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Sample records for pseudomorphic ultraviolet light-emitting

  1. 270 nm Pseudomorphic Ultraviolet Light-Emitting Diodes with Over 60 mW Continuous Wave Output Power

    Science.gov (United States)

    Grandusky, James R.; Chen, Jianfeng; Gibb, Shawn R.; Mendrick, Mark C.; Moe, Craig G.; Rodak, Lee; Garrett, Gregory A.; Wraback, Michael; Schowalter, Leo J.

    2013-03-01

    In this letter, the achievement of over 60 mW output power from pseudomorphic ultraviolet light-emitting diodes in continuous wave operation is reported. Die thinning and encapsulation improved the photon extraction efficiency to over 15%. Improved thermal management and a high characteristic temperature resulted in a low thermal rolloff up to 300 mA injection current with an output power of 67 mW, an external quantum efficiency (EQE) of 4.9%, and a wall plug efficiency (WPE) of 2.5% for a single-chip device emitting at 271 nm in continuous wave operation.

  2. High extraction efficiency ultraviolet light-emitting diode

    Science.gov (United States)

    Wierer, Jonathan; Montano, Ines; Allerman, Andrew A.

    2015-11-24

    Ultraviolet light-emitting diodes with tailored AlGaN quantum wells can achieve high extraction efficiency. For efficient bottom light extraction, parallel polarized light is preferred, because it propagates predominately perpendicular to the QW plane and into the typical and more efficient light escape cones. This is favored over perpendicular polarized light that propagates along the QW plane which requires multiple, lossy bounces before extraction. The thickness and carrier density of AlGaN QW layers have a strong influence on the valence subband structure, and the resulting optical polarization and light extraction of ultraviolet light-emitting diodes. At Al>0.3, thinner QW layers (<2.5 nm are preferred) result in light preferentially polarized parallel to the QW plane. Also, active regions consisting of six or more QWs, to reduce carrier density, and with thin barriers, to efficiently inject carriers in all the QWs, are preferred.

  3. Modeling Ultraviolet (UV) Light Emitting Diode (LED) Energy Propagation in Reactor Vessels

    Science.gov (United States)

    2014-03-27

    concern is through Advanced Oxidation Processes (AOP). One such process uses ultraviolet (UV) energy to decompose hydrogen peroxide ( H2O2 ) to create...MODELING ULTRAVIOLET (UV) LIGHT EMITTING DIODE (LED) ENERGY PROPAGATION IN REACTOR VESSELS THESIS...

  4. Tunnel-injected sub-260 nm ultraviolet light emitting diodes

    Science.gov (United States)

    Zhang, Yuewei; Krishnamoorthy, Sriram; Akyol, Fatih; Bajaj, Sanyam; Allerman, Andrew A.; Moseley, Michael W.; Armstrong, Andrew M.; Rajan, Siddharth

    2017-05-01

    We report on tunnel-injected deep ultraviolet light emitting diodes (UV LEDs) configured with a polarization engineered Al0.75Ga0.25 N/In0.2Ga0.8 N tunnel junction structure. Tunnel-injected UV LED structure enables n-type contacts for both bottom and top contact layers. However, achieving Ohmic contact to wide bandgap n-AlGaN layers is challenging and typically requires high temperature contact metal annealing. In this work, we adopted a compositionally graded top contact layer for non-alloyed metal contact and obtained a low contact resistance of ρc = 4.8 × 10-5 Ω cm2 on n-Al0.75Ga0.25 N. We also observed a significant reduction in the forward operation voltage from 30.9 V to 19.2 V at 1 kA/cm2 by increasing the Mg doping concentration from 6.2 × 1018 cm-3 to 1.5 × 1019 cm-3. Non-equilibrium hole injection into wide bandgap Al0.75Ga0.25 N with Eg>5.2 eV was confirmed by light emission at 257 nm. This work demonstrates the feasibility of tunneling hole injection into deep UV LEDs and provides a structural design towards high power deep-UV emitters.

  5. Status of Growth of Group III-Nitride Heterostructures for Deep Ultraviolet Light-Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Kai Ding

    2017-10-01

    Full Text Available We overview recent progress in growth aspects of group III-nitride heterostructures for deep ultraviolet (DUV light-emitting diodes (LEDs, with particular emphasis on the growth approaches for attaining high-quality AlN and high Al-molar fraction AlGaN. The discussion commences with the introduction of the current status of group III-nitride DUV LEDs and the remaining challenges. This segues into discussion of LED designs enabling high device performance followed by the review of advances in the methods for the growth of bulk single crystal AlN intended as a native substrate together with a discussion of its UV transparency. It should be stated, however, that due to the high-cost of bulk AlN substrates at the time of writing, the growth of DUV LEDs on foreign substrates such as sapphire still dominates the field. On the deposition front, the heteroepitaxial growth approaches incorporate high-temperature metal organic chemical vapor deposition (MOCVD and pulsed-flow growth, a variant of MOCVD, with the overarching goal of enhancing adatom surface mobility, and thus epitaxial lateral overgrowth which culminates in minimization the effect of lattice- and thermal-mismatches. This is followed by addressing the benefits of pseudomorphic growth of strained high Al-molar fraction AlGaN on AlN. Finally, methods utilized to enhance both p- and n-type conductivity of high Al-molar fraction AlGaN are reviewed.

  6. Photon extraction from nitride ultraviolet light-emitting devices

    Science.gov (United States)

    Schowalter, Leo J; Chen, Jianfeng; Grandusky, James R

    2015-02-24

    In various embodiments, a rigid lens is attached to a light-emitting semiconductor die via a layer of encapsulant having a thickness insufficient to prevent propagation of thermal expansion mismatch-induced strain between the rigid lens and the semiconductor die.

  7. Bias-polarity dependent ultraviolet/visible switchable light-emitting devices.

    Science.gov (United States)

    Ni, Pei-Nan; Shan, Chong-Xin; Li, Bing-Hui; Wang, Shuang-Peng; Shen, De-Zhen

    2014-06-11

    By taking semiconductors with different band-gap energies as the active layers and controlling the electron-hole recombination region through the electric field, bias-polarity dependent ultraviolet/visible switchable light-emitting devices have been realized in Au/MgO/Mg0.49Zn0.51O/MgxZn1-xO/n-ZnO structures, of which the emission bands can be switched from the ultraviolet region to the orange region by changing the polarity of the applied bias. The results reported here may provide a feasible idea to multicolor-switchable light-emitting devices.

  8. Luminescence enhancement of near ultraviolet light-emitting diodes

    DEFF Research Database (Denmark)

    Lin, Li; Jensen, Flemming; Herstrøm, Berit

    2016-01-01

    Nanopillars were applied on the p-GaN layer of the InGaN-based near ultraviolet epiwafer to improve the light extraction efficiency. A photoluminescence enhancement of 74 % is reported with a nanopillar height of around 105 nm.......Nanopillars were applied on the p-GaN layer of the InGaN-based near ultraviolet epiwafer to improve the light extraction efficiency. A photoluminescence enhancement of 74 % is reported with a nanopillar height of around 105 nm....

  9. An assessment of ultraviolet radiation components of light emitted ...

    African Journals Online (AJOL)

    The study of Ultraviolet Radiation has of recent become interesting because of the health hazards it poses to human. Apart from its intensity reaching the earth from the sun, other man-made sources have been identified. We have undertaken the measurement of UV radiation from electric arc welding light generated by 240 ...

  10. Current Spreading Layer with High Transparency and Conductivity for near-ultraviolet light emitting diodes

    DEFF Research Database (Denmark)

    Lin, Li; Jensen, Flemming; Herstrøm, Berit

    Transparent conductive aluminum-doped zinc oxide (AZO) layer was deposited on GaN-based near-ultraviolet (NUV) light emitting epitaxial wafers as current spreading layer by a sputtering process. Efforts were made to improve the electrical properties of AZO in order to produce ohmic contact....

  11. Bactericidal effects of deep ultraviolet light-emitting diode for solutions during intravenous infusion

    OpenAIRE

    Omotani, Sachiko; Tani, Katsuji; Aoe, Mai; Esaki, Seiji; Nagai, Katsuhito; Hatsuda, Yasutoshi; Mukai, Junji; Teramachi, Hitomi; Myotoku, Michiaki

    2018-01-01

    Background: Ultraviolet irradiation is effectively used as a disinfection method for inactivating microorganisms. Methods: We investigated the bactericidal effects by irradiation with a deep-ultraviolet light-emitting diode (DUV-LED) on the causative microorganisms of catheter related blood stream infection contaminating the solution for intravenous infusion. For irradiation, prototype modules for water disinfection with a DUV-LED were used. Experiments were conducted on five kinds of microor...

  12. Fully inorganic oxide-in-oxide ultraviolet nanocrystal light emitting devices

    Science.gov (United States)

    Brovelli, Sergio; Chiodini, Norberto; Lorenzi, Roberto; Lauria, Alessandro; Romagnoli, Marco; Paleari, Alberto

    2012-02-01

    The development of integrated photonics and lab-on-a-chip platforms for environmental and biomedical diagnostics demands ultraviolet electroluminescent materials with high mechanical, chemical and environmental stability and almost complete compatibility with existing silicon technology. Here we report the realization of fully inorganic ultraviolet light-emitting diodes emitting at 390 nm with a maximum external quantum efficiency of ~0.3%, based on SnO2 nanoparticles embedded in SiO2 thin films obtained from a solution-processed method. The fabrication involves a single deposition step onto a silicon wafer followed by a thermal treatment in a controlled atmosphere. The fully inorganic architecture ensures superior mechanical robustness and optimal chemical stability in organic solvents and aqueous solutions. The versatility of the fabrication process broadens the possibility of optimizing this strategy and extending it to other nanostructured systems for designed applications, such as active components of wearable health monitors or biomedical devices.

  13. Thermally stable conformal encapsulation material for high-power ultraviolet light-emitting diodes

    Science.gov (United States)

    Huang, Shun-Yuan; Wang, Jau-Sheng

    2017-07-01

    A conformal encapsulation material for use in high-power, thermally stable ultraviolet (UV) light-emitting diodes was successfully developed. For silicone, thermal degradation started at ˜200°C, and the transmittance was 85.5% at 365 nm. The transmittance decreased by 55% after thermal aging at 250°C for 72 h and it decreased further by 2.5%, even at room temperature, under continuous exposure to UV light at 365 nm for 72 h. By contrast, for the sol-gel material, thermal degradation started at ˜300°C, and the transmittance was 90% at 365 nm. The transmittance decreased negligibly after thermal aging at 250°C for 72 h and it did not decrease further even at 75°C under continuous exposure to UV light at 365 nm for 72 h.

  14. Disinfection of Pseudomonas aeruginosa biofilm contaminated tube lumens with ultraviolet C light emitting diodes

    DEFF Research Database (Denmark)

    Bak, Jimmy; Ladefoged, S.D.; Tvede, M.

    2010-01-01

    , however, be applied to obtain 99.9% disinfection rates. The major reason was that besides cells the mature biofilm contained absorbing and scattering particulates, which made the biofilm opaque. The potential of UVC light emitting diodes ( LED) for disinfection purposes in catheter-like tubes contaminated...... with biofilm was investigated. It was shown that UVC light propagation was possible through both Teflon and catheter tubes ( silicone). The disinfection efficiency of the diodes was demonstrated on tubes contaminated artificially with a Pseudomonas aeruginosa biofilm. The tubes were connected to a flow system......Bacterial biofilms on long-term catheters are a major source of infection. Exposure to ultraviolet C (UVC - 265 nm) light was shown in an earlier study to reduce the number of bacteria substantially on ex vivo treated urinary patient catheters. Very large doses ( long treatment times) should...

  15. Disinfection of Pseudomonas aeruginosa biofilm contaminated tube lumens with ultraviolet C light emitting diodes

    DEFF Research Database (Denmark)

    Bak, Jimmy; Ladefoged, Søren D; Tvede, Michael

    2010-01-01

    , however, be applied to obtain 99.9% disinfection rates. The major reason was that besides cells the mature biofilm contained absorbing and scattering particulates, which made the biofilm opaque. The potential of UVC light emitting diodes (LED) for disinfection purposes in catheter-like tubes contaminated...... with biofilm was investigated. It was shown that UVC light propagation was possible through both Teflon and catheter tubes (silicone). The disinfection efficiency of the diodes was demonstrated on tubes contaminated artificially with a Pseudomonas aeruginosa biofilm. The tubes were connected to a flow system......Bacterial biofilms on long-term catheters are a major source of infection. Exposure to ultraviolet C (UVC - 265 nm) light was shown in an earlier study to reduce the number of bacteria substantially on ex vivo treated urinary patient catheters. Very large doses (long treatment times) should...

  16. Advanced Oxidation of Tartrazine and Brilliant Blue with Pulsed Ultraviolet Light Emitting Diodes.

    Science.gov (United States)

    Scott, Robert; Mudimbi, Patrick; Miller, Michael E; Magnuson, Matthew; Willison, Stuart; Phillips, Rebecca; Harper, Willie F

    2017-01-01

      This study investigated the effect of ultraviolet light-emitting diodes (UVLEDs) coupled with hydrogen peroxide as an advanced oxidation process (AOP) for the degradation of two test chemicals. Brilliant Blue FCF consistently exhibited greater degradation than tartrazine, with 83% degradation after 300 minutes at the 100% duty cycle compared with only 17% degradation of tartrazine under the same conditions. These differences are attributable to the structural properties of the compounds. Duty cycle was positively correlated with the first-order rate constants (k) for both chemicals but, interestingly, negatively correlated with the normalized first-order rate constants (k/duty cycle). Synergistic effects of both hydraulic mixing and LED duty cycle were manifested as novel oscillations in the effluent contaminant concentration. Further, LED output and efficiency were dependent upon duty cycle and less efficient over time perhaps due to heating effects on semiconductor performance.

  17. Fabrication and characterization of 395 nm ultraviolet GaN light-emitting diodes

    Science.gov (United States)

    Lin, Min-Pang; Chen, Chien-Ju; Shan, Li-Wei; Wu, Meng-Chyi

    2017-09-01

    In this article, we demonstrated the fabrication and characterization of 395 nm GaN ultraviolet light-emitting diodes grown on patterned sapphire substrates. The current confining aperture is designed as 45, 55, 65, 75 and 85 μm. The indium tin oxide (ITO) was used as a current spreading layer. Use the metals of nickel and gold to form ohmic contact with P-AlGaN layer prior to dry etching. The 45-μm-diameter LED exhibits a 3-dB modulation bandwidth of 134 MHz at 50 mA and a light output power density of 1.2 mW (78 W/cm2) at 30 mA. In addition, the 3-dB frequency bandwidth is proportional to the square root of the injected current density.

  18. Application of ultraviolet light-emitting diodes (UV-LEDs) for water disinfection: A review.

    Science.gov (United States)

    Song, Kai; Mohseni, Madjid; Taghipour, Fariborz

    2016-05-01

    Ultraviolet (UV) disinfection is an effective technology for the inactivation of pathogens in water and is of growing interest for industrial application. A new UV source - ultraviolet light-emitting diode (UV-LED) - has emerged in the past decade with a number of advantages compared to traditional UV mercury lamps. This promising alternative raises great interest in the research on application of UV-LEDs for water treatment. Studies on UV-LED water disinfection have increased during the past few years. This article presents a comprehensive review of recent studies on UV-LEDs with various wavelengths for the inactivation of different microorganisms. Many inconsistent and incomparable data were found from published studies, which underscores the importance of establishing a standard protocol for studying UV-LED inactivation of microorganisms. Different UV sensitivities to UV-LEDs and traditional UV lamps were observed in the literature for some microorganisms, which requires further investigation for a better understanding of microorganism response to UV-LEDs. The unique aspects of UV-LEDs improve inactivation effectiveness by applying LED special features, such as multiple wavelengths and pulsed illumination; however, more studies are needed to investigate the influencing factors and mechanisms. The special features of UV-LEDs offer the flexibility of novel reactor designs for a broad application of UV-LED reactors. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Bactericidal effects of deep ultraviolet light-emitting diode for solutions during intravenous infusion.

    Science.gov (United States)

    Omotani, Sachiko; Tani, Katsuji; Aoe, Mai; Esaki, Seiji; Nagai, Katsuhito; Hatsuda, Yasutoshi; Mukai, Junji; Teramachi, Hitomi; Myotoku, Michiaki

    2018-01-01

    Background: Ultraviolet irradiation is effectively used as a disinfection method for inactivating microorganisms. Methods: We investigated the bactericidal effects by irradiation with a deep-ultraviolet light-emitting diode (DUV-LED) on the causative microorganisms of catheter related blood stream infection contaminating the solution for intravenous infusion. For irradiation, prototype modules for water disinfection with a DUV-LED were used. Experiments were conducted on five kinds of microorganisms. We examined the dependence of bactericidal action on eleven solutions. Administration sets were carried out three types. Results: When the administration set JY-PB343L containing the infusion tube made of polybutadiene was used, the bactericidal action of the DUV-LED against all tested microorganisms in the physiological saline solutions was considered to be effective. We confirmed that the number of viable bacteria decreased in 5% glucose solution and electrolyte infusions with DUV-LED irradiation. Conclusions: These results indicate that the DUV-LED irradiation has bactericidal effects in glucose infusion and electrolyte infusions by irradiating via a plasticizer-free polybutadiene administration set. We consider DUV-LED irradiation to be clinically applicable.

