joseph; Ma, Dakang; Munday, Jeremy

    Windows are an interesting target for photovoltaics due to the potential for large area of deployment and because glass is already a ubiquitous component of solar cell devices. Many demonstrations of solar windows in recent years have used photovoltaic devices which are semitransparent in the visible region. Much research has focused on enhancing device absorption in the UV and IR ranges as a means to circumvent the basic tradeoff between efficiency and transparency to visible light. Use of switchable solar window is a less investigated alternative approach; these windows utilize the visible spectrum but can toggle between high transparency and high efficiency as needed. We present a novel switchable solar window device based on Polymer Dispersed Liquid Crystals (PDLC). By applying an electric field to the PDLC layer, the device can be switched from an opaque, light diffusing, efficient photovoltaic cell to a clear, transparent window. In the off state (i.e. scattering state), these devices have the added benefits of increased reflectivity for reduced lighting and cooling costs and haze for privacy. Further, we demonstrate that these windows have the potential for self-powering due to the very low power required to maintain the on, or high transparency, state. Support From: University of Maryland and Maryland Nano-center and its Fablab.

  9. Game theory-based mode cooperative selection mechanism for device-to-device visible light communication

    NASA Astrophysics Data System (ADS)

    Liu, Yuxin; Huang, Zhitong; Li, Wei; Ji, Yuefeng

    2016-03-01

    Various patterns of device-to-device (D2D) communication, from Bluetooth to Wi-Fi Direct, are emerging due to the increasing requirements of information sharing between mobile terminals. This paper presents an innovative pattern named device-to-device visible light communication (D2D-VLC) to alleviate the growing traffic problem. However, the occlusion problem is a difficulty in D2D-VLC. This paper proposes a game theory-based solution in which the best-response dynamics and best-response strategies are used to realize a mode-cooperative selection mechanism. This mechanism uses system capacity as the utility function to optimize system performance and selects the optimal communication mode for each active user from three candidate modes. Moreover, the simulation and experimental results show that the mechanism can attain a significant improvement in terms of effectiveness and energy saving compared with the cases where the users communicate via only the fixed transceivers (light-emitting diode and photo diode) or via only D2D.

  10. Micro Electromechanical Systems (MEMS) Based Microfluidic Devices for Biomedical Applications.

    PubMed

    Ashraf, Muhammad Waseem; Tayyaba, Shahzadi; Afzulpurkar, Nitin

    2011-01-01

    Micro Electromechanical Systems (MEMS) based microfluidic devices have gained popularity in biomedicine field over the last few years. In this paper, a comprehensive overview of microfluidic devices such as micropumps and microneedles has been presented for biomedical applications. The aim of this paper is to present the major features and issues related to micropumps and microneedles, e.g., working principles, actuation methods, fabrication techniques, construction, performance parameters, failure analysis, testing, safety issues, applications, commercialization issues and future prospects. Based on the actuation mechanisms, the micropumps are classified into two main types, i.e., mechanical and non-mechanical micropumps. Microneedles can be categorized according to their structure, fabrication process, material, overall shape, tip shape, size, array density and application. The presented literature review on micropumps and microneedles will provide comprehensive information for researchers working on design and development of microfluidic devices for biomedical applications.

  11. Micro Electromechanical Systems (MEMS) Based Microfluidic Devices for Biomedical Applications

    PubMed Central

    Ashraf, Muhammad Waseem; Tayyaba, Shahzadi; Afzulpurkar, Nitin

    2011-01-01

    Micro Electromechanical Systems (MEMS) based microfluidic devices have gained popularity in biomedicine field over the last few years. In this paper, a comprehensive overview of microfluidic devices such as micropumps and microneedles has been presented for biomedical applications. The aim of this paper is to present the major features and issues related to micropumps and microneedles, e.g., working principles, actuation methods, fabrication techniques, construction, performance parameters, failure analysis, testing, safety issues, applications, commercialization issues and future prospects. Based on the actuation mechanisms, the micropumps are classified into two main types, i.e., mechanical and non-mechanical micropumps. Microneedles can be categorized according to their structure, fabrication process, material, overall shape, tip shape, size, array density and application. The presented literature review on micropumps and microneedles will provide comprehensive information for researchers working on design and development of microfluidic devices for biomedical applications. PMID:21747700

  12. Mini array of quantum Hall devices based on epitaxial graphene

    NASA Astrophysics Data System (ADS)

    Novikov, S.; Lebedeva, N.; Hämäläinen, J.; Iisakka, I.; Immonen, P.; Manninen, A. J.; Satrapinski, A.

    2016-05-01

    Series connection of four quantum Hall effect (QHE) devices based on epitaxial graphene films was studied for realization of a quantum resistance standard with an up-scaled value. The tested devices showed quantum Hall plateaux RH,2 at a filling factor v = 2 starting from a relatively low magnetic field (between 4 T and 5 T) when the temperature was 1.5 K. The precision measurements of quantized Hall resistance of four QHE devices connected by triple series connections and external bonding wires were done at B = 7 T and T = 1.5 K using a commercial precision resistance bridge with 50 μA current through the QHE device. The results showed that the deviation of the quantized Hall resistance of the series connection of four graphene-based QHE devices from the expected value of 4×RH,2 = 2 h/e2 was smaller than the relative standard uncertainty of the measurement (<1 × 10-7) limited by the used resistance bridge.

  13. Nano-Bio Electronic Devices Based on DNA Bases and Proteins

    NASA Astrophysics Data System (ADS)

    Rinaldi, R.; Maruccio, G.; Bramanti, A.; Visconti, P.; Biasco, A.; Arima, V.; D'Amico, S.; Cingolani, R.

    A key challenge of the current research in nanoelectronics is the realization of biomolecular devices. The biomolecules have specific functionalies that can be exploited for the implementation of electronic and optoelectronic devices. Different nanotechnological strategies have been pursued to implement the biomolecular devices, following a bottom-up or a topdown approach depending on the used biomolecule and on its functionality. In this paper we present our results on the implementation of nano-biomolecular devices based on modified DNA nucleosides and metalloproteins.

  14. Field-Based Experiential Learning Using Mobile Devices

    NASA Astrophysics Data System (ADS)

    Hilley, G. E.

    2015-12-01

    Technologies such as GPS and cellular triangulation allow location-specific content to be delivered by mobile devices, but no mechanism currently exists to associate content shared between locations in a way that guarantees the delivery of coherent and non-redundant information at every location. Thus, experiential learning via mobile devices must currently take place along a predefined path, as in the case of a self-guided tour. I developed a mobile-device-based system that allows a person to move through a space along a path of their choosing, while receiving information in a way that guarantees delivery of appropriate background and location-specific information without producing redundancy of content between locations. This is accomplished by coupling content to knowledge-concept tags that are noted as fulfilled when users take prescribed actions. Similarly, the presentation of the content is related to the fulfillment of these knowledge-concept tags through logic statements that control the presentation. Content delivery is triggered by mobile-device geolocation including GPS/cellular navigation, and sensing of low-power Bluetooth proximity beacons. Together, these features implement a process that guarantees a coherent, non-redundant educational experience throughout a space, regardless of a learner's chosen path. The app that runs on the mobile device works in tandem with a server-side database and file-serving system that can be configured through a web-based GUI, and so content creators can easily populate and configure content with the system. Once the database has been updated, the new content is immediately available to the mobile devices when they arrive at the location at which content is required. Such a system serves as a platform for the development of field-based geoscience educational experiences, in which students can organically learn about core concepts at particular locations while individually exploring a space.

  15. Electron mobility of rare earth complexes measured by transient electroluminescence method

    NASA Astrophysics Data System (ADS)

    Zang, F. X.; Lengyel, O.; Li, Wenlian; Hong, Z. R.; Liu, Ze; Lee, C. S.; Lee, S. T.

    2006-09-01

    Electron mobility of gadolinium/europium (dibenzoylmethanato) 3(bathophenanthroline) (Gd/Eu(DBM) 3 bath) was measured by transient electroluminescence (EL) method. Although electron mobility of the two complexes were expected to be same, the value of mobility (1.2 × 10 -4 cm 2/Vs at electric field of 1 MV/cm) of Eu(DBM) 3 bath complex was bigger than that (8 × 10 -5 cm 2/Vs at electric field of 1 MV/cm) of Gd(DBM) 3 bath complex. It was found to be related to the different luminescent mechanisms of active materials and recombination zones in the devices. According to this, penetration length of hole injected into electron transport layer of Eu(DBM) 3 bath was estimated.

  16. Electroluminescence from individual air-suspended carbon nanotubes within split-gate structures

    NASA Astrophysics Data System (ADS)

    Higashide, N.; Uda, T.; Yoshida, M.; Ishii, A.; Kato, Y. K.

    Electrically induced light emission from chirality-identified single-walled carbon nanotubes are investigated by utilizing split-gate field-effect devices fabricated on silicon-on-insulator substrates. We begin by etching trenches through the top silicon layer into the buried oxide, and the silicon layer is thermally oxidized for use as local gates. We partially remove the oxide and form gate electrodes, then contacts for nanotubes are deposited on both sides of the trench. Catalyst particles are placed on the contacts, and nanotubes are grown over the trench by chemical vapor deposition. We use photoluminescence microscopy to locate the nanotubes and perform excitation spectroscopy to identify their chirality. Gate-induced photoluminescence quenching is used to confirm carrier doping, and electroluminescence intensity is investigated as a function of the split-gate and bias voltages. Work supported by JSPS (KAKENHI 24340066, 26610080), MEXT (Photon Frontier Network Program, Nanotechnology Platform), Canon Foundation, and Asahi Glass Foundation.

  17. Experimental and theoretical study of photo- and electroluminescence of divinyldiphenyl and divinylphenanthrene derivatives

    NASA Astrophysics Data System (ADS)

    Samsonova, L. G.; Valiev, R. R.; Degtyarenko, K. M.; Sunchugashev, D. A.; Kukhta, I. N.; Kukhta, A. V.; Kopylova, T. N.

    2017-02-01

    Electronic absorption and luminescence spectra of four new compounds of divinyldiphenyl and divinylphenanthrene derivatives are investigated experimentally in tetrahydrofuran solutions and thin films obtained by thermal vacuum deposition and by spin coating of these substances embedded into polyvinylcarbazole matrix. Molecular geometry optimizations and electronic spectra have been calculated in the framework of XMC-QDPT2/6-31G (d, p) and TDDFT/B3LYP/6-31G (d, p) levels of theory. We have fabricated and studied OLED devices with the structure ITO/PEDOT:PSS/NPD/L/Ca/Al and ITO/PEDOT:PSS/PVK + L/Ca, where L is the luminophore. It is demonstrated that the photo-and electroluminescence spectra of divinyldiphenyl are not identical and undergo strong changes depending on the method of sample preparation.

  18. Si-photonics based passive device packaging and module performance.

    PubMed

    Song, Jeong Hwan; Zhang, Jing; Zhang, Huijuan; Li, Chao; Lo, Guo Qiang

    2011-09-12

    We report a fully packaged silicon passive waveguide device designed for a tunable filter based on a ring-resonator. Polarization diversity circuits prevent polarization dependant issues in the silicon ring-resonator. For the device packaging, the YAG laser welding technique has been used for pigtailing both of the input and output fibers. Post welding misalignment was compensated by mechanical fine tuning using the seesaw effect via power monitoring. Packaging loss less than 1.5 dB with respect to chip measurement has been achieved using 10 µm-curvature radius lensed fibers. In addition, the packaging process and the module performance are presented.

  19. Electrocaloric devices based on thini-film heat switches

    SciTech Connect

    Epstein, Richard I; Malloy, Kevin J

    2009-01-01

    We describe a new approach to refrigeration and electrical generation that exploits the attractive properties of thin films of electrocaloric materials. Layers of electrocaloric material coupled with thin-film heat switches can work as either refrigerators or electrical generators, depending on the phasing of the applied voltages and heat switching. With heat switches based on thin layers of liquid crystals, the efficiency of these thin-film heat engines can be at least as high as that of current thermoelectric devices. Advanced heat switches would enable thin-film heat engines to outperform conventional vaporcompression devices.

  20. Safety of energy based devices for hemostasis in thyroid surgery.

    PubMed

    Dionigi, Gianlorenzo; Wu, Che-Wei; Kim, Hoon-Yub; Liu, Xiaoli; Liu, Renbin; Randolph, Gregory W; Anuwong, Angkoon

    2016-10-01

    Energy based devices (EBD) have been developed, implemented and increasingly applied in thyroid surgery because they can provide a combined dissection and haemostatic effect. In particular, advantages of EBD have been described in terms of efficacious haemostasis, reduction of procedure-associated time, reduced incision length, less operative blood loss and transfusion need, decreased postoperative drain, pain and hospital stay. In addition, EBD are essential for endoscopic procedures. On the contrary, a potential drawback is the increased health care costs. This paper reviews relevant medical literature published on the safety of new devices for achieving hemostasis and dissection around the recurrent laryngeal nerve (RLN).

  1. Sub-bandgap Voltage Electroluminescence and Magneto-oscillations in a WSe2 Light-Emitting van der Waals Heterostructure.

    PubMed

    Binder, Johannes; Withers, Freddie; Molas, Maciej R; Faugeras, Clement; Nogajewski, Karol; Watanabe, Kenji; Taniguchi, Takashi; Kozikov, Aleksey; Geim, Andre K; Novoselov, Kostya S; Potemski, Marek

    2017-03-08

    We report on experimental investigations of an electrically driven WSe2 based light-emitting van der Waals heterostructure. We observe a threshold voltage for electroluminescence significantly lower than the corresponding single particle band gap of monolayer WSe2. This observation can be interpreted by considering the Coulomb interaction and a tunneling process involving excitons, well beyond the picture of independent charge carriers. An applied magnetic field reveals pronounced magneto-oscillations in the electroluminescence of the free exciton emission intensity with a 1/B periodicity. This effect is ascribed to a modulation of the tunneling probability resulting from the Landau quantization in the graphene electrodes. A sharp feature in the differential conductance indicates that the Fermi level is pinned and allows for an estimation of the acceptor binding energy.

  2. Antimonide-Based Compound Semiconductors for Electronic Devices: A Review

    DTIC Science & Technology

    2005-04-01

    currents, apparently due to exten- sive interface recombination [137]. Dodd et al. fabricated npn InAs bipolar transistors on InP in an attempt to achieve...Demonstration of npn InAs bipolar transistors with inverted base doping. IEEE Electron Dev Lett 1996;17(4):166–8. [139] Moran PD, Chow D, Hunter A, Kuech TF...based electronic devices: high electron mobility transistors (HEMTs), resonant tunneling diodes (RTDs), and heterojunction bipolar transistors (HBTs

  3. Cell-Based Biosensors: Electrical Sensing in Microfluidic Devices

    PubMed Central

    Kiilerich-Pedersen, Katrine; Rozlosnik, Noemi

    2012-01-01

    Cell-based biosensors provide new horizons for medical diagnostics by adopting complex recognition elements such as mammalian cells in microfluidic devices that are simple, cost efficient and disposable. This combination renders possible a new range of applications in the fields of diagnostics and personalized medicine. The review looks at the most recent developments in cell-based biosensing microfluidic systems with electrical and electrochemical transduction, and relevance to medical diagnostics. PMID:26859401

  4. A cloud-based multimodality case file for mobile devices.

    PubMed

    Balkman, Jason D; Loehfelm, Thomas W

    2014-01-01

    Recent improvements in Web and mobile technology, along with the widespread use of handheld devices in radiology education, provide unique opportunities for creating scalable, universally accessible, portable image-rich radiology case files. A cloud database and a Web-based application for radiologic images were developed to create a mobile case file with reasonable usability, download performance, and image quality for teaching purposes. A total of 75 radiology cases related to breast, thoracic, gastrointestinal, musculoskeletal, and neuroimaging subspecialties were included in the database. Breast imaging cases are the focus of this article, as they best demonstrate handheld display capabilities across a wide variety of modalities. This case subset also illustrates methods for adapting radiologic content to cloud platforms and mobile devices. Readers will gain practical knowledge about storage and retrieval of cloud-based imaging data, an awareness of techniques used to adapt scrollable and high-resolution imaging content for the Web, and an appreciation for optimizing images for handheld devices. The evaluation of this software demonstrates the feasibility of adapting images from most imaging modalities to mobile devices, even in cases of full-field digital mammograms, where high resolution is required to represent subtle pathologic features. The cloud platform allows cases to be added and modified in real time by using only a standard Web browser with no application-specific software. Challenges remain in developing efficient ways to generate, modify, and upload radiologic and supplementary teaching content to this cloud-based platform. Online supplemental material is available for this article.

  5. Dual pitch plasmonic devices for polarization enhanced colour based sensing

    NASA Astrophysics Data System (ADS)

    Langley, D.; Balaur, E.; Sadatnajafi, C.; Abbey, B.

    2016-12-01

    Plasmonic devices provide a unique sensitivity to changes in the permittivity of the immediate, near-surface environment. In this work we explore the use of dual pitch plasmonic devices combined with microfluidics for polarization enhanced colour sensing of a chemicals' refractive index. We demonstrate that the use of cross-shaped apertures can produce polarization tunable color based sensing in the optical regime and show that the spectral variations as a function of the incident polarization can be decomposed into contributions from the two orthogonal modes that characterize the dual pitch plasmonic device. Finally we demonstrate that the use of the full colour spectrum in the visible range in combination with polarization control enables sensing `by-eye' of refractive index changes below 1 × 10-3 RIU.

  6. A triple quantum dot based nano-electromechanical memory device

    SciTech Connect

    Pozner, R.; Lifshitz, E.; Peskin, U.

    2015-09-14

    Colloidal quantum dots (CQDs) are free-standing nano-structures with chemically tunable electronic properties. This tunability offers intriguing possibilities for nano-electromechanical devices. In this work, we consider a nano-electromechanical nonvolatile memory (NVM) device incorporating a triple quantum dot (TQD) cluster. The device operation is based on a bias induced motion of a floating quantum dot (FQD) located between two bound quantum dots (BQDs). The mechanical motion is used for switching between two stable states, “ON” and “OFF” states, where ligand-mediated effective interdot forces between the BQDs and the FQD serve to hold the FQD in each stable position under zero bias. Considering realistic microscopic parameters, our quantum-classical theoretical treatment of the TQD reveals the characteristics of the NVM.

  7. Quantum key distribution based on quantum dimension and independent devices

    NASA Astrophysics Data System (ADS)

    Li, Hong-Wei; Yin, Zhen-Qiang; Chen, Wei; Wang, Shuang; Guo, Guang-Can; Han, Zheng-Fu

    2014-03-01

    In this paper, we propose a quantum key distribution (QKD) protocol based on only a two-dimensional Hilbert space encoding a quantum system and independent devices between the equipment for state preparation and measurement. Our protocol is inspired by the fully device-independent quantum key distribution (FDI-QKD) protocol and the measurement-device-independent quantum key distribution (MDI-QKD) protocol. Our protocol only requires the state to be prepared in the two-dimensional Hilbert space, which weakens the state preparation assumption in the original MDI-QKD protocol. More interestingly, our protocol can overcome the detection loophole problem in the FDI-QKD protocol, which greatly limits the application of FDI-QKD. Hence our protocol can be implemented with practical optical components.

  8. Measurement-device-independent entanglement-based quantum key distribution

    NASA Astrophysics Data System (ADS)

    Yang, Xiuqing; Wei, Kejin; Ma, Haiqiang; Sun, Shihai; Liu, Hongwei; Yin, Zhenqiang; Li, Zuohan; Lian, Shibin; Du, Yungang; Wu, Lingan

    2016-05-01

    We present a quantum key distribution protocol in a model in which the legitimate users gather statistics as in the measurement-device-independent entanglement witness to certify the sources and the measurement devices. We show that the task of measurement-device-independent quantum communication can be accomplished based on monogamy of entanglement, and it is fairly loss tolerate including source and detector flaws. We derive a tight bound for collective attacks on the Holevo information between the authorized parties and the eavesdropper. Then with this bound, the final secret key rate with the source flaws can be obtained. The results show that long-distance quantum cryptography over 144 km can be made secure using only standard threshold detectors.

  9. Performance Estimation of Silicon-Based Self-Cooling Device

    NASA Astrophysics Data System (ADS)

    Fukuda, Shinji; Sabi, Yuichi; Kawahara, Toshio; Yamaguchi, Satarou

    2013-05-01

    Since self-cooling devices were first proposed, several materials have been tested for their suitability to be used in them. A self-cooling device requires a high Seebeck coefficient, a low electrical resistivity, and a high thermal conductivity. Here, we report experimental results for single-crystal silicon doped with boron. Samples were fabricated with carrier densities in the range of 2.0×1015 to 1.6×1019 cm-3, and their Seebeck coefficient and electrical resistivity were measured. Silicon with a carrier density of 1.6×1019 cm-3 has a power factor of 4.8×10-3 W/(K2.m) at room temperature. The cooling capability of a self-cooling device was estimated using a one-dimensional model. The results suggest that a self-cooling device based on silicon with a high carrier density can have a higher heat removal performance than a conventional silicon power device of the same size.

  10. Small Dosimeter based on Timepix device for International Space Station

    NASA Astrophysics Data System (ADS)

    Turecek, D.; Pinsky, L.; Jakubek, J.; Vykydal, Z.; Stoffle, N.; Pospisil, S.

    2011-12-01

    The radiation environment in space is different, more complex and more intense than on Earth. Conventional devices and detection methods used nowadays do not allow to discriminate single particle types and the energy of the single particles. The Timepix detector is a position sensitive pixelated detector developed at CERN in a frame of the Medipix collaboration that provides capability to visualize tracks and measure energy of single particles. This information can be used for sorting the particles into different categories. It is possible to distinguish light charged particles such as electrons or heavy charged particles such as ions. Moreover, the Linear Energy Transfer (LET) for charged particles can be determined. Each category is assigned a quality factor corresponding to the energy a particle would deposit in the human tissue. By summing the dose of all particles an estimate of the dose rate can be calculated. For space dosimetry purposes a miniature device with the Timepix detector and a custom made integrated USB based readout interface has been constructed. The entire device has dimensions of a USB flash memory stick. The whole compact device is connected to a control PC and is operated continuously. The PC runs a software that controls data acquisition, adjusts the acquisition time adaptively according to the particle rate, analyzes the particle tracks, evaluates the deposited energy and the LET and visualizes in a simple display the estimated dose rate. The performance of the device will be tested during a mission on International Space Station planned towards the beginning of year 2012.

  11. Optical system designs based on bi-directional sensor devices

    NASA Astrophysics Data System (ADS)

    Grossmann, Constanze; Gawronski, Ute; Perske, Franziska; Notni, Gunther; Tünnermann, Andreas

    2012-10-01

    Small and compact optical system designs are needed in nearly all application scenarios of optical projection and imaging systems, e.g. automotive, metrology, medical or multimedia. Most active optical systems are based on separated imaging (e.g. camera unit) and image generating units (e.g. projection unit). This fact limits the geometrical miniaturization of the system. We present compact optical system designs using the new technology of bi-directional sensor devices. These devices combine light emitting and light detecting elements on one single chip. The application of such innovative opto-electronic devices - so-called bi-directional OLED microdisplays (BiMiDs) - offer a huge potential for miniaturization with a simultaneous increase of performance due to a new integration step. For these new bi-directional sensor devices new optical design concepts for simultaneous and sequential emission and detection are necessary. Because the simultaneous emission and detection can disturb the functionality of the optical system. New concepts has to be applied. A first concept is an exemplary 3-D metrology system applying fringe projection. A second concept is a pico-projection system with an integrated camera function. For both concepts the system configurations and the optical design are discussed. Due to the application of the bi-directional sensor device ultra-compact systems are presented.

  12. An implantable thermoresponsive drug delivery system based on Peltier device.

    PubMed

    Yang, Rongbing; Gorelov, Alexander V; Aldabbagh, Fawaz; Carroll, William M; Rochev, Yury

    2013-04-15

    Locally dropping the temperature in vivo is the main obstacle to the clinical use of a thermoresponsive drug delivery system. In this paper, a Peltier electronic element is incorporated with a thermoresponsive thin film based drug delivery system to form a new drug delivery device which can regulate the release of rhodamine B in a water environment at 37 °C. Various current signals are used to control the temperature of the cold side of the Peltier device and the volume of water on top of the Peltier device affects the change in temperature. The pulsatile on-demand release profile of the model drug is obtained by turning the current signal on and off. The work has shown that the 2600 mAh power source is enough to power this device for 1.3 h. Furthermore, the excessive heat will not cause thermal damage in the body as it will be dissipated by the thermoregulation of the human body. Therefore, this simple novel device can be implanted and should work well in vivo.

  13. Empirically based device modeling of bulk heterojunction organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Pierre, Adrien; Lu, Shaofeng; Howard, Ian A.; Facchetti, Antonio; Arias, Ana Claudia

    2013-04-01

    We develop an empirically based optoelectronic model to accurately simulate the photocurrent in organic photovoltaic (OPV) devices with novel materials including bulk heterojunction OPV devices based on a new low band gap dithienothiophene-DPP donor polymer, P(TBT-DPP), blended with PC70BM at various donor-acceptor weight ratios and solvent compositions. Our devices exhibit power conversion efficiencies ranging from 1.8% to 4.7% at AM 1.5G. Electron and hole mobilities are determined using space-charge limited current measurements. Bimolecular recombination coefficients are both analytically calculated using slowest-carrier limited Langevin recombination and measured using an electro-optical pump-probe technique. Exciton quenching efficiencies in the donor and acceptor domains are determined from photoluminescence spectroscopy. In addition, dielectric and optical constants are experimentally determined. The photocurrent and its bias-dependence that we simulate using the optoelectronic model we develop, which takes into account these physically measured parameters, shows less than 7% error with respect to the experimental photocurrent (when both experimentally and semi-analytically determined recombination coefficient is used). Free carrier generation and recombination rates of the photocurrent are modeled as a function of the position in the active layer at various applied biases. These results show that while free carrier generation is maximized in the center of the device, free carrier recombination is most dominant near the electrodes even in high performance devices. Such knowledge of carrier activity is essential for the optimization of the active layer by enhancing light trapping and minimizing recombination. Our simulation program is intended to be freely distributed for use in laboratories fabricating OPV devices.

  14. Optical sensor array platform based on polymer electronic devices

    NASA Astrophysics Data System (ADS)

    Koetse, Marc M.; Rensing, Peter A.; Sharpe, Ruben B. A.; van Heck, Gert T.; Allard, Bart A. M.; Meulendijks, Nicole N. M. M.; Kruijt, Peter G. M.; Tijdink, Marcel W. W. J.; De Zwart, René M.; Houben, René J.; Enting, Erik; van Veen, Sjaak J. J. F.; Schoo, Herman F. M.

    2007-10-01

    Monitoring of personal wellbeing and optimizing human performance are areas where sensors have only begun to be used. One of the reasons for this is the specific demands that these application areas put on the underlying technology and system properties. In many cases these sensors will be integrated in clothing, be worn on the skin, or may even be placed inside the body. This implies that flexibility and wearability of the systems is essential for their success. Devices based on polymer semiconductors allow for these demands since they can be fabricated with thin film technology. The use of thin film device technology allows for the fabrication of very thin sensors (e.g. integrated in food product packaging), flexible or bendable sensors in wearables, large area/distributed sensors, and intrinsically low-cost applications in disposable products. With thin film device technology a high level of integration can be achieved with parts that analyze signals, process and store data, and interact over a network. Integration of all these functions will inherently lead to better cost/performance ratios, especially if printing and other standard polymer technology such as high precision moulding is applied for the fabrication. In this paper we present an optical transmission sensor array based on polymer semiconductor devices made by thin film technology. The organic devices, light emitting diodes, photodiodes and selective medium chip, are integrated with classic electronic components. Together they form a versatile sensor platform that allows for the quantitative measurement of 100 channels and communicates wireless with a computer. The emphasis is given to the sensor principle, the design, fabrication technology and integration of the thin film devices.

  15. Carbazole-based polymers for organic photovoltaic devices.

    PubMed

    Li, Jiaoli; Grimsdale, Andrew C

    2010-07-01

    Polymers based upon 2,7-disubstituted carbazole have recently become of great interest as electron-donating materials in organic photovoltaic devices. In this tutorial review the synthesis of such polymers and their relative performances in such devices are surveyed. In particular structure-property relationships are investigated and the potential for the rational design of materials for high efficiency solar cells is discussed. In the case of the 2,7-carbazole homopolymer it has been found that electron acceptors other than fullerenes produce higher energy conversion efficiencies. To get around possible problems with the build-up of charge density at the 3- and 6-positions and to improve the solar light harvesting ability of the polymers by reducing the bandgap, ladder- and step-ladder type 2,7-carbazole polymers have been synthesised. The fully ladderised polymers gave very poor results in devices, but efficiencies of over 1% have been obtained from a step-ladder polymer with a diindenocarbazole monomer unit. Donor-acceptor copolymers containing 2,7-carbazole donors and various electron-accepting comonomer units have been prepared. An efficiency of 6% has been reported from a device using such a copolymer and by suitable choice of the acceptor comonomer, polymers can be designed with potential theoretical power conversion efficiencies of 10%. While such efficiencies remain to be obtained, the results to date certainly suggest that carbazole-based polymers and copolymers are among the most promising materials yet proposed for obtaining high efficiency organic solar cells.

  16. In plane optical sensor based on organic electronic devices

    NASA Astrophysics Data System (ADS)

    Koetse, Marc; Rensing, Peter; van Heck, Gert; Sharpe, Ruben; Allard, Bart; Wieringa, Fokko; Kruijt, Peter; Meulendijks, Nicole; Jansen, Henk; Schoo, Herman

    2008-08-01

    Sensors based on organic electronic devices are emerging in a wide range of application areas. Here we present a sensor platform using organic light emitting diodes (OLED) and organic photodiodes (OPD) as active components. By means of lamination and interconnection technology the functional foils with OLED and OPD arrays form an in-plane optical sensor platform (IPOS). This platform can be extended with a wireless data and signal processing unit yielding a sensor node. The focus of our research is to engage the node in a healthcare application, in which a bandage is able to monitor the vital signs of a person, a so-called Smart Bandage. One of the principles that is described here is based on measuring the absorption modulation of blood volume induced by the pulse (photoplethysmography). The information from such a bandage could be used to monitor wound healing by measuring the perfusion in the skin. The OLED and OPD devices are manufactured on separate foils and glass substrates by means of printing and coating technologies. Furthermore, the modular approach allows for the application of the optical sensing unit in a variety of other fields including chemical sensing. This, ultimately enables the measurement of a large variety of physiological parameters using the same bandage and the same basic sensor architecture. Here we discuss the build-up of our device in general terms. Specific characteristics of the used OLEDs and OPDs are shown and finally we demonstrate the functionality by simultaneously recorded photoplethysmograms of our device and a clinical pulseoximeter.

  17. Efficient Blue Electroluminescence Using Quantum-Confined Two-Dimensional Perovskites.

    PubMed

    Kumar, Sudhir; Jagielski, Jakub; Yakunin, Sergii; Rice, Peter; Chiu, Yu-Cheng; Wang, Mingchao; Nedelcu, Georgian; Kim, Yeongin; Lin, Shangchao; Santos, Elton J G; Kovalenko, Maksym V; Shih, Chih-Jen

    2016-10-03

    Solution-processed hybrid organic-inorganic lead halide perovskites are emerging as one of the most promising candidates for low-cost light-emitting diodes (LEDs). However, due to a small exciton binding energy, it is not yet possible to achieve an efficient electroluminescence within the blue wavelength region at room temperature, as is necessary for full-spectrum light sources. Here, we demonstrate efficient blue LEDs based on the colloidal, quantum-confined 2D perovskites, with precisely controlled stacking down to one-unit-cell thickness (n = 1). A variety of low-k organic host compounds are used to disperse the 2D perovskites, effectively creating a matrix of the dielectric quantum wells, which significantly boosts the exciton binding energy by the dielectric confinement effect. Through the Förster resonance energy transfer, the excitons down-convert and recombine radiatively in the 2D perovskites. We report room-temperature pure green (n = 7-10), sky blue (n = 5), pure blue (n = 3), and deep blue (n = 1) electroluminescence, with record-high external quantum efficiencies in the green-to-blue wavelength region.

  18. Novel device-based interventional strategies for advanced heart failure

    PubMed Central

    Vanderheyden, Marc; Bartunek, Jozef

    2016-01-01

    While heart failure is one of the leading causes of mortality and morbidity, our tools to provide ultimate treatment solutions are still limited. Recent developments in new devices are designed to fill this therapeutic gap. The scope of this review is to focus on two particular targets, namely (1) left ventricular geometric restoration and (2) atrial depressurization. (1) Reduction of the wall stress by shrinking the ventricular cavity has been traditionally attempted surgically. Recently, the Parachute device (CardioKinetix Inc., Menlo Park, CA, USA) has been introduced to restore ventricular geometry and cardiac mechanics. The intervention aims to partition distal dysfunctional segments that are non-contributory to the ventricular mechanics and forward cardiac output. (2) Diastolic heart failure is characterized by abnormal relaxation and chamber stiffness. The main therapeutic goal achieved should be the reduction of afterload and diastolic pressure load. Recently, new catheter-based approaches were proposed to reduce left atrial pressure and ventricular decompression: the InterAtrial Shunt Device (IASD™) (Corvia Medical Inc., Tewksbury, MA, USA) and the V-Wave Shunt (V-Wave Ltd, Or Akiva, Israel). Both are designed to create a controlled atrial septal defect in symptomatic patients with heart failure. While the assist devices are aimed at end-stage heart failure, emerging device-based percutaneous or minimal invasive techniques comprise a wide spectrum of innovative concepts that target ventricular remodeling, cardiac contractility or neuro-humoral modulation. The clinical adoption is in the early stages of the initial feasibility and safety studies, and clinical evidence needs to be gathered in appropriately designed clinical trials. PMID:26966444

  19. Chemically modified graphene based supercapacitors for flexible and miniature devices

    NASA Astrophysics Data System (ADS)

    Ghosh, Debasis; Kim, Sang Ouk

    2015-09-01

    Rapid progress in the portable and flexible electronic devises has stimulated supercapacitor research towards the design and fabrication of high performance flexible devices. Recent research efforts for flexible supercapacitor electrode materials are highly focusing on graphene and chemically modified graphene owing to the unique properties, including large surface area, high electrical and thermal conductivity, excellent mechanical flexibility, and outstanding chemical stability. This invited review article highlights current status of the flexible electrode material research based on chemically modified graphene for supercapacitor application. A variety of electrode architectures prepared from chemically modified graphene are summarized in terms of their structural dimensions. Novel prototypes for the supercapacitor aiming at flexible miniature devices, i.e. microsupercapacitor with high energy and power density are highlighted. Future challenges relevant to graphene-based flexible supercapacitors are also suggested. [Figure not available: see fulltext.

  20. The use of silk-based devices for fracture fixation

    NASA Astrophysics Data System (ADS)

    Perrone, Gabriel S.; Leisk, Gary G.; Lo, Tim J.; Moreau, Jodie E.; Haas, Dylan S.; Papenburg, Bernke J.; Golden, Ethan B.; Partlow, Benjamin P.; Fox, Sharon E.; Ibrahim, Ahmed M. S.; Lin, Samuel J.; Kaplan, David L.

    2014-03-01

    Metallic fixation systems are currently the gold standard for fracture fixation but have problems including stress shielding, palpability and temperature sensitivity. Recently, resorbable systems have gained interest because they avoid removal and may improve bone remodelling due to the lack of stress shielding. However, their use is limited to paediatric craniofacial procedures mainly due to the laborious implantation requirements. Here we prepare and characterize a new family of resorbable screws prepared from silk fibroin for craniofacial fracture repair. In vivo assessment in rat femurs shows the screws to be self-tapping, remain fixed in the bone for 4 and 8 weeks, exhibit biocompatibility and promote bone remodelling. The silk-based devices compare favourably with current poly-lactic-co-glycolic acid fixation systems, however, silk-based devices offer numerous advantages including ease of implantation, conformal fit to the repair site, sterilization by autoclaving and minimal inflammatory response.

  1. Passivation of III-V Compound Semiconductor Based Devices

    DTIC Science & Technology

    1993-11-29

    approximately 60 A/s. The AES, Rutherford Backscattering, FIIR and stress measurements were also carried out. This work was done in collaboration with Dr ...begun to collaborate with us on the project. A brief description of these projects are listed below: 8 a) HP Research Laboratory ( Drs . S. Camnitz, K. L...DC characterization of devices. b) University of California. Santa Barbara ( Drs . B. Young, L. A. Coldren and V. Malhotra): Passivation of GaAs-based

  2. Electrochemiluminescence detection in microfluidic cloth-based analytical devices.

    PubMed

    Guan, Wenrong; Liu, Min; Zhang, Chunsun

    2016-01-15

    This work describes the first approach at combining microfluidic cloth-based analytical devices (μCADs) with electrochemiluminescence (ECL) detection. Wax screen-printing is employed to make cloth-based microfluidic chambers which are patterned with carbon screen-printed electrodes (SPEs) to create truly disposable, simple, inexpensive sensors which can be read with a low-cost, portable charge coupled device (CCD) imaging sensing system. And, the two most commonly used ECL systems of tris(2,2'-bipyridyl)ruthenium(II)/tri-n-propylamine (Ru(bpy)3(2+)/TPA) and 3-aminophthalhydrazide/hydrogen peroxide (luminol/H2O2) are applied to demonstrate the quantitative ability of the ECL μCADs. In this study, the proposed devices have successfully fulfilled the determination of TPA with a linear range from 2.5 to 2500μM with a detection limit of 1.265μM. In addition, the detection of H2O2 can be performed in the linear range of 0.05-2.0mM, with a detection limit of 0.027mM. It has been shown that the ECL emission on the wax-patterned cloth device has an acceptable sensitivity, stability and reproducibility. Finally, the applicability of cloth-based ECL is demonstrated for determination of glucose in phosphate buffer solution (PBS) and artificial urine (AU) samples, with the detection limits of 0.032mM and 0.038mM, respectively. It can be foreseen, therefore, that μCADs with ECL detection could provide a new sensing platform for point-of-care testing, public health, food safety detection and environmental monitoring in remote regions, developing or developed countries.

  3. Blood separation on microfluidic paper-based analytical devices.

    PubMed

    Songjaroen, Temsiri; Dungchai, Wijitar; Chailapakul, Orawon; Henry, Charles S; Laiwattanapaisal, Wanida

    2012-09-21

    A microfluidic paper-based analytical device (μPAD) for the separation of blood plasma from whole blood is described. The device can separate plasma from whole blood and quantify plasma proteins in a single step. The μPAD was fabricated using the wax dipping method, and the final device was composed of a blood separation membrane combined with patterned Whatman No.1 paper. Blood separation membranes, LF1, MF1, VF1 and VF2 were tested for blood separation on the μPAD. The LF1 membrane was found to be the most suitable for blood separations when fabricating the μPAD by wax dipping. For blood separation, the blood cells (both red and white) were trapped on blood separation membrane allowing pure plasma to flow to the detection zone by capillary force. The LF1-μPAD was shown to be functional with human whole blood of 24-55% hematocrit without dilution, and effectively separated blood cells from plasma within 2 min when blood volumes of between 15-22 μL were added to the device. Microscopy was used to confirm that the device isolated plasma with high purity with no blood cells or cell hemolysis in the detection zone. The efficiency of blood separation on the μPAD was studied by plasma protein detection using the bromocresol green (BCG) colorimetric assay. The results revealed that protein detection on the μPAD was not significantly different from the conventional method (p > 0.05, pair t-test). The colorimetric measurement reproducibility on the μPAD was 2.62% (n = 10) and 5.84% (n = 30) for within-day and between day precision, respectively. Our proposed blood separation on μPAD has the potential for reducing turnaround time, sample volume, sample preparation and detection processes for clinical diagnosis and point-of care testing.

  4. Silicon based materials for drug delivery devices and implants.

    PubMed

    Bernik, Delia L

    2007-01-01

    This patent review focuses on silicon based materials for drug delivery systems and implant devices devoted to medical applications. The article describes some representative examples of the most depictive silicon based compounds associated with drug release formulations and tissue engineering biomaterials. Ranging from inorganic to organic and hybrid inorganic-organic silicon compounds, the paper referrers to patents describing inventions which make use of the best properties of silicon dioxide, silica aerogel and xerogel, silicon bioactive materials, silicones and ormosils, pointing out the usefulness of each kind of compound within the invention embodiment.

  5. Paper-based analytical devices for environmental analysis.

    PubMed

    Meredith, Nathan A; Quinn, Casey; Cate, David M; Reilly, Thomas H; Volckens, John; Henry, Charles S

    2016-03-21

    The field of paper-based microfluidics has experienced rapid growth over the past decade. Microfluidic paper-based analytical devices (μPADs), originally developed for point-of-care medical diagnostics in resource-limited settings, are now being applied in new areas, such as environmental analyses. Low-cost paper sensors show great promise for on-site environmental analysis; the theme of ongoing research complements existing instrumental techniques by providing high spatial and temporal resolution for environmental monitoring. This review highlights recent applications of μPADs for environmental analysis along with technical advances that may enable μPADs to be more widely implemented in field testing.

  6. Photonic devices based on black phosphorus and related hybrid materials

    NASA Astrophysics Data System (ADS)

    Vitiello, M. S.; Viti, L.

    2016-08-01

    Artificial semiconductor heterostructures played a pivotal role in modern electronic and photonic technologies, providing a highly effective means for the manipulation and control of carriers, from the visible to the far-infrared, leading to the development of highly efficient devices like sources, detectors and modulators. The discovery of graphene and the related fascinating capabilities have triggered an unprecedented interest in devices based on inorganic two-dimensional (2D) materials. Amongst them, black phosphorus (BP) recently showed an extraordinary potential in a variety of applications across micro-electronics and photonics. With an energy gap between the gapless graphene and the larger gap transition metal dichalcogenides, BP can form the basis for a new generation of high-performance photonic devices that could be specifically engineered to comply with different applications, like transparent saturable absorbers, fast photocounductive switches and low noise photodetectors, exploiting its peculiar electrical, thermal and optical anisotropy. This paper will review the latest achievements in black-phosphorus-based THz photonics and discuss future perspectives of this rapidly developing research field.

  7. Analysis of Android Device-Based Solutions for Fall Detection.

    PubMed

    Casilari, Eduardo; Luque, Rafael; Morón, María-José

    2015-07-23

    Falls are a major cause of health and psychological problems as well as hospitalization costs among older adults. Thus, the investigation on automatic Fall Detection Systems (FDSs) has received special attention from the research community during the last decade. In this area, the widespread popularity, decreasing price, computing capabilities, built-in sensors and multiplicity of wireless interfaces of Android-based devices (especially smartphones) have fostered the adoption of this technology to deploy wearable and inexpensive architectures for fall detection. This paper presents a critical and thorough analysis of those existing fall detection systems that are based on Android devices. The review systematically classifies and compares the proposals of the literature taking into account different criteria such as the system architecture, the employed sensors, the detection algorithm or the response in case of a fall alarms. The study emphasizes the analysis of the evaluation methods that are employed to assess the effectiveness of the detection process. The review reveals the complete lack of a reference framework to validate and compare the proposals. In addition, the study also shows that most research works do not evaluate the actual applicability of the Android devices (with limited battery and computing resources) to fall detection solutions.

  8. Analysis of Android Device-Based Solutions for Fall Detection

    PubMed Central

    Casilari, Eduardo; Luque, Rafael; Morón, María-José

    2015-01-01

    Falls are a major cause of health and psychological problems as well as hospitalization costs among older adults. Thus, the investigation on automatic Fall Detection Systems (FDSs) has received special attention from the research community during the last decade. In this area, the widespread popularity, decreasing price, computing capabilities, built-in sensors and multiplicity of wireless interfaces of Android-based devices (especially smartphones) have fostered the adoption of this technology to deploy wearable and inexpensive architectures for fall detection. This paper presents a critical and thorough analysis of those existing fall detection systems that are based on Android devices. The review systematically classifies and compares the proposals of the literature taking into account different criteria such as the system architecture, the employed sensors, the detection algorithm or the response in case of a fall alarms. The study emphasizes the analysis of the evaluation methods that are employed to assess the effectiveness of the detection process. The review reveals the complete lack of a reference framework to validate and compare the proposals. In addition, the study also shows that most research works do not evaluate the actual applicability of the Android devices (with limited battery and computing resources) to fall detection solutions. PMID:26213928

  9. Stress-sensor device based on flexoelectric liquid crystalline membranes.

    PubMed

    Rey, Alejandro D; Servio, Phillip; Herrera Valencia, Edtson Emilio

    2014-05-19

    Membrane flexoelectricity is an electromechanical coupling process that describes membrane bending and membrane electrical polarization caused by bending under electric fields. In this paper we propose, formulate, and characterize a stress-sensor device for mechanically loaded solids, consisting of a soft flexoelectric thin membrane attached to the loaded deformed solid. Because the curvature of the deformed solid is transferred to the attached flexoelectric membrane, the electromechanical transduction of the latter produces a charge that is proportional to the stress of the solid. The model of the stress-sensor device is based on the integration of the thermodynamics of polarizable membranes with isotropic solid elasticity, leading to a transfer function that identifies the elastic, electromechanical, and geometrical parameters involved in electrical-signal generation. The model is applied to representative normal bending and then to more complex off-axis bending of elastic bars. In all cases, a common transfer function shows the generic material and its geometric contributions. The sensor sensitivity increases linearly with flexoelectricity and the membrane-solid interface, and the sensitivity decreases with increasing membrane thickness and Young's modulus of the solid. The theoretical results contribute to ongoing experimental efforts towards the development of anisotropic soft-matter-based stress-sensor devices through solid-membrane interactions and electromechanical transduction.

  10. Analytical Devices Based on Direct Synthesis of DNA on Paper.

    PubMed

    Glavan, Ana C; Niu, Jia; Chen, Zhen; Güder, Firat; Cheng, Chao-Min; Liu, David; Whitesides, George M

    2016-01-05

    This paper addresses a growing need in clinical diagnostics for parallel, multiplex analysis of biomarkers from small biological samples. It describes a new procedure for assembling arrays of ssDNA and proteins on paper. This method starts with the synthesis of DNA oligonucleotides covalently linked to paper and proceeds to assemble microzones of DNA-conjugated paper into arrays capable of simultaneously capturing DNA, DNA-conjugated protein antigens, and DNA-conjugated antibodies. The synthesis of ssDNA oligonucleotides on paper is convenient and effective with 32% of the oligonucleotides cleaved and eluted from the paper substrate being full-length by HPLC for a 32-mer. These ssDNA arrays can be used to detect fluorophore-linked DNA oligonucleotides in solution, and as the basis for DNA-directed assembly of arrays of DNA-conjugated capture antibodies on paper, detect protein antigens by sandwich ELISAs. Paper-anchored ssDNA arrays with different sequences can be used to assemble paper-based devices capable of detecting DNA and antibodies in the same device and enable simple microfluidic paper-based devices.

  11. Enhanced photocoagulation with catheter-based diffusing optical device

    NASA Astrophysics Data System (ADS)

    Kang, Hyun Wook; Kim, Jeehyun; Oh, Jungwhan

    2012-11-01

    A novel balloon catheter-based diffusing optical device was designed and evaluated to assist in treating excessive menstrual bleeding. A synthetic fused-silica fiber was micro-machined precisely to create scattering segments on a 25 mm long fiber tip for uniform light distribution. A visible wavelength (λ=532 nm) was used to specifically target the endometrium due to the high vascularity of the uterine wall. Optical simulation presented 30% wider distribution of photons along with approximately 40% higher irradiance induced by addition of a glass cap to the diffuser tip. Incorporation of the optical diffuser with a polyurethane balloon catheter considerably enhanced coagulation depth and area (i.e., 3.5 mm and 18.9 cm2 at 1 min irradiation) in tissue in vitro. The prototype device demonstrated the coagulation necrosis of 2.8±1.2 mm (n=18) and no thermal damage to myometrium in in vivo caprine models. A prototype 5 cm long balloon catheter-assisted optical diffuser was also evaluated with a cadaveric human uterus to confirm the coagulative response of the uterine tissue as well as to identify the further design improvement and clinical applicability. The proposed catheter-based diffusing optical device can be a feasible therapeutic tool to photocoagulate endometrial cell layers in an efficient and safe manner.

  12. Opto-electronic transport properties of graphene oxide based devices

    SciTech Connect

    Das, Poulomi; Ibrahim, Sk; Pal, Tanusri; Chakraborty, Koushik; Ghosh, Surajit

    2015-06-24

    Large area, solution-processed, graphene oxide (GO)nanocomposite based photo FET has been successfully fabricated. The device exhibits p-type charge transport characteristics in dark condition. Our measurements indicate that the transport characteristics are gate dependent and extremely sensitive to solar light. Photo current decay mechanism of GO is well explained and is associated with two phenomena: a) fast response process and b) slow response process. Slow response photo decay can be considered as the intrinsic phenomena which are present for both GO and reduced GO (r-GO), whereas the first response photo decay is controlled by the surface defect states. Demonstration of photo FET performance of GO thin film is a significant step forward in integrating these devices in various optoelectronic circuits.

  13. Tunable photonic devices and modules based on micro-optomechatronics

    NASA Astrophysics Data System (ADS)

    Katagiri, Yoshitada

    2001-10-01

    Photonic devices with ultra-wide and precise controllability for lightwaves are essential for constructing flexible optical networks to serve versatile multimedia applications. However, conventional monolithically fabricated photonic devices suffer from their controllability being limited by the physical characteristics. Micro-optomechatronics based on precise positional control of optical elements is a promising method of meeting the above requirements. This paper presents typical examples, which include repetition- rate tunable optical pulse sources with a micro mechanically controllable cavity length and synchro-scanned tunable disk- shaped optical fiber modules. The operations of these modules were demonstrated to confirm the validity of micro- optomechatronics as the ultimate lightwave control scheme, which will be useful for future optical telecommunications systems.

  14. Gold-based electrical interconnections for microelectronic devices

    DOEpatents

    Peterson, Kenneth A.; Garrett, Stephen E.; Reber, Cathleen A.; Watson, Robert D.

    2002-01-01

    A method of making an electrical interconnection from a microelectronic device to a package, comprising ball or wedge compression bonding a gold-based conductor directly to a silicon surface, such as a polysilicon bonding pad in a MEMS or IMEMS device, without using layers of aluminum or titanium disposed in-between the conductor and the silicon surface. After compression bonding, optional heating of the bond above 363 C. allows formation of a liquid gold-silicon eutectic phase containing approximately 3% (by weight) silicon, which significantly improves the bond strength by reforming and enhancing the initial compression bond. The same process can be used for improving the bond strength of Au--Ge bonds by forming a liquid Au-12Ge eutectic phase.

  15. An electromagnetic inerter-based vibration suppression device

    NASA Astrophysics Data System (ADS)

    Gonzalez-Buelga, A.; Clare, L. R.; Neild, S. A.; Jiang, J. Z.; Inman, D. J.

    2015-05-01

    This paper describes how an inerter-based device for structural vibration suppression can be realized using an electromagnetic transducer such as a linear motor. When the motor shaft moves, a difference of voltage is generated across the transducer coil. The voltage difference is proportional to the relative velocity between its two terminals. The electromagnetic transducer will exert a force proportional to current following the Lorentz principle if the circuit is closed around the transducer coil. If an electronic circuit consisting of a capacitor, an inductance and a resistance with the appropriate configuration is connected, the resulting force reflected back into the mechanical domain is equivalent to that achieved by a mechanical inerter-based device. The proposed configuration is easy to implement and very versatile, provided a high quality conversion system with negligible losses. With the use of electromagnetic devices, a new generation of vibration absorbers can be realized, for example in the electrical domain it would be relatively uncomplicated to synthesize multi-frequency or real time tunable vibration absorbers by adding electrical components in parallel. In addition by using resistance emulators in the electrical circuits, part of the absorbed vibration energy can be converted into usable power. Here an electromagnetic tuned inerter damper (E-TID) is tested experimentally using real time dynamic substructuring. A voltage compensation unit was developed in order to compensate for coil losses. This voltage compensation unit requires power, which is acquired through harvesting from the vibration energy using a resistance emulator. A power balance analysis was developed in order to ensure the device can be self sufficient. Promising experimental results, using this approach, have been obtained and are presented in this paper. The ultimate goal of this research is the development of autonomous electromagnetic vibration absorbers, able to harvest energy

  16. TOPICAL REVIEW: Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers

    NASA Astrophysics Data System (ADS)

    Willander, M.; Nur, O.; Zhao, Q. X.; Yang, L. L.; Lorenz, M.; Cao, B. Q.; Zúñiga Pérez, J.; Czekalla, C.; Zimmermann, G.; Grundmann, M.; Bakin, A.; Behrends, A.; Al-Suleiman, M.; El-Shaer, A.; Che Mofor, A.; Postels, B.; Waag, A.; Boukos, N.; Travlos, A.; Kwack, H. S.; Guinard, J.; LeSi Dang, D.