  20. Surface-Passivated AlGaN Nanowires for Enhanced Luminescence of Ultraviolet Light Emitting Diodes

    KAUST Repository

    Sun, Haiding

    2017-12-19

    Spontaneously-grown, self-aligned AlGaN nanowire ultraviolet light emitting diodes still suffer from low efficiency partially because of the strong surface recombination caused by surface states, i.e., oxidized surface and high density surface states. Several surface passivation methods have been introduced to reduce surface non-radiative recombination by using complex and toxic chemicals. Here, we present an effective method to suppress such undesirable surface recombination of the AlGaN nanowires via diluted potassium hydroxide (KOH) solution; a commonly used chemical process in semiconductor fabrication which is barely used as surface passivation solution in self-assembled nitride-based nanowires. The transmission electron microscopy investigation on the samples reveals almost intact nanowire structures after the passivation process. We demonstrated an approximately 49.7% enhancement in the ultraviolet light output power after 30-s KOH treatment on AlGaN nanowires grown on titanium-coated silicon substrates. We attribute such a remarkable enhancement to the removal of the surface dangling bonds and oxidized nitrides (Ga-O or Al-O bonds) at the surface as we observe the change of the carrier lifetime before and after the passivation. Thus, our results highlight the possibility of employing this process for the realization of high performance nanowire UV emitters.

  1. Ultraviolet Light Emitting Diodes Employing Nanoscale Compositional Inhomogeneities: A New Approach for Transforming Army Ultraviolet Applications

    National Research Council Canada - National Science Library

    Sampath, A. V; Garrett, G. A; Reed, M. L; Readinger, E. D; Wraback, M; Chua, C; Johnson, N. M

    2006-01-01

    Nitride semiconductor ultraviolet optical sources offer the possibility of compact, light-weight, low-cost, low-power-consumption optoelectronic sensors that would enable a new generation of fieldable...

  2. NANOSTRUCTURED HIGH PERFORMANCE ULTRAVIOLET AND BLUE LIGHT EMITTING DIODES FOR SOLID STATE LIGHTING

    Energy Technology Data Exchange (ETDEWEB)

    Arto V. Nurmikko; Jung Han

    2004-10-01

    We report on research results in this project which synergize advanced material science approaches with fundamental optical physics concepts pertaining to light-matter interaction, with the goal of solving seminal problems for the development of very high performance light emitting diodes (LEDs) in the blue and near ultraviolet for Solid State Lighting applications. Accomplishments in the first 12 month contract period include (1) new means of synthesizing zero- and one-dimensional GaN nanostructures, (2) establishment of the building blocks for making GaN-based microcavity devices, and (3) demonstration of top-down approach to nano-scale photonic devices for enhanced spontaneous emission and light extraction. These include a demonstration of eight-fold enhancement of the external emission efficiency in new InGaN QW photonic crystal structures. The body of results is presented in this report shows how a solid foundation has been laid, with several noticeable accomplishments, for innovative research, consistent with the stated milestones.

  3. Nanostructured High Performance Ultraviolet and Blue Light Emitting Diodes for Solid State Lighting

    Energy Technology Data Exchange (ETDEWEB)

    Arto V. Nurmikko; Jung Han

    2007-03-31

    We report on research results in this project which synergize advanced material science approaches with fundamental optical physics concepts pertaining to light-matter interaction, with the goal of solving seminal problems for the development of very high performance light emitting diodes (LEDs) in the blue and near ultraviolet for Solid State Lighting applications. Accomplishments in the duration of the contract period include (i) new means of synthesizing AlGaN and InN quantum dots by droplet heteroepitaxy, (ii) synthesis of AlGaInN nanowires as building blocks for GaN-based microcavity devices, (iii) progress towards direct epitaxial alignment of the dense arrays of nanowires, (iv) observation and measurements of stimulated emission in dense InGaN nanopost arrays, (v) design and fabrication of InGaN photonic crystal emitters, and (vi) observation and measurements of enhanced fluorescence from coupled quantum dot and plasmonic nanostructures. The body of results is presented in this report shows how a solid foundation has been laid, with several noticeable accomplishments, for innovative research, consistent with the stated milestones.

  4. Nanostructured High Performance Ultraviolet and Blue Light Emitting Diodes for Solid State Lighting

    Energy Technology Data Exchange (ETDEWEB)

    Arto V. Nurmikko; Jung Han

    2005-09-30

    We report on research results in this project which synergize advanced material science approaches with fundamental optical physics concepts pertaining to light-matter interaction, with the goal of solving seminal problems for the development of very high performance light emitting diodes (LEDs) in the blue and near ultraviolet for Solid State Lighting applications. Accomplishments in the second 12 month contract period include (i) new means of synthesizing AlGaN and InN quantum dots by droplet heteroepitaxy, (ii) synthesis of AlGaInN nanowires as building blocks for GaN-based microcavity devices, (iii) progress towards direct epitaxial alignment of the dense arrays of nanowires, (iv) observation and measurements of stimulated emission in dense InGaN nanopost arrays, (v) design and fabrication of InGaN photonic crystal emitters, and (vi) observation and measurements of enhanced fluorescence from coupled quantum dot and plasmonic nanostructures. The body of results is presented in this report shows how a solid foundation has been laid, with several noticeable accomplishments, for innovative research, consistent with the stated milestones.

  5. High performance near-ultraviolet flip-chip light-emitting diodes with distributed Bragg reflector

    Science.gov (United States)

    Choi, Il-Gyun; Jin, Geun-Mo; Park, Jun-Cheon; Jeon, Soo-Kun; Park, Eun-Hyun

    2015-09-01

    We have fabricated the near-ultraviolet (NUV) flip-chip (FC) light-emitting diodes (LEDs) with the high external quantum efficiency (EQE) using distributed Bragg reflectors (DBRs) and compared with conventional FC-LED using silver (Ag) reflector. Reflectance of Ag is very high (90 ~ 95 %) at visible spectrum region, but sharply decrease at NUV region. Therefore we used DBR composed of two different materials which have high-index contrast, such as TiO2 and SiO2. However, to achieve high-performance NUV flip-chip LEDs, we used Ta2O5 instead of TiO2 that absorbs lights of NUV region. Thus, we have designed a DBR composed of twenty pairs of Ta2O5 and SiO2 using optical coating design software. The DBR designed by our group achieves a reflectance of ~99 % in the NUV region (350 ~ 500 nm), which is much better than Ag reflector. Optical power is higher than the Ag-LED up to 22 % @ 390 nm.

  6. Structural design and optimization of near-ultraviolet light-emitting diodes with wide wells

    Energy Technology Data Exchange (ETDEWEB)

    Kuo, Yen-Kuang, E-mail: ykuo@cc.ncue.edu.tw [Department of Physics, National Changhua University of Education, Changhua 500, Taiwan (China); Chen, Fang-Ming [Institute of Photonics, National Changhua University of Education, Changhua 500, Taiwan (China); Chang, Jih-Yuan [Center for Teacher Education, National Changhua University of Education, Changhua 500, Taiwan (China); Shih, Ya-Hsuan [Department of Photonics, National Cheng Kung University, Tainan 701, Taiwan (China)

    2016-03-07

    The characteristics of the near-ultraviolet (NUV) light-emitting diodes (LEDs) with wide (14-nm-thick) and narrow (2-nm-thick) wells under the situations of different numbers of wells and degree of polarization are systematically investigated. The simulation results show that the Auger recombination can be efficiently suppressed with the increase of number of wells in NUV LEDs. For the LEDs with wide wells, the quantum-confined Stark effect and Shockley–Read–Hall recombination play an important role when the number of wells increases, especially when the LED is under low current injection or high degree of polarization. In order to take the advantage of using wide wells, it is proposed that the quaternary Al{sub 0.1}In{sub 0.05}Ga{sub 0.85}N barriers be used in wide-well NUV LEDs along with the use of Al{sub 0.3}Ga{sub 0.7}N/Al{sub 0.1}Ga{sub 0.9}N superlattice electron-blocking layer to mitigate the polarization effect and electron overflow. With this band-engineering structural design, the optical performance of the wide-well NUV LEDs is much better than its thin-well counterpart even under the situation of high degree of polarization.

  7. InGaN/AlGaInN-based ultraviolet light-emitting diodes with indium gallium tin oxide electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sukwon; Kim, Tae Geun, E-mail: tgkim1@korea.ac.kr

    2015-09-30

    In this study, In- and Sn-doped GaO (IGTO) is proposed as an alternative transparent conductive electrode for indium tin oxide (ITO) to improve the performance of InGaN/AlGaInN-based near ultraviolet light-emitting diodes (NUV LEDs). IGTO films were prepared by co-sputtering the ITO and Ga{sub 2}O{sub 3} targets under various target power ratios. Among those, IGTO films post-annealed at 700 °C under a hydrogen environment gave rise to a transmittance of 94% at 385 nm and a contact resistance of 9.4 × 10{sup −3} Ω-cm{sup 2} with a sheet resistance of 124 Ω/ϒ. Compared to ITO-based NUV LEDs, the IGTO-based NUV LED showed a 9% improvement in the light output power, probably due to IGTO's higher transmittance, although the forward voltage was still higher by 0.23 V. - Highlights: • Indium gallium tin oxide (IGTO) for near-ultraviolet light-emitting diode is proposed. • IGTO is fabricated by co-sputtering the ITO and Ga{sub 2}O{sub 3} targets and hydrogen annealing. • IGTO shows a 94% transmittance at 385 nm and a 9.4 × 10{sup −3} Ω-cm{sup 2} contact resistance. • Near-ultraviolet light-emitting diode with IGTO shows improved optical performance.

  8. Inactivation of Pseudomonas aeruginosa biofilm after ultraviolet light-emitting diode treatment: a comparative study between ultraviolet C and ultraviolet B

    DEFF Research Database (Denmark)

    Argyraki, Aikaterini; Markvart, Merete; Bjørndal, Lars

    2017-01-01

    GaN light-emitting diodes (LEDs) was used to deliver UV irradiation on the biofilms. The effectiveness of the UVB at 296 nm and UVC at 266 nm irradiations was quantified by counting colony-forming units. The survival of less mature biofilms (24 h grown) was studied as a function of UV-radiant exposure. All......The objective of this study was to test the inactivation efficiency of two different light-based treatments, namely ultraviolet B (UVB) and ultraviolet C (UVC) irradiation, on Pseudomonas aeruginosa biofilms at different growth stages (24, 48, and 72 h grown). In our experiments, a type of Al...

  9. The Development of Ultraviolet Light Emitting Diodes on p-SiC Substrates

    Science.gov (United States)

    Brummer, Gordon

    Ultraviolet (UV) light emitting diodes (LEDs) are promising light sources for purification, phototherapy, and resin curing applications. Currently, commercial UV LEDs are composed of AlGaN-based n-i-p junctions grown on sapphire substrates. These devices suffer from defects in the active region, inefficient p-type doping, and poor light extraction efficiency. This dissertation addresses the development of a novel UV LED device structure, grown on p-SiC substrates. In this device structure, the AlGaN-based intrinsic (i) and n-layers are grown directly on the p-type substrate, forming a p-i-n junction. The intrinsic layer (active region) is composed of an AlN buffer layer followed by three AlN/Al0.30Ga0.70N quantum wells. After the intrinsic layer, the n-layer is formed from n-type AlGaN. This device architecture addresses the deficiencies of UV LEDs on sapphire substrates while providing a vertical device geometry, reduced fabrication complexity, and improved thermal management. The device layers were grown by molecular beam epitaxy (MBE). The material properties were optimized by considering varying growth conditions and by considering the role of the layer within the device. AlN grown at 825 C and with a Ga surfactant yielded material with screw dislocation density of 1x10 7 cm-2 based on X-ray diffraction (XRD) analysis. AlGaN alloys grown in this work contained compositional inhomogeneity, as verified by high-resolution XRD, photoluminescence, and absorption measurements. Based on Stokes shift measurements, the degree of compositional inhomogeneity was correlated with the amount of excess Ga employed during growth. Compositional inhomogeneity yields carrier localizing potential fluctuations, which are advantages in light emitting device layers. Therefore, excess Ga growth conditions were used to grow AlN/Al0.30Ga0.70N quantum wells (designed using a wurtzite k.p model) with 35% internal quantum efficiency. Potential fluctuations limit the mobility of carriers

  10. Bactericidal effects of 310 nm ultraviolet light-emitting diode irradiation on oral bacteria.

    Science.gov (United States)

    Takada, Ayuko; Matsushita, Kenji; Horioka, Satoru; Furuichi, Yasushi; Sumi, Yasunori

    2017-06-06

    Ultraviolet (UV) light is used for phototherapy in dermatology, and UVB light (around 310 nm) is effective for treatment of psoriasis and atopic dermatitis. In addition, it is known that UVC light (around 265 nm) has a bactericidal effect, but little is known about the bactericidal effect of UVB light. In this study, we examined the bactericidal effects of UVB-light emitting diode (LED) irradiation on oral bacteria to explore the possibility of using a 310 nm UVB-LED irradiation device for treatment of oral infectious diseases. We prepared a UVB (310 nm) LED device for intraoral use to examine bactericidal effects on Streptococcus mutans, Streptococcus sauguinis, Porphyromonas gingivalis, and Fusobacterium nucleatum and also to examine the cytotoxicity to a human oral epithelial cell line (Ca9-22). We also examined the production of nitric oxide and hydrogen peroxide from Ca9-22 cells after irradiation with UVB-LED light. Irradiation with the 310 nm UVB-LED at 105 mJ/cm(2) showed 30-50% bactericidal activity to oral bacteria, though 17.1 mJ/cm(2) irradiation with the 265 nm UVC-LED completely killed the bacteria. Ca9-22 cells were strongly injured by irradiation with the 265 nm UVC-LED but were not harmed by irradiation with the 310 nm UVB-LED. Nitric oxide and hydrogen peroxide were produced by Ca9-22 cells with irradiation using the 310 nm UVB-LED. P. gingivalis was killed by applying small amounts of those reactive oxygen species (ROS) in culture, but other bacteria showed low sensitivity to the ROS. Narrowband UVB-LED irradiation exhibited a weak bactericidal effect on oral bacteria but showed low toxicity to gingival epithelial cells. Its irradiation also induces the production of ROS from oral epithelial cells and may enhance bactericidal activity to specific periodontopathic bacteria. It may be useful as a new adjunctive therapy for periodontitis.

  11. Feasibility of Ultraviolet Light Emitting Diodes as an Alternative Light Source for Photocatalysis

    Science.gov (United States)

    Levine, Langanf H.; Richards, Jeffrey T.; Soler, Robert; Maxik, Fred; Coutts, Janelle; Wheeler, Raymond M.

    2011-01-01

    The objective of this study was to determine whether ultraviolet light emitting diodes (UV-LEDs) could serve as an alternative photon source efficiently for heterogeneous photocatalytic oxidation (PCO). An LED module consisting of 12 high-power UV-A LEDs was designed to be interchangeable with a UV-A fluorescent black light blue (BLB) lamp in a Silica-Titania Composite (STC) packed bed annular reactor. Lighting and thermal properties were characterized to assess the uniformity and total irradiant output. A forward current of (I(sub F)) 100 mA delivered an average irradiance of 4.0 m W cm(exp -2), which is equivalent to the maximum output of the BLB, but the irradiance of the LED module was less uniform than that of the BLB. The LED- and BLB-reactors were tested for the oxidization of 50 ppmv ethanol in a continuous flow-through mode with 0.94 sec space time. At the same irradiance, the UV-A LED reactor resulted in a lower PCO rate constant than the UV-A BLB reactor (19.8 vs. 28.6 nM CO2 sec-I), and consequently lower ethanol removal (80% vs. 91%) and mineralization efficiency (28% vs. 44%). Ethanol mineralization increased in direct proportion to the irradiance at the catalyst surface. This result suggests that reduced ethanol mineralization in the LED- reactor could be traced to uneven irradiance over the photocatalyst, leaving a portion of the catalyst was under-irradiated. The potential of UV-A LEDs may be fully realized by optimizing the light distribution over the catalyst and utilizing their instantaneous "on" and "off' feature for periodic irradiation. Nevertheless, the current UV-A LED module had the same wall plug efficiency (WPE) of 13% as that of the UV-A BLB. These results demonstrated that UV-A LEDs are a viable photon source both in terms of WPE and PCO efficiency.

  12. Effects of ultraviolet light emitting diodes (LEDs) on microbial and enzyme inactivation of apple juice.

    Science.gov (United States)

    Akgün, Merve Pelvan; Ünlütürk, Sevcan

    2017-11-02

    In this study, the effects of Ultraviolet light-emitting diodes (UV-LEDs) on the inactivation of E. coli K12 (ATCC 25253), an indicator organism of E. coli O157:H7, and polyphneoloxidase (PPO) in cloudy apple juice (CAJ) were investigated. The clear (AJ) and cloudy apple juice were exposed to UV rays for 40min by using a UV device composed of four UV-LEDs with peak emissions at 254 and 280nm and coupled emissions as follows: 254/365, 254/405, 280/365, 280/405 and 254/280/365/405nm. UV-LEDs at 254nm achieved 1.6±0.1 log10 CFU/mL inactivation of E. coli K12 at UV dose of 707.2mJ/cm2. The highest inactivation of E. coli K12 (2.0±0.1log10 CFU/mL and 2.0±0.4log10CFU/mL) was achieved when the cloudy apple juice was treated with both 280nm and 280/365nm UV-LEDs. For clear apple juice the highest inactivation 4.4log10CFU/mL obtained for E. coli K12 was achieved using 4 lamps emitting light at 280nm for 40min exposure time. For the same treatment time, the experiments using a combination of lamps emitting light at 280 and 365nm (2lamp/2lamp) were resulted in 3.9±0.2log10CFU/mL reductions. UV-A and UV-C rays in combination showed a better inactivation effect on PPO than UV-C rays used separately. Residual activity of PPO in CAJ was reduced to 32.58% when treated with UV-LED in combination of UV-C (280nm) and UV-A (365nm) rays. Additionally, the total color change (ΔE) of CAJ subjected to combined UV-LED irradiation at 280/365nm was the lowest compared to other studied processing conditions. This study provides key implications for the future application of UV-LEDs to fruit juice pasteurization. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Low-threshold voltage ultraviolet light-emitting diodes based on (Al,Ga)N metal–insulator–semiconductor structures

    Science.gov (United States)

    Liang, Yu-Han; Towe, Elias

    2017-12-01

    Al-rich III–nitride-based deep-ultraviolet (UV) (275–320 nm) light-emitting diodes are plagued with a low emission efficiency and high turn-on voltages. We report Al-rich (Al,Ga)N metal–insulator–semiconductor UV light-emitting Schottky diodes with low turn-on voltages of insulator and an n-type Al0.58Ga0.42N film as the semiconductor. To improve the efficiency, we inserted a GaN quantum-well structure between the AlN insulator and the n-type Al x Ga1‑ x N semiconductor. The benefits of the quantum-well structure include the potential to tune the emission wavelength and the capability to confine carriers for more efficient radiative recombination.