    2009-08-01

    Zinc oxide (ZnO), with its excellent luminescent properties and the ease of growth of its nanostructures, holds promise for the development of photonic devices. The recent advances in growth of ZnO nanorods are discussed. Results from both low temperature and high temperature growth approaches are presented. The techniques which are presented include metal-organic chemical vapour deposition (MOCVD), vapour phase epitaxy (VPE), pulse laser deposition (PLD), vapour-liquid-solid (VLS), aqueous chemical growth (ACG) and finally the electrodeposition technique as an example of a selective growth approach. Results from structural as well as optical properties of a variety of ZnO nanorods are shown and analysed using different techniques, including high resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), photoluminescence (PL) and cathodoluminescence (CL), for both room temperature and for low temperature performance. These results indicate that the grown ZnO nanorods possess reproducible and interesting optical properties. Results on obtaining p-type doping in ZnO micro- and nanorods are also demonstrated using PLD. Three independent indications were found for p-type conducting, phosphorus-doped ZnO nanorods: first, acceptor-related CL peaks, second, opposite transfer characteristics of back-gate field effect transistors using undoped and phosphorus doped wire channels, and finally, rectifying I-V characteristics of ZnO:P nanowire/ZnO:Ga p-n junctions. Then light emitting diodes (LEDs) based on n-ZnO nanorods combined with different technologies (hybrid technologies) are suggested and the recent electrical, as well as electro-optical, characteristics of these LEDs are shown and discussed. The hybrid LEDs reviewed and discussed here are mainly presented for two groups: those based on n-ZnO nanorods and p-type crystalline substrates, and those based on n-ZnO nanorods and p-type amorphous substrates. Promising electroluminescence

  17. Influence of the molecular weight and size dispersion of the electroluminescent polymer on the performance of air-stable hybrid light-emitting diodes.

    PubMed

    Martinez-Ferrero, Eugenia; Grigorian, Souren; Ryan, James W; Cambarau, Werther; Palomares, Emilio

    2015-01-21

    The influence of the chain length and the molecular weight distribution of the electroluminescent polymer on the carrier transport properties and morphology of air stable hybrid light-emitting diodes is reported. It is found that variations between diverse as-received commercial batches play a major role in the performance of the devices, whose maximum luminance can differ up to 2 orders of magnitude. Through complementary optoelectronic, structural, and morphological characterization techniques, we provide insights into the relationship between charge dynamics and the structure of polymeric electroluminescent materials. The carrier dynamics are found to be dominated by both the polymeric chain length and the hole transport, which in turn is dependent on the concentration of trap states. Furthermore, the chain length is seen to affect the morphology of the active layer.

  18. Medical Devices; Immunology and Microbiology Devices; Classification of Gastrointestinal Microorganism Multiplex Nucleic Acid-Based Assay. Final order.

    PubMed

    2015-11-02

    The Food and Drug Administration (FDA) is classifying a gastrointestinal microorganism multiplex nucleic acid-based assay into class II (special controls). The Agency is classifying the device into class II (special controls) in order to provide a reasonable assurance of safety and effectiveness of the device.

  19. Near-infrared electroluminescence at room temperature from neodymium-doped gallium nitride thin films

    SciTech Connect

    Kim, Joo Han; Holloway, Paul H.

    2004-09-06

    Strong near-infrared (NIR) electroluminescence (EL) at room temperature from neodymium (Nd)-doped gallium nitride (GaN) thin films is reported. The Nd-doped GaN films were grown by radio-frequency planar magnetron cosputtering of separate GaN and metallic Nd targets in a pure nitrogen ambient. X-ray diffraction data did not identify the presence of any secondary phases and revealed that the Nd-doped GaN films had a highly textured wurtzite crystal structure with the c-axis normal to the surface of the film. The EL devices were fabricated with a thin-film multilayered structure of Al/Nd-doped GaN/Al{sub 2}O{sub 3}-TiO{sub 2}/indium-tin oxide and tested at room temperate. Three distinct NIR EL emission peaks were observed from the devices at 905, 1082, and 1364 nm, arising from the radiative relaxation of the {sup 4}F{sub 3sol2} excited-state energy level to the {sup 4}I{sub 9sol2}, {sup 4}I{sub 11sol2}, and {sup 4}I{sub 13sol2} levels of the Nd{sup 3+} ion, respectively. The threshold voltage for all the three emission peaks was {approx}150 V. The external power efficiency of the fabricated EL devices was {approx}1x10{sup -5} measured at 40 V above the threshold voltage.

  20. 3D Printed Graphene Based Energy Storage Devices.

    PubMed

    Foster, Christopher W; Down, Michael P; Zhang, Yan; Ji, Xiaobo; Rowley-Neale, Samuel J; Smith, Graham C; Kelly, Peter J; Banks, Craig E

    2017-03-03

    3D printing technology provides a unique platform for rapid prototyping of numerous applications due to its ability to produce low cost 3D printed platforms. Herein, a graphene-based polylactic acid filament (graphene/PLA) has been 3D printed to fabricate a range of 3D disc electrode (3DE) configurations using a conventional RepRap fused deposition moulding (FDM) 3D printer, which requires no further modification/ex-situ curing step. To provide proof-of-concept, these 3D printed electrode architectures are characterised both electrochemically and physicochemically and are advantageously applied as freestanding anodes within Li-ion batteries and as solid-state supercapacitors. These freestanding anodes neglect the requirement for a current collector, thus offering a simplistic and cheaper alternative to traditional Li-ion based setups. Additionally, the ability of these devices' to electrochemically produce hydrogen via the hydrogen evolution reaction (HER) as an alternative to currently utilised platinum based electrodes (with in electrolysers) is also performed. The 3DE demonstrates an unexpectedly high catalytic activity towards the HER (-0.46 V vs. SCE) upon the 1000th cycle, such potential is the closest observed to the desired value of platinum at (-0.25 V vs. SCE). We subsequently suggest that 3D printing of graphene-based conductive filaments allows for the simple fabrication of energy storage devices with bespoke and conceptual designs to be realised.

  1. The electroluminescence mechanism of Er³⁺ in different silicon oxide and silicon nitride environments

    SciTech Connect

    Rebohle, L. Wutzler, R.; Braun, M.; Helm, M.; Skorupa, W.; Berencén, Y.; Ramírez, J. M.; Garrido, B.; Hiller, D.

    2014-09-28

    Rare earth doped metal-oxide-semiconductor (MOS) structures are of great interest for Si-based light emission. However, several physical limitations make it difficult to achieve the performance of light emitters based on compound semiconductors. To address this point, in this work the electroluminescence (EL) excitation and quenching mechanism of Er-implanted MOS structures with different designs of the dielectric stack are investigated. The devices usually consist of an injection layer made of SiO₂ and an Er-implanted layer made of SiO₂, Si-rich SiO₂, silicon nitride, or Si-rich silicon nitride. All structures implanted with Er show intense EL around 1540 nm with EL power efficiencies in the order of 2 × 10⁻³ (for SiO₂:Er) or 2 × 10⁻⁴(all other matrices) for lower current densities. The EL is excited by the impact of hot electrons with an excitation cross section in the range of 0.5–1.5 × 10⁻¹⁵cm⁻². Whereas the fraction of potentially excitable Er ions in SiO₂ can reach values up to 50%, five times lower values were observed for other matrices. The decrease of the EL decay time for devices with Si-rich SiO₂ or Si nitride compared to SiO₂ as host matrix implies an increase of the number of defects adding additional non-radiative de-excitation paths for Er³⁺. For all investigated devices, EL quenching cross sections in the 10⁻²⁰ cm² range and charge-to-breakdown values in the range of 1–10 C cm⁻² were measured. For the present design with a SiO₂ acceleration layer, thickness reduction and the use of different host matrices did not improve the EL power efficiency or the operation lifetime, but strongly lowered the operation voltage needed to achieve intense EL.

  2. Investigation of bacterial chemotaxis in flow-based microfluidic devices.

    PubMed

    Englert, Derek L; Manson, Michael D; Jayaraman, Arul

    2010-05-01

    The plug-in-pond and capillary assays are convenient methods for measuring attractant and repellent bacterial chemotaxis. However, these assays do not provide quantitative information on the extent of migration and are not well-suited for investigating repellent taxis. Here, we describe a protocol for a flow-based microfluidic system (microFlow) to quantitatively investigate chemotaxis in response to concentration gradients of attractants and repellents. The microFlow device uses diffusive mixing to generate concentration gradients that are stable throughout the chemotaxis chamber and for the duration of the experiment. The gradients may be of any desired absolute concentration and gradient strength. GFP-expressing bacteria immediately encounter a stable concentration gradient when they enter the chemotaxis chamber, and the migration in response to the gradient is monitored by microscopy. The effects of different parameters that influence the extent of migration in the microFlow device-preparation of the motile bacterial population preparation, strength of the concentration gradient and duration of exposure to the gradient-are discussed in the context of repellent taxis of chemotactically wild-type Escherichia coli cells in a gradient of NiSO(4). Fabrication of the microfluidic device takes 1 d while preparing motile cells and carrying out the chemotaxis experiment takes 4-6 h to complete.

  3. Neutron hardness of silicon-based semiconductor devices

    SciTech Connect

    Baratta, A.J.; Kenney, E.S.

    1988-01-01

    The effects of radiation on silicon-based semiconductor devices have been the subject of research for many years. In an effort to understand these effects, a series of experiments was conducted on gamma-hardened MOSFETs. Experiments concentrated on MOSFETs in rad-hard form and on off-the-shelf items. Because of the need to maintain bias voltages at set levels to enhance damage and because of concerns over possible rapid annealing, active testing during irradiation was performed. In general, MOSFETs are expected to perform well in fast neutron environments. With the advances in rad-hard technologies, exposures to several-megarad gamma rays can be tolerated. In nuclear systems, the normal concurrent neutron fluence can reach over 10{sup 16} n/cm{sup 2}. At these levels, current research indicates that the devices fail. Such failure is not altogether unexpected, although the degree of induced structural disorder in the semiconductor's crystalline makeup is still small. However, the damage done appears to carry the silicon back to a nearly intrinsic state. Knowing that each primary knock-on atom causes 10 to 6000 secondary atomic dislocations, the fluences of 10{sup 16}/cm{sup 2} are clearly at a level able to markedly change semiconductor dopant-induced behavior. Thus, one can conclude that for current devices, the gamma dose in a mixed neutron gamma field may no longer be limiting.

  4. A microfluidic paper-based device to assess acetylcholinesterase activity.

    PubMed

    Liu, Chunye; Gomez, Frank A

    2017-04-01

    Neurotransmitters play key roles in cell-to-cell communication. These chemical messengers are involved in many functional processes, including growth, reproduction, memory, and behavior. In this communication, we describe a novel microfluidic paper-based analytical device (μPAD) to detect acetylcholinesterase (AChE) activity and inhibitor screening through a colorimetric analysis. The μPAD is easily fabricated via a wax printing process whereby wax is deposited onto the surface of chromatographic paper, and heated to create a hydrophobic barrier. Separate solutions of 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) and samples containing AChE and acetylthiocholine iodide (ATC) (or cysteine, Cys), respectively, are directly spotted onto the μPAD. DTNB and AChE/ATC (or Cys) flow towards each other where a reaction occurs to form the yellow colored 2-nitro-5-thiobenzoic acid anion (TNB(2-) ). The device is dried, scanned, and analyzed yielding a linear range of average inverse yellow intensities versus substrate concentration. An IC50 value (0.045 nM) with a known inhibitor, neostigmine bromide (NB), is obtained on the device. μPADs are low cost and easy to fabricate and have great potential to quantify neurotransmitter activity.

  5. MEMS- and NEMS-based smart devices and systems

    NASA Astrophysics Data System (ADS)

    Varadan, Vijay K.

    2001-11-01

    structures and food and medical industries. This unique combination of technologies also results in novel conformal sensors that can be remotely sensed by an antenna system with the advantage of no power requirements at the sensor site. This paper provides a brief review of MEMS and NEMS based smart systems for various applications mentioned above. Carbon Nano Tubes (CNT) with their unique structure, have already proven to be valuable in their application as tips for scanning probe microscopy, field emission devices, nanoelectronics, H2-storage, electromagnetic absorbers, ESD, EMI films and coatings and structural composites. For many of these applications, highly purified and functionalized CNT which are compatible with many host polymers are needed. A novel microwave CVD processing technique to meet these requirements has been developed at Penn State Center for the engineering of Electronic and Acoustic Materials and Devices (CEEAMD). This method enables the production of highly purified carbon nano tubes with variable size (from 5-40 nm) at low cost (per gram) and high yield. Whereas, carbon nano tubes synthesized using the laser ablation or arc discharge evaporation method always include impurity due to catalyst or catalyst support. The Penn State research is based on the use of zeolites over other metal/metal oxides in the microwave field for a high production and uniformity of the product. An extended conventional purification method has been employed to purify our products in order to remove left over impurity. A novel composite structure can be tailored by functionalizing carbon nano tubes and chemically bonding them with the polymer matrix e.g. block or graft copolymer, or even cross- linked copolymer, to impart exceptional structural, electronic and surface properties. Bio- and Mechanical-MEMS devices derived from this hybrid composites will be presented.

  6. Luminescent Photoelectrochemical Cells. 6. Spatial Aspects of the Photoluminescence and Electroluminescence of Cadmium Selenide Electrodes.

    DTIC Science & Technology

    1981-10-06

    NO. 8 Luminescent Photoelectrochemical Cells. 6. Spatial Aspects of the Photoluminescence and Electroluminescence of Cadmium Selenide Electrodes by...Photoelectrochemistry; photoluminescence; electroluminescence; cadmium selenide electrodes 20. ABSTRACT (Continue. on reverse aide flnocosee7 and...REPORT A PERIOD COVERED Luminescent Photoelectrochemical Cells. 6.1 1 Spatial Aspects of the Photoluminescence and Elect roluminescence of Cadmium

  7. A microfluidic device based on an evaporation-driven micropump.

    PubMed

    Nie, Chuan; Frijns, Arjan J H; Mandamparambil, Rajesh; den Toonder, Jaap M J

    2015-04-01

    In this paper we introduce a microfluidic device ultimately to be applied as a wearable sweat sensor. We show proof-of-principle of the microfluidic functions of the device, namely fluid collection and continuous fluid flow pumping. A filter-paper based layer, that eventually will form the interface between the device and the skin, is used to collect the fluid (e.g., sweat) and enter this into the microfluidic device. A controllable evaporation driven pump is used to drive a continuous fluid flow through a microfluidic channel and over a sensing area. The key element of the pump is a micro-porous membrane mounted at the channel outlet, such that a pore array with a regular hexagonal arrangement is realized through which the fluid evaporates, which drives the flow within the channel. The system is completely fabricated on flexible polyethylene terephthalate (PET) foils, which can be the backbone material for flexible electronics applications, such that it is compatible with volume production approaches like Roll-to-Roll technology. The evaporation rate can be controlled by varying the outlet geometry and the temperature. The generated flows are analyzed experimentally using Particle Tracking Velocimetry (PTV). Typical results show that with 1 to 61 pores (diameter = 250 μm, pitch = 500 μm) flow rates of 7.3 × 10(-3) to 1.2 × 10(-1) μL/min are achieved. When the surface temperature is increased by 9.4°C, the flow rate is increased by 130 %. The results are theoretically analyzed using an evaporation model that includes an evaporation correction factor. The theoretical and experimental results are in good agreement.

  8. Three-Dimensional Printing Based Hybrid Manufacturing of Microfluidic Devices.

    PubMed

    Alapan, Yunus; Hasan, Muhammad Noman; Shen, Richang; Gurkan, Umut A

    2015-05-01

    Microfluidic platforms offer revolutionary and practical solutions to challenging problems in biology and medicine. Even though traditional micro/nanofabrication technologies expedited the emergence of the microfluidics field, recent advances in advanced additive manufacturing hold significant potential for single-step, stand-alone microfluidic device fabrication. One such technology, which holds a significant promise for next generation microsystem fabrication is three-dimensional (3D) printing. Presently, building 3D printed stand-alone microfluidic devices with fully embedded microchannels for applications in biology and medicine has the following challenges: (i) limitations in achievable design complexity, (ii) need for a wider variety of transparent materials, (iii) limited z-resolution, (iv) absence of extremely smooth surface finish, and (v) limitations in precision fabrication of hollow and void sections with extremely high surface area to volume ratio. We developed a new way to fabricate stand-alone microfluidic devices with integrated manifolds and embedded microchannels by utilizing a 3D printing and laser micromachined lamination based hybrid manufacturing approach. In this new fabrication method, we exploit the minimized fabrication steps enabled by 3D printing, and reduced assembly complexities facilitated by laser micromachined lamination method. The new hybrid fabrication method enables key features for advanced microfluidic system architecture: (i) increased design complexity in 3D, (ii) improved control over microflow behavior in all three directions and in multiple layers, (iii) transverse multilayer flow and precisely integrated flow distribution, and (iv) enhanced transparency for high resolution imaging and analysis. Hybrid manufacturing approaches hold great potential in advancing microfluidic device fabrication in terms of standardization, fast production, and user-independent manufacturing.

  9. Research progress of Si-based germanium materials and devices

    NASA Astrophysics Data System (ADS)

    Buwen, Cheng; Cheng, Li; Zhi, Liu; Chunlai, Xue

    2016-08-01

    Si-based germanium is considered to be a promising platform for the integration of electronic and photonic devices due to its high carrier mobility, good optical properties, and compatibility with Si CMOS technology. However, some great challenges have to be confronted, such as: (1) the nature of indirect band gap of Ge; (2) the epitaxy of dislocation-free Ge layers on Si substrate; and (3) the immature technology for Ge devices. The aim of this paper is to give a review of the recent progress made in the field of epitaxy and optical properties of Ge heterostructures on Si substrate, as well as some key technologies on Ge devices. High crystal quality Ge epilayers, as well as Ge/SiGe multiple quantum wells with high Ge content, were successfully grown on Si substrate with a low-temperature Ge buffer layer. A local Ge condensation technique was proposed to prepare germanium-on-insulator (GOI) materials with high tensile strain for enhanced Ge direct band photoluminescence. The advances in formation of Ge n+p shallow junctions and the modulation of Schottky barrier height of metal/Ge contacts were a significant progress in Ge technology. Finally, the progress of Si-based Ge light emitters, photodetectors, and MOSFETs was briefly introduced. These results show that Si-based Ge heterostructure materials are promising for use in the next-generation of integrated circuits and optoelectronic circuits. Project supported in part by the National Natural Science Foundation (Nos. 61036003, 61435013) and the Major State Basic Research Development Program of China (No. 2013CB632103).

  10. Memory devices based on self-assembled materials and processes (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Lee, Jang-Sik

    2016-09-01

    Device fabrication based on top-down approach will reach its limit due to difficulties in patterning and processes below 10 nm node. The bottom-up approach using self-assembled materials and processes can be a viable candidate for further device scaling, but the fabrication processes are mostly not compatible with current device fabrication. In this presentation, device fabrication strategy for next-generation data-storage devices will be discussed in detail based on self-assembled materials and processes. The emphasis is placed on compatibility with current device fabrication strategies. Ordered array of various materials and systems based on bottom-up nanotechnology can be utilized as the charge storage layer for memory devices and the templates for nanoscale device fabrication. Novel device applications, for example, printed/flexible/transparent electronic devices, will be explored based on the self-assembly processes.

  11. High-temperature superconducting thin-film-based electronic devices

    SciTech Connect

    Wu, X.D; Finokoglu, A.; Hawley, M.; Jia, Q.; Mitchell, T.; Mueller, F.; Reagor, D.; Tesmer, J.

    1996-09-01

    This the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The project involved optimization of processing of Y123 and Tl-2212 thin films deposited on novel substrates for advanced electronic devices. The Y123 films are the basis for development of Josephson Junctions to be utilized in magnetic sensors. Microwave cavities based on the Tl-2212 films are the basis for subsequent applications as communication antennas and transmitters in satellites.

  12. Interventional and device-based autonomic modulation in heart failure.

    PubMed

    Shen, Mark J; Zipes, Douglas P

    2015-04-01

    "Heart failure is an increasingly prevalent disease with high mortality and public health burden. It is associated with autonomic imbalance characterized by sympathetic hyperactivity and parasympathetic hypoactivity. Evolving novel interventional and device-based therapies have sought to restore autonomic balance by neuromodulation. Results of preclinical animal studies and early clinical trials have demonstrated the safety and efficacy of these therapies in heart failure. This article discusses specific neuromodulatory treatment modalities individually-spinal cord stimulation, vagus nerve stimulation, baroreceptor activation therapy, and renal sympathetic nerve denervation."

  13. Effect of annealing treatment on electroluminescence from GaN/Si nanoheterostructure array.

    PubMed

    Han, Chang Bao; He, Chuan; Meng, Xiao Bo; Wan, Ya Rui; Tian, Yong Tao; Zhang, Ying Jiu; Li, Xin Jian

    2012-02-27

    A GaN/Si nanoheterostructure array was prepared by growing GaN nanostructures on silicon nanoporous pillar array (Si-NPA). Based on as-grown and annealed GaN/Si-NPA, two light-emitting diodes (LEDs) were fabricated. It was found that after the annealing treatment, both the turn-on voltage and the leakage current density of the nanoheterostructure varied greatly, together with the electroluminescence (EL) changed from a yellow band to a near infrared band. The EL variation was attributed to the radiative transition being transformed from a defect-related recombination in GaN to an interfacial recombination of GaN/Si-NPA. Ours might have provided an effective approach for fabricating GaN/Si-based LEDs with different emission wavelengths.

  14. Electroluminescence and cathodoluminescence from polyethylene and polypropylene films: Spectra reconstruction from elementary components and underlying mechanisms

    SciTech Connect

    Qiao, B.; Teyssedre, G.; Laurent, C.

    2016-01-14

    The mechanisms of electroluminescence from large band gap polymers used as insulation in electric components are still under debate. It becomes important to unravel the underlying physics of the emission because of increasing thermo-electric stress and a possible relationship between electroluminescence and field withstand. We report herein on the cathodoluminescence spectra of polyethylene and polypropylene films as a way to uncover the nature of its contributions to electroluminescence emission. It is shown that spectra from the two materials are structured around four elementary components, each of them being associated with a specific process contributing to the overall emission with different weights depending on excitation conditions and on materials. The cathodoluminescence and electroluminescence spectra of each material are reconstructed from the four spectral components and their relative contribution are discussed. It is shown that electroluminescence from polyethylene and polypropylene has the same origin pointing towards generic mechanisms in both.

  15. An investigation of paper based microfluidic devices for size based separation and extraction applications.

    PubMed

    Zhong, Z W; Wu, R G; Wang, Z P; Tan, H L

    2015-09-01

    Conventional microfluidic devices are typically complex and expensive. The devices require the use of pneumatic control systems or highly precise pumps to control the flow in the devices. This work investigates an alternative method using paper based microfluidic devices to replace conventional microfluidic devices. Size based separation and extraction experiments conducted were able to separate free dye from a mixed protein and dye solution. Experimental results showed that pure fluorescein isothiocyanate could be separated from a solution of mixed fluorescein isothiocyanate and fluorescein isothiocyanate labeled bovine serum albumin. The analysis readings obtained from a spectrophotometer clearly show that the extracted tartrazine sample did not contain any amount of Blue-BSA, because its absorbance value was 0.000 measured at a wavelength of 590nm, which correlated to Blue-BSA. These demonstrate that paper based microfluidic devices, which are inexpensive and easy to implement, can potentially replace their conventional counterparts by the use of simple geometry designs and the capillary action. These findings will potentially help in future developments of paper based microfluidic devices.

  16. Dispenser printed electroluminescent lamps on textiles for smart fabric applications

    NASA Astrophysics Data System (ADS)

    de Vos, Marc; Torah, Russel; Tudor, John

    2016-04-01

    Flexible electroluminescent (EL) lamps are fabricated onto woven textiles using a novel dispenser printing process. Dispenser printing utilizes pressurized air to deposit ink onto a substrate through a syringe and nozzle. This work demonstrates the first use of this technology to fabricate EL lamps. The luminance of the dispenser printed EL lamps is compared to screen-printed EL lamps, both printed on textile, and also commercial EL lamps on polyurethane film. The dispenser printed lamps are shown to have a 1.5 times higher luminance than the best performing commercially available lamp, and have a comparable performance to the screen-printed lamps.

  17. Mechanosynthesis of a phenylenedivinylidenebisquinoline. Optical, morphological and electroluminescence properties

    NASA Astrophysics Data System (ADS)

    Gutiérrez, A. R.; Vázquez, R. A.; Moggio, I.; Arias, E.; Coreño, O.; Maldonado, J. L.; Ramos-Ortíz, G.; Rodríguez, O.; Jiménez-Barrera, R. M.

    2015-04-01

    A phenylenedivinylidenebisquinoline oligomer was obtained by reacting quinaldine with 2,5-bis(octyloxy)terephtalaldehyde via the Knoevenagel reaction by mechanosynthesis. The product was characterized by 1H Homo-J-Resolved NMR, 13C NMR, FT-IR, Fluorescence, UV-Vis spectroscopy and by FAB+ mass spectrometry. X-ray diffraction studies indicate that the molecule is semicrystalline, while laser scanning confocal microscopy shows that the emission comes from the crystals. As a consequence, the morphology and accordingly the PL values in spun films can be changed by varying the spinning conditions. Intrinsic electroluminescent properties are reported using the ITO/M1AMec/Al single layer configuration.

  18. Encapsulation methods and dielectric layers for organic electrical devices

    DOEpatents

    Blum, Yigal D; Chu, William Siu-Keung; MacQueen, David Brent; Shi, Yijan

    2013-07-02

    The disclosure provides methods and materials suitable for use as encapsulation barriers and dielectric layers in electronic devices. In one embodiment, for example, there is provided an electroluminescent device or other electronic device with a dielectric layer comprising alternating layers of a silicon-containing bonding material and a ceramic material. The methods provide, for example, electronic devices with increased stability and shelf-life. The invention is useful, for example, in the field of microelectronic devices.

  19. Liquid crystal devices based on photoalignment and photopatterning materials

    NASA Astrophysics Data System (ADS)

    Chigrinov, Vladimir

    2014-02-01

    Liquid crystal (LC) display and photonics devices based on photo-alignment and photo-patterning LC cells are developed. A fast switchable grating based on ferroelectric liquid crystals and orthogonal planar alignment by means of photo alignments. Both 1D and 2D gratings have been constructed. The proposed diffracting element provides fast response time of around 20 μs, contrast of 7000:1 and high diffraction efficiency, at the electric field of 6V/μm. A switchable LC Fresnel zone lens was also developed with the efficiency of ~42% that can be further improved, and the switching time for the 3 μm thick cell is ~6.7 ms which is relatively fast in comparison of existing devices. Thus, because of the photoalignment technology the fabrication of Fresnel lens became considerably simpler than others. A thin high spatial resolution, photo-patterned micropolarizer array for complementary metal-oxide-semiconductor (CMOS) image sensors was implemented for the complete optical visualization of so called "invisible" objects, which are completely transparent (reflective) and colorless. Four Stokes parameters, which fully characterized the reflected light beam can be simultaneously detected using the array of photo-patterned polarizers on CMOS sensor plate. The cheap, high resolution photo-patterned LC matrix sensor was developed to be able successfully compete with the expensive and low reliable wire grid polarizer patterned arrays currently used for the purpose.