  14. Development of ultraviolet electroabsorption modulators and light emitting diodes based on AlGaN alloys

    Science.gov (United States)

    Kao, Chen-Kai

    The research in this dissertation addressed the development of ultraviolet (UV) electroabsorption modulators and ultraviolet light emitting diodes (UV-LEDs), covering the spectral range from 360 to 265 nm. The materials system for both types of devices is the AlGaN alloys, either in bulk or quantum well (QW) form, grown by plasma-assisted molecular beam epitaxy (MBE). Potential applications of these devices either individually or in combination include UV non-line-of-sight free-space-optical communications, UV sensing and spectroscopic systems, Q-switched pulsed lasers, water/air purification and various medical applications. Optical modulators based on cubic III-V semiconductors have been the subject of extensive research over the past several years. Such devices are typically based on the quantum-confined Stark effect to modify the absorption spectrum of multiple-quantum-well active regions. On the other hand, in wurtzite III-Nitride semiconductors, strong electric fields are already present in the quantum wells due to intrinsic and piezoelectric polarizations; as a result, an even greater change in absorption is achievable, especially if the internal fields are compensated by the external bias so that the net field in the quantum wells is reduced. A number of UV electroabsorption modulators based on Schottky barriers on bulk GaN and GaN /AlGaN multiple quantum wells (MQWs) were designed, fabricated and characterized. Record modulation ratio of 30 % was obtained from bulk GaN Schottky barrier modulators at the excitonic resonant energy of 3.45 eV (360 nm) upon the application of 12 V reverse bias. Similarly, record modulation ratio of 43% was obtained from GaN / AlGaN MQWs Schottky barrier modulators at the excitonic resonant energy of 3.48 eV (356 nm) upon the application of 17 V reverse bias. The external quantum efficiency (EQE) of AlGaN based deep UV LEDS is relatively low (˜1% at 270 nm). This is generally attributed to the poor internal quantum efficiency

  15. Development of polychromatic ultraviolet light-emitting diodes based on three-dimensional AlGaN quantum wells

    Science.gov (United States)

    Kataoka, Ken; Funato, Mitsuru; Kawakami, Yoichi

    2017-12-01

    We present polychromatic ultraviolet (UV) spectra from electrically driven light-emitting diodes (LEDs) based on three-dimensional (3D) AlGaN quantum wells (QWs). The LED structure is fabricated on AlN composed of (0001) facets, \\{ 1\\bar{1}01\\} facets, and vicinal (0001) facets with bunched steps. Although subsequent n-AlGaN growth tends to eliminate step bunching, appropriate design of the growth procedures preserves the 3D structure of AlN even in the LED structure. Because the QWs on the (0001) facets and bunched steps emit different colors, the fabricated LED exhibits polychromatic deep UV emission.

  16. Structural, electrical and luminescent characteristics of ultraviolet light emitting structures grown by hydride vapor phase epitaxy

    Directory of Open Access Journals (Sweden)

    A.Y. Polyakov

    2017-03-01

    Full Text Available Electrical and luminescent properties of near-UV light emitting diode structures (LEDs prepared by hydride vapor phase epitaxy (HVPE were studied. Variations in photoluminescence and electroluminescence efficiency observed for LEDs grown under nominally similar conditions could be attributed to the difference in the structural quality (dislocation density, density of dislocations agglomerates of the GaN active layers, to the difference in strain relaxation achieved by growth of AlGaN/AlGaN superlattice and to the presence of current leakage channels in current confining AlGaN layers of the double heterostructure.

  17. Ultraviolet electroluminescence properties from devices based on n-ZnO/i-NiO/p-Si light-emitting diode

    Science.gov (United States)

    Wang, Hui; Zhao, Yang; Wu, Chao; Wu, Guoguang; Ma, Yan; Dong, Xin; Zhang, Baolin; Du, Guotong

    2017-07-01

    We fabricated the Ultraviolet light-emitting diode (LED) based on n-ZnO/i-NiO/p-Si heterostructure by metal-organic chemical vapor deposition (MOCVD). The device exhibited diode-like rectifying characteristics with a turn-on voltage of 3.2 V. The NiO film with high resistance state and [200] preferred orientation acted as an electron blocking layer, which produced a larger ZnO/NiO conduction band offset of 2.93 eV than that of ZnO/Si (0.30 eV). Under forward bias, prominent ultraviolet emissions peaked around 375 nm accompanying with rather weak blue-white emissions peaked around 480 nm were observed at room temperature. Furthermore, the mechanism of the electroluminescence was tentatively discussed in terms of the band diagram of the diode.

  18. A fiber optic, ultraviolet light-emitting diode-based, two wavelength fluorometer for monitoring reactive adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Granz, Christopher D.; Whitten, James E., E-mail: James-Whitten@uml.edu [Department of Chemistry, University of Massachusetts Lowell, Lowell, Massachusetts 01854 (United States); Schindler, Bryan J. [Leidos, Inc., P.O. Box 68, Gunpowder, Maryland 21010 (United States); Peterson, Gregory W. [U.S. Army Edgewood Chemical and Biological Center, Aberdeen Proving Ground, Maryland 21010 (United States)

    2016-03-15

    Construction and use of an ultraviolet light-emitting diode-based fluorometer for measuring photoluminescence (PL) from powder samples with a fiber optic probe is described. Fluorescence at two wavelengths is detected by miniature photomultiplier tubes, each equipped with a different band pass filter, whose outputs are analyzed by a microprocessor. Photoluminescent metal oxides and hydroxides, and other semiconducting nanoparticles, often undergo changes in their emission spectra upon exposure to reactive gases, and the ratio of the PL intensities at two wavelengths is diagnostic of adsorption. Use of this instrument for reactive gas sensing and gas filtration applications is illustrated by measuring changes in the PL ratio for zirconium hydroxide and zinc oxide particles upon exposure to air containing low concentrations of sulfur dioxide.

  19. Inactivation of Pseudomonas aeruginosa biofilm after ultraviolet light-emitting diode treatment: a comparative study between ultraviolet C and ultraviolet B

    Science.gov (United States)

    Argyraki, Aikaterini; Markvart, Merete; Bjørndal, Lars; Bjarnsholt, Thomas; Petersen, Paul Michael

    2017-06-01

    The objective of this study was to test the inactivation efficiency of two different light-based treatments, namely ultraviolet B (UVB) and ultraviolet C (UVC) irradiation, on Pseudomonas aeruginosa biofilms at different growth stages (24, 48, and 72 h grown). In our experiments, a type of AlGaN light-emitting diodes (LEDs) was used to deliver UV irradiation on the biofilms. The effectiveness of the UVB at 296 nm and UVC at 266 nm irradiations was quantified by counting colony-forming units. The survival of less mature biofilms (24 h grown) was studied as a function of UV-radiant exposure. All treatments were performed on three different biological replicates to test reproducibility. It was shown that UVB irradiation was significantly more effective than UVC irradiation in inactivating P. aeruginosa biofilms. UVC irradiation induced insignificant inactivation on mature biofilms. The fact that the UVB at 296 nm exists in daylight and has such disinfection ability on biofilms provides perspectives for the treatment of infectious diseases.

  20. Point-of-use water disinfection using ultraviolet and visible light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Lui, Gough Yumu, E-mail: gough@student.unsw.edu.au [UNSW Water Research Centre, School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); School of Photovoltaics and Renewable Energy Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); Roser, David, E-mail: djroser@unsw.edu.au [UNSW Water Research Centre, School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); Corkish, Richard, E-mail: r.corkish@unsw.edu.au [School of Photovoltaics and Renewable Energy Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); Ashbolt, Nicholas J., E-mail: ashbolt@ualberta.ca [UNSW Water Research Centre, School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); School of Public Health, South Academic Building, University of Alberta, Edmonton, Alberta T6G 2G7 (Canada); Stuetz, Richard, E-mail: r.stuetz@unsw.edu.au [UNSW Water Research Centre, School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052 (Australia)

    2016-05-15

    Improvements in point-of-use (POU) drinking water disinfection technologies for remote and regional communities are urgently needed. Conceptually, UV-C light-emitting diodes (LEDs) overcome many drawbacks of low-pressure mercury tube based UV devices, and UV-A or visible light LEDs also show potential. To realistically evaluate the promise of LED disinfection, our study assessed the performance of a model 1.3 L reactor, similar in size to solar disinfection bottles. In all, 12 different commercial or semi-commercial LED arrays (270–740 nm) were compared for their ability to inactivate Escherichia coli K12 ATCC W3110 and Enterococcus faecalis ATCC 19433 over 6 h. Five log{sub 10} and greater reductions were consistently achieved using the 270, 365, 385 and 405 nm arrays. The output of the 310 nm array was insufficient for useful disinfection while 430 and 455 nm performance was marginal (≈ 4.2 and 2.3-log{sub 10}s E. coli and E. faecalis over the 6 h). No significant disinfection was observed with the 525, 590, 623, 660 and 740 nm arrays. Delays in log-phase inactivation of E. coli were observed, particularly with UV-A wavelengths. The radiation doses required for > 3-log{sub 10} reduction of E. coli and E. faecalis differed by 10 fold at 270 nm but only 1.5–2.5 fold at 365–455 nm. Action spectra, consistent with the literature, were observed with both indicators. The design process revealed cost and technical constraints pertaining to LED electrical efficiency, availability and lifetime. We concluded that POU LED disinfection using existing LED technology is already technically possible. UV-C LEDs offer speed and energy demand advantages, while UV-A/violet units are safer. Both approaches still require further costing and engineering development. Our study provides data needed for such work. - Highlights: • Disinfection of E. coli and E. faecalis achieved with 270 and 365–455 nm LEDs • No significant disinfection was found with 310 and > 455 nm LEDs

  1. An Analysis of the Far-Field Radiation Pattern of the Ultraviolet Light-Emitting Diode (LED) Engin LZ4-00UA00 Diode with and without Beam Shaping Optics

    Science.gov (United States)

    2015-09-01

    SEP 2015 US Army Research Laboratory An Analysis of the Far-Field Radiation Pattern of the Ultraviolet Light - Emitting Diode (LED) Engin...Radiation Pattern of the Ultraviolet Light - Emitting Diode (LED) Engin LZ4-00UA00 Diode with and without Beam Shaping Optics 5a. CONTRACT NUMBER... light - emitting diode (LED), with and without beam shaping optics. This LED has 4 emitters arranged in a square pattern that are off-center from the

  2. Modularized and water-cooled photo-catalyst cleaning devices for aquaponics based on ultraviolet light-emitting diodes

    Science.gov (United States)

    Yang, Henglong; Lung, Louis; Wei, Yu-Chien; Huang, Yi-Bo; Chen, Zi-Yu; Chou, Yu-Yang; Lin, Anne-Chin

    2017-08-01

    The feasibility of applying ultraviolet light-emitting diodes (UV-LED's) as triggering sources of photo-catalyst based on titanium dioxide (TiO2) nano-coating specifically for water-cleaning process in an aquaponics system was designed and proposed. The aquaponics system is a modern farming system to integrate aquaculture and hydroponics into a single system to establish an environmental-friendly and lower-cost method for farming fish and vegetable all together in urban area. Water treatment in an aquaponics system is crucial to avoid mutual contamination. we proposed a modularized watercleaning device composed of all commercially available components and parts to eliminate organic contaminants by using UV-LED's for TiO2 photo-catalyst reaction. This water-cleaning module consisted of two coaxial hollowed cylindrical pipes can be submerged completely in water for water treatment and cooling UV-LED's. The temperature of the UV-LED after proper thermal management can be reduced about 16% to maintain the optimal operation condition. Our preliminary experimental result by using Methylene Blue solution to simulate organic contaminants indicated that TiO2 photo-catalyst triggered by UV-LED's can effectively decompose organic compound and decolor Methylene Blue solution.

  3. Time Effectiveness of Ultraviolet C Light (UVC) Emitted by Light Emitting Diodes (LEDs) in Reducing Stethoscope Contamination.

    Science.gov (United States)

    Messina, Gabriele; Fattorini, Mattia; Nante, Nicola; Rosadini, Daniele; Serafini, Andrea; Tani, Marco; Cevenini, Gabriele

    2016-09-23

    Today it is well demonstrated that stethoscopes can be as contaminated as hands, which are a recognized source of Health-Care Associated Infections (HCAIs). Ultraviolet C (UVC) light has proven disinfection capacity and the innovative UVC technology of Light Emitting Diode (LED) shows several potential benefits. To verify whether the use of UVC LEDs is effective and reliable in stethoscope membrane disinfection after prolonged use, a pre-post intervention study was conducted. A total of 1668 five-minute cycles were performed on two UVC LEDs to simulate their use; thereafter, their disinfection capacity was tested on stethoscope membranes used on a previously auscultated volunteer. Then, a further 1249 cycles were run and finally the LEDs were tested to assess performance in reducing experimental contamination by Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli on the stethoscope membrane. Baseline volunteer contamination identified 104 Colony Forming Units (CFUs) while treated Petri dishes had 12 and 15 CFUs (p LEDs demonstrated the capacity to maintain high levels of disinfection after more than 240 h of use and they were effective against common microorganisms that are causative agents of HCAIs.

  4. Flexible deep-ultraviolet light-emitting diodes for significant improvement of quantum efficiencies by external bending

    KAUST Repository

    Shervin, Shahab

    2018-01-26

    Deep ultraviolet (DUV) light at the wavelength range of 250‒280 nm (UVC spectrum) is essential for numerous applications such as sterilization, purification, sensing, and communication. III-nitride-based DUV light-emitting diodes (DUV LEDs), like other solid-state lighting sources, offer a great potential to replace the conventional gas-discharged lamps with short lifetimes and toxic-element-bearing nature. However, unlike visible LEDs, the DUV LEDs are still suffering from low quantum efficiencies (QEs) and low optical output powers. In this work, reported is a new route to improve QEs of AlGaN-based DUV LEDs using mechanical flexibility of recently developed bendable thin-film structures. Numerical studies show that electronic band structures of AlGaN heterostructures and resulting optical and electrical characteristics of the devices can be significantly modified by external bending through active control of piezoelectric polarization. Internal quantum efficiency (IQE) is enhanced higher than three times, when the DUV LEDs are moderately bent to induce in-plane compressive strain in the heterostructure. Furthermore, efficiency droop at high injection currents is mitigated and turn-on voltage of diodes decreases with the same bending condition. The concept of bendable DUV LEDs with a controlled external strain can provide a new path for high-output-power and high-efficiency devices.

  5. Ultraviolet-enhanced light emitting diode employing individual ZnO microwire with SiO2 barrier layers

    Science.gov (United States)

    Xu, Yingtian; Xu, Li; Dai, Jun; Ma, Yan; Chu, Xianwei; Zhang, Yuantao; Du, Guotong; Zhang, Baolin; Yin, Jingzhi

    2015-05-01

    This paper details the fabrication of n-ZnO single microwire (SMW)-based high-purity ultraviolet light-emitting diodes (UV-LEDs) with an added SiO2 barrier layer on the p-Si substrate. However, the current-voltage (I-V) curve exhibited non-ideal rectifying characteristics. Under forward bias, both UV and visible emissions could be detected by electroluminescence (EL) measurement. When bias voltage reached 60 V at room temperature, a UV emission spike occurred at 390 nm originating from the n-ZnO SMW. Compared with the EL spectrum of the n-ZnO SMW/p-Si heterojunction device without the SiO2 barrier layer, we saw improved UV light extraction efficiency from the current-blocking effect of the SiO2 layer. The intense UV emission in the n-ZnO SMW/SiO2/p-Si heterojunction indicated that the SiO2 barrier layer can restrict the movement of electrons as expected and result in effective electron-hole recombination in ZnO SMW.

  6. Calibration of optimal use parameters for an ultraviolet light-emitting diode in eliminating bacterial contamination on needleless connectors.

    Science.gov (United States)

    Hutchens, M P; Drennan, S L; Cambronne, E D

    2015-06-01

    Needleless connectors may develop bacterial contamination and cause central-line-associated bloodstream infections (CLABSI) despite rigorous application of best-practice. Ultraviolet (UV) light-emitting diodes (LED) are an emerging, increasingly affordable disinfection technology. We tested the hypothesis that a low-power UV LED could reliably eliminate bacteria on needleless central-line ports in a laboratory model of central-line contamination. Needleless central-line connectors were inoculated with Staphylococcus aureus. A 285 nm UV LED was used in calibrated fashion to expose contaminated connectors. Ports were directly applied to agar plates and flushed with sterile saline, allowing assessment of bacterial survival on the port surface and in simulated usage flow-through fluid. UV applied to needleless central-line connectors was highly lethal at 0·5 cm distance at all tested exposure times. At distances >1·5 cm both simulated flow-through and port surface cultures demonstrated significant bacterial growth following UV exposure. Logarithmic-phase S. aureus subcultures were highly susceptible to UV induction/maintenance dosing. Low-power UV LED doses at fixed time and distance from needleless central-line connector ports reduced cultivable S. aureus from >10(6) CFU to below detectable levels in this laboratory simulation of central-line port contamination. Low-power UV LEDs may represent a feasible alternative to current best-practice in connector decontamination. © 2015 The Society for Applied Microbiology.

  7. 234 nm and 246 nm AlN-Delta-GaN quantum well deep ultraviolet light-emitting diodes

    Science.gov (United States)

    Liu, Cheng; Ooi, Yu Kee; Islam, S. M.; Xing, Huili Grace; Jena, Debdeep; Zhang, Jing

    2018-01-01

    Deep ultraviolet (DUV) AlN-delta-GaN quantum well (QW) light-emitting diodes (LEDs) with emission wavelengths of 234 nm and 246 nm are proposed and demonstrated in this work. Our results reveal that the use of AlN-delta-GaN QW with ˜1-3 monolayer GaN delta-layer can achieve a large transverse electric (TE)-polarized spontaneous emission rate instead of transverse magnetic-polarized emission, contrary to what is observed in conventional AlGaN QW in the 230-250 nm wavelength regime. The switching of light polarization in the proposed AlN-delta-GaN QW active region is attributed to the rearrangement of the valence subbands near the Γ-point. The light radiation patterns obtained from angle-dependent electroluminescence measurements for the Molecular Beam Epitaxy (MBE)-grown 234 nm and 246 nm AlN-delta-GaN QW LEDs show that the photons are mainly emitted towards the surface rather than the edge, consistent with the simulated patterns achieved by the finite-difference time-domain modeling. The results demonstrate that the proposed AlN-delta-GaN QWs would potentially lead to high-efficiency TE-polarized surface-emitting DUV LEDs.

  8. Time Effectiveness of Ultraviolet C Light (UVC Emitted by Light Emitting Diodes (LEDs in Reducing Stethoscope Contamination

    Directory of Open Access Journals (Sweden)

    Gabriele Messina

    2016-09-01

    Full Text Available Today it is well demonstrated that stethoscopes can be as contaminated as hands, which are a recognized source of Health-Care Associated Infections (HCAIs. Ultraviolet C (UVC light has proven disinfection capacity and the innovative UVC technology of Light Emitting Diode (LED shows several potential benefits. To verify whether the use of UVC LEDs is effective and reliable in stethoscope membrane disinfection after prolonged use, a pre-post intervention study was conducted. A total of 1668 five-minute cycles were performed on two UVC LEDs to simulate their use; thereafter, their disinfection capacity was tested on stethoscope membranes used on a previously auscultated volunteer. Then, a further 1249 cycles were run and finally the LEDs were tested to assess performance in reducing experimental contamination by Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli on the stethoscope membrane. Baseline volunteer contamination identified 104 Colony Forming Units (CFUs while treated Petri dishes had 12 and 15 CFUs (p < 0.001. Statistically significant differences (p < 0.001 were also found relating to the reduction of specific bacteria: in particular, after treatment no CFU were observed for S. aureus and E. coli. UVC LEDs demonstrated the capacity to maintain high levels of disinfection after more than 240 h of use and they were effective against common microorganisms that are causative agents of HCAIs.

  9. Optimization of structure parameters for highly efficient AlGaN based deep ultraviolet light emitting diodes

    Science.gov (United States)

    Mondal, Ramit Kumar; Chatterjee, Vijay; Singh, Sumitra; Islam, Sk Masiul; Pal, Suchandan

    2017-12-01

    The efficiency of any LEDs critically depends on its base structure. In this paper, we have reported the dependence of active layer structure on the performance of AlGaN based deep ultraviolet light emitting diodes (LEDs) having emission wavelength at 265 nm which is very crucial for DNA manipulation of most of the water borne harmful pathogens. Advanced device simulations have been performed for the deep UV-LEDs by using SiLENSE module of the SimuLED software tool. We have optimized the number of quantum well, quantum well thickness, aluminum content in electron blocking layer (EBL) and the aluminum content in the barrier region. We have observed that optimization of structural properties plays a crucial role in improving the internal quantum efficiency leading to improvement of overall efficiency of the LEDs. The internal quantum efficiency of the UVsbnd LED having an emission wavelength of 265 nm reaches up to 55% when the number of quantum well is fixed to five and each well has a thickness in the order of 1.8 nm with aluminum content as 95% and 62% in EBL and barrier region respectively.

  10. Indium gallium nitride-based ultraviolet, blue, and green light-emitting diodes functionalized with shallow periodic hole patterns.

    Science.gov (United States)

    Jeong, Hyun; Salas-Montiel, Rafael; Lerondel, Gilles; Jeong, Mun Seok

    2017-04-04

    In this study, we investigated the improvement in the light output power of indium gallium nitride (InGaN)-based ultraviolet (UV), blue, and green light-emitting diodes (LEDs) by fabricating shallow periodic hole patterns (PHPs) on the LED surface through laser interference lithography and inductively coupled plasma etching. Noticeably, different enhancements were observed in the light output powers of the UV, blue, and green LEDs with negligible changes in the electrical properties in the light output power versus current and current versus voltage curves. In addition, confocal scanning electroluminescence microscopy is employed to verify the correlation between the enhancement in the light output power of the LEDs with PHPs and carrier localization of InGaN/GaN multiple quantum wells. Light propagation through the PHPs on the UV, blue, and green LEDs is simulated using a three-dimensional finite-difference time-domain method to confirm the experimental results. Finally, we suggest optimal conditions of PHPs for improving the light output power of InGaN LEDs based on the experimental and theoretical results.

  11. Light extraction enhancement of AlGaN-based ultraviolet light-emitting diodes by substrate sidewall roughening

    Science.gov (United States)

    Guo, Yanan; Zhang, Yun; Yan, Jianchang; Xie, Haizhong; Liu, Lei; Chen, Xiang; Hou, Mengjun; Qin, Zhixin; Wang, Junxi; Li, Jinmin

    2017-07-01

    The effect of sapphire substrate's sidewall roughening on light extraction of AlGaN-based ultraviolet light-emitting diodes (UV LEDs) is investigated. Finite-difference time-domain simulation reveals that a roughening region for effective light extraction enhancement exists on the substrate's sidewall. Roughening outside the effective roughening region will result in undesirable inward photon scattering and absorption. For TM-polarization-dominated deep-UV LEDs, the effective roughening region is from the substrate's backside to the position about L/2 × tan(θc) away from the substrate's front side, where L is the side length of the LED device and θc is the critical angle of total reflection. In the LED device fabrication, picosecond laser dicing is employed to realize roughening layers on the sapphire substrate's sidewalls. The UV LEDs with three roughening layers have 13.2% higher average light output power (LOP) at 20 mA than those with two roughening layers, thanks to the larger roughening area in the effective roughening region. When additional roughening layers beyond the effective roughening region are applied, the LOP decreases as the simulation predicts. Furthermore, the values of leakage current and forward voltage of these LEDs are consistently below 0.2 μA at -10 V and 5.8-6.0 V at 20 mA, respectively, showing no thermal damage to intrinsic diode performance by the laser processing.

  12. Ultraviolet light-emitting diode irradiation-induced cell death in HL-60 human leukemia cells in vitro

    Science.gov (United States)

    XIE, DONG; SUN, YAN; WANG, LINGZHEN; LI, XIAOLING; ZANG, CHUANNONG; ZHI, YUNLAI; SUN, LIRONG

    2016-01-01

    Ultraviolet (UV) radiation is considered to be a potent cell-damaging agent in various cell lineages; however, the effect of UV light-emitting diode (LED) irradiation on human cells remains unclear. The aim of the present study was to examine the effect of UV LED irradiation emitting at 280 nm on cultured HL-60 human leukemia cells, and to explore the underlying mechanisms. HL-60 cells were irradiated with UV LED (8, 15, 30 and 60 J/m2) and incubated for 2 h after irradiation. The rates of cell proliferation and apoptosis, the cell cycle profiles and the mRNA expression of B-cell lymphoma 2 (Bcl-2) were detected using cell counting kit-8, multicaspase assays, propidium iodide staining and reverse transcription-quantitative polymerase chain reaction, respectively. The results showed that UV LED irradiation (8–60 J/m2) inhibited the proliferation of HL-60 cells in a dose-dependent manner. UV LED at 8–30 J/m2 induced dose-dependent apoptosis and G0/G1 cell cycle arrest, and inhibited the expression of Bcl-2 mRNA, while UV LED at 60 J/m2 induced necrosis. In conclusion, 280 nm UV LED irradiation inhibits proliferation and induces apoptosis and necrosis in cultured HL-60 cells. In addition, the cell cycle arrest at the G0/G1 phase and the downregulation of Bcl-2 mRNA expression were shown to be involved in UV LED-induced apoptosis. PMID:26820261

  13. Improved Turn-On and Operating Voltages in AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes

    Science.gov (United States)

    Hao, Guo-Dong; Taniguchi, Manabu; Tamari, Naoki; Inoue, Shin-ichiro

    2017-10-01

    While good ohmic contact formation has been achieved on both p-GaN and n-AlGaN surfaces, the turn-on and operating voltages of AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) remain very high. We find that this critical problem is mainly caused by the large difference between the annealing temperatures required for ohmic contact formation on the p-GaN and high Al-fraction n-AlGaN surfaces. We studied the effects of the high-temperature annealing treatments required for n-ohmic contact formation on the subsequent p-ohmic contact formation process in DUV-LEDs. The results show that post-annealing treatment at high temperature is necessary to form an ohmic contact on n-Al0.7Ga0.3N, but a treatment temperature of 900°C or more could cause severe degradation of the specific contact resistivity and the bulk resistivity of p-GaN. We conclude that 900°C is the optimum temperature to form an ohmic contact on n-Al0.7Ga0.3N in DUV-LEDs, where p-GaN and n-Al0.7Ga0.3N act as the p- and n-ohmic contact layers, respectively. We also found that the specific contact resistivity of p-GaN can be reduced by an additional low-temperature annealing treatment after the high-temperature annealing step; this effect can be attributed to the enhancement of the hole concentration in the p-GaN surface contact region. Finally, DUV-LEDs that emit at 280 nm were fabricated using four different annealing treatments during processing. A considerable reduction in the series resistance and thereby in the operating voltage was confirmed using the annealing process proposed above, consisting of a high-temperature anneal at 900°C followed by a low-temperature anneal at 500°C for 3 min.

  14. Performance enhancement of AlGaN-based ultraviolet light-emitting diodes by inserting the last quantum well into electron blocking layer

    Science.gov (United States)

    Li, Fangzheng; Wang, Lianshan; Zhao, Guijuan; Meng, Yulin; Li, Huijie; Yang, Shaoyan; Wang, Zhanguo

    2017-10-01

    The characteristics of AlGaN-based ultraviolet light-emitting diodes (UV LEDs) with the last quantum well inserted into electron blocking layer(EBL) have been investigated numerically in this study. The simulation results indicate that the light-emitting EBL(LEEBL) can suppress electron leakage better than traditional EBL due to the superior electron confinement and hole injection of the quantum well in LEEBL. Besides, the LEEBL with a quantum well closer to active region can further improve the performance of the UV LED owning to better electron blocking and hole injection for the quantum wells in active region. As a result, the output power of the UV LED with the quantum well located in the middle of LEEBL increases by 17.83% and the utilization of LEEBL with a quantum well located closer to the active region can further enhance the output power by 54.11% compared with traditional UV LED.

  15. Inactivation of Pseudomonas aeruginosa biofilm after ultraviolet light-emitting diode treatment: a comparative study between ultraviolet C and ultraviolet B

    DEFF Research Database (Denmark)

    Argyraki, Aikaterini; Markvart, Merete; Bjørndal, Lars

    2017-01-01

    The objective of this study was to test the inactivation efficiency of two different light-based treatments, namely ultraviolet B (UVB) and ultraviolet C (UVC) irradiation, on Pseudomonas aeruginosa biofilms at different growth stages (24, 48, and 72 h grown). In our experiments, a type of Al...

  16. Performance improvement of AlGaN-based ultraviolet light-emitting diodes by amending inverted-Y-shaped barriers with alternate doped Si and Mg

    Science.gov (United States)

    Hou, Yufei; Guo, Zhiyou; Liu, Yang; Guo, Min; Huang, Jing; Yao, Shunyu; Zhang, Xiu; Gong, Xing; Xu, Zhihong

    2017-07-01

    The effect of using inverted-Y-shaped barriers with alternate doped Si and Mg in traditional AlGaN-based ultraviolet light-emitting diodes (UV-LEDs) has been investigated through APSYS simulation program. The results indicated that the specially designed UV-LED has better light output power and internal quantum efficiency (IQE) compared with the conventional AlGaN barriers and the AlGaN composition-graded barriers. Efficiency droop of the new structure reduced to 2.17% while 41.73% in conventional LED. In addition, alternating doped Si and Mg in AlGaN composition-graded barriers obviously improves the hole injection efficiency, modulate carrier distribution and suppress electron spill out from active region, and thus enhances the carrier radiation recombination rate, ameliorate IQE and optical output power.

  17. AlGaN-based deep-ultraviolet light-emitting diodes grown on high-quality AlN template using MOVPE

    KAUST Repository

    Yan, Jianchang

    2015-03-01

    In this article, we report the growth of high-quality AlN film using metal-organic vapor phase epitaxy. Three layers of middle-temperature (MT) AlN were introduced during the high-temperature (HT) AlN growth. During the MT-AlN layer growth, aluminum and nitrogen sources were closed for 6 seconds after every 5-nm MT-AlN, while H2 carrier gas was always on. The threading dislocation density in an AlN epi-layer on a sapphire substrate was reduced by almost half. AlGaN-based deep-ultraviolet light-emitting diodes were further fabricated based on the AlN/sapphire template. At 20 mA driving current, the emitted peak wavelength is 284.5 nm and the light output power exceeds 3 mW.

  18. GaN/AlGaN ultraviolet light-emitting diode with an embedded porous-AlGaN distributed Bragg reflector

    Science.gov (United States)

    Wang, Guan-Jhong; Hong, Bo-Syun; Chen, Yi-Yun; Yang, Zhong-Jie; Tsai, Tzong-Liang; Lin, Yung-Sen; Lin, Chia-Feng

    2017-12-01

    A GaN/AlGaN-based ultraviolet light-emitting diode (LED) structure with an embedded porous-AlGaN reflector was fabricated by a doping-selective electrochemical (EC) wet-etching process. The n+-AlGaN/undoped-AlGaN (u-AlGaN) stack structures with different Al contents were transformed into porous-AlGaN/u-AlGaN stack structures that acted as the embedded distributed Bragg reflectors (DBRs). The porosity of the EC-treated AlGaN layer was increased by decreasing the Al content in the n+-AlGaN layer. The reflectivity of the porous-AlGaN DBR structure was measured to be 90% at 379.3 nm with a 37.2 nm stopband width. The photoluminescence emission intensity of the DBR-LED was enhanced by forming the embedded porous-AlGaN DBR structure.

  19. Current crowding and self-heating effects in AlGaN-based flip-chip deep-ultraviolet light-emitting diodes

    Science.gov (United States)

    Hao, Guo-Dong; Taniguchi, Manabu; Tamari, Naoki; Inoue, Shin-ichiro

    2018-01-01

    We thoroughly explored the physical origin of the efficiency decrease with increasing injection current and current crowding effect in 280 nm AlGaN-based flip-chip deep-ultraviolet (DUV) light-emitting diodes (LEDs). The current spreading length was experimentally determined to be much smaller in DUV LEDs than that in conventional InGaN-based visible LEDs. The severe self-heating caused by the low power conversion efficiency of DUV LEDs should be mainly responsible for the considerable decrease of efficiency when current crowding is present. The wall-plug efficiency of the DUV LEDs was markedly enhanced by using a well-designed p-electrode pattern to improve the current distribution.

  20. Note: Design and characterization of an optical light source based on mixture of white and near-ultraviolet light emitting diode spectra

    Science.gov (United States)

    Sametoglu, Ferhat; Celikel, Oguz

    2011-04-01

    An optical light source based on a solid-state lighting technology is designed. Main components of the light source are a phosphor-converted white and a near-ultraviolet (near-UV) light emitting diodes (LEDs), the spectral power distributions (SPDs) of which are mixed using a fiber optic combiner. The near-UV LED is used for improving insufficient SPDs of the white LED at shorter wavelengths of the visible radiation. Stable direct current power supplies are also designed and used to operate each of the LED separately. Three steps of the driving current can be selected by means of serial resistors altered with a commutator at nominal current values of ˜40%, ˜50%, and ˜69%. The light source can be used for many characteristic measurements within the scope of photometry and colorimetry.

  1. Absorbance detector for high-performance liquid chromatography based on light-emitting diodes for the deep-ultraviolet range.

    Science.gov (United States)

    Bomastyk, Benjamin; Petrovic, Igor; Hauser, Peter C

    2011-06-17

    A HPLC-detector has been designed which employs light-emitting diodes in the deep-UV-range below 300 nm as wavelength specific radiation sources and special UV-photodiodes for measuring the signal. A monochromator is therefore not needed. The design features a beam splitter and a reference photodiode, precision mechanics for adjustment of the light beams and electronics for stabilization of the LED-current. The processing of the photodiode currents is carried out with a high performance log-ratio amplifier which allows direct absorbance measurements. The optical and electronic performance of the detector was characterised and high precision over several absorbance units was obtained. Testing of analytical separation methods in isocratic as well as gradient modes employing UV-detection at 255 and 280 nm showed a very similar performance to a commercial photodiode-array detector used in the fixed wavelength mode in terms of linearity, precision and detection limits. The chief advantages of the new device are small size, low power consumption, and low cost. Copyright © 2011 Elsevier B.V. All rights reserved.