  20. Green electroluminescence from Tb4O7 films on silicon: Impact excitation of Tb3+ ions by hot carriers

    NASA Astrophysics Data System (ADS)

    Zhu, Chen; Lv, Chunyan; Jiang, Miaomiao; Zhou, Junwei; Li, Dongsheng; Ma, Xiangyang; Yang, Deren

    2016-02-01

    We report on green electroluminescence (EL) due to the intra-4f transitions of the trivalent terbium (Tb3+) ions inherent in a Tb4O7 film that is sandwiched between the ITO film and heavily phosphorous- or boron-doped silicon (n+-Si or p+-Si) substrate, thus forming the so-called metal-oxide-semiconductor (MOS) device. The onset voltage of such EL is below 10 V. From the current-voltage characteristic and voltage-dependent EL spectra of the aforementioned MOS device, it is derived that the Tb-related green EL results from the impact excitation of Tb3+ ions by the hot electrons (holes), which stem from the electric-field acceleration of the electrons (holes) injected from the n+-Si (p+-Si) substrate via the trap-assisted tunneling mechanism.

  1. Smartphone-Based Electrocardiographic and Cardiac Implantable Electronic Device Monitoring.

    PubMed

    Mittal, Suneet

    The field of arrhythmia monitoring is changing rapidly. The rapid advent of technology in combination with marked improvements in cellular communication and an increased desire by patients to be actively engaged in their care has ushered in a new era of clinical care. Today, physicians need to think about their patients outside the traditional in-office setting. Two technologies that embody this changing landscape are smartphone-based electrocardiographic (ECG) monitors and remote monitoring of cardiac implantable electronic devices (CIEDs). Smartphone-based ECG monitors allow the patient to assume a greater stake in their own care. They purchase the monitor, couple it to their smartphone, own it forever, and can capture a representative ECG whenever they want to assess symptoms. The physician needs to accept that this approach is vastly different from the use of standard ambulatory external ECG monitors that have been used for years in clinical practice. A similar paradigm shift is underway with respect to the care of the CIED patient. Remote follow-up was once considered an acceptable alternative to in-office calendar-based follow-up of CIEDs. Today, guidelines recommend remote monitoring to be the preferred method for device follow-up. Remote monitoring is tailor-made for the current evolution to a value-based healthcare system, having been demonstrated to reduce scheduled office visits, hospital admissions, and mortality. It is now time to educate patients and physicians on the value of remote monitoring and to ensure that clinical practices develop the infrastructure needed to enroll, monitor, and manage their patients.

  2. Neuromorphic System Based on CMOS Inverters and Si-Based Synaptic Device.

    PubMed

    Park, Jungjin; Kwon, Min-Woo; Kim, Hyungjin; Park, Byung-Gook

    2016-05-01

    We developed an analog neuron circuit that can work with Si-based synaptic devices. N-channel and p-channel synaptic devices connected to current mirrors constitute the synaptic connection and integration parts to implement the excitation and inhibition mechanisms of biological neurons. The normal inverter controlling delay time and the modified inverter making negative pulse constitute the action-potential generation part to generate output action-potential. Connecting output potential to the synaptic device, we implement the spike-timing-dependent-plasticity (STDP) mechanism, adjusting the conductance of synapse. As we have constituted the analog neuron circuit using 4-terminal synaptic device without additional switch and logic operation, we can emulate the operation of the neuron with minimum number of devices and power dissipation.

  3. Room temperature direct-bandgap electroluminescence from a horizontal Ge ridge waveguide on Si

    NASA Astrophysics Data System (ADS)

    He, Chao; Liu, Zhi; Cheng, Bu-Wen

    2016-12-01

    We report a lateral Ge-on-Si ridge waveguide light emitting diode (LED) grown by ultrahigh vacuum chemical vapor deposition (UHV-CVD). Direct-bandgap electroluminescence (EL) of Ge waveguide under continuous current is observed at room temperature. The heat-enhancing luminescence and thermal radiation-induced superlinear increase of edge output optical power are found. The spontaneous emission and thermal radiation based on the generalized Planck radiation law are calculated and fit very well to the experimental results. The Ge waveguides with different lengths are studied and the shorter one shows stronger EL intensity. Project supported by the National Basic Research Program of China (Grant No. 2013CB632103), the National Natural Science Foundation of China (Grant Nos. 61176013 and 61036003), and the Science Fund from Beijing Science and Technology Commission, China (Grant No. Z151100003315019).

  4. Tunable white light from photo- and electroluminescence of ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Oliva, Jorge; Perez Mayen, Leonardo; De la Rosa, Elder; Diaz-Torres, Luis A.; Torres Castro, Alejandro; Salas, Pedro

    2014-01-01

    Tunable white light emission was obtained from ZnO nanorods with lengths ranging from 125 to 165 nm and quantum dots with an average size of 5 nm, synthesized with dodecylamine (DCA) as surfactant. It was possible to tailor the emission from cool to warm white light by changing the concentration of DCA in the synthesis process. The CIE coordinates for the white light obtained were (0.33, 0.32) in the case of photoluminescence and (0.31, 0.33) for electroluminescence from ZnO-based LEDs with a turn-on voltage of 4 and 6 V and a maximum current consumption of 2.32 mA at 10 V.

  5. Surface Lattice Resonances for Enhanced and Directional Electroluminescence at High Current Densities.

    PubMed

    Zakharko, Yuriy; Held, Martin; Graf, Arko; Rödlmeier, Tobias; Eckstein, Ralph; Hernandez-Sosa, Gerardo; Hähnlein, Bernd; Pezoldt, Jörg; Zaumseil, Jana

    2016-12-21

    Hybrid photonic-plasmonic modes in periodic arrays of metallic nanostructures offer a promising trade-off between high-quality cavities and subdiffraction mode confinement. However, their application in electrically driven light-emitting devices is hindered by their sensitivity to the surrounding environment and to charge injecting metallic electrodes in particular. Here, we demonstrate that the planar structure of light-emitting field-effect transistor (LEFET) ensures undisturbed operation of the characteristic modes. We incorporate a square array of gold nanodisks into the charge transporting and emissive layer of a polymer LEFET in order to tailor directionality and emission efficiency via the Purcell effect and variation of the fractional local density of states in particular. Angle- and polarization-resolved spectra confirm that the enhanced electroluminescence correlates with the dispersion curves of the surface lattice resonances supported by these structures. These LEFETs reach current densities on the order of 10 kA/cm(2), which may pave the way toward practical optoelectronic devices with tailored emission patterns and potentially electrically pumped plasmonic lasers.

  6. Origin of White Electroluminescence in Graphene Quantum Dots Embedded Host/Guest Polymer Light Emitting Diodes

    PubMed Central

    Kyu Kim, Jung; Bae, Sukang; Yi, Yeonjin; Jin Park, Myung; Jin Kim, Sang; Myoung, NoSoung; Lee, Chang-Lyoul; Hee Hong, Byung; Hyeok Park, Jong

    2015-01-01

    Polymer light emitting diodes (PLEDs) using quantum dots (QDs) as emissive materials have received much attention as promising components for next-generation displays. Despite their outstanding properties, toxic and hazardous nature of QDs is a serious impediment to their use in future eco-friendly opto-electronic device applications. Owing to the desires to develop new types of nano-material without health and environmental effects but with strong opto-electrical properties similar to QDs, graphene quantum dots (GQDs) have attracted great interest as promising luminophores. However, the origin of electroluminescence from GQDs incorporated PLEDs is unclear. Herein, we synthesized graphene oxide quantum dots (GOQDs) using a modified hydrothermal deoxidization method and characterized the PLED performance using GOQDs blended poly(N-vinyl carbazole) (PVK) as emissive layer. Simple device structure was used to reveal the origin of EL by excluding the contribution of and contamination from other layers. The energy transfer and interaction between the PVK host and GOQDs guest were investigated using steady-state PL, time-correlated single photon counting (TCSPC) and density functional theory (DFT) calculations. Experiments revealed that white EL emission from the PLED originated from the hybridized GOQD-PVK complex emission with the contributions from the individual GOQDs and PVK emissions. PMID:26067060

  7. Surface Lattice Resonances for Enhanced and Directional Electroluminescence at High Current Densities

    PubMed Central

    2016-01-01

    Hybrid photonic-plasmonic modes in periodic arrays of metallic nanostructures offer a promising trade-off between high-quality cavities and subdiffraction mode confinement. However, their application in electrically driven light-emitting devices is hindered by their sensitivity to the surrounding environment and to charge injecting metallic electrodes in particular. Here, we demonstrate that the planar structure of light-emitting field-effect transistor (LEFET) ensures undisturbed operation of the characteristic modes. We incorporate a square array of gold nanodisks into the charge transporting and emissive layer of a polymer LEFET in order to tailor directionality and emission efficiency via the Purcell effect and variation of the fractional local density of states in particular. Angle- and polarization-resolved spectra confirm that the enhanced electroluminescence correlates with the dispersion curves of the surface lattice resonances supported by these structures. These LEFETs reach current densities on the order of 10 kA/cm2, which may pave the way toward practical optoelectronic devices with tailored emission patterns and potentially electrically pumped plasmonic lasers. PMID:28042593

  8. A rhenium complex with diamine ligand containing oxadiazole group and fluorine atom: Synthesis, characterization, photoluminescence and electroluminescence performances

    NASA Astrophysics Data System (ADS)

    Yang, Wensheng; Yang, Wan; Liu, Weisheng; Qin, Wenwu

    2013-03-01

    In this paper, a diamine ligand of 2-(4-fluorophenyl)-5-(pyridin-2-yl)-1,3,4-oxadiazole (FPYOZ), which owned both enlarged conjugation chain with electron-pulling group and fluorine atom, was synthesized. Its corresponding Re(I) complex was also synthesized and studied in detail, including single crystal analysis, electronic structure, photophysical performance, thermal stability and electrochemical property. Single crystal analysis suggested that there was a coordination ability difference between the N atom from pyridine ring and the one from oxadiazole moiety. Theoretical calculation on the complex suggested that the onset electronic transition owned a mixed character of metal-to-ligand-charge-transfer and ligand-to-ligand-charge-transfer. Upon photoexcitation of 375 nm, this complex showed a yellow emission peaking at 537 nm with excited state lifetime of 8.35 μs. Cyclic voltammetry result suggested that this complex owned HOMO and LUMO energy levels of -5.37 eV and -3.04 eV. The decomposition temperature of this complex was as high as 300 °C, as revealed by thermogravimetric analysis data. The optimal electroluminescence device using this complex as the emitting dopant showed an electroluminescence peaking at 562 nm, with a maximum luminance of 6250 cd/m2 and a maximum current efficiency of 7.3 cd/A.

  9. Electroluminescence properties of In-doped Zn2SiO4 thin films prepared by sol-gel process

    NASA Astrophysics Data System (ADS)

    Ogawa, Hirotaka; Kan, Akinori; Ikeda, Norihiro; Fujita, Akihiro

    2012-11-01

    The effect of In doping on the electroluminescence (EL) properties of Zn2SiO4:In thin films was investigated. In-doped Zn2SiO4 thin films were deposited on BaTiO3 substrates and their EL properties were characterized in this study. X-ray powder diffraction patterns of In-doped Zn2SiO4 powders revealed a single phase of Zn2SiO4 for In concentrations up to approximately 1.5 mol%, whereas a secondary phase of In2O3 was observed for In concentrations in the range of 2-10 mol%. The maximum luminance of thin film electroluminescent (TFEL) devices varied significantly with the amount of In doping. The highest luminance with blue emission was obtained when 2 mol% In was doped. The blue emission of In-doped Zn2SiO4 thin film may be related to the In substitution for Zn. The 2 mol% In-doped Zn2SiO4 thin film exhibited blue emission with CIE color coordinates of x=0.208 and y=0.086.

  10. Detection of base-pair mismatches in DNA using graphene-based nanopore device

    NASA Astrophysics Data System (ADS)

    Kundu, Sourav; Karmakar, S. N.

    2016-04-01

    We present a unique way to detect base-pair mismatches in DNA, leading to a different epigenetic disorder by the method of nanopore sequencing. Based on a tight-binding formulation of a graphene-based nanopore device, using the Green’s function approach we study the changes in the electronic transport properties of the device as we translocate a double-stranded DNA through the nanopore embedded in a zigzag graphene nanoribbon. In the present work we are not only successful in detecting the usual AT and GC pairs but also a set of possible mismatches in the complementary base pairing.

  11. Detection of base-pair mismatches in DNA using graphene-based nanopore device.

    PubMed

    Kundu, Sourav; Karmakar, S N

    2016-04-01

    We present a unique way to detect base-pair mismatches in DNA, leading to a different epigenetic disorder by the method of nanopore sequencing. Based on a tight-binding formulation of a graphene-based nanopore device, using the Green's function approach we study the changes in the electronic transport properties of the device as we translocate a double-stranded DNA through the nanopore embedded in a zigzag graphene nanoribbon. In the present work we are not only successful in detecting the usual AT and GC pairs but also a set of possible mismatches in the complementary base pairing.

  12. High-sensitivity strain visualization using electroluminescence technologies

    NASA Astrophysics Data System (ADS)

    Xu, Jian; Jo, Hongki

    2016-04-01

    Visualizing mechanical strain/stress changes is an emerging area in structural health monitoring. Several ways are available for strain change visualization through the color/brightness change of the materials subjected to the mechanical stresses, for example, using mechanoluminescence (ML) materials and mechanoresponsive polymers (MRP). However, these approaches were not effectively applicable for civil engineering system yet, due to insufficient sensitivity to low-level strain of typical civil structures and limitation in measuring both static and dynamic strain. In this study, design and validation for high-sensitivity strain visualization using electroluminescence technologies are presented. A high-sensitivity Wheatstone bridge, of which bridge balance is precisely controllable circuits, is used with a gain-adjustable amplifier. The monochrome electroluminescence (EL) technology is employed to convert both static and dynamic strain change into brightness/color change of the EL materials, through either brightness change mode (BCM) or color alternation mode (CAM). A prototype has been made and calibrated in lab, the linearity between strain and brightness change has been investigated.

  13. Colorless to Neutral Color Electrochromic Devices Based on Asymmetric Viologens.

    PubMed

    Alesanco, Yolanda; Viñuales, Ana; Cabañero, Germán; Rodriguez, Javier; Tena-Zaera, Ramón

    2016-11-02

    Electrochromic materials have extensively been investigated because of their potential fields of application, with a significant growing interest in expanding the provided colorations. However, among all palette of colors, colorless electrochromic devices (ECDs) that provide neutral-grayish colorations with a simple configuration remain a key challenge. The present study reports on the synthesis of asymmetrically 1-alkyl-1'-aryl-substituted viologens and their incorporation in PVA-borax gel polyelectrolytes for ECDs that constitute the simplest device architecture (glass/TCO/EC gel/TCO/glass). We demonstrate herein that these EC gels based on single asymmetric viologens provide more neutral-colored state than their corresponding symmetric viologens (a* and b* ≤ |15|), while maintaining satisfactory colorless bleached state (%Tb > 70% in the whole visible range), transmittance changes (i.e., ∼60%) and cyclability (i.e., ∼15 000 cycles). Additionally, the effect of the solvent on the observed coloration has also been investigated. This easy-to-make neutral-grayish color ECDs may significantly extend the potential of the electrochromic technology, because they adapt better aesthetically to the surrounding environment, as they are easier to implement in different applications.

  14. Device-independent quantum key distribution based on measurement inputs

    NASA Astrophysics Data System (ADS)

    Rahaman, Ramij; Parker, Matthew G.; Mironowicz, Piotr; Pawłowski, Marcin

    2015-12-01

    We provide an analysis of a family of device-independent quantum key distribution (QKD) protocols that has the following features. (a) The bits used for the secret key do not come from the results of the measurements on an entangled state but from the choices of settings. (b) Instead of a single security parameter (a violation of some Bell inequality) a set of them is used to estimate the level of trust in the secrecy of the key. The main advantage of these protocols is a smaller vulnerability to imperfect random number generators made possible by feature (a). We prove the security and the robustness of such protocols. We show that using our method it is possible to construct a QKD protocol which retains its security even if the source of randomness used by communicating parties is strongly biased. As a proof of principle, an explicit example of a protocol based on the Hardy's paradox is presented. Moreover, in the noiseless case, the protocol is secure in a natural way against any type of memory attack, and thus allows one to reuse the device in subsequent rounds. We also analyze the robustness of the protocol using semidefinite programming methods. Finally, we present a postprocessing method, and observe a paradoxical property that rejecting some random part of the private data can increase the key rate of the protocol.

  15. Engineering aperiodic nanostructured surfaces for scattering-based optical devices

    NASA Astrophysics Data System (ADS)

    Lee, Yuk Kwan Sylvanus

    Novel optical devices such as biosensors, color displays and authentication devices can be obtained from the distinctive light scattering properties of resonant nanoparticles and nanostructured arrays. These arrays can be optimized through the choice of material, particle morphology and array geometry. In this thesis, by engineering the multi-frequency colorimetric responses of deterministic aperiodic nanostructured surfaces (DANS) with various spectral Fourier properties, I designed, fabricated and characterized scattering-based devices for optical biosensing and structural coloration applications. In particular, using analytical and numerical optimization, colorimetric biosensors are designed and fabricated with conventional electron beam lithography, and characterized using dark-field scattering imaging as well as image autocorrelation analysis of scattered intensity in the visible spectral range. These sensors, which consist of aperiodic surfaces ranging from quasi-periodic to pseudo-random structures with flat Fourier spectra, sustain highly complex structural resonances that enable a novel optical sensing approach beyond the traditional Bragg scattering. To this end, I have experimentally demonstrated that DANS with engineered structural colors are capable of detecting nanoscale protein monolayers with significantly enhanced sensitivity over periodic structures. In addition, different aperiodic arrays of gold (Au) nanoparticles are integrated with polydimethylsiloxane (PDMS) microfluidic structures by soft-lithographic micro-imprint techniques. Distinctive scattering spectral shifts and spatial modifications of structural color patterns in response to refractive index variations were simultaneously measured. The successful integration of DANS with microfluidics technology has introduced a novel opto-fluidic sensing platform for label-free and multiplexed lab-on-a-chip applications. Moreover, by studying the isotropic scattering properties of homogenized

  16. 3D Printed Graphene Based Energy Storage Devices

    PubMed Central

    Foster, Christopher W.; Down, Michael P.; Zhang, Yan; Ji, Xiaobo; Rowley-Neale, Samuel J.; Smith, Graham C.; Kelly, Peter J.; Banks, Craig E.

    2017-01-01

    3D printing technology provides a unique platform for rapid prototyping of numerous applications due to its ability to produce low cost 3D printed platforms. Herein, a graphene-based polylactic acid filament (graphene/PLA) has been 3D printed to fabricate a range of 3D disc electrode (3DE) configurations using a conventional RepRap fused deposition moulding (FDM) 3D printer, which requires no further modification/ex-situ curing step. To provide proof-of-concept, these 3D printed electrode architectures are characterised both electrochemically and physicochemically and are advantageously applied as freestanding anodes within Li-ion batteries and as solid-state supercapacitors. These freestanding anodes neglect the requirement for a current collector, thus offering a simplistic and cheaper alternative to traditional Li-ion based setups. Additionally, the ability of these devices’ to electrochemically produce hydrogen via the hydrogen evolution reaction (HER) as an alternative to currently utilised platinum based electrodes (with in electrolysers) is also performed. The 3DE demonstrates an unexpectedly high catalytic activity towards the HER (−0.46 V vs. SCE) upon the 1000th cycle, such potential is the closest observed to the desired value of platinum at (−0.25 V vs. SCE). We subsequently suggest that 3D printing of graphene-based conductive filaments allows for the simple fabrication of energy storage devices with bespoke and conceptual designs to be realised. PMID:28256602

  17. 3D Printed Graphene Based Energy Storage Devices

    NASA Astrophysics Data System (ADS)

    Foster, Christopher W.; Down, Michael P.; Zhang, Yan; Ji, Xiaobo; Rowley-Neale, Samuel J.; Smith, Graham C.; Kelly, Peter J.; Banks, Craig E.

    2017-03-01

    3D printing technology provides a unique platform for rapid prototyping of numerous applications due to its ability to produce low cost 3D printed platforms. Herein, a graphene-based polylactic acid filament (graphene/PLA) has been 3D printed to fabricate a range of 3D disc electrode (3DE) configurations using a conventional RepRap fused deposition moulding (FDM) 3D printer, which requires no further modification/ex-situ curing step. To provide proof-of-concept, these 3D printed electrode architectures are characterised both electrochemically and physicochemically and are advantageously applied as freestanding anodes within Li-ion batteries and as solid-state supercapacitors. These freestanding anodes neglect the requirement for a current collector, thus offering a simplistic and cheaper alternative to traditional Li-ion based setups. Additionally, the ability of these devices’ to electrochemically produce hydrogen via the hydrogen evolution reaction (HER) as an alternative to currently utilised platinum based electrodes (with in electrolysers) is also performed. The 3DE demonstrates an unexpectedly high catalytic activity towards the HER (‑0.46 V vs. SCE) upon the 1000th cycle, such potential is the closest observed to the desired value of platinum at (‑0.25 V vs. SCE). We subsequently suggest that 3D printing of graphene-based conductive filaments allows for the simple fabrication of energy storage devices with bespoke and conceptual designs to be realised.

  18. Model-based pattern dummy generation for logic devices

    NASA Astrophysics Data System (ADS)

    Jang, Jongwon; Kim, Cheolkyun; Ko, Sungwoo; Byun, Seokyoung; Yang, Hyunjo; Yim, Donggyu

    2014-03-01

    The insertion of SRAF(Sub-Resolution Assist Feature) is one of the most frequently used method to enlarge the process window area. In most cases, the size of SRAF is proportional to the focus margin of drawn patterns. However, there is a trade-off between the SRAF size and SRAF printing, because SRAF is not supposed to be patterned on a wafer. For this reason, a lot of OPC engineers have been tried to put bigger and more SRAFs within the limits of the possible. The fact that many papers about predicting SRAF printability have been published recent years reflects this circumstance. Pattern dummy is inserted to enhance the lithographic process margin and CD uniformity unlike CMP dummy for uniform metal line height. It is ordinary to put pattern dummy at the designated location under consideration of the pitch of real patterns at design step. However, it is not always desirable to generate pattern dummies based on rules at the lithographic point of view. In this paper, we introduce the model based pattern dummy insertion method, which is putting pattern dummies at the location that model based SRAF is located. We applied the model based pattern dummy to the layers in logic devices, and studied which layer is more efficient for the insertion of dummies.

  19. Optical properties of heavily doped GaAs nanowires and electroluminescent nanowire structures.

    PubMed

    Lysov, A; Offer, M; Gutsche, C; Regolin, I; Topaloglu, S; Geller, M; Prost, W; Tegude, F-J

    2011-02-25

    We present GaAs electroluminescent nanowire structures fabricated by metal organic vapor phase epitaxy. Electroluminescent structures were realized in both axial pn-junctions in single GaAs nanowires and free-standing nanowire arrays with a pn-junction formed between nanowires and substrate, respectively. The electroluminescence emission peak from single nanowire pn-junctions at 10 K was registered at an energy of around 1.32 eV and shifted to 1.4 eV with an increasing current. The line is attributed to the recombination in the compensated region present in the nanowire due to the memory effect of the vapor-liquid-solid growth mechanism. Arrayed nanowire electroluminescent structures with a pn-junction formed between nanowires and substrate demonstrated at 5 K a strong electroluminescence peak at 1.488 eV and two shoulder peaks at 1.455 and 1.519 eV. The main emission line was attributed to the recombination in the p-doped GaAs. The other two lines correspond to the tunneling-assisted photon emission and band-edge recombination in the abrupt junction, respectively. Electroluminescence spectra are compared with the micro-photoluminescence spectra taken along the single p-, n- and single nanowire pn-junctions to find the origin of the electroluminescence peaks, the distribution of doping species and the sharpness of the junctions.

  20. Amyloid detection using a Peltier-based device.

    PubMed

    Cabrera, Miguel A; Ferreyra, Martin G; Cortez, Leonardo; Grupalli, Silvina A; Alvarez, L Leguina; Chehin, Rosana

    2012-01-01

    Amyloid aggregation of polypeptides is related to a growing number of pathologic states known as amyloid disorders. At present, it is clear that any proteins submitted to appropriate physicochemical environment can acquire fibrilar conformation. Fourier transform infrared spectroscopy (FTIR) has been a widely used technique to study temperature- induced amyloid-fibrils formation in vitro. In this way, strict changes and temperature controls are required to characterize the physicochemical basis of the amyloid-fibrils formation. In this article, the development of a highly efficient and accurate Peltier-based system to improve FTIR measurements is presented (see An Old Physics Phenomenon Applied to a Serious Biomedical Pathology. The accuracy of the thermostatic control was tested with biophysical parameters on biological samples probing its reproducibility. The design of the present device contributes to maintain the FTIR environment stable, which represents a real contribution to improve the spectral quality and thus, the reliability of the results.

  1. Very High Output Thermoelectric Devices Based on ITO Nanocomposites

    NASA Technical Reports Server (NTRS)

    Fralick, Gustave; Gregory, Otto J.

    2009-01-01

    A material having useful thermoelectric properties was synthesized by combining indium-tin-oxide (ITO) with a NiCoCrAlY alloy/alumina cermet. This material had a very large Seebeck coefficient with electromotive-force-versustemperature behavior that is considered to be excellent with respect to utility in thermocouples and other thermoelectric devices. When deposited in thin-film form, ceramic thermocouples offer advantages over precious-metal (based, variously, on platinum or rhodium) thermocouples that are typically used in gas turbines. Ceramic thermocouples exhibit high melting temperatures, chemical stability at high temperatures, and little or no electromigration. Oxide ceramics also resist oxidation better than metal thermocouples, cost substantially less than precious-metal thermocouples, and, unlike precious-metal thermocouples, do not exert catalytic effects.

  2. Recent developments in InP-based optoelectronic devices

    NASA Astrophysics Data System (ADS)

    Venghaus, H.; Bach, H.-G.; Bauer, S.; Beling, A.; Heidrich, H.; Hoffman, D.; Hüttl, B.; Kaiser, R.; Kreissl, J.; Mekonnen, G. G.; Möhrle, M.; Rehbein, W.; Sartorius, B.; Velthaus, K.-O.

    2005-09-01

    Recent development trends in InP-based optoelectronic devices are illustrated by means of selected examples. These include lasers for uncooled operation and direct modulation at 10 Gbit/s, complex-coupled lasers, which exhibit particularly low sensitivity to back reflections as well as monolithic mode-locked semiconductor lasers as ps-pulse sources for OTDM applications. Furthermore, a Mach-Zehnder interferometer modulator for high bit rate applications (40 Gbit/s and beyond) is described, and finally, photoreceivers and ultra high-speed waveguide-integrated photodiodes with > 100 GHz bandwidth are presented, which are key component for high bit rate systems, advanced modulation format transmission links, and for high speed measurement equipment as well.

  3. Surface geometry based hydrophobicity of the PDMS for microfluidic devices

    NASA Astrophysics Data System (ADS)

    Pelayo, J. C.; Badiola, R. A.; Castañares, J.; Pili, U.; Violanda, R.; Bacabac, R.

    2015-06-01

    In this report, the surface hydrophobicity of PDMS was investigated using two methods of preparations. The first method was performed by changing the surface roughness through the use of different molds. The second method was performed by varying the reconstitution ratio (volume of elastomer base to volume of elastomer curing) of the PDMS. Variation in the hydrophobicity of the PDMS was characterized by measuring the contact angle of a liquid droplet against the surface of the PDMS. The results showed that both the surface roughness and the reconstitution ratio of the PDMS positively correlated with the contact angle measured regardless of the liquid used. The maximum and minimum contact angle obtained were θr = (138 ± 3)° and θr = (99 ± 3)°, respectively. The results demonstrate a straightforward way of fabricating microfluidic devices using PDMS with controlled hydrophobicity.

  4. Energy-based control of a haptic device using brakes.

    PubMed

    Cho, Changhyun; Song, Jae-Bok; Kim, Munsang

    2007-04-01

    This paper proposes an energy-based control method of a haptic device with electric brakes. Unsmooth motion is frequently observed in a haptic system using brakes during a wall-following task. Since it is generally known that a haptic system using brakes is passive due to brake's characteristics, its energy behavior has seldom been investigated. However, force distribution at the end effector reveals that the unsmooth motion of a haptic system using brakes represents active behavior of the system in the specific direction. A force control scheme is proposed that computes the gain for smooth motion by considering the energy behavior of a system. Experiments show that smooth wall following is possible with a proposed force control scheme.

  5. Calibration of CR-39-based thoron progeny device.

    PubMed

    Fábián, F; Csordás, A; Shahrokhi, A; Somlai, J; Kovács, T

    2014-07-01

    Radon isotopes and their progenies have proven significant role in respiratory tumour formation. In most cases, the radiological effect of one of the radon isotopes (thoron) and its progenies has been neglected together with its measurement technique; however, latest surveys proved that thoron's existence is expectable in flats and in workplace in Europe. Detectors based on different track detector measurement technologies have recently spread for measuring thoron progenies; however, the calibration is not yet completely elaborated. This study deals with the calibration of the track detector measurement method suitable for measuring thoron progenies using different devices with measurement techniques capable of measuring several progenies (Pylon AB5 and WLx, Sarad EQF 3220). The calibration factor values related to the thoron progeny monitors, the measurement uncertainty, reproducibility and other parameters were found using the calibration chamber. In the future, the effects of the different parameters (aerosol distribution, etc.) will be determined.

  6. Fabrication and Operation of Paper-Based Analytical Devices.

    PubMed

    Jiang, Xiao; Fan, Z Hugh

    2016-06-12

    This review focuses on the fabrication techniques and operational components of microfluidic paper-based analytical devices (μPADs). Being low-cost, user-friendly, fast, and simple, μPADs have seen explosive growth in the literature in the last decade. Many different materials and technologies have been employed to fabricate μPADs for various applications, including those that employ patterning, the creation of physical boundaries, and three-dimensional structures. In addition to fabrication techniques, flow control and other operational components in μPADs are of great interest. These components enable μPADs to control flow rates, direct flow paths via valves, sequentially deliver reagents automatically, and display test results, all of which will make μPADs more suitable for point-of-care applications.

  7. A nanomechanical device based on light-driven proton pumps.

    PubMed

    Ren, Quan; Zhao, Ya-Pu; Han, Li; Zhao, Hui-Bin

    2006-03-28

    In this paper, a hybrid device based on a microcantilever interfaced with bacteriorhodopsin (bR) is constructed. The microcantilever, on which the highly oriented bR film is self-assembled, undergoes controllable and reversible bending when the light-driven proton pump protein, bR, on the microcantilever surface is activated by visible light. Several control experiments are carried out to preclude the influence of heat and photothermal effects. It is shown that the nanomechanical motion is induced by the resulting gradient of protons, which are transported from the KCl solution on the cytoplasmic side of the bR film towards the extracellular side of the bR film. Along with a simple physical interpretation, the microfabricated cantilever interfaced with the organized molecular film of bR can simulate the natural machinery in converting solar energy to mechanical energy.

  8. ELOPTA: a novel microcontroller-based operant device.

    PubMed

    Hoffman, Adam M; Song, Jianjian; Tuttle, Elaina M

    2007-11-01

    Operant devices have been used for many years in animal behavior research, yet such devices a regenerally highly specialized and quite expensive. Although commercial models are somewhat adaptable and resilient, they are also extremely expensive and are controlled by difficult to learn proprietary software. As an alternative to commercial devices, we have designed and produced a fully functional, programmable operant device, using a PICmicro microcontroller (Microchip Technology, Inc.). The electronic operant testing apparatus (ELOPTA) is designed to deliver food when a study animal, in this case a bird, successfully depresses the correct sequence of illuminated keys. The device logs each keypress and can detect and log whenever a test animal i spositioned at the device. Data can be easily transferred to a computer and imported into any statistical analysis software. At about 3% the cost of a commercial device, ELOPTA will advance behavioral sciences, including behavioral ecology, animal learning and cognition, and ethology.

  9. 77 FR 8900 - Certain Vaginal Ring Birth Control Devices; Termination of the Investigation Based on Withdrawal...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-15

    ... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION Certain Vaginal Ring Birth Control Devices; Termination of the Investigation Based on Withdrawal... within the United States after importation of certain vaginal birth control devices by reason...

  10. Multiplex fluorescent immunoassay device based on magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Godjevargova, T. I.; Ivanov, Y. L.; Dinev, D. D.

    2017-02-01

    Immunofluorescent analyzer based compact disc for simultaneous detection of 3 antibiotics in the same milk sample is consisting of two parts: CD-based immunofluorescence kit and optoelectronic fluorometer. Kit consists of 2 parts: Lyophilized immobilized antibodies on supermagnetic nanoparticles in Eppendorf tubes and CD-based microfluidic disk, in which are formed five chamber systems for simultaneous detecting of 5 separate samples. Each system consists of 2 chambers connected by a special micro channel acting as a hydrophobic valve. In the first chamber lyophilised conjugates of 3 antibiotics with accordingly 3 different fluorescent dyes are placed. The second chamber is for detection of fluorescent signal. The optoelectronic fluorometer is comprising of: integrated thermostatic block; mechanical-detecting unit (fluorometer) and block with controlling and visualizing electronics.The disc gets into a second block of the analyzer, where centrifugation is performed and also reporting of the fluorescent signals. This unit comprises a rotor on which the disc is fixed, permanent electromagnet in the form of a ring inserted under the disc and module of 3 LED diodes with emission filters for the relevant wavelengths corresponding to the used fluorescent dyes and 1 integrated photodiode, in front of which is mounted filter with 3 spectral peaks.The signal from the photodiode is detected by the electronic unit which is sensitive "lock-in" amplifier, the engine rotor management, control of thermostatic device and management of periphery of the analyzer, consisting of display and communications with computer.

  11. Swarm Optimization-Based Magnetometer Calibration for Personal Handheld Devices

    PubMed Central

    Ali, Abdelrahman; Siddharth, Siddharth; Syed, Zainab; El-Sheimy, Naser

    2012-01-01

    Inertial Navigation Systems (INS) consist of accelerometers, gyroscopes and a processor that generates position and orientation solutions by integrating the specific forces and rotation rates. In addition to the accelerometers and gyroscopes, magnetometers can be used to derive the user heading based on Earth's magnetic field. Unfortunately, the measurements of the magnetic field obtained with low cost sensors are usually corrupted by several errors, including manufacturing defects and external electro-magnetic fields. Consequently, proper calibration of the magnetometer is required to achieve high accuracy heading measurements. In this paper, a Particle Swarm Optimization (PSO)-based calibration algorithm is presented to estimate the values of the bias and scale factor of low cost magnetometers. The main advantage of this technique is the use of the artificial intelligence which does not need any error modeling or awareness of the nonlinearity. Furthermore, the proposed algorithm can help in the development of Pedestrian Navigation Devices (PNDs) when combined with inertial sensors and GPS/Wi-Fi for indoor navigation and Location Based Services (LBS) applications.

  12. Nanoporous noninvasive cellular electrical activity-based analysis devices.

    PubMed

    Prasad, Shalini; Quijano, Jorge

    2007-03-01

    In recent years, rapid advancements have been made in the biomedical applications of microtechnology and nanotechnology. While the focus of such technologies have been primarily on in vitro analytical and diagnostic tools, more recently in vivo therapeutic and sensing applications have gained attention. The long-term integration of cells with inorganic materials provides the basis for novel sensing platforms. The work presented here focuses on the ability to maintain cells long-term in nanoporous silicon-based microenvironments. This article describes the creation of nanoporous, biocompatible, alumina membranes as a platform for incorporation into a cell-based device targeted for in situ recording of cellular electrical activity variations due to the changes associated with the surrounding microenvironments. Studies described herein focus on the interaction of nanoporous alumina substrates embedded in silicon patterned with cells of interest. The fidelity of such a system is demonstrated in terms of viability, proliferation, and functionality. The capability of such microfabricated nanoporous membranes, as in vitro for cell-based assays for sensing and drug delivery applications, is also demonstrated. It has potential in vivo application for therapeutic immunoisolation.

  13. Graphene-Based Integrated Photovoltaic Energy Harvesting/Storage Device.

    PubMed

    Chien, Chih-Tao; Hiralal, Pritesh; Wang, Di-Yan; Huang, I-Sheng; Chen, Chia-Chun; Chen, Chun-Wei; Amaratunga, Gehan A J

    2015-06-24

    Energy scavenging has become a fundamental part of ubiquitous sensor networks. Of all the scavenging technologies, solar has the highest power density available. However, the energy source is erratic. Integrating energy conversion and storage devices is a viable route to obtain self-powered electronic systems which have long-term maintenance-free operation. In this work, we demonstrate an integrated-power-sheet, consisting of a string of series connected organic photovoltaic cells (OPCs) and graphene supercapacitors on a single substrate, using graphene as a common platform. This results in lighter and more flexible power packs. Graphene is used in different forms and qualities for different functions. Chemical vapor deposition grown high quality graphene is used as a transparent conductor, while solution exfoliated graphene pastes are used as supercapacitor electrodes. Solution-based coating techniques are used to deposit the separate components onto a single substrate, making the process compatible with roll-to-roll manufacture. Eight series connected OPCs based on poly(3-hexylthiophene)(P3HT):phenyl-C61-butyric acid methyl ester (PC60 BM) bulk-heterojunction cells with aluminum electrodes, resulting in a ≈5 V open-circuit voltage, provide the energy harvesting capability. Supercapacitors based on graphene ink with ≈2.5 mF cm(-2) capacitance provide the energy storage capability. The integrated-power-sheet with photovoltaic (PV) energy harvesting and storage functions had a mass of 0.35 g plus the substrate.

  14. Origami paper-based fluidic batteries for portable electrophoretic devices.

    PubMed

    Chen, Sung-Sheng; Hu, Chih-Wei; Yu, I-Fan; Liao, Ying-Chih; Yang, Jing-Tang

    2014-06-21

    A manufacturing approach for paper-based fluidic batteries was developed based on the origami principle (three-dimension paper folding). Microfluidic channels were first created on a filter paper by a wax-printing method. Copper and aluminium sheets were then glued onto the paper as electrodes for the redox reaction. After the addition of copper sulphate and aluminium chloride, commonly available cellophane paper was attached as a membrane to separate the two electrodes. The resulting planar paper sheets were then folded into three-dimensional structures and compiled as a single battery with glue. The two half reactions (Al/Al(3+) and Cu/Cu(2+)) in the folded batteries provided an open-circuit potential from 0.82 V (one cell) to 5.0 V (eight cells in series) depending on the origami design. The prepared battery can provide a stable current of 500 μA and can light a regular LED for more than 65 min. These paper-based fluidic batteries in a set can also be compiled into a portable power bank to provide electric power for many electric or biomedical applications, such as LED lights and electrophoretic devices, as we report here.

  15. Language-based color editing for mobile device

    NASA Astrophysics Data System (ADS)

    Zhao, Yonghui; Bala, Raja; Braun, Karen M.; Langford, Zahra; Rolleston, Robert J.; Stevens, Michael T.

    2011-03-01

    Natural language color (NLC) was initially developed as a web-based application and then deployed in one Xerox print driver. NLC changes the image-editing paradigm from the use of curves, sliders, and knobs, to the use of verbal text-based commands such as "make light green much less yellowish". The technology appeals to a common user who has no expert knowledge in color science, and this naturally leads one to think about its use in mobile devices. A prototype GUI design for a language-based color editing on iPhone platform will be presented that uses several of its haptic interfaces (e.g. "slot-machine", shaking, swiping, etc.). A textual interface is provided to select a color to be modified within the image and a direction of change for the modification. A swipe interface is provided to select a magnitude and polarity for the modification. Actions on the textual and swipe interface are converted to natural language commands that are in turn used to derive a color transformation that is applied to relevant portions of the image to yield a modified image. The modifications are displayed in real time to the user.

  16. Simple, distance-based measurement for paper analytical devices.

    PubMed

    Cate, David M; Dungchai, Wijitar; Cunningham, Josephine C; Volckens, John; Henry, Charles S

    2013-06-21

    Paper-based analytical devices (PADs) represent a growing class of elegant, yet inexpensive chemical sensor technologies designed for point-of-use applications. Most PADs, however, still utilize some form of instrumentation such as a camera for quantitative detection. We describe here a simple technique to render PAD measurements more quantitative and straightforward using the distance of colour development as a detection motif. The so-called distance-based detection enables PAD chemistries that are more portable and less resource intensive compared to classical approaches that rely on the use of peripheral equipment for quantitative measurement. We demonstrate the utility and broad applicability of this technique with measurements of glucose, nickel, and glutathione using three different detection chemistries: enzymatic reactions, metal complexation, and nanoparticle aggregation, respectively. The results show excellent quantitative agreement with certified standards in complex sample matrices. This work provides the first demonstration of distance-based PAD detection with broad application as a class of new, inexpensive sensor technologies designed for point-of-use applications.

  17. A new series of short axially symmetrically and asymmetrically 1,3,6,8-tetrasubstituted pyrenes with two types of substituents: Syntheses, structures, photophysical properties and electroluminescence

    NASA Astrophysics Data System (ADS)

    Zhang, Ran; Zhang, Tengfei; Xu, Lu; Han, Fangfang; Zhao, Yun; Ni, Zhonghai

    2017-01-01

    A new series of short axially symmetrically (4a and 4b) and asymmetrically (4c and 4d) 1,3,6,8-tetrasubstituted pyrene-based compounds with two phenyl moieties and two diphenylamine units on the pyrene core were designed and synthesized based on stepwise synthetic strategy. These compounds were structurally characterized and their photoelectric properties were investigated by spectroscopy, electrochemical and theoretical studies. The structures of 4a and 4b were determined by single-crystal X-ray diffraction analysis, indicating that the compounds are twisted by the peripheral substituents and the intermolecular π-π interactions have been efficiently interrupted. The four compounds exhibit high absolute fluorescence quantum yields (VF) in dichloromethane (83.31-88.45%) and moderate VFs in film states (20.78-38.68%). In addition, compounds 4a and 4b display relatively higher absolute VFs than those of 4c and 4d in film states. All the compounds exhibit high thermal stability with decomposition temperatures above 358 °C and the values of 4c and 4d are higher than 4a and 4b. Compounds 4a and 4b can form morphologically stable amorphous thin films with Tg values of 146 °C and 149 °C, respectively. However, there are no obvious Tg observed in compounds 4c and 4d. Electroluminescent devices using 4a and 4b as doped emission layer show promising device performance with low turn-on voltage (3.0 V), maximum brightness around 15100 cd/m2 and 16100 cd/m2, maximum luminance efficiency of 12.4 cd/A and 13.6 cd/A and maximum external quantum efficiency of 5.34% and 5.63%, respectively.

  18. Solution-processed low dimensional nanomaterials with self-assembled polymers for flexible photo-electronic devices (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Park, Cheolmin

    2015-09-01

    Self assembly driven by complicated but systematic hierarchical interactions offers a qualified alternative for fabricating functional micron or nanometer scale pattern structures that have been potentially useful for various organic and nanotechnological devices. Self assembled nanostructures generated from synthetic polymer systems such as controlled polymer blends, semi-crystalline polymers and block copolymers have gained a great attention not only because of the variety of nanostructures they can evolve but also because of the controllability of these structures by external stimuli. In this presentation, various novel photo-electronic materials and devices are introduced based on the solution-processed low dimensional nanomaterials such as networked carbon nanotubes (CNTs), reduced graphene oxides (rGOs) and 2 dimensional transition metal dichalcogenides (TMDs) with self assembled polymers including field effect transistor, electroluminescent device, non-volatile memory and photodetector. For instance, a nanocomposite of networked CNTs and a fluorescent polymer turned out an efficient field induced electroluminescent layer under alternating current (AC) as a potential candidate for next generation displays and lightings. Furthermore, scalable and simple strategies employed for fabricating rGO as well as TMD nanohybrid films allowed for high performance and mechanically flexible non-volatile resistive polymer memory devices and broad band photo-detectors, respectively.

  19. Highly luminescent yellow and yellowish-green light-emitting electrochemical cells based on cationic iridium complexes with phenanthroline based ancillary ligands

    NASA Astrophysics Data System (ADS)

    Sunesh, Chozhidakath Damodharan; Chandran, Midhun; Mathai, George; Choe, Youngson

    2013-01-01

    Highly luminescent light-emitting electrochemical cells (LECs) based on cationic iridium complexes [Ir(ppz)2(dpphen)]PF6 (1) and [Ir(ppz)2(tmphen)]PF6 (2) (ppz is 1-phenylpyrazole, dpphen is 4,7-diphenyl-1,10-phenanthroline and tmphen is 3,4,7,8-tetramethyl-1,10-phenanthroline) with phenanthroline based ancillary ligands were fabricated using air stable electrodes and their electroluminescent properties were investigated. LECs based on complex 1 emitted yellow electroluminescence (λmax 574 nm) with Commission Internationale de L'Eclairage (CIE) coordinates of (0.49, 0.50) while the complex 2 gave yellowish-green electroluminescence (λmax 537 nm) with CIE coordinates of (0.35, 0.58). The work done here reveals that the alkyl substituted phenanthroline ancillary ligand, tmphen shifts the light emission to the shorter wavelength region than the phenyl substituted dpphen ligand, resulting in the color tuning of the light-emitting devices. Density functional theory (DFT) calculations were performed to gain insight into the molecular surfaces of cationic iridium complexes and their electrochemical behaviors. Single layer LECs based on these complexes exhibited a high luminescence of 5199 and 4751 cd/m2 for complexes 1 and 2 respectively. The ionic liquid, 1-ethyl-3-methylimidazolium hexafluorophosphate (EMIMPF6) was added to the light emitting layer and hence higher luminances were obtained than the pristine device.

  20. Mg2(Si,Sn)-based thermoelectric materials and devices

    NASA Astrophysics Data System (ADS)

    Gao, Peng

    Thermoelectric effects are phenomena found in materials that can achieve direct conversion between heat flow and electricity. One important application of thermoelectric effects is thermoelectric generators, which can generate electricity when a temperature gradient is applied. Thermoelectric generators make use of various sources of heat and it is considered a promising solution for waste heat recovery. The conversion efficiency of thermoelectric generators depends on the materials used in the devices. Significant improvement in the performance of thermoelectric materials has been made in the past few decades. However, most of the good thermoelectric materials being investigated have limitations, such as the high materials cost, high materials density and toxicity of the constituent elements. The Mg2(Si,Sn)-based materials studied in this work are promising candidates for thermoelectric generators in the mid-temperature range and have drawn increasing research interest in recent years because these materials are high performance thermoelectrics that are low cost, low-density and non-toxic. In this work, systematic studies were performed on the Mg2(Si,Sn) thermoelectric materials. Thermal phase stability was studied for different compositions of Mg2Si1-xSnx and Mg2Si0.4Sn 0.6 was used as base material for further optimization. Both n-type and p-type samples were obtained by doping the materials with different elements. Peak ZT ˜ 1.5 for the n-type and ZT ˜ 0.7 for the p-type materials were obtained, both of which are among the best reported results so far. Experimental work was also done to study the techniques to develop the Mg2Si 0.4Sn0.6 materials into working devices. Different electrode materials were tested in bonding experiment for this compound, and copper was found to be the best electrode material for Mg2Si 0.4Sn0.6. Preliminary work was done to demonstrate the possibility of fabricating a Mg2Si0.4Sn0.6-based thermoelectric generator and the result is

  1. Optimal alignment of mirror based pentaprisms for scanning deflectometric devices

    SciTech Connect

    Barber, Samuel K.; Geckeler, Ralf D.; Yashchuk, Valeriy V.; Gubarev, Mikhail V.; Buchheim, Jana; Siewert, Frank; Zeschke, Thomas

    2011-03-04

    In the recent work [Proc. of SPIE 7801, 7801-2/1-12 (2010), Opt. Eng. 50(5) (2011), in press], we have reported on improvement of the Developmental Long Trace Profiler (DLTP), a slope measuring profiler available at the Advanced Light Source Optical Metrology Laboratory, achieved by replacing the bulk pentaprism with a mirror based pentaprism (MBPP). An original experimental procedure for optimal mutual alignment of the MBPP mirrors has been suggested and verified with numerical ray tracing simulations. It has been experimentally shown that the optimally aligned MBPP allows the elimination of systematic errors introduced by inhomogeneity of the optical material and fabrication imperfections of the bulk pentaprism. In the present article, we provide the analytical derivation and verification of easily executed optimal alignment algorithms for two different designs of mirror based pentaprisms. We also provide an analytical description for the mechanism for reduction of the systematic errors introduced by a typical high quality bulk pentaprism. It is also shown that residual misalignments of an MBPP introduce entirely negligible systematic errors in surface slope measurements with scanning deflectometric devices.

  2. Emission intensity in the visible and IR spectral ranges from Si-based structures formed by direct bonding with simultaneous doping with erbium (Er) and europium (Eu)

    SciTech Connect

    Mezdrogina, M. M. Kostina, L. S.; Beliakova, E. I.; Kuzmin, R. V.

    2013-09-15

    The photo- and electroluminescence spectra of silicon-based structures formed by direct bonding with simultaneous doping with rare-earth metals are studied. It is shown that emission in the visible and IR spectral ranges can be obtained from n-Si:Er/p-Si and n-Si:Eu/p-Si structures fabricated by the method suggested in the study. The results obtained make this method promising for the fabrication of optoelectronic devices.

  3. Organic light-emitting devices using spin-dependent processes

    DOEpatents

    Vardeny, Z. Valy; Wohlgenannt, Markus

    2010-03-23

    The maximum luminous efficiency of organic light-emitting materials is increased through spin-dependent processing. The technique is applicable to all electro-luminescent processes in which light is produced by singlet exciton decay, and all devices which use such effects, including LEDs, super-radiant devices, amplified stimulated emission devices, lasers, other optical microcavity devices, electrically pumped optical amplifiers, and phosphorescence (Ph) based light emitting devices. In preferred embodiments, the emissive material is doped with an impurity, or otherwise modified, to increase the spin-lattice relaxation rate (i.e., decrease the spin-lattice time), and hence raise the efficiency of the device. The material may be a polymer, oligomer, small molecule, single crystal, molecular crystal, or fullerene. The impurity is preferably a magnetic or paramagnetic substance. The invention is applicable to IR, UV, and other electromagnetic radiation generation and is thus not limited to the visible region of the spectrum. The methods of the invention may also be combined with other techniques used to improve device performance.

  4. Photonic variable delay devices based on optical birefringence

    NASA Technical Reports Server (NTRS)

    Yao, X. Steve (Inventor)

    2005-01-01

    Optical variable delay devices for providing variable true time delay to multiple optical beams simultaneously. A ladder-structured variable delay device comprises multiple basic building blocks stacked on top of each other resembling a ladder. Each basic building block has two polarization beamsplitters and a polarization rotator array arranged to form a trihedron; Controlling an array element of the polarization rotator array causes a beam passing through the array element either going up to a basic building block above it or reflect back towards a block below it. The beams going higher on the ladder experience longer optical path delay. An index-switched optical variable delay device comprises of many birefringent crystal segments connected with one another, with a polarization rotator array sandwiched between any two adjacent crystal segments. An array element in the polarization rotator array controls the polarization state of a beam passing through the element, causing the beam experience different refractive indices or path delays in the following crystal segment. By independently control each element in each polarization rotator array, variable optical path delays of each beam can be achieved. Finally, an index-switched variable delay device and a ladder-structured variable device are cascaded to form a new device which combines the advantages of the two individual devices. This programmable optic device has the properties of high packing density, low loss, easy fabrication, and virtually infinite bandwidth. The device is inherently two dimensional and has a packing density exceeding 25 lines/cm2. The delay resolution of the device is on the order of a femtosecond (one micron in space) and the total delay exceeds 10 nanosecond. In addition, the delay is reversible so that the same delay device can be used for both antenna transmitting and receiving.

  5. Single-photon electroluminescence for on-chip quantum networks

    NASA Astrophysics Data System (ADS)

    Bentham, C.; Hallett, D.; Prtljaga, N.; Royall, B.; Vaitiekus, D.; Coles, R. J.; Clarke, E.; Fox, A. M.; Skolnick, M. S.; Itskevich, I. E.; Wilson, L. R.

    2016-10-01

    An electrically driven single-photon source has been monolithically integrated with nano-photonic circuitry. Electroluminescent emission from a single InAs/GaAs quantum dot (QD) is channelled through a suspended nanobeam waveguide. The emission line has a linewidth of below 6 μeV, demonstrating the ability to have a high coherence, electrically driven, waveguide coupled QD source. The single-photon nature of the emission is verified by g ( 2 ) ( τ ) correlation measurements. Moreover, in a cross-correlation experiment, with emission collected from the two ends of the waveguide, the emission and propagation of single photons from the same QD is confirmed. This work provides the basis for the development of electrically driven on-chip single-photon sources, which can be readily coupled to waveguide filters, directional couplers, phase shifters, and other elements of quantum photonic networks.