  2. Absorbance detector for capillary electrophoresis based on light-emitting diodes and photodiodes for the deep-ultraviolet range.

    Science.gov (United States)

    Bui, Duy Anh; Hauser, Peter C

    2015-11-20

    A new absorbance detector for capillary electrophoresis featuring relatively high intensity light-emitting diodes as radiation sources and photodiodes for the deep-UV range was developed. The direct relationship of absorbance values and concentrations was obtained by emulating Lambert-Beer's law with the application of a beam splitter to obtain a reference signal and a log-ratio amplifier circuitry. The performance of the cell was investigated at 255 nm with the detection of sulfanilic, 4-nitrobenzoic, 4-hydroxybenzoic and 4-aminobenzoic acid and the indirect detection of acetate, propionate, butyrate and caproate using benzoate as the displacement dye molecule. Vanillic acid, L-tyrosine and DL-tryptophan as well as the sulfonamides sulfamerazine, sulfathiazole and sulfamethazine were determined at 280 nm. Good linearities over 3 orders of magnitude were obtained. The noise level recorded was as low as 50 μAU and the drift typically <200 μAU/5 min. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Enhancing the Light-Extraction Efficiency of AlGaN Nanowires Ultraviolet Light-Emitting Diode by using Nitride/Air Distributed Bragg Reflector Nanogratings

    KAUST Repository

    Alias, Mohd Sharizal

    2017-09-11

    The performance and efficiency of AlGaN ultraviolet light-emitting diodes have been limited by the extremely low light-extraction efficiency (LEE) due to the intrinsic material properties of AlGaN. Here, to enhance the LEE of the device, we demonstrate an AlGaN nanowires light-emitting diode (NWs-LED) integrated with nitride/air Distributed Bragg Reflector (DBR) nanogratings. Compared to a control device (only mesa), the AlGaN NWs-LED with the nitride/air DBR nanogratings exhibit enhancement in the light output power and external quantum efficiency (EQE) by a factor of ∼1.67. The higher light output power and EQE are attributed mainly to the multiple reflectances laterally for the transverse magnetic (TM)-polarized light and scattering introduced by the nanogratings. To further understand the LEE enhancement, the electrical field distribution, extraction ratio and polar pattern of the AlGaN NWs-LED with and without the nitride/air DBR nanogratings were analyzed using the finite-difference-time-domain method. It was observed that the TM-field emission was confined and scattered upward whereas the polar pattern was intensified for the AlGaN NWs-LED with the nanogratings. Our approach to enhance the LEE via the nitride/air DBR nanogratings can provide a promising route for increasing the efficiency of AlGaN-based LEDs, also, to functioning as facet mirror for AlGaN-based laser diodes.

  4. Time-resolved ultraviolet near-field scanning optical microscope for characterizing photoluminescence lifetime of light-emitting devices.

    Science.gov (United States)

    Park, Kyoung-Duck; Jeong, Hyun; Kim, Yong Hwan; Yim, Sang-Youp; Lee, Hong Seok; Suh, Eun-Kyung; Jeong, Mun Seok

    2013-03-01

    We developed a instrument consisting of an ultraviolet (UV) near-field scanning optical microscope (NSOM) combined with time-correlated single photon counting, which allows efficient observation of temporal dynamics of near-field photoluminescence (PL) down to the sub-wavelength scale. The developed time-resolved UV NSOM system showed a spatial resolution of 110 nm and a temporal resolution of 130 ps in the optical signal. The proposed microscope system was successfully demonstrated by characterizing the near-field PL lifetime of InGaN/GaN multiple quantum wells.

  5. High-Performance 348 nm AlGaN/GaN-Based Ultraviolet-Light-Emitting Diode with a SiN Buffer Layer

    Science.gov (United States)

    Lee, Young-Bae; Wang, Tao; Liu, Yu-Huai; Ao, Jin-Ping; Izumi, Yuji; Lacroix, Yves; Li, Hong-Dong; Bai, Jie; Naoi, Yoshiki; Sakai, Shiro

    2002-07-01

    A 348 nm ultraviolet-light-emitting diode (UV-LED) based on an AlGaN/GaN single quantum well (SQW) with a high optical power is reported. In this structure, a thin SiN buffer is introduced before the growth of a conventional low-temperature GaN buffer layer. Such a buffer layer can dramatically reduce the density of threading dislocation as we have previously reported. Since the optical performance of UV-LED is generally known to be sensitive to the density of threading dislocations, unlike the InGaN/GaN- based blue LED, our UV-LED has a higher optical power than that of a similar structure but without a SiN buffer layer. Since our new buffer technology is much easier than the so-called epitaxial lateral overgrowth (ELO) or pendeo-epitaxy method, it is highly recommended for use in the fabrication of GaN-based optical devices, particularly AlGaN/GaN-based UV-LED.

  6. An AlGaN Core-Shell Tunnel Junction Nanowire Light-Emitting Diode Operating in the Ultraviolet-C Band.

    Science.gov (United States)

    Sadaf, S M; Zhao, S; Wu, Y; Ra, Y-H; Liu, X; Vanka, S; Mi, Z

    2017-02-08

    To date, semiconductor light emitting diodes (LEDs) operating in the deep ultraviolet (UV) spectral range exhibit very low efficiency due to the presence of large densities of defects and extremely inefficient p-type conduction of conventional AlGaN quantum well heterostructures. We have demonstrated that such critical issues can be potentially addressed by using nearly defect-free AlGaN tunnel junction core-shell nanowire heterostructures. The core-shell nanowire arrays exhibit high photoluminescence efficiency (∼80%) in the UV-C band at room temperature. With the incorporation of an epitaxial Al tunnel junction, the p-(Al)GaN contact-free nanowire deep UV LEDs showed nearly one order of magnitude reduction in the device resistance, compared to the conventional nanowire p-i-n device. The unpackaged Al tunnel junction deep UV LEDs exhibit an output power >8 mW and a peak external quantum efficiency ∼0.4%, which are nearly one to two orders of magnitude higher than previously reported AlGaN nanowire devices. Detailed studies further suggest that the maximum achievable efficiency is limited by electron overflow and poor light extraction efficiency due to the TM polarized emission.

  7. Efficiency improvement of GaN-based ultraviolet light-emitting diodes with reactive plasma deposited AlN nucleation layer on patterned sapphire substrate.

    Science.gov (United States)

    Lee, Chia-Yu; Tzou, An-Jye; Lin, Bing-Cheng; Lan, Yu-Pin; Chiu, Ching-Hsueh; Chi, Gou-Chung; Chen, Chi-Hsiang; Kuo, Hao-Chung; Lin, Ray-Ming; Chang, Chun-Yen

    2014-01-01

    The flip chip ultraviolet light-emitting diodes (FC UV-LEDs) with a wavelength of 365 nm are developed with the ex situ reactive plasma deposited (RPD) AlN nucleation layer on patterned sapphire substrate (PSS) by an atmospheric pressure metal-organic chemical vapor deposition (AP MOCVD). The ex situ RPD AlN nucleation layer can significantly reduce dislocation density and thus improve the crystal quality of the GaN epitaxial layers. Utilizing high-resolution X-ray diffraction, the full width at half maximum of the rocking curve shows that the crystalline quality of the epitaxial layer with the (RPD) AlN nucleation layer is better than that with the low-temperature GaN (LT-GaN) nucleation layer. The threading dislocation density (TDD) is estimated by transmission electron microscopy (TEM), which shows the reduction from 6.8 × 10(7) cm(-2) to 2.6 × 10(7) cm(-2). Furthermore, the light output power (LOP) of the LEDs with the RPD AlN nucleation layer has been improved up to 30 % at a forward current of 350 mA compared to that of the LEDs grown on PSS with conventional LT-GaN nucleation layer.

  8. Light-emitting Diodes

    Science.gov (United States)

    Opel, Daniel R.; Hagstrom, Erika; Pace, Aaron K.; Sisto, Krisanne; Hirano-Ali, Stefanie A.; Desai, Shraddha

    2015-01-01

    Background: In the early 1990s, the biological significance of light-emitting diodes was realized. Since this discovery, various light sources have been investigated for their cutaneous effects. Study design: A Medline search was performed on light-emitting diode lights and their therapeutic effects between 1996 and 2010. Additionally, an open-label, investigator-blinded study was performed using a yellow light-emitting diode device to treat acne, rosacea, photoaging, alopecia areata, and androgenetic alopecia. Results: The authors identified several case-based reports, small case series, and a few randomized controlled trials evaluating the use of four different wavelengths of light-emitting diodes. These devices were classified as red, blue, yellow, or infrared, and covered a wide range of clinical applications. The 21 patients the authors treated had mixed results regarding patient satisfaction and pre- and post-treatment evaluation of improvement in clinical appearance. Conclusion: Review of the literature revealed that differing wavelengths of light-emitting diode devices have many beneficial effects, including wound healing, acne treatment, sunburn prevention, phototherapy for facial rhytides, and skin rejuvenation. The authors’ clinical experience with a specific yellow light-emitting diode device was mixed, depending on the condition being treated, and was likely influenced by the device parameters. PMID:26155326

  9. Variation of the external quantum efficiency with temperature and current density in red, blue, and deep ultraviolet light-emitting diodes

    Science.gov (United States)

    Park, Jun Hyuk; Lee, Jong Won; Kim, Dong Yeong; Cho, Jaehee; Schubert, E. Fred; Kim, Jungsub; Lee, Jinsub; Kim, Yong-Il; Park, Youngsoo; Kim, Jong Kyu

    2016-01-01

    The temperature-dependent external quantum efficiencies (EQEs) were investigated for a 620 nm AlGaInP red light-emitting diodes (LEDs), a 450 nm GaInN blue LED, and a 285 nm AlGaN deep-ultraviolet (DUV) LED. We observed distinct differences in the variation of the EQE with temperature and current density for the three types of LEDs. Whereas the EQE of the AlGaInP red LED increases as temperature decreases below room temperature, the EQEs of GaInN blue and AlGaN DUV LEDs decrease for the same change in temperature in a low-current density regime. The free carrier concentration, as determined from the dopant ionization energy, shows a strong material-system-specific dependence, leading to different degrees of asymmetry in carrier concentration for the three types of LEDs. We attribute the EQE variation of the red, blue, and DUV LEDs to the different degrees of asymmetry in carrier concentration, which can be exacerbated at cryogenic temperatures. As for the EQE variation with temperature in a high-current density regime, the efficiency droop for the AlGaInP red and GaInN blue LEDs becomes more apparent as temperature decreases, due to the deterioration of the asymmetry in carrier concentration. However, the EQE of the AlGaN DUV LED initially decreases, then reaches an EQE minimum point, and then increases again due to the field-ionization of acceptors by the Poole-Frenkel effect. The results elucidate that carrier transport phenomena allow for the understanding of the droop phenomenon across different material systems, temperatures, and current densities.

  10. Variation of the external quantum efficiency with temperature and current density in red, blue, and deep ultraviolet light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jun Hyuk; Lee, Jong Won; Kim, Dong Yeong; Kim, Jong Kyu, E-mail: kimjk@postech.ac.kr [Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784 (Korea, Republic of); Cho, Jaehee, E-mail: jcho@chonbuk.ac.kr [School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center, Chonbuk National University, Jeonju 54896 (Korea, Republic of); Schubert, E. Fred [Department for Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Kim, Jungsub; Lee, Jinsub; Kim, Yong-Il; Park, Youngsoo [LED Business, Samsung Electronics, Yongin 446-920 (Korea, Republic of)

    2016-01-14

    The temperature-dependent external quantum efficiencies (EQEs) were investigated for a 620 nm AlGaInP red light-emitting diodes (LEDs), a 450 nm GaInN blue LED, and a 285 nm AlGaN deep-ultraviolet (DUV) LED. We observed distinct differences in the variation of the EQE with temperature and current density for the three types of LEDs. Whereas the EQE of the AlGaInP red LED increases as temperature decreases below room temperature, the EQEs of GaInN blue and AlGaN DUV LEDs decrease for the same change in temperature in a low-current density regime. The free carrier concentration, as determined from the dopant ionization energy, shows a strong material-system-specific dependence, leading to different degrees of asymmetry in carrier concentration for the three types of LEDs. We attribute the EQE variation of the red, blue, and DUV LEDs to the different degrees of asymmetry in carrier concentration, which can be exacerbated at cryogenic temperatures. As for the EQE variation with temperature in a high-current density regime, the efficiency droop for the AlGaInP red and GaInN blue LEDs becomes more apparent as temperature decreases, due to the deterioration of the asymmetry in carrier concentration. However, the EQE of the AlGaN DUV LED initially decreases, then reaches an EQE minimum point, and then increases again due to the field-ionization of acceptors by the Poole-Frenkel effect. The results elucidate that carrier transport phenomena allow for the understanding of the droop phenomenon across different material systems, temperatures, and current densities.

  11. Effectiveness and intermediates of microcystin-LR degradation by UV/H2O2 via 265 nm ultraviolet light-emitting diodes.

    Science.gov (United States)

    Liu, Juan; Ye, Jin-Shao; Ou, Hua-Se; Lin, Jialing

    2017-02-01

    Although the degradation of cyanotoxins by 254 nm UV/H2O2 has been well elucidated, the efficiency and mechanism involved are not necessarily true for other UV wavelengths. The degradation of microcystin-LR (MC-LR), a representative cyanotoxin, was explored by UV/H2O2 using 265 nm ultraviolet light-emitting diode (UV-LED). The results indicated that 265 nm UV/H2O2 treatment had a high removal efficiency of MC-LR ([MC-LR] = 0.1 μM, apparent rate constants reached 0.2077 min-1, half-time at 3.3 min). The qualitative analyses demonstrated that three novel intermediates, C48H74N10O15 (molecular weight = 1030.5335), C36H58N10O14 (854.4134), and C33H54N10O14 (814.3821), were generated in 265 nm UV/H2O2. Five published intermediates were also confirmed. The generative pathway of these products mainly involved free hydroxyl radical oxidation, resulting in consecutive hydroxyl substitutions and hydroxyl additions of unsaturated bonds in MC-LR. The toxicity of MC-LR was weaken with a relative low mineralization. The electrical energy per order values were calculated to be in the range of 0.00447 to 0.00612 kWh m-3 order-1 for 100-5000 μg L-1 MC-LR. Overall, 265 nm UV-LED/H2O2 can be used as an alternative effective technology to improve the removal efficiency of MC-LR in water.

  12. Cr/ITO semi-transparent n-type electrode for high-efficiency AlGaN/InGaN-based near ultraviolet light-emitting diodes

    Science.gov (United States)

    Kim, Hwankyo; Kim, Dae-Hyun; Seong, Tae-Yeon

    2017-11-01

    We investigated the electrical performance of near ultraviolet (NUV) (390 nm) light-emitting diodes (LEDs) fabricated with various semi-transparent Cr/ITO n-type contacts. It was shown that after annealing at 400 °C, Cr/ITO (10 nm/40 nm) contact was ohmic with a specific contact resistance of 9.8 × 10-4 Ωcm2. NUV AlGaN-based LEDs fabricated with different Cr/ITO (6-12 nm/40 nm) electrodes exhibited forward-bias voltages of 3.27-3.30 V at an injection current of 20 mA, which are similar to that of reference LED with Cr/Ni/Au (20 nm/25 nm/200 nm) electrode (3.29 V). The LEDs with the Cr/ITO electrodes gave series resistances of 10.69-11.98 Ω, while the series resistance is 10.84 Ohm for the reference LED. The transmittance of the Cr/ITO samples significantly improved when annealed at 400 °C. The transmittance (25.8-45.2% at 390 nm) of the annealed samples decreased with increasing Cr layer thickness. The LEDs with the Cr/ITO electrodes exhibited higher light output power than reference LED (with Cr/Ni/Au electrode). In particular, the LED with the Cr/ITO (12 nm/40 nm) electrode showed 9.3% higher light output power at 100 mA than reference LED. Based on the X-ray photoemission spectroscopy (XPS) and electrical results, the ohmic formation mechanism is described and discussed.

  13. Effects of GaN/AlGaN/Sputtered AlN nucleation layers on performance of GaN-based ultraviolet light-emitting diodes

    Science.gov (United States)

    Hu, Hongpo; Zhou, Shengjun; Liu, Xingtong; Gao, Yilin; Gui, Chengqun; Liu, Sheng

    2017-03-01

    We report on the demonstration of GaN-based ultraviolet light-emitting diodes (UV LEDs) emitting at 375 nm grown on patterned sapphire substrate (PSS) with in-situ low temperature GaN/AlGaN nucleation layers (NLs) and ex-situ sputtered AlN NL. The threading dislocation (TD) densities in GaN-based UV LEDs with GaN/AlGaN/sputtered AlN NLs were determined by high-resolution X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (TEM), which revealed that the TD density in UV LED with AlGaN NL was the highest, whereas that in UV LED with sputtered AlN NL was the lowest. The light output power (LOP) of UV LED with AlGaN NL was 18.2% higher than that of UV LED with GaN NL owing to a decrease in the absorption of 375 nm UV light in the AlGaN NL with a larger bandgap. Using a sputtered AlN NL instead of the AlGaN NL, the LOP of UV LED was further enhanced by 11.3%, which is attributed to reduced TD density in InGaN/AlInGaN active region. In the sputtered AlN thickness range of 10-25 nm, the LOP of UV LED with 15-nm-thick sputtered AlN NL was the highest, revealing that optimum thickness of the sputtered AlN NL is around 15 nm.

  14. Dominant transverse-electric polarized emission from 298 nm MBE-grown AlN-delta-GaN quantum well ultraviolet light-emitting diodes

    Science.gov (United States)

    Liu, Cheng; Ooi, Yu Kee; Islam, S. M.; Xing, Huili Grace; Jena, Debdeep; Zhang, Jing

    2017-02-01

    III-nitride based ultraviolet (UV) light emitting diodes (LEDs) are of considerable interest in replacing gas lasers and mercury lamps for numerous applications. Specifically, AlGaN quantum well (QW) based LEDs have been developed extensively but the external quantum efficiencies of which remain less than 10% for wavelengths dislocation density, difficult p-type doping and most importantly, the physics and band structure from the three degeneration valence subbands. One solution to address this issue at deep UV wavelengths is by the use of the AlGaN-delta-GaN QW where the insertion of the delta-GaN layer can ensure the dominant conduction band (C) - heavyhole (HH) transition, leading to large transverse-electric (TE) optical output. Here, we proposed and investigated the physics and polarization-dependent optical characterizations of AlN-delta- GaN QW UV LED at 300 nm. The LED structure is grown by Molecular Beam Epitaxy (MBE) where the delta-GaN layer is 3-4 monolayer (QW-like) sandwiched by 2.5-nm AlN sub-QW layers. The physics analysis shows that the use of AlN-delta-GaN QW ensures a larger separation between the top HH subband and lower-energy bands, and strongly localizes the electron and HH wave functions toward the QW center and hence resulting in 30-time enhancement in TEpolarized spontaneous emission rate, compared to that of a conventional Al0.35Ga0.65N QW. The polarization-dependent electroluminescence measurements confirm our theoretical analysis; a dominant TE-polarized emission was obtained at 298 nm with a minimum transverse-magnetic (TM) polarized emission, indicating the feasibility of high-efficiency TEpolarized UV emitters based on our proposed QW structure.

  15. Light emitting ceramic device

    Science.gov (United States)

    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.

  16. Light-Emitting Pickles

    Science.gov (United States)

    Vollmer, M.; Mollmann, K-P.

    2015-01-01

    We present experiments giving new insights into the classical light-emitting pickle experiment. In particular, measurements of the spectra and temperatures, as well as high-speed recordings, reveal that light emission is connected to the polarity of the electrodes and the presence of hydrogen.

  17. Material and device studies for the development of ultra-violet light emitting diodes (UV-LEDS) along polar, non-polar and semi-polar directions

    Science.gov (United States)

    Chandrasekaran, Ramya

    Over the past few years, significant effort was dedicated to the development of ultraviolet light emitting diodes (UV-LEDs) for a variety of applications. Such applications include chemical and biological detection, water purification and solid-state lighting. III-Nitride LEDs based on multiple quantum wells (MQWs) grown along the conventional [0001] (polar) direction suffer from the quantum confined Stark effect (QCSE), due to the existence of strong electric fields that arise from spontaneous and piezoelectric polarization. Thus, there is strong motivation to develop MQW-based III-nitride LED structures grown along non-polar and semi-polar directions. The goal of this dissertation is to develop UV-LEDs along the [0001] polar and [11 2¯ 0] non-polar directions by the method of Molecular Beam Epitaxy (MBE). The polar and non-polar LEDs were grown on the C-plane and R-plane sapphire substrates respectively. This work is a combination of materials science studies related to the nucleation, growth and n- and p-type doping of III-nitride films on these two substrates, as well as device studies related to fabrication and characterization of UV-LEDs. It was observed that the crystallographic orientation of the III-nitride films grown on R-plane sapphire depends strongly on the kinetic conditions of growth of the Aluminum Nitride (AIN) buffer. Specifically, growth of the AIN buffer under group III-rich conditions leads to nitride films having the (11 2¯ 0) non polar planes parallel to the sapphire surface, while growth of the buffer under nitrogen rich conditions leads to nitride films with the (11 2¯ 6) semi-polar planes parallel to the sapphire surface. The electron concentration and mobility for the films grown along the polar, non-polar and semi-polar directions were investigated. P-type doping of Gallium Nitride (GaN) films grown on the nonpolar (11 2¯ 0) plane do not suffer from polarity inversion and thus the material was doped p-type with a hole concentration

  18. Light-emitting diode.

    Science.gov (United States)

    Gold, Michael H

    2011-01-01

    Light-emitting diode (LED) photomodulation has become a recognized player in the world of lasers and light sources. It is used to treat a variety of clinical entities, including photorejuvenation, erythema-induced injury following laser and other cosmetic procedures, and acne vulgaris. Its use has increased and will increase further as our understanding of LED devices deepens. Copyright © 2011 S. Karger AG, Basel.

  19. Light Emitting Diode (LED)

    Science.gov (United States)

    1997-01-01

    A special lighting technology was developed for space-based commercial plant growth research on NASA's Space Shuttle. Surgeons have used this technology to treat brain cancer on Earth, in two successful operations. The treatment technique called photodynamic therapy, requires the surgeon to use tiny pinhead-size Light Emitting Diodes (LEDs) (a source releasing long wavelengths of light) to activate light-sensitive, tumor-treating drugs. Laser light has been used for this type of surgery in the past, but the LED light illuminates through all nearby tissues, reaching parts of a tumor that shorter wavelengths of laser light carnot. The new probe is safer because the longer wavelengths of light are cooler than the shorter wavelengths of laser light, making the LED less likely to injure normal brain tissue near the tumor. It can also be used for hours at a time while still remaining cool to the touch. The LED probe consists of 144 tiny pinhead-size diodes, is 9-inches long, and about one-half-inch in diameter. The small balloon aids in even distribution of the light source. The LED light source is compact, about the size of a briefcase, and can be purchased for a fraction of the cost of a laser. The probe was developed for photodynamic cancer therapy by the Marshall Space Flight Center under a NASA Small Business Innovative Research program grant.

  20. Light Emitting Diodes (LEDs)

    Science.gov (United States)

    1997-01-01

    A special lighting technology was developed for space-based commercial plant growth research on NASA's Space Shuttle. Surgeons have used this technology to treat brain cancer on Earth, in two successful operations. The treatment technique, called Photodynamic Therapy, requires the surgeon to use tiny, pinhead-size Light Emitting Diodes (LEDs) (a source that releases long wavelengths of light ) to activate light-sensitive, tumor-treating drugs. 'A young woman operated on in May 1999 has fully recovered with no complications and no evidence of the tumor coming back,' said Dr. Harry Whelan, a pediatric neurologist at the Medical Hospital of Wisconsin in Milwaukee. Laser light has been used for this type of surgery in the past, but the LED light illuminates through all nearby tissues, reaching parts of a tumor that shorter wavelengths of laser light carnot. The new probe is safer because the longer wavelengths of light are cooler than the shorter wavelengths of laser light, making the LED less likely to injure normal brain tissue near the tumor. It can be used for hours at a time while still remaining cool to the touch. The LED light source is compact, about the size of a briefcase, and can be purchased for a fraction of the cost of a laser. The LEDs, developed and managed by NASA's Marshall Space Flight Center, have been used on seven Space Shuttle flights inside the Microgravity Astroculture Facility. This technology has also been successfully used to further commercial research in crop growth.

  1. Preparation of Phi29 DNA polymerase free of amplifiable DNA using ethidium monoazide, an ultraviolet-free light-emitting diode lamp and trehalose.

    Directory of Open Access Journals (Sweden)

    Hirokazu Takahashi

    Full Text Available We previously reported that multiply-primed rolling circle amplification (MRPCA using modified random RNA primers can amplify tiny amounts of circular DNA without producing any byproducts. However, contaminating DNA in recombinant Phi29 DNA polymerase adversely affects the outcome of MPRCA, especially for negative controls such as non-template controls. The amplified DNA in negative control casts doubt on the result of DNA amplification. Since Phi29 DNA polymerase has high affinity for both single-strand and double-stranded DNA, some amount of host DNA will always remain in the recombinant polymerase. Here we describe a procedure for preparing Phi29 DNA polymerase which is essentially free of amplifiable DNA. This procedure is realized by a combination of host DNA removal using appropriate salt concentrations, inactivation of amplifiable DNA using ethidium monoazide, and irradiation with visible light from a light-emitting diode lamp. Any remaining DNA, which likely exists as oligonucleotides captured by the Phi29 DNA polymerase, is degraded by the 3'-5' exonuclease activity of the polymerase itself in the presence of trehalose, used as an anti-aggregation reagent. Phi29 DNA polymerase purified by this procedure has little amplifiable DNA, resulting in reproducible amplification of at least ten copies of plasmid DNA without any byproducts and reducing reaction volume. This procedure could aid the amplification of tiny amounts DNA, thereby providing clear evidence of contamination from laboratory environments, tools and reagents.

  2. Combustion synthesis and luminescent properties of a new material Li 2(Ba 0.99,Eu 0.01)SiO 4:B 3+ for ultraviolet light emitting diodes

    Science.gov (United States)

    Yao, Shanshan; Chen, Donghua

    2008-04-01

    Using urea as fuel and boric as flux, a novel bluish green emitting phosphor Li 2(Ba 0.99,Eu 0.01)SiO 4:B 3+ has been successfully synthesized using a combustion method. The material has potential application as the fluorescent material for ultraviolet light-emitting diodes (UV-LEDs). The dependence of the properties of Li 2(Ba 0.99,Eu 0.01)SiO 4:B 3+ phosphors upon urea concentration, boric acid doping and initiating combustion temperature were investigated. The crystallization and particle sizes of Li 2(Ba 0.99,Eu 0.01)SiO 4:B 3+ have been investigated by using powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Luminescence measurements showed that the phosphors can be efficiently excited by ultraviolet (UV) to visible region, emitting a bluish green light with peak wavelength of 490 nm. The results showed that the boric acid was effective in improving the luminescence intensity of Li 2(Ba 0.99,Eu 0.01)SiO 4 and the optimum molar ratio of boric acid to barium nitrate was about 0.06. The optimized phosphors Li 2(Ba 0.99,Eu 0.01)SiO 4:B 0.063+ showed 160% improved emission intensity compared with that of the Li 2(Ba 0.99,Eu 0.01)SiO 4 phosphors under UV ( λex=350 nm) excitation.

  3. Luminescent properties of Li2 (Ca0.99, Eu0.01) SiO4: B3+ particles as a potential bluish green phosphor for ultraviolet light-emitting diodes

    Science.gov (United States)

    Yao, Shanshan; Chen, Donghua

    2007-12-01

    In our study, the 1% mol Eu2+ doped Li2CaSiO4: B3+ phosphors were prepared by the combustion method as fluorescent material for ultraviolet, light-emitting diodes (UV-LEDs) used as a light source. The properties of Li2 (Ca0.99, Eu0.01) SiO4: B3+ phosphors with urea concentration, doping boric acid and a series of initiating combustion temperature were investigated. The crystallization and particle sizes of Li2 (Ca0.99, Eu0.01) SiO4: B3+ has been investigated by using powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Luminescence measurements showed that the phosphors can be efficiently excited by UV to the visible region, and exhibited bluish green light with a peak of 480 nm. The results showed that the boric acid was effective in improving the luminescence intensity of Li2 (Ca0.99, Eu0.01) SiO4: B3+ and the optimum molar ratio of boric acid to calcium nitrate was about 0.06. The optimized phosphors Li2 (Ca0.99, Eu0.01) SiO4: B0.063+ showed 180% improved emission intensity compared with that of the Li2 (Ca0.99, Eu0.01) SiO4 phosphors under ultraviolet (λex =287 nm) excitation.

  4. Electrochemical Light-Emitting Gel

    Directory of Open Access Journals (Sweden)

    Nobuyuki Itoh

    2010-06-01

    Full Text Available Light-emitting gel, a gel state electroluminescence material, is reported. It is composed of a ruthenium complex as the emitter, an ionic liquid as the electrolyte, and oxide nanoparticles as the gelation filler. Emitted light was produced via electrogenerated chemiluminescence. The light-emitting gel operated at low voltage when an alternating current was passed through it, regardless of its structure, which is quite thick. The luminescence property of the gel is strongly affected by nanoparticle materials. TiO2 nanoparticles were a better gelation filler than silica or ZnO was, with respect to luminescence stability, thus indicating a catalytic effect. It is demonstrated that the light-emitting gel device, with quite a simple fabrication process, flashes with the application of voltage.

  5. Synthesis and photoluminescence properties of Eu2+ activated CaO ceramic powders for near-ultraviolet chip based white light emitting diodes

    Science.gov (United States)

    Hao, Zhendong; Wang, Ying; Zhang, Liangliang; Pan, Guohui; Zhang, Xia; Wu, Huajun; Luo, Yongshi; Zhang, Jiahua

    2017-09-01

    In this paper, we synthesized series of Eu2+ activated CaO ceramic powders by conventional solid state reaction. Using NH4Cl as a reducing additives, the Eu3+ has been successfully reduced to Eu2+. An intense blue emission peaked at 460 nm from Eu2+ was observed. The luminescent intensity of the doping-optimized CaO:Eu2+ sample can be as high as 106% of commercial BAM blue phosphor under 400 nm near-ultraviolet (NUV) excitation. The effect of Eu2+ and NH4Cl contents on photoluminescence properties and crystal phase formation have been investigated, respectively. The thermal stable property which is an important performance for LED application has also been measured. The emission intensity at 120 °C can maintain 94% of that at room temperature. Our results suggest that CaO: Eu2+ ceramic powder could be used as a promising blue emitting phosphor for NUV chip based white LEDs.

  6. Ultraviolet/violet dual-color electroluminescence based on n-ZnO single crystal/p-GaN direct-contact light-emitting diode

    Energy Technology Data Exchange (ETDEWEB)

    Li, Songzhan [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Department of Electronic Science and Technology, School of Physics and Technology, Wuhan University, Wuhan, Hubei 430072 (China); School of Electronic and Electrical Engineering, Wuhan Textile University, Wuhan, Hubei 430073 (China); Lin, Wenwen [Laboratory of Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Fang, Guojia, E-mail: gjfang@whu.edu.cn [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Department of Electronic Science and Technology, School of Physics and Technology, Wuhan University, Wuhan, Hubei 430072 (China); Huang, Feng, E-mail: fhuang@fjirsm.ac.cn [Laboratory of Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Huang, Huihui; Long, Hao; Mo, Xiaoming; Wang, Haoning; Guan, Wenjie; Zhao, Xingzhong [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Department of Electronic Science and Technology, School of Physics and Technology, Wuhan University, Wuhan, Hubei 430072 (China)

    2013-08-15

    We have fabricated a fully transparent ultraviolet (UV)/violet dual-color electroluminescence (EL) device based on n-ZnO single crystal and p-GaN via a simple direct-contact method. The device presents dual-color EL under forward and reverse biases—an intense violet emission centered at 400 nm from ZnO and a sharp UV emission peaked at 365 nm from GaN, respectively. The reason for dual color emissions is proposed in terms of the energy band theory and the transmission spectra of ZnO single crystal and p-GaN. -- Highlights: ► A fully transparent LED based on n-ZnO SC and p-GaN is fabricated via the direct-contact method. ► The n-ZnO SC/p-GaN device shows UV/violet dual-color emission under electrically pumped. ► The device presents a violet emission 400 nm and a UV emission 365 nm under forward and reverse biases. ► The EL of the dual-color device displays good stability and reproducibility.

  7. An elegant route to overcome fundamentally-limited light extraction in AlGaN deep-ultraviolet light-emitting diodes: preferential outcoupling of strong in-plane emission (Conference Presentation)

    Science.gov (United States)

    Kim, Jong Kyu; Lee, Jong Won; Kim, Dong-Yeong; Park, Jun Hyuk; Schubert, E. Fred; Kim, Jungsub; Kim, Yong-Il

    2016-09-01

    AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) are being developed for their numerous applications such as purification of air and water, sterilization in food processing, UV curing, medical-, and defense-related light sources. However, external quantum efficiency (EQE) of AlGaN-based DUV LEDs is very poor (magnetic (TM) polarized, that is, the electric field vector is parallel to the (0001) c-axis and shows strong sidewall emission through m- or a-plane due to crystal-field split-off hole band being top most valence band. Therefore, a new LEE-enhancing approach addressing the unique intrinsic property of AlGaN DUV LEDs is strongly desired. In this study, an elegant approach based on a DUV LED having multiple mesa stripes whose inclined sidewalls are covered by a MgF2/Al omni-directional mirror to take advantage of the strongly anisotropic transverse-magnetic polarized emission pattern of AlGaN quantum wells is presented. The sidewall-emission-enhanced DUV LED breaks through the fundamental limitations caused by the intrinsic properties of AlGaN, thus shows a remarkable improvement in light extraction as well as operating voltage simultaneously. Furthermore, an analytic model is developed to understand and precisely estimate the extraction of DUV photons from AlGaN DUV LEDs, and hence to provide promising routes to maximize the power conversion efficiency.

  8. High external quantum efficiency (10%) AlGaN-based deep-ultraviolet light-emitting diodes achieved by using highly reflective photonic crystal on p-AlGaN contact layer

    Science.gov (United States)

    Kashima, Yukio; Maeda, Noritoshi; Matsuura, Eriko; Jo, Masafumi; Iwai, Takeshi; Morita, Toshiro; Kokubo, Mitsunori; Tashiro, Takaharu; Kamimura, Ryuichiro; Osada, Yamato; Takagi, Hideki; Hirayama, Hideki

    2018-01-01

    We increased the light-extraction efficiency (LEE) of AlGaN-based deep-ultraviolet light-emitting diodes (DUV LEDs) by introducing a highly reflective photonic crystal (HR-PhC) into the surface of the p-AlGaN contact layer, thereby achieving a high external quantum efficiency (EQE). A low-damage HR-PhC with a lattice period of approximately 250 nm was fabricated using nanoimprinting and dry etching. A reflective Ni/Mg p-type electrode was deposited on the HR-PhC layer using a tilted-evaporation method. The EQE of a conventional DUV LED with emission around 283 nm was increased from 4.8 to 10% by introducing the HR-PhC and the reflective Ni/Mg electrode. A simple estimation of the effective reflectance of the HR-PhC p-AlGaN contact layer with the Ni/Mg electrode indicated a value exceeding 90%.