  6. Contactless Electroluminescence Imaging for Cell and Module Characterization

    SciTech Connect

    Johnston, Steve

    2015-06-14

    Module performance can be characterized by imaging using baseline and periodic images to track defects and degradation. Both thermal images, which can be acquired during sunny operating conditions, and photoluminescence images, which could be acquired at night, can be collected without electrical connection. Electroluminescence (EL) images, which are useful to detect many types of defects such as cracks, interconnect and solder faults, and resistances, have typically required electrical connection to drive current in the cells and modules. Here, a contactless EL imaging technique is proposed, which provides an EL image without the need for electrical connection to drive current through the module. Such EL imaging has the capability to be collected at night without disruption to daytime power generation.

  7. Highly stretchable electroluminescent skin for optical signaling and tactile sensing.

    PubMed

    Larson, C; Peele, B; Li, S; Robinson, S; Totaro, M; Beccai, L; Mazzolai, B; Shepherd, R

    2016-03-04

    Cephalopods such as octopuses have a combination of a stretchable skin and color-tuning organs to control both posture and color for visual communication and disguise. We present an electroluminescent material that is capable of large uniaxial stretching and surface area changes while actively emitting light. Layers of transparent hydrogel electrodes sandwich a ZnS phosphor-doped dielectric elastomer layer, creating thin rubber sheets that change illuminance and capacitance under deformation. Arrays of individually controllable pixels in thin rubber sheets were fabricated using replica molding and were subjected to stretching, folding, and rolling to demonstrate their use as stretchable displays. These sheets were then integrated into the skin of a soft robot, providing it with dynamic coloration and sensory feedback from external and internal stimuli.

  8. Flat-panel, full-color, electroluminescent display

    NASA Astrophysics Data System (ADS)

    Robertson, James B.

    1987-08-01

    This invention relates to a flat-panel, electroluminescent display capable of achieving full color and is particularly useful in achieving a bright display with high resolution. The invention uses red, green and blue phosphors in two layers separated by layers of insulating material and layers of electrodes that are used to excite the phosphors. In operation, the display is addressed by supplying sufficient voltage between selected electrodes. This places an electric field across the phosphor at each picture element located between the overlap of the selected electrodes causing the phosphor to emit light at this location. These and other matrix-addressed displays can be addressed line-at-a-time (row or column) fashion in rapid enough sequence to display information at standard TV frame rates.

  9. Ex post manipulation of barriers in InGaAs tunnel injection devices

    SciTech Connect

    Talalaev, Vadim G.; Cirlin, George E.; Novikov, Boris V.; Fuhrmann, Bodo; Werner, Peter; Tomm, Jens W.

    2015-01-05

    Ex post manipulation of ∼1.1 μm emitting InGaAs/GaAs-based quantum dot–quantum well tunnel injection light emitting devices is demonstrated experimentally. The devices were operated at elevated forward currents until irreversible alterations were observed. As a result, changes in the steady-state optical spectra (electroluminescence, photoluminescence, and photocurrent), in carrier kinetics, in transport properties, and real structure are found. Except for degradation effects, e.g., of larger quantum dots, also restoration/annealing effects such as increased tunnel barriers are observed. The results furnish evidence for a generic degradation mode of nanostructures. We qualitatively interpret the mechanisms involved on both the nanoscopic and the device scales.

  10. Charge transfer devices. Citations from the NTIS data base

    NASA Astrophysics Data System (ADS)

    Reed, W. E.

    1980-04-01

    The technology, design, fabrication, and applications of charge transfer devices are presented in the cited research reports. Applications include imaging, signal processing, detectors, filters, amplifiers, and memory devices. This updated bibliography contains 107 abstracts, all of which are new entries to the previous edition.

  11. Methods of use for sensor based fluid detection devices

    NASA Technical Reports Server (NTRS)

    Lewis, Nathan S. (Inventor)

    2001-01-01

    Methods of use and devices for detecting analyte in fluid. A system for detecting an analyte in a fluid is described comprising a substrate having a sensor comprising a first organic material and a second organic material where the sensor has a response to permeation by an analyte. A detector is operatively associated with the sensor. Further, a fluid delivery appliance is operatively associated with the sensor. The sensor device has information storage and processing equipment, which is operably connected with the device. This device compares a response from the detector with a stored ideal response to detect the presence of analyte. An integrated system for detecting an analyte in a fluid is also described where the sensing device, detector, information storage and processing device, and fluid delivery device are incorporated in a substrate. Methods for use for the above system are also described where the first organic material and a second organic material are sensed and the analyte is detected with a detector operatively associated with the sensor. The method provides for a device, which delivers fluid to the sensor and measures the response of the sensor with the detector. Further, the response is compared to a stored ideal response for the analyte to determine the presence of the analyte. In different embodiments, the fluid measured may be a gaseous fluid, a liquid, or a fluid extracted from a solid. Methods of fluid delivery for each embodiment are accordingly provided.

  12. Structural, morphological and electroluminescence studies of Zno:Co nanophosphor

    NASA Astrophysics Data System (ADS)

    Singh, Anju; Vishwakarma, H. L.

    2016-09-01

    The nanoparticles of zinc oxide (ZnO) doped with various concentrations of cobalt (Co) were synthesized by chemical precipitation method in the presence of capping agent polyvinylpyrrolidone (PVP). The effect of doping concentration on structural and morphological properties has been studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). Cell volume, bond length, texture coefficient, lattice constants and dislocation density are also studied. Here, we also compared the interplaner spacing and relative peak intensities from their standard values with different angles. Crystallite sizes have been calculated by Debye-Scherrer's formula whose values are decreasing with increase in cobalt content up to 3 %. It has been seen that the growth orientation of the prepared ZnO nanorods was (101). The XRD analysis also ensures that ZnO has a hexagonal (wurtzite) crystal structure. The electroluminescence (EL) cells were prepared by placing pure and cobalt-doped ZnO nanoparticles between ITO-coated conducting glass plate and aluminium foil. Alternating voltage of various frequencies was applied, and EL brightness at different voltages was measured and corresponding current was also recorded. The voltage dependence of electroluminescence (EL) brightness of the ZnO:Co shows exponential increase. The linear voltage-current characteristic indicates ohmic nature. The EL brightness at a particular voltage is found to increase by increasing Co doping, but for higher percentage of Co the EL brightness is reduced. It is also seen that Co does not influence the threshold voltage. The brightness is also affected by increasing the frequency of AC signal.

  13. Photoluminescence and electroluminescence from Ge/strained GeSn/Ge quantum wells

    NASA Astrophysics Data System (ADS)

    Lin, Chung-Yi; Huang, Chih-Hsiung; Huang, Shih-Hsien; Chang, Chih-Chiang; Liu, C. W.; Huang, Yi-Chiau; Chung, Hua; Chang, Chorng-Ping

    2016-08-01

    Ge/strained GeSn/Ge quantum wells are grown on a 300 mm Si substrate by chemical vapor deposition. The direct bandgap emission from strained GeSn is observed in the photoluminescence spectra and is enhanced by Al2O3/SiO2 passivation due to the field effect. The electroluminescence of the direct bandgap emission of strained GeSn is also observed from the Ni/Al2O3/GeSn metal-insulator-semiconductor tunneling diodes. Electroluminescence is a good indicator of GeSn material quality, since defects in GeSn layers degrade the electroluminescence intensity significantly. At the accumulation bias, the holes in the Ni gate electrode tunnel to the strained n-type GeSn layer through the ultrathin Al2O3 and recombine radiatively with electrons. The emission wavelength of photoluminescence and electroluminescence can be tuned by the Sn content.

  14. I. Electroluminescence from Hydrogen Uranyl Phosphate. I. Indium-Substituted Bismuth Copper Oxide Superconductors

    NASA Astrophysics Data System (ADS)

    Dieckmann, Gunnar Rudolph

    1990-01-01

    Chapter 1. A review of the general aspects of solid electrolytes is presented along with a summary of the electrical and optical properties of hydrogen uranyl phosphate (HUO_2PO_4 bullet4H_2O, HUP). A review of impedance spectroscopy, as it relates to the determination of ionic conductivities and dielectric constants of solid electrolytes is presented. The final section covers some aspects of gas plasma display devices. Chapter 2. Electroluminescence (EL) cells have been constructed with the ionically conducting solid HUP as the emissive medium. With ac excitation, both uranyl emission and molecular nitrogen plasma emission are observed, with the latter appearing to excite the former. Similar results were obtained with fully-substituted sodium (NaUP), magnesium (Mg_{0.5}UP), and pyridinium (pyHUP) derivatives of HUP. For all of these solids, the dependence of the EL intensity on sample thickness, ac frequency, and applied voltage has been determined. Impedance measurements permitted acquisition of dielectric constants and ionic conductivities for these solids, both of which decrease in the order HUP > NaUP > Mg_{0.5}UP > pyHUP. A model describing the dependence of EL intensity on cell parameters is presented. Chapter 3. The copper oxide superconductors can be structurally classified into five major families, represented by the compositions, (La,Sr)_2CuO _4, YBa_2Cu_3O_7, Pb_2Sr_2(Y,Ca)Cu_3O_8, (TIO)_{m}Ca_{n-1}Ba_2Cu _{n}O_{2n+2}, and Bi_2Sr_2(Ln_{1-x}Ce _{x})_2Cu_2O_{10+y }. All families are linked by a CuO _2 layer, which is crucial for superconductivity. The structural and chemical aspects of each family is covered with emphasis on the bismuth and thallium systems. The effects of substitution and oxygen annealing are also briefly considered. Chapter 4. The attempted substitution of indium into the rm Bi_2(Ca,Sr)_2CuO _6 and Bi_2(Ca,Sr) _3Cu_2O _8 systems is reported. Previously unreported side products, (Ca,Sr)In_2O _4 and Bi-Ca-Sr-O, viz., produced in the

  15. The preparation of ZnS:Mn electroluminescent layers by MOCVD using new manganese sources

    NASA Astrophysics Data System (ADS)

    Migita, M.; Kanehisa, O.; Shiiki, M.; Yamamoto, H.

    1988-12-01

    In the preparation of ZnS:Mn polycrystalline films by MOCVD, CPM [(C 5H 5) 2Mn: di-π-cyclopentadienyl manganese] and BCPM [(CH 3C 5H 4) 2Mn: bismethylcyclopentadienyl manganese] are employed as new doping sources, and are compared with previously reported TCM [(CH 3C 5H 4)Mn(CO) 3: tricarbonyl methylcyclopentadienyl manganese]. In contrast to TCM, which is only partially decomposed even at 400 ˜ 500°C, CPM and BCPM are completely decomposed around the optimum growth temperature of ZnS, i.e. 280-350°C. When thermally decomposed, TCM produces a by-product containing Mn and carbonyl, which does not contribute to the luminescence, but CPM and BCPM do not. By these advantages, the double-insulator type electroluminescent (EL) devices prepared with CPM or BCPM show higher luminance than those prepared with TCM. A 500 nm thick ZnS:Mn layer by CPM gives the maximum efficiency ( ηmax) of 4.8 lm/W and a saturated luminance ( Lsat) of 4300 cd/m 2 at 1 kHz sine wave excitation. By BCPM, Lsat of 3150 cd/m 2 was obtained. Meanwhile, the devices prepared with TCM in this investigation show Lsat to be less than 1000 cd/m 2 and a low efficiency of less than 1 lm/W. By the combination with red filters, ZnS:Mn by MOCVD with CPM or BCPM can also provide efficient red EL. When a glass filter (the cut-off wavelength is 590 nm) is used, the EL device prepared with CPM gives Lsat=1420 cd/m 2 and ηmax=1.6 lm/W (the color coordinates, x=0.626 and y=0.373) at 1 kHz sine wave excitation.

  16. Strong visible electroluminescence from silicon nanocrystals embedded in a silicon carbide film

    SciTech Connect

    Huh, Chul Kim, Tae-Youb; Ahn, Chang-Geun; Kim, Bong Kyu

    2015-05-25

    We report the strong visible light emission from silicon (Si) nanocrystals (NCs) embedded in a Si carbide (SiC) film. Compared to Si NC light-emitting diode (LED) by employing the Si nitride (SiN{sub x}) film as a surrounding matrix, the turn-on voltage of the Si NC LED with the SiC film was significantly decreased by 4 V. This was attributed to a smaller barrier height for injecting the electrons into the Si NCs due to a smaller band gap of SiC film than a SiN{sub x} film. The electroluminescence spectra increases with increasing forward voltage, indicating that the electrons are efficiently injected into the Si NCs in the SiC film. The light output power shows a linear increase with increasing forward voltage. The light emission originated from the Si NCs in a SiC film was quite uniform. The power efficiency of the Si NC LED with the SiC film was 1.56 times larger than that of the Si NC LED with the SiN{sub x} film. The Si NCs in a SiC film show unique advantages and are a promising candidate for application in optical devices.

  17. Blue and green electroluminescence from CdSe nanocrystal quantum-dot-quantum-wells

    SciTech Connect

    Lu, Y. F.; Cao, X. A.

    2014-11-17

    CdS/CdSe/ZnS quantum dot quantum well (QDQW) nanocrystals were synthesized using the successive ion layer adsorption and reaction technique, and their optical properties were tuned by bandgap and strain engineering. 3-monolayer (ML) CdSe QWs emitted blue photoluminescence at 467 nm with a spectral full-width-at-half-maximum of ∼30 nm. With a 3 ML ZnS cladding layer, which also acts as a passivating and strain-compensating layer, the QDQWs acquired a ∼35% quantum yield of the QW emission. Blue and green electroluminescence (EL) was obtained from QDQW light-emitting devices with 3–4.5 ML CdSe QWs. It was found that as the peak blueshifted, the overall EL was increasingly dominated by defect state emission due to poor hole injection into the QDQWs. The weak EL was also attributed to strong field-induced charge separation resulting from the unique QDQW geometry, weakening the oscillator strength of optical transitions.

  18. Ultrabroad Photoluminescence and Electroluminescence at New Wavelengths from Doped Organometal Halide Perovskites.

    PubMed

    Zhou, Yang; Yong, Zi-Jun; Zhang, Kai-Cheng; Liu, Bo-Mei; Wang, Zhao-Wei; Hou, Jing-Shan; Fang, Yong-Zheng; Zhou, Yi; Sun, Hong-Tao; Song, Bo

    2016-07-21

    Doping of semiconductors by introducing foreign atoms enables their widespread applications in microelectronics and optoelectronics. We show that this strategy can be applied to direct bandgap lead-halide perovskites, leading to the realization of ultrawide photoluminescence (PL) at new wavelengths enabled by doping bismuth (Bi) into lead-halide perovskites. Structural and photophysical characterization reveals that the PL stems from one class of Bi doping-induced optically active center, which is attributed to distorted [PbI6] units coupled with spatially localized bipolarons. Additionally, we find that compositional engineering of these semiconductors can be employed as an additional way to rationally tune the PL properties of doped perovskites. Finally, we accomplished the electroluminescence at cryogenic temperatures by using this system as an emissive layer, marking the first electrically driven devices using Bi-doped photonic materials. Our results suggest that low-cost, earth-abundant, solution-processable Bi-doped perovskite semiconductors could be promising candidate materials for developing optical sources operating at new wavelengths.

  19. Spectrally resolved hyperfine interactions between polaron and nuclear spins in organic light emitting diodes: Magneto-electroluminescence studies

    SciTech Connect

    Crooker, S. A.; Kelley, M. R.; Martinez, N. J. D.; Nie, W.; Mohite, A.; Nayyar, I. H.; Tretiak, S.; Smith, D. L.; Liu, F.; Ruden, P. P.

    2014-10-13

    We use spectrally resolved magneto-electroluminescence (EL) measurements to study the energy dependence of hyperfine interactions between polaron and nuclear spins in organic light-emitting diodes. Using layered devices that generate bright exciplex emission, we show that the increase in EL emission intensity I due to small applied magnetic fields of order 100 mT is markedly larger at the high-energy blue end of the EL spectrum (ΔI/I ∼ 11%) than at the low-energy red end (∼4%). Concurrently, the widths of the magneto-EL curves increase monotonically from blue to red, revealing an increasing hyperfine coupling between polarons and nuclei and directly providing insight into the energy-dependent spatial extent and localization of polarons.

  20. Electroluminescence of hot electrons in AlGaN/GaN high-electron-mobility transistors under radio frequency operation

    SciTech Connect

    Brazzini, Tommaso Sun, Huarui; Uren, Michael J.; Kuball, Martin; Casbon, Michael A.; Lees, Jonathan; Tasker, Paul J.; Jung, Helmut; Blanck, Hervé

    2015-05-25

    Hot electrons in AlGaN/GaN high electron mobility transistors are studied during radio frequency (RF) and DC operation by means of electroluminescence (EL) microscopy and spectroscopy. The measured EL intensity is decreased under RF operation compared to DC at the same average current, indicating a lower hot electron density. This is explained by averaging the DC EL intensity over the measured load line used in RF measurements, giving reasonable agreement. In addition, the hot electron temperature is lower by up to 15% under RF compared to DC, again at least partially explainable by the weighted averaging along the specific load line. However, peak electron temperature under RF occurs at high V{sub DS} and low I{sub DS} where EL is insignificant suggesting that any wear-out differences between RF and DC stress of the devices will depend on the balance between hot-carrier and field driven degradation mechanisms.

  1. Remarkable improvement in electroluminescence benefited from appropriate electron injection and transporting in ultraviolet organic light-emitting diode

    NASA Astrophysics Data System (ADS)

    You, Fengjiao; Mo, Bingjie; Liu, Liming; Wang, Honghang; Bin Wei; Xu, Jiwen; Zhang, Xiaowen

    2016-08-01

    Suitable thickness of LiF and 4,7-diphenyl-1, 10-phenanthroline with slightly weakened electron injection and transporting is proposed to match the intractable hole injection capacity in ultraviolet organic light-emitting diode (UV OLED). By using this strategy, the device performance is remarkably improved. With 4,4‧-bis(carbazol-9-yl)biphenyl (CBP) and 3-(4-biphenyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ) as emitters, the UV OLED shows maximum radiance of 5.8 mW/cm2 and external quantum efficiency of 2.1% with emission peak of ~380 nm predominantly from TAZ and noticeable shoulder emission of ~410 nm from CBP. The retarded electron injection and transporting contribute to optimizing hole-electron recombination zone and balance within the emitting layers, which accounts for the improved electroluminescent intensity. The detailed mechanism is further clarified with impedance spectroscopy.

  2. Blue--green to near-IR switching electroluminescence from Si-rich silicon oxide/nitride bilayer structures

    NASA Astrophysics Data System (ADS)

    Berencén, Y.; Jambois, O.; Ramírez, J. M.; Rebled, J. M.; Estradé, S.; Peiró, F.; Domínguez, C.; Rodríguez, J. A.; Garrido, B.

    2011-07-01

    Blue--green to near-IR switching electroluminescence (EL) has been achieved in a metal-oxide-semiconductor light emitting device, where the dielectric has been replaced by a Si-rich silicon oxide/nitride bilayer structure. To form Si nanostructures, the layers were implanted with Si ions at high energy, resulting in a Si excess of 19%, and subsequently annealed at 1000°C. Transmission electron microscopy and EL studies allowed ascribing the blue--green emission to the Si nitride related defects and the near-IR band with the emission of the Si-nanoclusters embedded into the SiO2 layer. Charge transport analysis is reported and allows for identifying the origin of this two-wavelength switching effect.

  3. Circularly polarized electroluminescence of light-emitting InGaAs/GaAs (III, Mn)V diodes on the basis of structures with a tunneling barrier

    SciTech Connect

    Malysheva, E. I. Dorokhin, M. V.; Ved’, M. V.; Kudrin, A. V.; Zdoroveishchev, A. V.

    2015-11-15

    The comparative investigation of circularly polarized electroluminescence in Zener diodes based on InGaAs/n-GaAs/n{sup +}-GaAs/GaMnAs and InGaAs/n-GaAs/n{sup +}-GaAs/GaMnSb is carried out. It is established that the circularly polarized electroluminescence is associated with the spin injection of electrons from a ferromagnetic semiconductor layer. The luminescence parameters are determined by the properties of these layers. It is shown that the ferromagnetic properties of the GaMnSb layer allow us to obtain circularly polarized emission at room temperature from InGaAs/n-GaAs/n{sup +}-GaAs/GaMnSb heterostructures.

  4. Screen printed paper-based diagnostic devices with polymeric inks.

    PubMed

    Sun, Ju-Yen; Cheng, Chao-Min; Liao, Ying-Chih

    2015-01-01

    A simple and low-cost fabrication method for paper-based diagnostic devices (PBDDs) is described in this study. Street-available polymer solutions were screen printed onto filter papers to create hydrophobic patterns for fluidic channels. In order to obtain fully functional hydrophobic patterns for fluids, the original polymer solutions were diluted with butyl acetate to yield a suitable viscosity range between 30-200 cP for complete patterning on paper. Typical pH and glucose tests with color indicators were performed on the screen printed PBDDs. Images of the PBDDs were analyzed by computers to obtain calibration curves for pH between 2 and 12 and glucose concentration ranging from 10-1000 mmol dm(-3). Detection of formaldehyde in acetone was also carried out to show the possibility of using this PBBD for analytical detection with organic solvents. An exemplar PBDD with simultaneous pH and glucose detection was also used to demonstrate the feasibility of applying this technique for realistic diagnostic applications.

  5. Carbon material based microelectromechanical system (MEMS): Fabrication and devices

    NASA Astrophysics Data System (ADS)

    Xu, Wenjun

    This PhD dissertation presents the exploration and development of two carbon materials, carbon nanotubes (CNTs) and carbon fiber (CF), as either key functional components or unconventional substrates for a variety of MEMS applications. Their performance in three different types of MEMS devices, namely, strain/stress sensors, vibration-powered generators and fiber solar cells, were evaluated and the working mechanisms of these two non-traditional materials in these systems were discussed. The work may potentially enable the development of new types of carbon-MEMS devices. Carbon nanotubes were selected from the carbon family due to several advantageous characteristics that this nanomaterial offers. They carry extremely high mechanical strength (Ey=1TPa), superior electrical properties (current density of 4x109 A/cm2), exceptional piezoresistivity (G=2900), and unique spatial format (high aspect ratio hollow nanocylinder), among other properties. If properly utilized, all these merits can give rise to a variety of new types of carbon nanotube based micro- and nanoelectronics that can greatly fulfill the need for the next generation of faster, smaller and better devices. However, before these functions can be fully realized, one substantial issue to cope with is how to implement CNTs into these systems in an effective and controllable fashion. Challenges associated with CNTs integration include very poor dispersibility in solvents, lack of melting/sublimation point, and unfavorable rheology with regard to mixing and processing highly viscous, CNT-loaded polymer solutions. These issues hinder the practical progress of CNTs both in a lab scale and in the industrial level. To this end, a MEMS-assisted electrophoretic deposition technique was developed, aiming to achieve controlled integration of CNT into both conventional and flexible microsystems at room temperature with a relatively high throughput. MEMS technology has demonstrated strong capability in developing

  6. Electron-doping of graphene-based devices by hydrazine

    SciTech Connect

    Feng, Tingting; Xie, Dan; Wang, Dongxia; Wen, Lang; Wu, Mengqiang

    2014-12-14

    A facile and effective technique to tune the electronic properties of graphene is essential to facilitate the flexibility of graphene-based device performances. Here, the use of hydrazine as a solution-processable and effective n-type dopant for graphene is described. By dropping hydrazine solutions at different concentrations on a graphene surface, the Dirac point of graphene can be remarkably tuned. The transport behavior of graphene can be changed from p-type to n-type accordingly, demonstrating the controllable and adjustable doping effect of the hydrazine solutions. Accompanying the Dirac point shift is an enhanced hysteretic behavior of the graphene conductance, indicating an increasing trap state density induced by the hydrazine adsorbates. The electron-doping of graphene by the hydrazine solutions can be additionally confirmed with graphene/p-type silicon heterojunctions. The decrease of the junction current after the hydrazine treatment demonstrates an increase of the junction barrier between graphene and silicon, which is essentially due to the electron-doping of graphene and the resultant upshift of the Fermi level. Finally, partially doped graphene is realized and its electrical property is studied to demonstrate the potential of the hydrazine solutions to selectively electron-doping graphene for future electronic applications.

  7. Fiber Bragg grating sensor-based communication assistance device

    NASA Astrophysics Data System (ADS)

    Padma, Srivani; Umesh, Sharath; Pant, Shweta; Srinivas, Talabattula; Asokan, Sundarrajan

    2016-08-01

    Improvements in emergency medicine in the form of efficient life supporting systems and intensive care have increased the survival rate in critically injured patients; however, in some cases, severe brain and spinal cord injuries can result in a locked-in syndrome or other forms of paralysis, and communication with these patients may become restricted or impossible. The present study proposes a noninvasive, real-time communication assistive methodology for those with restricted communication ability, employing a fiber Bragg grating (FBG) sensor. The communication assistive methodology comprises a breath pattern analyzer using an FBG sensor, which acquires the exhalation force that is converted into strain variations on a cantilever. The FBG breath pattern analyzer along with specific breath patterns, which are programmed to give specific audio output commands, constitutes the proposed fiber Bragg grating sensor-based communication assistive device. The basic communication can be carried out by instructing the patients with restricted communication ability to perform the specific breath patterns. The present approach is intended to be an alternative to the common approach of brain-computer interface in which an instrument is utilized for learning of brain responses.

  8. Integrated electronic circuits and devices based on interactive paper

    NASA Astrophysics Data System (ADS)

    Garnier, Francis

    1997-08-01

    Various organic conjugated materials, e.g. conjugated polymers and short conjugated oligomers, have been up to now proposed as active semiconducting layers in organic-base devices, such as thin film transistors, TFTs, or light emitting diodes. The mode of operation of TFTs shows that a high carrier mobility together with a low conductivity are required for their figure of merit. Experimental results from literature indicate that, whereas conjugated polymers exhibit a low carrier mobility, of the order of 10-4 to 10-5 cm2V-1s-1, conjugated oligomers appear much more promising. It is thus shown that carrier mobility is directly related to the long range structural order in conjugated oligomer films, i.e. to the decrease of grain boundaries, leading to values of the order of 10-1 cm-2V-1s-1, comparable to that of amorphous hydrogenated silicon. Conjugated oligomers are well defined materials, offering various physical and chemical ways for control of the structural organization of thin films made from them. Besides, conductivity in thin films of conjugated oligomers is mainly determined by the purity of the materials, allowing values lower than 10-7 Scm-1, with a high on/off ratio. The low melting and evaporation temperatures of conjugated oligomers, together with the solubility of some of these materials, allows the construction of TFTs by the use of room temperature techniques, following a process compatible with paper technology.