  9. Electrical and optical properties of poly(3,4-ethylenedioxythiophene) oxidized with poly(4-styrenesulfonate) and AuCl3-doped reduced graphene oxide/single-walled carbon nanotube films for ultraviolet light-emitting diodes.

    Science.gov (United States)

    Lee, Byeong Ryong; Lee, Jae Hoon; Kim, Kyeong Heon; Kim, Hee-Dong; Kim, Tae Geun

    2014-12-01

    We report the effects of poly(3,4-ethylenedioxythiophene) oxidized with poly(4-styrenesulfonate) ( PSS) and gold chloride (AuCl) co-doping on the electrical and optical properties of reduced graphene oxide (RGO)/single-walled carbon nanotube (SWNT) films fabricated by dipcoating methods. The RGO/SWNT films were doped with both AuCl3 dissolved in nitromethane and PSS hole injection layers by spin coating to improve their electrical properties by increasing the work function of the RGO/SWNT films, thereby reducing the Schottky barrier height between the RGO/SWNT and p-GaN films. As a result, we obtained a reduced sheet resistance of 851.9 Ω/Ω and a contact resistance of 1.97 x 10(-1) Ω x cm2, together with a high transmittance of 84.1% at 380 nm. The contact resistance of these films should be further reduced to fully utilize the feature of the electrode scheme proposed in this work, but the current result suggests its potential use as a transparent conductive electrode for ultraviolet light-emitting diodes.

  10. Ultraviolet Light Emitting Diode Optical Power Characterization

    Science.gov (United States)

    2014-03-01

    The heart of the driver board was an opamp , which operated off of the DAQ output voltage. The opamp created an isolated circuit with the power...then flowed from the power supply to the opamp to the UV LED. Each branch had a resistor and pin holes for electrical measurement in series with...with the available equipment. The oscilloscope could be used to show the trace and measure a voltage drop across a known resistance in line with the

  11. Ultraviolet light emitting diodes by ammonia molecular beam epitaxy on metamorphic (KAUST Repository

    Young, Erin C.

    2015-09-01

    © 2015. In this paper we demonstrate ultraviolet (UV) light emitting diodes (LEDs) grown on metamorphic AlGaN buffers on freestanding GaN (202-1) substrates by ammonia assisted molecular beam epitaxy (MBE). Misfit and related threading dislocations were confined to the stress relaxed, compositionally graded buffer layers, and single quantum well devices emitting at 355, 310 and 274. nm were grown on top of the graded buffers. The devices showed excellent structural and electrical (I-. V) characteristics.

  12. Broadband light-emitting diode

    Science.gov (United States)

    Fritz, Ian J.; Klem, John F.; Hafich, Michael J.

    1998-01-01

    A broadband light-emitting diode. The broadband light-emitting diode (LED) comprises a plurality of III-V compound semiconductor layers grown on a semiconductor substrate, with the semiconductor layers including a pair of cladding layers sandwiched about a strained-quantum-well active region having a plurality of different energy bandgaps for generating light in a wavelength range of about 1.3-2 .mu.m. In one embodiment of the present invention, the active region may comprise a first-grown quantum-well layer and a last-grown quantum-well layer that are oppositely strained; whereas in another embodiment of the invention, the active region is formed from a short-period superlattice structure (i.e. a pseudo alloy) comprising alternating thin layers of InGaAs and InGaAlAs. The use a short-period superlattice structure for the active region allows different layers within the active region to be simply and accurately grown by repetitively opening and closing one or more shutters in an MBE growth apparatus to repetitively switch between different growth states therein. The broadband LED may be formed as either a surface-emitting LED or as an edge-emitting LED for use in applications such as chemical sensing, fiber optic gyroscopes, wavelength-division-multiplexed (WDM) fiber-optic data links, and WDM fiber-optic sensor networks for automobiles and aircraft.

  13. Quantum Dot Light Emitting Diode

    Energy Technology Data Exchange (ETDEWEB)

    Keith Kahen

    2008-07-31

    The project objective is to create low cost coatable inorganic light emitting diodes, composed of quantum dot emitters and inorganic nanoparticles, which have the potential for efficiencies equivalent to that of LEDs and OLEDs and lifetime, brightness, and environmental stability between that of LEDs and OLEDs. At the end of the project the Recipient shall gain an understanding of the device physics and properties of Quantum-Dot LEDs (QD-LEDs), have reliable and accurate nanocrystal synthesis routines, and have formed green-yellow emitting QD-LEDs with a device efficiency greater than 3 lumens/W, a brightness greater than 400 cd/m2, and a device operational lifetime of more than 1000 hours. Thus the aim of the project is to break the current cost-efficiency paradigm by creating novel low cost inorganic LEDs composed of inorganic nanoparticles.

  14. Quantum Dot Light Emitting Diode

    Energy Technology Data Exchange (ETDEWEB)

    Kahen, Keith

    2008-07-31

    The project objective is to create low cost coatable inorganic light emitting diodes, composed of quantum dot emitters and inorganic nanoparticles, which have the potential for efficiencies equivalent to that of LEDs and OLEDs and lifetime, brightness, and environmental stability between that of LEDs and OLEDs. At the end of the project the Recipient shall gain an understanding of the device physics and properties of Quantum-Dot LEDs (QD-LEDs), have reliable and accurate nanocrystal synthesis routines, and have formed green-yellow emitting QD-LEDs with a device efficiency greater than 3 lumens/W, a brightness greater than 400 cd/m{sup 2}, and a device operational lifetime of more than 1000 hours. Thus the aim of the project is to break the current cost-efficiency paradigm by creating novel low cost inorganic LEDs composed of inorganic nanoparticles.

  15. Light Converting Inorganic Phosphors for White Light-Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Chiao-Wen Yeh

    2010-03-01

    Full Text Available White light-emitting diodes (WLEDs have matched the emission efficiency of florescent lights and will rapidly spread as light source for homes and offices in the next 5 to 10 years. WLEDs provide a light element having a semiconductor light emitting layer (blue or near-ultraviolet (nUV LEDs and photoluminescence phosphors. These solid-state LED lamps, rather than organic light emitting diode (OLED or polymer light-emitting diode (PLED, have a number of advantages over conventional incandescent bulbs and halogen lamps, such as high efficiency to convert electrical energy into light, reliability and long operating lifetime. To meet with the further requirement of high color rendering index, warm light with low color temperature, high thermal stability and higher energy efficiency for WLEDs, new phosphors that can absorb excitation energy from blue or nUV LEDs and generate visible emissions efficiently are desired. The criteria of choosing the best phosphors, for blue (450-480 nm and nUV (380-400 nm LEDs, strongly depends on the absorption and emission of the phosphors. Moreover, the balance of light between the emission from blue-nUV LEDs and the emissions from phosphors (such as yellow from Y3Al5O12:Ce3+ is important to obtain white light with proper color rendering index and color temperature. Here, we will review the status of phosphors for LEDs and prospect the future development.

  16. Photocapacitance measurements on MOS light emitting devices

    Energy Technology Data Exchange (ETDEWEB)

    Seeger, Michael; Buerger, Danilo; Rebohle, Lars; Skorupa, Wolfgang; Helm, Manfred; Schmidt, Heidemarie [Institute of Ion Beam Physics and Materials Research, Forschungszentrum Dresden-Rossendorf, Dresden (Germany)

    2009-07-01

    The photocapacitance (PC) has been probed on MOS diodes with an Eu-implanted SiO{sub 2} layer. In general, rare earth implanted SiO{sub 2} layers in MOS diodes are of great interest for possible applications in integrated metal-oxide-semiconductor light emitting devices (MOSLEDs). For example, green and ultraviolet electroluminescence has been probed on SiO{sub 2}:Tb-MOSLEDs and SiO{sub 2}:Gd-MOSLEDs, respectively. MOSLEDs reach external quantum efficiencies between 1% and 16%, and the electroluminescence peaks are typically ascribed to 4f-intrashell transitions of trivalent rare earth ions. A clear capacitance change has been observed for different wavelengths under monochromatic illumination. Some of the detected peaks correspond to the energies of 4f-intrashell transitions of the Eu ions. According to this, the number of active luminescence centers in MOSLEDs may be determined from PC measurements. Some 4f-intrashell transitions have been also observed by means of electroluminescence measurements on the same MOSLEDs. To emphasize the physical significance of the PC data recorded on SiO{sub 2}:Eu-MOSLEDs, we also compare PC data recorded on different MOSLEDs implanted with other rare earth ions.

  17. Light-emitting diodes - Their potential in biomedical applications

    Energy Technology Data Exchange (ETDEWEB)

    Yeh, Naichia Gary; Wu, Chia-Hao [College of Applied Sciences, MingDao University, 369 Wen-Hua Road, Peetou, Changhua 52345 (China); Cheng, Ta Chih [Department of Tropical Agriculture and International Cooperation, National Pingtung University of Science and Technology, 1 Hseuh-Fu Rd., Nei-Pu Hsiang, Pingtung 91201 (China)

    2010-10-15

    The rapid development of high brightness light-emitting diodes (LEDs) makes feasible the use of LEDs, among other light sources (such as laser, intense pulse light and other incoherent light systems), for medical treatment and light therapy. This paper provides a general review on red, green, blue, ultraviolet LED applications in photo rejuvenation and medical treatments of a variety of physical abnormalities, as well as the relief of stress, circadian rhythm disorders, and seasonal affective disorder. The review, concentrated in the papers published after 1990, intends to show that LEDs are well qualified to succeed its more energy demanding counterparts in the named areas and beyond. (author)

  18. Photon recycling semiconductor light-emitting diode

    Science.gov (United States)

    Guo, Xiaoyun; Graff, John W.; Schubert, E. F.; Karlicek, Robert F., Jr.

    2000-04-01

    A new white light emitting diode, the photon recycling semiconductor light emitting diode (PRS-LED) is demonstrated. The device consists of a GaInN/GaN LED emitting in the blue spectral range and an AlGaInP photon recycling semiconductor emitting at the complementary color. Thus the PRS-LED has two emission peaks, one in the blue and one in the amber wavelength range. The theoretical luminous performance of the PRS-LED exceeds 300 lm/W, higher than the performance of phosphor-based white LEDs.

  19. Fluorescence lifetime imaging using light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Kennedy, Gordon T; Munro, Ian; Poher, Vincent; French, Paul M W; Neil, Mark A A [Blackett Laboratory, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom); Elson, Daniel S [Institute of Biomedical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom); Hares, Jonathan D [Kentech Instruments Ltd, Unit 9, Hall Farm Workshops, South Moreton, Didcot, Oxfordshire, OX11 9AG (United Kingdom)], E-mail: gordon.kennedy@imperial.ac.uk

    2008-05-07

    We demonstrate flexible use of low cost, high-power light emitting diodes as illumination sources for fluorescence lifetime imaging (FLIM). Both time-domain and frequency-domain techniques have been implemented at wavelengths spanning the range 450-640 nm. Additionally, we demonstrate optically sectioned fluorescence lifetime imaging by combining structured illumination with frequency-domain FLIM.

  20. Light-Emitting Diodes: A Hidden Treasure

    Science.gov (United States)

    Planinšic, Gorazd; Etkina, Eugenia

    2014-01-01

    LEDs, or light-emitting diodes, are cheap, easy to purchase, and thus commonly used in physics instruction as indicators of electric current or as sources of light (Fig. 1). In our opinion LEDs represent a unique piece of equipment that can be used to collect experimental evidence, and construct and test new ideas in almost every unit of a general…

  1. Highly efficient silicon light emitting diode

    NARCIS (Netherlands)

    Le Minh, P.; Holleman, J.; Wallinga, Hans

    2002-01-01

    In this paper, we describe the fabrication, using standard silicon processing techniques, of silicon light-emitting diodes (LED) that efficiently emit photons with energy around the silicon bandgap. The improved efficiency had been explained by the spatial confinement of charge carriers due to a

  2. Light-Emitting Diodes: Learning New Physics

    Science.gov (United States)

    Planinšic, Gorazd; Etkina, Eugenia

    2015-01-01

    This is the third paper in our Light-Emitting Diodes series. The series aims to create a systematic library of LED-based materials and to provide the readers with the description of experiments and pedagogical treatment that would help their students construct, test, and apply physics concepts and mathematical relations. The first paper, published…

  3. Light-Emitting Diodes: Solving Complex Problems

    Science.gov (United States)

    Planinšic, Gorazd; Etkina, Eugenia

    2015-01-01

    This is the fourth paper in our Light-Emitting Diodes series. The series aims to create a systematic library of LED-based materials and to provide readers with the description of experiments and the pedagogical treatment that would help their students construct, test, and apply physics concepts and mathematical relations. The first paper provided…

  4. Light emitting fabric technologies for photodynamic therapy.

    Science.gov (United States)

    Mordon, Serge; Cochrane, Cédric; Tylcz, Jean Baptiste; Betrouni, Nacim; Mortier, Laurent; Koncar, Vladan

    2015-03-01

    Photodynamic therapy (PDT) is considered to be a promising method for treating various types of cancer. A homogeneous and reproducible illumination during clinical PDT plays a determinant role in preventing under- or over-treatment. The development of flexible light sources would considerably improve the homogeneity of light delivery. The integration of optical fiber into flexible structures could offer an interesting alternative. This paper aims to describe different methods proposed to develop Side Emitting Optical Fibers (SEOF), and how these SEOF can be integrated in a flexible structure to improve light illumination of the skin during PDT. Four main techniques can be described: (i) light blanket integrating side-glowing optical fibers, (ii) light emitting panel composed of SEOF obtained by micro-perforations of the cladding, (iii) embroidery-based light emitting fabric, and (iv) woven-based light emitting fabric. Woven-based light emitting fabrics give the best performances: higher fluence rate, best homogeneity of light delivery, good flexibility. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. Silicon light emitting devices for integrated applications

    NARCIS (Netherlands)

    Le Minh, P.

    2003-01-01

    This thesis brings up new facts on the integration capability, photochemistry, and properties of the prototype devices based on the light emitting diode antifuse. The chapters are arranged with increasing level of sophistication. The fist chapter also reviews the current trends of the research on

  6. Method of making organic light emitting devices

    Science.gov (United States)

    Shiang, Joseph John [Niskayuna, NY; Janora, Kevin Henry [Schenectady, NY; Parthasarathy, Gautam [Saratoga Springs, NY; Cella, James Anthony [Clifton Park, NY; Chichak, Kelly Scott [Clifton Park, NY

    2011-03-22

    The present invention provides a method for the preparation of organic light-emitting devices comprising a bilayer structure made by forming a first film layer comprising an electroactive material and an INP precursor material, and exposing the first film layer to a radiation source under an inert atmosphere to generate an interpenetrating network polymer composition comprising the electroactive material. At least one additional layer is disposed on the reacted first film layer to complete the bilayer structure. The bilayer structure is comprised within an organic light-emitting device comprising standard features such as electrodes and optionally one or more additional layers serving as a bipolar emission layer, a hole injection layer, an electron injection layer, an electron transport layer, a hole transport layer, exciton-hole transporting layer, exciton-electron transporting layer, a hole transporting emission layer, or an electron transporting emission layer.

  7. Nanostructured Materials for Organic Light Emitting Diodes

    OpenAIRE

    Dinh, Nguyen Nang

    2010-01-01

    We have given an overview of the recent works on nanocomposites used for optoelectronic devices. From the review it is seen that a very rich publication has been issued regarding the nanostructured composites and nano-hybrid layers or heterojunctions which can be applied for different practical purposes. Among them there are organic light emitting diodes (OLED) and excitonic or organic solar cells (OSC). Our recent achievements on the use of nanocomposites for OLEDs were also presented. There...

  8. Light-emitting device test systems

    Energy Technology Data Exchange (ETDEWEB)

    McCord, Mark; Brodie, Alan; George, James; Guan, Yu; Nyffenegger, Ralph

    2018-01-23

    Light-emitting devices, such as LEDs, are tested using a photometric unit. The photometric unit, which may be an integrating sphere, can measure flux, color, or other properties of the devices. The photometric unit may have a single port or both an inlet and outlet. Light loss through the port, inlet, or outlet can be reduced or calibrated for. These testing systems can provide increased reliability, improved throughput, and/or improved measurement accuracy.

  9. III-nitride based light emitting diodes and applications

    CERN Document Server

    Han, Jung; Amano, Hiroshi; Morkoç, Hadis

    2017-01-01

    The revised edition of this important book presents updated and expanded coverage of light emitting diodes (LEDs) based on heteroepitaxial GaN on Si substrates, and includes new chapters on tunnel junction LEDs, green/yellow LEDs, and ultraviolet LEDs. Over the last two decades, significant progress has been made in the growth, doping and processing technologies of III-nitride based semiconductors, leading to considerable expectations for nitride semiconductors across a wide range of applications. LEDs are already used in traffic signals, signage lighting, and automotive applications, with the ultimate goal of the global replacement of traditional incandescent and fluorescent lamps, thus reducing energy consumption and cutting down on carbon-dioxide emission. However, some critical issues must be addressed to allow the further improvements required for the large-scale realization of solid-state lighting, and this book aims to provide the readers with details of some contemporary issues on which the performanc...