  9. Magnetophoretic-based microfluidic device for DNA isolation.

    PubMed

    Hale, C; Darabi, J

    2014-07-01

    This paper presents a continuous flow microfluidic device for the separation of DNA from blood using magnetophoresis for biological applications and analysis. This microfluidic bio-separation device has several benefits, including decreased sample handling, smaller sample and reagent volumes, faster isolation time, and decreased cost to perform DNA isolation. One of the key features of this device is the use of short-range magnetic field gradients, generated by a micro-patterned nickel array on the bottom surface of the separation channel. In addition, the device utilizes an array of oppositely oriented, external permanent magnets to produce strong long-range field gradients at the interfaces between magnets, further increasing the effectiveness of the device. A comprehensive simulation is performed using COMSOL Multiphysics to study the effect of various parameters on the magnetic flux within the separation channel. Additionally, a microfluidic device is designed, fabricated, and tested to isolate DNA from blood. The results show that the device has the capability of separating DNA from a blood sample with a purity of 1.8 or higher, a yield of up to 33 μg of polymerase chain reaction ready DNA per milliliter of blood, and a volumetric throughput of up to 50 ml/h.

  10. Controlled assembly and electronics in semiconductor nanocrystal-based devices

    NASA Astrophysics Data System (ADS)

    Drndic, Marija

    2006-03-01

    I will discuss the assembly of semiconductor nanocrystals (CdSe and PbSe) into electronic devices and the basic mechanisms of charge transport in nanocrystal arrays [1-4]. Spherical CdSe nanocrystals show robust memory effects that can be exploited for memory applications [1]. Nanocrystal memory can be erased electrically or optically and is rewritable. In PbSe nanocrystal arrays, as the interdot coupling is increased, the system evolves from an insulating regime dominated by Coulomb blockade to a semiconducting regime, where hopping conduction is the dominant transport mechanism [2]. Two-dimensional CdSe nanorod arrays show striking and anomalous transport properties, including strong and reproducible non-linearities and current oscillations with dc-voltage [4]. I will also discuss imaging of the charge transport in nanocrystal-based electronic devices. Nanocrystal arrays were investigated using electrostatic force microscopy (EFM) and transmission electron microscopy (TEM) [3]. Changes in lattice and transport properties upon annealing in vacuum were revealed. Local charge transport was directly imaged by EFM and correlated to nanopatterns observed with TEM. This work shows how charge transport in complex nanocrystal networks can be identified with nm resolution [3]. This work was supported by the ONR grant N000140410489, the NSF grants DMR-0449553 and MRSEC DMR00-79909, and the ACS PRF grant 41256-G10. References:1) Fischbein M. D. and Drndic M., ``CdSe nanocrystal quantum-dot memory,'' Applied Physics Letters, 86 (19), 193106, 2005.2) H. E. Romero and Drndic M., ``Coulomb blockade and hopping conduction in PbSe quantum dots,'' Physical Review Letters 95, 156801, 2005.3) Hu Z., Fischbein M. D. and Drndic M., ``Local charge transport in two-dimensional PbSe nanocrystal arrays studied by electrostatic force microscopy",'' Nano Letters 5 (7), 1463, 2005.4) Romero H.E., Calusine G. and Drndic M., ``Current oscillations, switching and hysteresis in CdSe nanorod

  11. Trace explosive sensor devices based on semiconductor nanomaterials

    NASA Astrophysics Data System (ADS)

    Wang, Danling

    This dissertation discusses an explosive sensing device based on semiconductor nanomaterials. Here, we mainly focus on two kinds of materials: titanium dioxide nanowires and silicon nanowires to detect explosive trace vapor. Herein, methods for the synthesis, fabrication, design of nanostructured sensing materials using low-cost hydrothermal process are present. In addition, the nanomaterials have been systemically tested on different explosive. The first part of dissertation is focused on the fabrication of TiO2(B) dominant nanowires and testing the response to explosives. It was found that the high porous TiO2(B) nanowires when mixed anatase TiO2, exhibit a very fast and highly sensitive response to nitro-containing explosives. The second part of dissertation has studied the basic sensing mechanism of TiO2(B) nanowire sensor to detect explosives. It shows the specific surface characteristics of TiO2 responsible for the nitro-containing explosives. This information is then used to propose a method using UV illumination to reduce the effect of water vapor on TiO2(B) nanowires. The third part discussed an explosive sensor based on silicon nanowires. We analyzed the mechanism of silicon nanowires to detect nitro-related explosive compounds. In order to further investigate the sensing mechanism of TiO2, the fourth part of dissertation studies the effect on sensor performance by using different crystal phases of TiO2, different microstructure of TiO2, surface modification of TiO2, and different kinds of nanostructured semiconductors such as ZnO nanowires, TiO2 coated ZnO nanowires, V2O5 nanowires, and CdS nanowires to detect explosives. It is found that only TiO2 related semiconductor shows good response to explosives.

  12. Light emitting ceramic device and method for fabricating the same

    DOEpatents

    Valentine, Paul; Edwards, Doreen D.; Walker Jr., William John; Slack, Lyle H.; Brown, Wayne Douglas; Osborne, Cathy; Norton, Michael; Begley, Richard

    2004-11-30

    A light-emitting ceramic based panel, hereafter termed "electroceramescent" panel, and alternative methods of fabrication for the same are claimed. The electroceramescent panel is formed on a substrate providing mechanical support as well as serving as the base electrode for the device. One or more semiconductive ceramic layers directly overlay the substrate, and electrical conductivity and ionic diffusion are controlled. Light emitting regions overlay the semiconductive ceramic layers, and said regions consist sequentially of a layer of a ceramic insulation layer and an electroluminescent layer, comprised of doped phosphors or the equivalent. One or more conductive top electrode layers having optically transmissive areas overlay the light emitting regions, and a multi-layered top barrier cover comprising one or more optically transmissive non-combustible insulation layers overlay said top electrode regions.

  13. Electronic and optoelectronic nano-devices based on carbon nanotubes.

    PubMed

    Scarselli, M; Castrucci, P; De Crescenzi, M

    2012-08-08

    The discovery and understanding of nanoscale phenomena and the assembly of nanostructures into different devices are among the most promising fields of material science research. In this scenario, carbon nanostructures have a special role since, in having only one chemical element, they allow physical properties to be calculated with high precision for comparison with experiment. Carbon nanostructures, and carbon nanotubes (CNTs) in particular, have such remarkable electronic and structural properties that they are used as active building blocks for a large variety of nanoscale devices. We review here the latest advances in research involving carbon nanotubes as active components in electronic and optoelectronic nano-devices. Opportunities for future research are also identified.

  14. Surface acoustic wave vapor sensors based on resonator devices

    NASA Astrophysics Data System (ADS)

    Grate, Jay W.; Klusty, Mark

    1991-05-01

    Surface acoustic wave (SAW) devices fabricated in the resonator configuration have been used as organic vapor sensors and compared with delay line devices more commonly used. The experimentally determined mass sensitivities of 200, 300, and 400 MHz resonators and 158 MHz delay lines coated with Langmuir-Blodgett films of poly(vinyl tetradecanal) are in excellent agreement with theoretical predictions. The response of LB- and spray-coated sensors to various organic vapors were determined, and scaling laws for mass sensitivities, vapor sensitivities, and detection limits are discussed. The 200 MHz resonators provide the lowest noise levels and detection limits of all the devices examined.

  15. Graphene Electronic Device Based Biosensors and Chemical Sensors

    NASA Astrophysics Data System (ADS)

    Jiang, Shan

    Two-dimensional layered materials, such as graphene and MoS2, are emerging as an exciting material system for a new generation of atomically thin electronic devices. With their ultrahigh surface to volume ratio and excellent electrical properties, 2D-layered materials hold the promise for the construction of a generation of chemical and biological sensors with unprecedented sensitivity. In my PhD thesis, I mainly focus on graphene based electronic biosensors and chemical sensors. In the first part of my thesis, I demonstrated the fabrication of graphene nanomesh (GNM), which is a graphene thin film with a periodic array of holes punctuated in it. The periodic holes introduce long periphery active edges that provide a high density of functional groups (e.g. carboxylic groups) to allow for covalent grafting of specific receptor molecules for chemical and biosensor applications. After covalently functionalizing the GNM with glucose oxidase, I managed to make a novel electronic sensor which can detect glucose as well as pH change. In the following part of my thesis I demonstrate the fabrication of graphene-hemin conjugate for nitric oxide detection. The non-covalent functionalization through pi-pi stacking interaction allows reliable immobilization of hemin molecules on graphene without damaging the graphene lattice to ensure the highly sensitive and specific detection of nitric oxide. The graphene-hemin nitric oxide sensor is capable of real-time monitoring of nitric oxide concentrations, which is of central importance for probing the diverse roles of nitric oxide in neurotransmission, cardiovascular systems, and immune responses. Our studies demonstrate that the graphene-hemin sensors can respond rapidly to nitric oxide in physiological environments with sub-nanomolar sensitivity. Furthermore, in vitro studies show that the graphene-hemin sensors can be used for the detection of nitric oxide released from macrophage cells and endothelial cells, demonstrating their

  16. Ultrathin flexible memory devices based on organic ferroelectric transistors

    NASA Astrophysics Data System (ADS)

    Sugano, Ryo; Hirai, Yoshinori; Tashiro, Tomoya; Sekine, Tomohito; Fukuda, Kenjiro; Kumaki, Daisuke; Domingues dos Santos, Fabrice; Miyabo, Atsushi; Tokito, Shizuo

    2016-10-01

    Here, we demonstrate ultrathin, flexible nonvolatile memory devices with excellent durability under compressive strain. Ferroelectric-gate field-effect transistors (FeFETs) employing organic semiconductor and polymer ferroelectric layers are fabricated on a 1-µm-thick plastic film substrate. The FeFETs are characterized by measuring their transfer characteristics, programming time, and data retention time. The data retention time is almost unchanged even when a 50% compressive strain is applied to the devices. To clarify the origin of the excellent durability of the devices against compressive strain, an intermediate plane is calculated. From the calculation result, the intermediate plane is placed close to the channel region of the FeFETs. The high flexibility of the ferroelectric polymer and ultrathin device structure contributes to achieving a bending radius of 0.8 µm without the degradation of memory characteristics.

  17. Memristor device based on carbon nanotubes decorated with gold nanoislands

    NASA Astrophysics Data System (ADS)

    Radoi, A.; Dragoman, M.; Dragoman, D.

    2011-08-01

    Memristors are passive nanoelectronics devices with applications in memories and switches which, although not containing magnetic components, have as distinct signature a hysteresis loop in the current-voltage dependence. Even if the prototype material for memristors is a binary oxide, we demonstrate that such devices can be easily implemented using carbon nanotubes decorated with metallic nanoislands, where the hysteretic action is a result of the thermionic emission of electrons trapped in the gold nanoislands.

  18. Maritime Improvised Explosive Devices: A Threat Based Technology Study

    DTIC Science & Technology

    2015-06-12

    SUPPLEMENTARY NOTES 14. ABSTRACT Over the last thirteen years, the world saw an increased use of improvised explosive devices (IEDs) by violent extremists...Over the last thirteen years, the world saw an increased use of improvised explosive devices (IEDs) by violent extremists and terrorist groups. Due to...last thirteen years, the world saw an increased use of IEDs by violent extremists and terrorist groups. Due to the simplicity and availability of IED

  19. Flexible energy storage devices based on nanocomposite paper.

    PubMed

    Pushparaj, Victor L; Shaijumon, Manikoth M; Kumar, Ashavani; Murugesan, Saravanababu; Ci, Lijie; Vajtai, Robert; Linhardt, Robert J; Nalamasu, Omkaram; Ajayan, Pulickel M

    2007-08-21

    There is strong recent interest in ultrathin, flexible, safe energy storage devices to meet the various design and power needs of modern gadgets. To build such fully flexible and robust electrochemical devices, multiple components with specific electrochemical and interfacial properties need to be integrated into single units. Here we show that these basic components, the electrode, separator, and electrolyte, can all be integrated into single contiguous nanocomposite units that can serve as building blocks for a variety of thin mechanically flexible energy storage devices. Nanoporous cellulose paper embedded with aligned carbon nanotube electrode and electrolyte constitutes the basic unit. The units are used to build various flexible supercapacitor, battery, hybrid, and dual-storage battery-in-supercapacitor devices. The thin freestanding nanocomposite paper devices offer complete mechanical flexibility during operation. The supercapacitors operate with electrolytes including aqueous solvents, room temperature ionic liquids, and bioelectrolytes and over record temperature ranges. These easy-to-assemble integrated nanocomposite energy-storage systems could provide unprecedented design ingenuity for a variety of devices operating over a wide range of temperature and environmental conditions.

  20. II-VI Materials-Based High Performance Intersubband Devices

    NASA Astrophysics Data System (ADS)

    Ravikumar, Arvind Pawan

    achieve normal-incident absorption, taking advantage of light-scattering in sloped surfaces; this method is wavelength independent and does not involve complicated fabrication techniques. With the performance of II-VI devices matching or surpassing existing commercial solutions, integrated mid-IR photonics based sensing is poised to play a big role in the future of sensing technologies.

  1. Strong electroluminescence from SiO{sub 2}-Tb{sub 2}O{sub 3}-Al{sub 2}O{sub 3} mixed layers fabricated by atomic layer deposition

    SciTech Connect

    Rebohle, L. Braun, M.; Wutzler, R.; Helm, M.; Skorupa, W.; Liu, B.; Sun, J. M.

    2014-06-23

    We report on the bright green electroluminescence (EL) with power efficiencies up to 0.15% of SiO{sub 2}-Tb{sub 2}O{sub 3}-mixed layers fabricated by atomic layer deposition and partly co-doped with Al{sub 2}O{sub 3}. The electrical, EL, and breakdown behavior is investigated as a function of the Tb and the Al concentration. Special attention has been paid to the beneficial role of Al{sub 2}O{sub 3} co-doping which improves important device parameters. In detail, it increases the maximum EL power efficiency and EL decay time, it nearly doubles the fraction of excitable Tb{sup 3+} ions, it shifts the region of high EL power efficiencies to higher injection currents, and it reduces the EL quenching over the device lifetime by an approximate factor of two. It is assumed that the presence of Al{sub 2}O{sub 3} interferes the formation of Tb clusters and related defects. Therefore, the system SiO{sub 2}-Tb{sub 2}O{sub 3}-Al{sub 2}O{sub 3} represents a promising alternative for integrated, Si-based light emitters.

  2. High brightness formamidinium lead bromide perovskite nanocrystal light emitting devices.

    PubMed

    Perumal, Ajay; Shendre, Sushant; Li, Mingjie; Tay, Yong Kang Eugene; Sharma, Vijay Kumar; Chen, Shi; Wei, Zhanhua; Liu, Qing; Gao, Yuan; Buenconsejo, Pio John S; Tan, Swee Tiam; Gan, Chee Lip; Xiong, Qihua; Sum, Tze Chien; Demir, Hilmi Volkan

    2016-11-09

    Formamidinium lead halide (FAPbX3) has attracted greater attention and is more prominent recently in photovoltaic devices due to its broad absorption and higher thermal stability in comparison to more popular methylammonium lead halide MAPbX3. Herein, a simple and highly reproducible room temperature synthesis of device grade high quality formamidinium lead bromide CH(NH2)2PbBr3 (FAPbBr3) colloidal nanocrystals (NC) having high photoluminescence quantum efficiency (PLQE) of 55-65% is reported. In addition, we demonstrate high brightness perovskite light emitting device (Pe-LED) with these FAPbBr3 perovskite NC thin film using 2,2',2″-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) commonly known as TPBi and 4,6-Bis(3,5-di(pyridin-3-yl)phenyl)-2-methylpyrimidine (B3PYMPM) as electron transport layers (ETL). The Pe-LED device with B3PYMPM as ETL has bright electroluminescence of up to 2714 cd/m(2), while the Pe-LED device with TPBi as ETL has higher peak luminous efficiency of 6.4 cd/A and peak luminous power efficiency of 5.7 lm/W. To our knowledge this is the first report on high brightness light emitting device based on CH(NH2)2PbBr3 widely known as FAPbBr3 nanocrystals in literature.

  3. High brightness formamidinium lead bromide perovskite nanocrystal light emitting devices

    PubMed Central

    Perumal, Ajay; Shendre, Sushant; Li, Mingjie; Tay, Yong Kang Eugene; Sharma, Vijay Kumar; Chen, Shi; Wei, Zhanhua; Liu, Qing; Gao, Yuan; Buenconsejo, Pio John S.; Tan, Swee Tiam; Gan, Chee Lip; Xiong, Qihua; Sum, Tze Chien; Demir, Hilmi Volkan

    2016-01-01

    Formamidinium lead halide (FAPbX3) has attracted greater attention and is more prominent recently in photovoltaic devices due to its broad absorption and higher thermal stability in comparison to more popular methylammonium lead halide MAPbX3. Herein, a simple and highly reproducible room temperature synthesis of device grade high quality formamidinium lead bromide CH(NH2)2PbBr3 (FAPbBr3) colloidal nanocrystals (NC) having high photoluminescence quantum efficiency (PLQE) of 55–65% is reported. In addition, we demonstrate high brightness perovskite light emitting device (Pe-LED) with these FAPbBr3 perovskite NC thin film using 2,2′,2″-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) commonly known as TPBi and 4,6-Bis(3,5-di(pyridin-3-yl)phenyl)-2-methylpyrimidine (B3PYMPM) as electron transport layers (ETL). The Pe-LED device with B3PYMPM as ETL has bright electroluminescence of up to 2714 cd/m2, while the Pe-LED device with TPBi as ETL has higher peak luminous efficiency of 6.4 cd/A and peak luminous power efficiency of 5.7 lm/W. To our knowledge this is the first report on high brightness light emitting device based on CH(NH2)2PbBr3 widely known as FAPbBr3 nanocrystals in literature. PMID:27827424

  4. High brightness formamidinium lead bromide perovskite nanocrystal light emitting devices

    NASA Astrophysics Data System (ADS)

    Perumal, Ajay; Shendre, Sushant; Li, Mingjie; Tay, Yong Kang Eugene; Sharma, Vijay Kumar; Chen, Shi; Wei, Zhanhua; Liu, Qing; Gao, Yuan; Buenconsejo, Pio John S.; Tan, Swee Tiam; Gan, Chee Lip; Xiong, Qihua; Sum, Tze Chien; Demir, Hilmi Volkan

    2016-11-01

    Formamidinium lead halide (FAPbX3) has attracted greater attention and is more prominent recently in photovoltaic devices due to its broad absorption and higher thermal stability in comparison to more popular methylammonium lead halide MAPbX3. Herein, a simple and highly reproducible room temperature synthesis of device grade high quality formamidinium lead bromide CH(NH2)2PbBr3 (FAPbBr3) colloidal nanocrystals (NC) having high photoluminescence quantum efficiency (PLQE) of 55–65% is reported. In addition, we demonstrate high brightness perovskite light emitting device (Pe-LED) with these FAPbBr3 perovskite NC thin film using 2,2‧,2″-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) commonly known as TPBi and 4,6-Bis(3,5-di(pyridin-3-yl)phenyl)-2-methylpyrimidine (B3PYMPM) as electron transport layers (ETL). The Pe-LED device with B3PYMPM as ETL has bright electroluminescence of up to 2714 cd/m2, while the Pe-LED device with TPBi as ETL has higher peak luminous efficiency of 6.4 cd/A and peak luminous power efficiency of 5.7 lm/W. To our knowledge this is the first report on high brightness light emitting device based on CH(NH2)2PbBr3 widely known as FAPbBr3 nanocrystals in literature.

  5. All optical logic operations using semiconductor optical amplifier based devices

    NASA Astrophysics Data System (ADS)

    Wang, Qiang

    High-speed optical processing technologies are essential for the construction of all-optical networks in the information era. In this Ph. D. thesis dissertation, essential mechanisms related to the semiconductor optical amplifier (SOA) based device such as the gain and phase dynamics when a short pulse in propagating inside SOA, and, all-optical Boolean function, XOR, AND and OR have been studied. In order to realize the all-optical logic using SOA, the nonlinear gain and phase dynamics in SOA need to be studied first. The experimental results of 10--90% gain recovery curve have been presented. The recovery time is related to the carrier lifetime of the SOA and it varies with gain compression and bias current. For pulse width of a few picosecond, intraband effects need to be considered. In the SOA, phase change is also induced when a short pulse is propagating inside SOA. Unlike the conventional way of estimating the phase shift using alpha factor, the maximum phase shift is obtained first, then the effective alpha factor is calculated. The experimental results of all optical Boolean function XOR and OR at 80 Gb/s are presented using SOA-MZI-DI and SOA-DI respectively. These are the highest operating speed that has been reported. The all optical AND operation at 40 Gb/s using SOA-MZI have also been reported here. The numerical simulation shows that the performance of these all-optical Boolean operations is limited by the carrier lifetime of the SOA. The Boolean functions are the first step towards all optical circuits. The designs of a parity checker and a pseudo-random binary sequence (PRBS) generator are demonstrated. The error analysis using quality factor and eye-diagram is also presented.

  6. Carbonitride based phosphors and light emitting devices using the same

    DOEpatents

    Li, Yuanqiang; Tian, Yongchi; Romanelli, Michael Dennis

    2013-08-20

    Disclosed herein is a novel group of carbidonitride phosphors and light emitting devices which utilize these phosphors. In certain embodiments, the present invention is directed to a novel family of carbidonitride-based phosphors expressed as follows: Ca.sub.1-xAl.sub.x-xySi.sub.1-x+xyN.sub.2-x-xyC.sub.xy:A; (1) Ca.sub.1-x-zNa.sub.zM(III).sub.x-xy-zSi.sub.1-x+xy+zN.sub.2-x-xyC.sub.xy:- A; (2) M(II).sub.1-x-zM(I).sub.zM(III).sub.x-xy-zSi.sub.1-x+xy+zN.sub.2-x- -xyC.sub.xy:A; (3) M(II).sub.1-x-zM(I).sub.zM(III).sub.x-xy-zSi.sub.1-x+xy+zN.sub.2-x-xy-2w/- 3C.sub.xyO.sub.w-v/2H.sub.v:A; and (4) M(II).sub.1-x-zM(I).sub.zM(III).sub.x-xy-zSi.sub.1-x+xy+zN.sub.2-x-xy-2w/- 3-v/3C.sub.xyO.sub.wH.sub.v:A, (4a) wherein 0xy+z, and 0

  7. Gradient-Doped Thermophotovoltaic Devices based on Colloidal Quantum Dots

    NASA Astrophysics Data System (ADS)

    Fayaz Movahed, Hamidreza

    Electromagnetic radiation emitted from hot objects represents a sizeable supply of energy; however, even for relatively hot bodies, its flux peaks in the short-wavelength infrared between 1 and 3 mum, standing in the way of its photovoltaic harvest using the most widely-available optoelectronic materials such as Si and CdTe. Colloidal quantum dots combine low-cost solution-processing with bandgap tunability in this spectral region, thereby offering a route to harnessing thermal power photovoltaically. Here we report thermophotovoltaic devices constructed using colloidal quantum dots that harvest infrared radiation from an 800°C blackbody source. Only by constructing a gradient-doped colloidal quantum dot thermophotovoltaic device were we able to achieve thermophotovoltaic power generation with a power conversion efficiency of 0.39%. The device showed stable operation at ambient temperatures above 100°C.

  8. A novel thermal acoustic device based on porous graphene

    NASA Astrophysics Data System (ADS)

    Tao, Lu-Qi; Liu, Ying; Tian, He; Ju, Zhen-Yi; Xie, Qian-Yi; Yang, Yi; Ren, Tian-Ling

    2016-01-01

    A thermal acoustic (TA) device was fabricated by laser scribing technology. Polyimide (PI) can be converted into patterned porous graphene (PG) by laser's irradiation in one step. The sound pressure level (SPL) of such TA device is related to laser power. The theoretical model of TA effect was established to analyze the relationship between the SPL and laser power. The theoretical results are in good agreement with experiment results. It was found that PG has a flat frequency response in the range of 5-20 kHz. This novel TA device has the advantages of one-step procedure, high flexibility, no mechanical vibration, low cost and so on. It can open wide applications in speakers, multimedia, medical, earphones, consumer electronics and many other aspects.

  9. A novel thermal acoustic device based on porous graphene

    SciTech Connect

    Tao, Lu-Qi; Liu, Ying; Ju, Zhen-Yi; Xie, Qian-Yi; Yang, Yi; Ren, Tian-Ling; Tian, He

    2016-01-15

    A thermal acoustic (TA) device was fabricated by laser scribing technology. Polyimide (PI) can be converted into patterned porous graphene (PG) by laser’s irradiation in one step. The sound pressure level (SPL) of such TA device is related to laser power. The theoretical model of TA effect was established to analyze the relationship between the SPL and laser power. The theoretical results are in good agreement with experiment results. It was found that PG has a flat frequency response in the range of 5-20 kHz. This novel TA device has the advantages of one-step procedure, high flexibility, no mechanical vibration, low cost and so on. It can open wide applications in speakers, multimedia, medical, earphones, consumer electronics and many other aspects.

  10. Picosecond dynamics of a silicon donor based terahertz detector device

    SciTech Connect

    Bowyer, Ellis T.; Li, Juerong; Litvinenko, K. L.; Murdin, B. N. E-mail: yuxm@pku.edu.cn; Villis, B. J.; Erfani, Morteza; Matmon, Guy; Aeppli, Gabriel; Ortega, Jean-Michel; Prazeres, Rui; Dong, Li; Yu, Xiaomei E-mail: yuxm@pku.edu.cn

    2014-07-14

    We report the characteristics of a simple complementary metal-oxide-semiconductor compatible terahertz detector device with low response time (nanoseconds) determined using a short-pulse, high intensity free-electron laser. The noise equivalent power was 1 × 10{sup −11} W Hz{sup −1/2}. The detector has an enhanced response over narrow bands, most notably at 9.5 THz, with a continuum response at higher frequencies. Using such a device, the dynamics of donors in silicon can be explored, a system which has great potential for quantum information processing.

  11. High frequency SAW devices based on third harmonic generation.

    PubMed

    Le Brizoual, L; Elmazria, O; Sarry, F; El Hakiki, M; Talbi, A; Alnot, P

    2006-12-01

    We demonstrate the third harmonic generation in a ZnO/Si layered structure to obtain high frequency SAW devices. This configuration eliminates the need of high lithography resolution and allows easy integration of such devices and electronics on the same wafer. A theoretical study was carried out for the determination of the phase velocity and the electromechanical coupling coefficient (K(2)) dispersion curves of the surface acoustic waves. These results are also in agreement with those measured on a SAW filter designed for the third harmonic generation and the operating frequency is up to 2468 MHz.

  12. A quantum optical firewall based on simple quantum devices

    NASA Astrophysics Data System (ADS)

    Amellal, H.; Meslouhi, A.; Hassouni, Y.; El Baz, M.

    2015-07-01

    In order to enhance the transmission security in quantum communications via coherent states, we propose a quantum optical firewall device to protect a quantum cryptosystem against eavesdropping through optical attack strategies. Similar to the classical model of the firewall, the proposed device gives legitimate users the possibility of filtering, controlling (input/output states) and making a decision (access or deny) concerning the traveling states. To prove the security and efficiency of the suggested optical firewall, we analyze its performances against the family of intercept and resend attacks, especially against one of the most prominent attack schemes known as "Faked State Attack."

  13. Polymer-based electrochemical devices for logic functions and paper displays

    NASA Astrophysics Data System (ADS)

    Berggren, Magnus; Nilsson, David; Chen, Miaoxiang; Andersson, Peter; Kugler, Thomas; Malmstroem, Anna; Haell, Jessica; Remonen, Tommi; Robinson, Nathaniel D.

    2003-07-01

    Here, we report on devices based on patterned thin films of the conducting polymer system poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulphonic acid) (PEDOT:PSS) combined with patterns of solid electrolyte. The key device functionalities base on the updating of the RedOx state of PEDOT. This results in control of the electronic properties of this conjugated polymer, i.e. the conductivity and optical properties are updated. Based on this we have achieved electric current rectifiers, transistors and display cells. Also, matrix addressed displays will be presented. Electrochemical switching is taking place when the oxidation and reduction potentials are overcome respectively. Therefore, these devices operate at voltage levels less then 2 Volts. Low voltage operation is achieved in devices not requiring any extremely narrow dimensions, as is the case for field effect driven devices. All devices reported can or has been made using standard printing techniques on flexible carriers.

  14. Nanotechnology Based Materials and Devices for Health Care

    NASA Technical Reports Server (NTRS)

    Srivastava, Deepaka; Cho, K.; Brenner, Don; Menon, Madhu; Andriotis, Antonis; Sagman, Uri; Biegel, Bryan A. (Technical Monitor)

    2002-01-01

    This viewgraph presentation provides information on trends in NASA nanotechnology research and development, and future biotechnological applications for that nanotechnology. The presentation covers nanoelectronics, nanosensors, and nanomaterials, biomimetics, devices and materials for health care, carbon nanotubes, biosensors for astrobiology, solid-state nanopores for DNA sequencing, and protein nanotubes.

  15. Night vision devices. Citations from the NTIS data base

    NASA Astrophysics Data System (ADS)

    Habercom, G. E., Jr.

    1980-08-01

    This bibliography contains 323 citations in which various types of night vision devices are investigated. Most were developed for military applications but they can readily be adapted for civil usage, as for example, law enforcement. Abstracts on display screens, equipment design and effectiveness, electronic components, spurious noise reduction, and test methods are cited.

  16. Novel compound semiconductor devices based on III-V nitrides

    SciTech Connect

    Pearton, S.J.; Abernathy, C.R.; Ren, F.

    1995-10-01

    New developments in dry and wet etching, ohmic contacts and epitaxial growth of Ill-V nitrides are reported. These make possible devices such as microdisk laser structures and GaAs/AlGaAs heterojunction bipolar transistors with improved InN ohmic contacts.

  17. Highly reproducible thermocontrolled electrospun fiber based organic photovoltaic devices.

    PubMed

    Kim, Taehoon; Yang, Seung Jae; Sung, Sae Jin; Kim, Yern Seung; Chang, Mi Se; Jung, Haesol; Park, Chong Rae

    2015-03-04

    In this work, we examined the reasons underlying the humidity-induced morphological changes of electrospun fibers and suggest a method of controlling the electrospun fiber morphology under high humidity conditions. We fabricated OPV devices composed of electrospun fibers, and the performance of the OPV devices depends significantly on the fiber morphology. The evaporation rate of a solvent at various relative humidity was measured to investigate the effects of the relative humidity during electrospinning process. The beaded nanofiber morphology of electrospun fibers was originated due to slow solvent evaporation rate under high humidity conditions. To increase the evaporation rate under high humidity conditions, warm air was applied to the electrospinning system. The beads that would have formed on the electrospun fibers were completely avoided, and the power conversion efficiencies of OPV devices fabricated under high humidity conditions could be restored. These results highlight the simplicity and effectiveness of the proposed method for improving the reproducibility of electrospun nanofibers and performances of devices consisting of the electrospun nanofibers, regardless of the relative humidity.

  18. Antimicrobial susceptibility assays in paper-based portable culture devices.

    PubMed

    Deiss, Frédérique; Funes-Huacca, Maribel E; Bal, Jasmin; Tjhung, Katrina F; Derda, Ratmir

    2014-01-07

    To detect antibiotic-resistant bacteria in areas remote from microbiology laboratories, we designed portable culture devices performing an analogue of the Kirby-Bauer disk diffusion test inside patterned papers embedded in tape. We quantified the antibiotic susceptibility of several strains of Escherichia coli and Salmonella typhimurium by measuring blue-colored zones of inhibited growth.

  19. Web-Based Spatial Training Using Handheld Touch Screen Devices

    ERIC Educational Resources Information Center

    Martin-Dorta, Norena; Saorin, Jose Luis; Contero, Manuel

    2011-01-01

    This paper attempts to harness the opportunities for mobility and the new user interfaces that handheld touch screen devices offer, in a non-formal learning context, with a view to developing spatial ability. This research has addressed two objectives: first, analyzing the effects that training can have on spatial visualisation using the…

  20. Shock Wave Based Biolistic Device for DNA and Drug Delivery

    NASA Astrophysics Data System (ADS)

    Nakada, Mutsumi; Menezes, Viren; Kanno, Akira; Hosseini, S. Hamid R.; Takayama, Kazuyoshi

    2008-03-01

    A shock wave assisted biolistic (biological ballistic) device has been developed to deliver DNA/drug-coated micro-projectiles into soft living targets. The device consists of an Nd:YAG laser, an optical setup to focus the laser beam and, a thin aluminum (Al) foil (typically 100 µm thick) which is a launch pad for the micro-projectiles. The DNA/drug-coated micro-particles to be delivered are deposited on the anterior surface of the foil and the posterior surface of the foil is ablated using the laser beam with an energy density of about 32×109 W/cm2. The ablation launches a shock wave through the foil that imparts an impulse to the foil surface, due to which the deposited particles accelerate and acquire sufficient momentum to penetrate soft targets. The device has been tested for particle delivery by delivering 1 µm size tungsten particles into liver tissues of experimental rats and in vitro test models made of gelatin. The penetration depths of about 90 and 800 µm have been observed in the liver and gelatin targets, respectively. The device has been tested for in vivo DNA [encoding β-glucuronidase (GUS) gene] transfer by delivering plasmid DNA-coated, 1-µm size gold (Au) particles into onion scale, tobacco leaf and soybean seed cells. The GUS activity was detected in the onion, tobacco and soybean cells after the DNA delivery. The present device is totally non-intrusive in nature and has a potential to get miniaturized to suit the existing medical procedures for DNA and/or drug delivery.

  1. Non-binary Colour Modulation for Display Device Based on Phase Change Materials

    PubMed Central

    Ji, Hong-Kai; Tong, Hao; Qian, Hang; Hui, Ya-Juan; Liu, Nian; Yan, Peng; Miao, Xiang-Shui

    2016-01-01

    A reflective-type display device based on phase change materials is attractive because of its ultrafast response time and high resolution compared with a conventional display device. This paper proposes and demonstrates a unique display device in which multicolour changing can be achieved on a single device by the selective crystallization of double layer phase change materials. The optical contrast is optimized by the availability of a variety of film thicknesses of two phase change layers. The device exhibits a low sensitivity to the angle of incidence, which is important for display and colour consistency. The non-binary colour rendering on a single device is demonstrated for the first time using optical excitation. The device shows the potential for ultrafast display applications. PMID:27991523

  2. Non-binary Colour Modulation for Display Device Based on Phase Change Materials.

    PubMed

    Ji, Hong-Kai; Tong, Hao; Qian, Hang; Hui, Ya-Juan; Liu, Nian; Yan, Peng; Miao, Xiang-Shui

    2016-12-19

    A reflective-type display device based on phase change materials is attractive because of its ultrafast response time and high resolution compared with a conventional display device. This paper proposes and demonstrates a unique display device in which multicolour changing can be achieved on a single device by the selective crystallization of double layer phase change materials. The optical contrast is optimized by the availability of a variety of film thicknesses of two phase change layers. The device exhibits a low sensitivity to the angle of incidence, which is important for display and colour consistency. The non-binary colour rendering on a single device is demonstrated for the first time using optical excitation. The device shows the potential for ultrafast display applications.

  3. Infrared Response and Optoelectronic Memory Device Fabrication Based on Epitaxial VO2 Film.

    PubMed

    Fan, Lele; Chen, Yuliang; Liu, Qianghu; Chen, Shi; Zhu, Lei; Meng, Qiangqiang; Wang, Baolin; Zhang, Qinfang; Ren, Hui; Zou, Chongwen

    2016-12-07

    In this work, high-quality VO2 epitaxial films were prepared on high-conductivity n-GaN (0001) crystal substrates via an oxide molecular beam epitaxy method. By fabricating a two-terminal VO2/GaN film device, we observed that the infrared transmittance and resistance of VO2 films could be dynamically controlled by an external bias voltage. Based on the hysteretic switching effect of VO2 in infrared range, an optoelectronic memory device was achieved. This memory device was operated under the "electrical writing-optical reading" mode, which shows promising applications in VO2-based optoelectronic device in the future.

  4. Status and Prospects of ZnO-Based Resistive Switching Memory Devices.

    PubMed

    Simanjuntak, Firman Mangasa; Panda, Debashis; Wei, Kung-Hwa; Tseng, Tseung-Yuen

    2016-12-01

    In the advancement of the semiconductor device technology, ZnO could be a prospective alternative than the other metal oxides for its versatility and huge applications in different aspects. In this review, a thorough overview on ZnO for the application of resistive switching memory (RRAM) devices has been conducted. Various efforts that have been made to investigate and modulate the switching characteristics of ZnO-based switching memory devices are discussed. The use of ZnO layer in different structure, the different types of filament formation, and the different types of switching including complementary switching are reported. By considering the huge interest of transparent devices, this review gives the concrete overview of the present status and prospects of transparent RRAM devices based on ZnO. ZnO-based RRAM can be used for flexible memory devices, which is also covered here. Another challenge in ZnO-based RRAM is that the realization of ultra-thin and low power devices. Nevertheless, ZnO not only offers decent memory properties but also has a unique potential to be used as multifunctional nonvolatile memory devices. The impact of electrode materials, metal doping, stack structures, transparency, and flexibility on resistive switching properties and switching parameters of ZnO-based resistive switching memory devices are briefly compared. This review also covers the different nanostructured-based emerging resistive switching memory devices for low power scalable devices. It may give a valuable insight on developing ZnO-based RRAM and also should encourage researchers to overcome the challenges.

  5. Status and Prospects of ZnO-Based Resistive Switching Memory Devices

    NASA Astrophysics Data System (ADS)

    Simanjuntak, Firman Mangasa; Panda, Debashis; Wei, Kung-Hwa; Tseng, Tseung-Yuen

    2016-08-01

    In the advancement of the semiconductor device technology, ZnO could be a prospective alternative than the other metal oxides for its versatility and huge applications in different aspects. In this review, a thorough overview on ZnO for the application of resistive switching memory (RRAM) devices has been conducted. Various efforts that have been made to investigate and modulate the switching characteristics of ZnO-based switching memory devices are discussed. The use of ZnO layer in different structure, the different types of filament formation, and the different types of switching including complementary switching are reported. By considering the huge interest of transparent devices, this review gives the concrete overview of the present status and prospects of transparent RRAM devices based on ZnO. ZnO-based RRAM can be used for flexible memory devices, which is also covered here. Another challenge in ZnO-based RRAM is that the realization of ultra-thin and low power devices. Nevertheless, ZnO not only offers decent memory properties but also has a unique potential to be used as multifunctional nonvolatile memory devices. The impact of electrode materials, metal doping, stack structures, transparency, and flexibility on resistive switching properties and switching parameters of ZnO-based resistive switching memory devices are briefly compared. This review also covers the different nanostructured-based emerging resistive switching memory devices for low power scalable devices. It may give a valuable insight on developing ZnO-based RRAM and also should encourage researchers to overcome the challenges.

  6. A new repeatable, optical writing and electrical erasing device based on photochromism and electrochromism of viologen

    NASA Astrophysics Data System (ADS)

    Gao, Li-ping; Wei, Jian; Wang, Yue-chuan; Ding, Guo-jing; Yang, Yu-lin

    2012-08-01

    New optical writing and electrical erasing devices have been successfully fabricated that exploit the photochromism and electrochromism of viologen. In a preliminary study, both the structures of viologen and device were investigated in detail by UV-vis spectra in order to confirm their effects on the optical writing and electrical erasing performances of corresponding devices. For sandwiched, single and complementary devices based on benzyl viologen (BV 2+), only optical writing can be performed, not electrical erasing operations, which indicated these devices cannot realize optical information rewriting. For single and complementary devices based on styrene-functional viologen (V BV 2+) and acrylic-functional viologen (ACV 2+), optical writing and electrical erasing operations can be reversibly performed and optical information rewriting realized. It is clear that single devices based on V BV2+ and ACV2+ possess better performance accompanied with contrast without significant degradation and bleaching times and without significant deterioration over 10 repeated writing/erasing cycles. Furthermore, we put forward possible mechanisms for sandwiched, single and complementary devices based on V BV2+ and ACV2+ for the optical writing and electrical erasing operations. This study provides a new strategy to design optical writing and electrical erasing devices to realize optical information rewriting.

  7. Spin-orbit-based device for electron spin polarization

    NASA Astrophysics Data System (ADS)

    Avishai, Y.; Band, Y. B.

    2017-03-01

    We propose quantum devices having spin-orbit coupling (but no magnetic fields or magnetic materials) that, when attached to leads, yield a high degree of transmitted electron polarization. An example of such a simple device is treated within a tight binding model composed of two one-dimensional chains coupled by several consecutive rungs (i.e., a ladder) and subject to a gate voltage. The ensuing scattering problem (with Rashba spin-orbit coupling) is solved, and a sizable polarization is predicted. When the ladder is twisted into a helix (as in DNA), the curvature energy augments the polarization. For a system with random spin-orbit coupling, the distribution of polarization is broad; hence a high degree of polarization can be obtained in a measurement of a given disorder realization. When disorder occurs in a double helix structure then, depending on scattering energy, the variance of the polarization distribution can increase even further due to helix curvature.

  8. Experimental study of blast mitigating devices based on combined construction

    NASA Astrophysics Data System (ADS)

    Takayama, K.; Silnikov, M. V.; Chernyshov, M. V.

    2016-09-01

    A robust blast inhibiting bin is the most often used device for damage blast effects suppression. In particular, a top open cylindrical bin significantly reduces a fragmentation effect resulted from a detonation of an explosive device placed inside the bin. However, reduction of blast wave overpressure and impulse by such cylindrical bins is not sufficient [1]. A reasonable alternative to endless increase of height and thickness of robust blast inhibiting bins is a development of destructible inhibitors having no solid elements in their structure and, therefore, excluding secondary fragmentation. So, the family of "Fountain" inhibitors [2,3] localizes and suppresses damaging blast effects due to multiphase working system. The present study is analyzing data obtained in testing of prototypes of new combined inhibitors. Their structure combines robust elements (bottoms, side surfaces) with elements responsible for blast loads reduction due to multi-phase working system (top and low transverse embeddings) and fairings impeding wave propagation in undesirable directions.

  9. Pure spin current devices based on ferromagnetic topological insulators

    PubMed Central

    Götte, Matthias; Joppe, Michael; Dahm, Thomas

    2016-01-01

    Two-dimensional topological insulators possess two counter propagating edge channels with opposite spin direction. Recent experimental progress allowed to create ferromagnetic topological insulators realizing a quantum anomalous Hall (QAH) state. In the QAH state one of the two edge channels disappears due to the strong ferromagnetic exchange field. We investigate heterostructures of topological insulators and ferromagnetic topological insulators by means of numerical transport calculations. We show that spin current flow in such heterostructures can be controlled with high fidelity. Specifically, we propose spintronic devices that are capable of creating, switching and detecting pure spin currents using the same technology. In these devices electrical currents are directly converted into spin currents, allowing a high conversion efficiency. Energy independent transport properties in combination with large bulk gaps in some topological insulator materials may allow operation even at room temperature. PMID:27782187

  10. Spin-Based Devices for Magneto-Optoelectronic Integrated Circuits

    DTIC Science & Technology

    2009-04-29

    Nanostructures to Nanosensing Applications, Proceedings of the International School of Physics " Enrico Fermi ," Course CLX, edited by A. D’Amico, G...parameter B which correlates nt(i) with u.^ through Fermi - Dirac distribution and density-of-states functions, and which is approximated by a linear...in these devices [17]. The model parameters, determined at 10 K, are as follows: (1) from Hall measurements, \\i = 3000 cm2/V.s; (2) from the Fermi

  11. Spectroscopy on Conjugated Polymer Devices

    NASA Astrophysics Data System (ADS)

    Dyakonov, Vladimir

    The following sections are included: * INTRODUCTION * EXPERIMENTAL * Sample Preparation * Experimental Set-up * Frequency Resolved ODMR * RESULTS * Studies on the Recombination and Transport in the Polymer Devices via Measurements of the Photoinduced Current and the Electroluminescence * ESR Detected via Photoinduced Current * Magnetic Field Effect on the Photocurrent * ESR Detected via Electroluminescence Intensity * Photoluminescence Studies on Films of PPV and PPPV * Changes of the Photoluminescence Intensity under Conditions of ESR * Dependence of the ODMR on the Excitation Intensity and the Temperature * Spectral Dependence of ODMR * Studies of the recombination kinetics by means of frequency resolved ODMR * The Influence of the Thermal Conversion of PPV on the ODMR Intensity * DISCUSSION * On the Nature of the States Participating in Photocurrent Detected Magnetic Resonance * Excitations Participating in Electroluminescence Detected Magnetic Resonance * Evidences for Photoinduced Inter-Chain Triplet Polaron Pairs and Their Transformations In PPV * Triplet Excitons Annihilation as Origin of the Delayed Photoluminescence * Kinetic Connection Between Magnetic Resonant Transitions and Photo-Luminescence Intensity * Dependence of the Magnitude of the Resonant Signals on the Light Intensity * Dependence of the Magnitude of the Resonant Signals on the Frequency of Microwave Power Modulation * On the Polarisation of Triplet Excitons * Temperature Dependence of the ODMR Intensity * The Influence of the Thermal Conversion of the Prepolymer on Recombination Processes * Remarks on the Previous Recombination Models in Magnetic Resonance Experiments * CONCLUSION * Acknowledgements * REFERENCES

  12. Co-deposition methods for the fabrication of organic optoelectronic devices

    DOEpatents

    Thompson, Mark E.; Liu, Zhiwei; Wu, Chao

    2016-09-06

    A method for fabricating an OLED by preparing phosphorescent metal complexes in situ is provided. In particular, the method simultaneously synthesizes and deposits copper (I) complexes in an organic light emitting device. Devices comprising such complexes may provide improved photoluminescent and electroluminescent properties.

  13. Fabrication of polyimide based microfluidic channels for biosensor devices

    NASA Astrophysics Data System (ADS)

    Zulfiqar, Azeem; Pfreundt, Andrea; Svendsen, Winnie Edith; Dimaki, Maria

    2015-03-01

    The ever-increasing complexity of the fabrication process of Point-of-care (POC) devices, due to high demand of functional versatility, compact size and ease-of-use, emphasizes the need of multifunctional materials that can be used to simplify this process. Polymers, currently in use for the fabrication of the often needed microfluidic channels, have limitations in terms of their physicochemical properties. Therefore, the use of a multipurpose biocompatible material with better resistance to the chemical, thermal and electrical environment, along with capability of forming closed channel microfluidics is inevitable. This paper demonstrates a novel technique of fabricating microfluidic devices using polyimide (PI) which fulfills the aforementioned properties criteria. A fabrication process to pattern microfluidic channels, using partially cured PI, has been developed by using a dry etching method. The etching parameters are optimized and compared to those used for fully cured PI. Moreover, the formation of closed microfluidic channel on wafer level by bonding two partially cured PI layers or a partially cured PI to glass with high bond strength has been demonstrated. The reproducibility in uniformity of PI is also compared to the most commonly used SU8 polymer, which is a near UV sensitive epoxy resin. The potential applications of PI processing are POC and biosensor devices integrated with microelectronics.

  14. Analysis of degradation mechanisms in donor-acceptor copolymer based organic photovoltaic devices using impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Srivastava, S. B.; Sonar, P.; Singh, S. P.

    2016-09-01

    The stability of organic photovoltaic (OPV) devices in ambient conditions has been a serious issue which needs to be addressed and resolved timely. In order to probe the degradation mechanism in a donor-acceptor polymer PDPP-TNT: PC71BM bulk heterojunction based OPV devices, we have studied current density-voltage (J-V) behavior and impedance spectroscopy of fresh and aged devices. The current-voltage characteristic of optimized fresh devices exhibit a short circuit current density (J sc) of 8.9 mA cm-2, open circuit voltage (V oc) of 0.79 V, fill factor (FF) of 54.6%, and power conversion efficiency (PCE) of 3.8%. For aged devices, J sc, V oc, FF, and PCE were reduced to 57.3%, 89.8%, 44.3% and 23.7% of its initial value, respectively. The impedance spectra measured under illumination for these devices were successfully fitted using a CPE-based circuit model. For aged devices, the low-frequency response in impedance spectra suggests an accumulation of the photo-generated charge carriers at the interfaces which leads to a significant lowering in fill factor. Such degradation in device performance is attributed to the incorporation of oxygen and water molecules in devices. An increase in the recombination resistance indicates a deterioration of free charge carrier generation and conduction in devices.

  15. Fourier transform infrared spectroscopy approach for measurements of photoluminescence and electroluminescence in mid-infrared.

    PubMed

    Zhang, Y G; Gu, Y; Wang, K; Fang, X; Li, A Z; Liu, K H

    2012-05-01

    An improved Fourier transform infrared spectroscopy approach adapting to photoluminescence and electroluminescence measurements in mid-infrared has been developed, in which diode-pumped solid-state excitation lasers were adopted for photoluminescence excitation. In this approach, three different Fourier transform infrared modes of rapid scan, double modulation, and step scan were software switchable without changing the hardware or connections. The advantages and limitations of each mode were analyzed in detail. Using this approach a group of III-V and II-VI samples from near-infrared extending to mid-infrared with photoluminescence intensities in a wider range have been characterized at room temperature to demonstrate the validity and overall performances of the system. The weaker electroluminescence of quantum cascade lasers in mid-infrared band was also surveyed at different resolutions. Results show that for samples with relatively strong photoluminescence or electroluminescence out off the background, rapid scan mode is the most preferable. For weaker photoluminescence or electroluminescence overlapped with background, double modulation is the most effective mode. To get a better signal noise ratio when weaker photoluminescence or electroluminescence signal has been observed in double modulation mode, switching to step scan mode should be an advisable option despite the long data acquiring time and limited resolution.

  16. Passive device based on plastic optical fibers to determine the indices of refraction of liquids.

    PubMed

    Zubia, J; Garitaonaindía, G; Arrúe, J

    2000-02-20

    We have designed and measured a passive device based on plastic optical fibers (POF's) that one can use to determine the indices of refraction of liquids. A complementary software has also been designed to simulate the behavior of the device. We report on the theoretical model developed for the device, its implementation in a simulation software program, and the results of the simulation. A comparison of the experimental and calculated results is also shown and discussed.

  17. [Development and application of a medical device maintenance information platform based on BS architecture].

    PubMed

    Liu, Shenglin; Zhang, Xutian; Wang, Guohong; Zhang, Qiang

    2012-03-01

    Based on specified demands on medical devices maintenance for clinical engineers and Browser/Server architecture technology, a medical device maintenance information platform was developed, which implemented the following modules such as repair, preventive maintenance, accessories management, training, document, system management and regional cooperation. The characteristics of this system were summarized and application in increase of repair efficiency, improvement of preventive maintenance and cost control was introduced. The application of this platform increases medical device maintenance service level.

  18. Integration of Multiple Components in Polystyrene-based Microfluidic Devices Part 1: Fabrication and Characterization

    PubMed Central

    Johnson, Alicia S.; Anderson, Kari B.; Halpin, Stephen T.; Kirkpatrick, Douglas C.; Spence, Dana M.; Martin, R. Scott

    2012-01-01

    In Part I of a two-part series, we describe a simple, and inexpensive approach to fabricate polystyrene devices that is based upon melting polystyrene (from either a Petri dish or powder form) against PDMS molds or around electrode materials. The ability to incorporate microchannels in polystyrene and integrate the resulting device with standard laboratory equipment such as an optical plate reader for analyte readout and micropipettors for fluid propulsion is first described. A simple approach for sample and reagent delivery to the device channels using a standard, multi-channel micropipette and a PDMS-based injection block is detailed. Integration of the microfluidic device with these off-chip functions (sample delivery and readout) enables high throughput screens and analyses. An approach to fabricate polystyrene-based devices with embedded electrodes is also demonstrated, thereby enabling the integration of microchip electrophoresis with electrochemical detection through the use of a palladium electrode (for a decoupler) and carbon-fiber bundle (for detection). The device was sealed against a PDMS-based microchannel and used for the electrophoretic separation and amperometric detection of dopamine, epinephrine, catechol, and 3,4-dihydroxyphenylacetic acid. Finally, these devices were compared against PDMS-based microchips in terms of their optical transparency and absorption of an anti-platelet drug, clopidogrel. Part I of this series lays the foundation for Part II, where these devices were utilized for various on-chip cellular analysis. PMID:23120747

  19. Methods and apparatus of spatially resolved electroluminescence of operating organic light-emitting diodes using conductive atomic force microscopy

    NASA Technical Reports Server (NTRS)

    Hersam, Mark C. (Inventor); Pingree, Liam S. C. (Inventor)

    2008-01-01

    A conductive atomic force microscopy (cAFM) technique which can concurrently monitor topography, charge transport, and electroluminescence with nanometer spatial resolution. This cAFM approach is particularly well suited for probing the electroluminescent response characteristics of operating organic light-emitting diodes (OLEDs) over short length scales.

  20. A chip scale electrocaloric effect based cooling device

    NASA Astrophysics Data System (ADS)

    Gu, Haiming; Qian, Xiaoshi; Li, Xinyu; Craven, Brent; Zhu, Wenyi; Cheng, Ailan; Yao, S. C.; Zhang, Q. M.

    2013-03-01

    The recent finding of large electrocaloric effect in several ferroelectric polymers creates unique opportunity for developing compact size solid state cooling cycles beyond the traditional mechanical vapor compression cycles. Here, we show that, by employing regeneration process with solid state regenerators, a chip scale Electrocaloric Oscillatory Refrigeration (ECOR) can be realized. A prototype ECOR is fabricated and characterized. More than 6 K temperature span is obtained near room temperature between the hot and cold sides of a 2 cm long device. Finite volume simulation validates the test results and shows the potential high performance of the ECOR.