  10. The AlGaAs light emitting particle detector

    CERN Document Server

    Pozela, J; Silenas, A; Juciene, V; Dapkus, L; Jasutis, V; Tamulaitis, G; Zukauskas, A; Bendorius, R A

    1999-01-01

    An AlGaAs light emitting particle detector was fabricated and investigated experimentally. Light emitting semiconductor Al sub x Ga sub 1 sub - sub x As layers with graded-gap energy band structure were grown, and luminescence spectra were investigated. A light emitting X-ray detector was also fabricated. (author)

  11. Improved light emitting UV curable PbS quantum dots-polymer composite optical waveguides

    Science.gov (United States)

    Shen, Kai; Baig, Sarfaraz; Jiang, Guomin; Paik, Young-hun; Kim, Sung Jin; Wang, Michael R.

    2017-11-01

    We present for the first-time light emitting ultraviolet (UV) curable active PbS quantum dots-polymer composite optical waveguides fabricated by vacuum assisted microfluidic (VAM) soft lithography technique. PbS quantum dots were synthesized by colloidal chemistry methods with tunable sizes resulting in light emissions in near infrared wavelengths. UV curable polymer of selective refractive index were synthesized facilitating waveguide mode confinement and good PbS quantum dots solubility. Photoluminescence of the composite exhibited ∼ 30 times better brightness than PbS-SU-8 composites. Light emitting multi-mode waveguides of about 50 × 42 μm cross-sectional dimension were successful demonstrated. Light emitting single-mode waveguides were fabricated by VAM technique with sectional flow tapers.

  12. Wheat Under LED's (Light Emitting Diodes)

    Science.gov (United States)

    2004-01-01

    Astroculture is a suite of technologies used to produce and maintain a closed controlled environment for plant growth. The two most recent missions supported growth of potato, dwarf wheat, and mustard plants, and provided scientists with the first opportunity to conduct true plant research in space. Light emitting diodes have particular usefulness for plant growth lighting because they emit a much smaller amount of radiant heat than do conventional lighting sources and because they have potential of directing a higher percentage of the emitted light onto plants surfaces. Furthermore, the high output LED's have emissions in the 600-700 nm waveband, which is of highest efficiency for photosynthesis by plants.

  13. Efficient organic light emitting-diodes (OLEDs)

    CERN Document Server

    Chang, Yi-Lu

    2015-01-01

    Following two decades of intense research globally, the organic light-emitting diode (OLED) has steadily emerged as the ultimate display technology of choice for the coming decades. Portable active matrix OLED displays have already become prevalent, and even large-sized ultra-high definition 4K TVs are being mass-produced. More exotic applications such as wearable displays have been commercialized recently. With the burgeoning success in displays, researchers are actively bringing the technology forward into the exciting solid-state lighting market. This book presents the knowledge needed for

  14. Organic light emitting devices for illumination

    Science.gov (United States)

    Hack, Michael [Lambertville, NJ; Lu, Min-Hao Michael [Lawrenceville, NJ; Weaver, Michael S [Princeton, NJ

    2012-01-24

    An organic light emitting device an a method of obtaining illumination from such a device is provided. The device has a plurality of regions, each region having an organic emissive layer adapted to emit a different spectrum of light. The regions in combination emit light suitable for illumination purposes. The area of each region may be selected such that the device is more efficient than an otherwise equivalent device having regions of equal size. The regions may have an aspect ratio of at least about four. All parts of any given region may be driven at the same current.

  15. Organic bistable light-emitting devices

    Science.gov (United States)

    Ma, Liping; Liu, Jie; Pyo, Seungmoon; Yang, Yang

    2002-01-01

    An organic bistable device, with a unique trilayer structure consisting of organic/metal/organic sandwiched between two outmost metal electrodes, has been invented. [Y. Yang, L. P. Ma, and J. Liu, U.S. Patent Pending, U.S. 01/17206 (2001)]. When the device is biased with voltages beyond a critical value (for example 3 V), the device suddenly switches from a high-impedance state to a low-impedance state, with a difference in injection current of more than 6 orders of magnitude. When the device is switched to the low-impedance state, it remains in that state even when the power is off. (This is called "nonvolatile" phenomenon in memory devices.) The high-impedance state can be recovered by applying a reverse bias; therefore, this bistable device is ideal for memory applications. In order to increase the data read-out rate of this type of memory device, a regular polymer light-emitting diode has been integrated with the organic bistable device, such that it can be read out optically. These features make the organic bistable light-emitting device a promising candidate for several applications, such as digital memories, opto-electronic books, and recordable papers.

  16. Electrically and Optically Readable Light Emitting Memories

    Science.gov (United States)

    Chang, Che-Wei; Tan, Wei-Chun; Lu, Meng-Lin; Pan, Tai-Chun; Yang, Ying-Jay; Chen, Yang-Fang

    2014-06-01

    Electrochemical metallization memories based on redox-induced resistance switching have been considered as the next-generation electronic storage devices. However, the electronic signals suffer from the interconnect delay and the limited reading speed, which are the major obstacles for memory performance. To solve this problem, here we demonstrate the first attempt of light-emitting memory (LEM) that uses SiO2 as the resistive switching material in tandem with graphene-insulator-semiconductor (GIS) light-emitting diode (LED). By utilizing the excellent properties of graphene, such as high conductivity, high robustness and high transparency, our proposed LEM enables data communication via electronic and optical signals simultaneously. Both the bistable light-emission state and the resistance switching properties can be attributed to the conducting filament mechanism. Moreover, on the analysis of current-voltage characteristics, we further confirm that the electroluminescence signal originates from the carrier tunneling, which is quite different from the standard p-n junction model. We stress here that the newly developed LEM device possesses a simple structure with mature fabrication processes, which integrates advantages of all composed materials and can be extended to many other material systems. It should be able to attract academic interest as well as stimulate industrial application.

  17. Ionic liquid polyoxometalates as light emitting materials

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz-acosta, Denisse [Los Alamos National Laboratory; Del Sesto, Rico E [Los Alamos National Laboratory; Scott, Brian [Los Alamos National Laboratory; Bennett, Bryan L [Los Alamos National Laboratory; Purdy, Geraldine M [Los Alamos National Laboratory; Muenchausen, Ross E [Los Alamos National Laboratory; Mc Kigney, Edward [Los Alamos National Laboratory; Gilbertson, Robert [Los Alamos National Laboratory

    2008-01-01

    The low melting point, negligible vapor pressure, good solubility, and thermal and chemical stability make ionic liquids useful materials for a wide variety of applications. Polyoxometalates are early transition metal oxygen clusters that can be synthesized in many different sizes and with a variety of heterometals. The most attractive feature of POMs is that their physical properties, in particular electrical, magnetic, and optical properties, can be easily modified following known procedures. It has been shown that POMs can exhibit cooperative properties, as superconductivity and energy transfer. POM ionic liquids can be obtained by selecting the appropliate cation. Different alkyl ammonium and alkyl phosphonium salts are being used to produce new POM ionic liquids together with organic or inorganic luminescent centers to design light emitting materials. Ammonium and phosphonium cations with activated, polymerizable groups are being used to further polymerize the ionic liquid into transparent, solid materials with high metal density.

  18. Light emitting device having peripheral emissive region

    Science.gov (United States)

    Forrest, Stephen R

    2013-05-28

    Light emitting devices are provided that include one or more OLEDs disposed only on a peripheral region of the substrate. An OLED may be disposed only on a peripheral region of a substantially transparent substrate and configured to emit light into the substrate. Another surface of the substrate may be roughened or include other features to outcouple light from the substrate. The edges of the substrate may be beveled and/or reflective. The area of the OLED(s) may be relatively small compared to the substrate surface area through which light is emitted from the device. One or more OLEDs also or alternatively may be disposed on an edge of the substrate about perpendicular to the surface of the substrate through which light is emitted, such that they emit light into the substrate. A mode expanding region may be included between each such OLED and the substrate.

  19. Light-emitting diodes for analytical chemistry.

    Science.gov (United States)

    Macka, Mirek; Piasecki, Tomasz; Dasgupta, Purnendu K

    2014-01-01

    Light-emitting diodes (LEDs) are playing increasingly important roles in analytical chemistry, from the final analysis stage to photoreactors for analyte conversion to actual fabrication of and incorporation in microdevices for analytical use. The extremely fast turn-on/off rates of LEDs have made possible simple approaches to fluorescence lifetime measurement. Although they are increasingly being used as detectors, their wavelength selectivity as detectors has rarely been exploited. From their first proposed use for absorbance measurement in 1970, LEDs have been used in analytical chemistry in too many ways to make a comprehensive review possible. Hence, we critically review here the more recent literature on their use in optical detection and measurement systems. Cloudy as our crystal ball may be, we express our views on the future applications of LEDs in analytical chemistry: The horizon will certainly become wider as LEDs in the deep UV with sufficient intensity become available.

  20. Printing of organic light emitting diodes on textile

    OpenAIRE

    Verboven, Inge; Gilissen, Koen; Vandevenne, Glen; Troia, Mariagrazia; Leins, Martina; Walker, Matthias; Schulz, Andreas; Deferme, Wim

    2015-01-01

    Smart textiles with light-emitting properties open a whole new world of innovative textile applications such as indoor and outdoor design and safety clothing. To achieve light-emitting properties on textiles, organic light emitting diodes are printed or integrated onto textile substrates. The advantage of this approach is that typical textile properties like flexibility and drapabilty are maintained. The authors would like to thank the research and funding partners of the European CORNET p...

  1. Pulsed Ultraviolet Light Emitting Diodes for Advanced Oxidation of Tartrazine

    Science.gov (United States)

    2015-03-26

    very aggressive and powerful oxidants that readily react with most organic compounds. The destructive effects of OH radicals are made possible due to...biofilms associated with periodontitis and peri- implantitis. Photodiagnosis and Photodynamic Therapy, Volume 10, Issue 2, May 2013, Pages 156–167

  2. Wirelessly powered ultraviolet light emitting diodes for photocatalytic oxidation

    NARCIS (Netherlands)

    Kuipers, J.; Bruning, H.; Yntema, D.R.; Rijnaarts, H.H.M.

    2015-01-01

    A method is presented to distribute small scale light sources in a photocatalytic slurry reactor. The goal of distributing the light sources is to increase photon transfer efficiency, and thereby increasing the reaction rate, compared to using one single light source. The light sources used in this

  3. Colloidal quantum dot light-emitting devices

    Directory of Open Access Journals (Sweden)

    Vanessa Wood

    2010-07-01

    Full Text Available Colloidal quantum dot light-emitting devices (QD-LEDs have generated considerable interest for applications such as thin film displays with improved color saturation and white lighting with a high color rendering index (CRI. We review the key advantages of using quantum dots (QDs in display and lighting applications, including their color purity, solution processability, and stability. After highlighting the main developments in QD-LED technology in the past 15 years, we describe the three mechanisms for exciting QDs – optical excitation, Förster energy transfer, and direct charge injection – that have been leveraged to create QD-LEDs. We outline the challenges facing QD-LED development, such as QD charging and QD luminescence quenching in QD thin films. We describe how optical downconversion schemes have enabled researchers to overcome these challenges and develop commercial lighting products that incorporate QDs to achieve desirable color temperature and a high CRI while maintaining efficiencies comparable to inorganic white LEDs (>65 lumens per Watt. We conclude by discussing some current directions in QD research that focus on achieving higher efficiency and air-stable QD-LEDs using electrical excitation of the luminescent QDs.

  4. Applications of Light Emitting Diodes in Health Care.

    Science.gov (United States)

    Dong, Jianfei; Xiong, Daxi

    2017-09-25

    Light emitting diodes (LEDs) have become the main light sources for general lighting, due to their high lumen efficiency and long life time. Moreover, their high bandwidth and the availability of diverse wavelength contents ranging from ultraviolet to infrared empower them with great controllability in tuning brightness, pulse durations and spectra. These parameters are the essential ingredients of the applications in medical imaging and therapies. Despite the fast advances in both LED technologies and their applications, few reviews have been seen to link the controllable emission properties of LEDs to these applications. The objective of this paper is to bridge this gap by reviewing the main control techniques of LEDs that enable creating enhanced lighting patterns for imaging and generating effective photon doses for photobiomodulation. This paper also provides the basic mechanisms behind the effective LED therapies in treating cutaneous and neurological diseases. The emerging field of optogenetics is also discussed with a focus on the application of LEDs. The multidisciplinary topics reviewed in this paper can help the researchers in LEDs, imaging, light therapy and optogenetics better understand the basic principles in each other's field; and hence to stimulate the application of LEDs in health care.

  5. Recent advances in conjugated polymers for light emitting devices.

    Science.gov (United States)

    Alsalhi, Mohamad Saleh; Alam, Javed; Dass, Lawrence Arockiasamy; Raja, Mohan

    2011-01-01

    A recent advance in the field of light emitting polymers has been the discovery of electroluminescent conjugated polymers, that is, kind of fluorescent polymers that emit light when excited by the flow of an electric current. These new generation fluorescent materials may now challenge the domination by inorganic semiconductor materials of the commercial market in light-emitting devices such as light-emitting diodes (LED) and polymer laser devices. This review provides information on unique properties of conjugated polymers and how they have been optimized to generate these properties. The review is organized in three sections focusing on the major advances in light emitting materials, recent literature survey and understanding the desirable properties as well as modern solid state lighting and displays. Recently, developed conjugated polymers are also functioning as roll-up displays for computers and mobile phones, flexible solar panels for power portable equipment as well as organic light emitting diodes in displays, in which television screens, luminous traffic, information signs, and light-emitting wallpaper in homes are also expected to broaden the use of conjugated polymers as light emitting polymers. The purpose of this review paper is to examine conjugated polymers in light emitting diodes (LEDs) in addition to organic solid state laser. Furthermore, since conjugated polymers have been approved as light-emitting organic materials similar to inorganic semiconductors, it is clear to motivate these organic light-emitting devices (OLEDs) and organic lasers for modern lighting in terms of energy saving ability. In addition, future aspects of conjugated polymers in LEDs were also highlighted in this review.

  6. Recent Advances in Conjugated Polymers for Light Emitting Devices

    Directory of Open Access Journals (Sweden)

    Mohan Raja

    2011-03-01

    Full Text Available A recent advance in the field of light emitting polymers has been the discovery of electroluminescent conjugated polymers, that is, kind of fluorescent polymers that emit light when excited by the flow of an electric current. These new generation fluorescent materials may now challenge the domination by inorganic semiconductor materials of the commercial market in light-emitting devices such as light-emitting diodes (LED and polymer laser devices. This review provides information on unique properties of conjugated polymers and how they have been optimized to generate these properties. The review is organized in three sections focusing on the major advances in light emitting materials, recent literature survey and understanding the desirable properties as well as modern solid state lighting and displays. Recently, developed conjugated polymers are also functioning as roll-up displays for computers and mobile phones, flexible solar panels for power portable equipment as well as organic light emitting diodes in displays, in which television screens, luminous traffic, information signs, and light-emitting wallpaper in homes are also expected to broaden the use of conjugated polymers as light emitting polymers. The purpose of this review paper is to examine conjugated polymers in light emitting diodes (LEDs in addition to organic solid state laser. Furthermore, since conjugated polymers have been approved as light-emitting organic materials similar to inorganic semiconductors, it is clear to motivate these organic light-emitting devices (OLEDs and organic lasers for modern lighting in terms of energy saving ability. In addition, future aspects of conjugated polymers in LEDs were also highlighted in this review.

  7. Recent Advances in Conjugated Polymers for Light Emitting Devices

    Science.gov (United States)

    AlSalhi, Mohamad Saleh; Alam, Javed; Dass, Lawrence Arockiasamy; Raja, Mohan

    2011-01-01

    A recent advance in the field of light emitting polymers has been the discovery of electroluminescent conjugated polymers, that is, kind of fluorescent polymers that emit light when excited by the flow of an electric current. These new generation fluorescent materials may now challenge the domination by inorganic semiconductor materials of the commercial market in light-emitting devices such as light-emitting diodes (LED) and polymer laser devices. This review provides information on unique properties of conjugated polymers and how they have been optimized to generate these properties. The review is organized in three sections focusing on the major advances in light emitting materials, recent literature survey and understanding the desirable properties as well as modern solid state lighting and displays. Recently, developed conjugated polymers are also functioning as roll-up displays for computers and mobile phones, flexible solar panels for power portable equipment as well as organic light emitting diodes in displays, in which television screens, luminous traffic, information signs, and light-emitting wallpaper in homes are also expected to broaden the use of conjugated polymers as light emitting polymers. The purpose of this review paper is to examine conjugated polymers in light emitting diodes (LEDs) in addition to organic solid state laser. Furthermore, since conjugated polymers have been approved as light-emitting organic materials similar to inorganic semiconductors, it is clear to motivate these organic light-emitting devices (OLEDs) and organic lasers for modern lighting in terms of energy saving ability. In addition, future aspects of conjugated polymers in LEDs were also highlighted in this review. PMID:21673938

  8. Plant Growth Under Light Emitting Diode Irradiation.

    Science.gov (United States)

    Tennessen, Daniel John

    Plant growth under light emitting diodes (LEDs) was investigated to determine if LEDs would be useful to provide radiant energy for two plant processes, photosynthesis and photomorphogenesis. Photosynthesis of tomato (Lycopersicon esculentum L.) and Kudzu (Pueraria lobata (Willd) Ohwi.) was measured using photons from LEDs to answer the following: (1) Are leaves able to use red LED light for photosynthesis? and (2) Is the efficiency of photosynthesis in pulsed light equal to that of continuous light? In 175 Pa CO _2, or in response to changes in CO _2,tomato (Lycopersicon esculentum Mill.) and transformed tobacco and tomato (expressing oat phytochrome-A) was assessed by growing plants under red LED lamps in an attempt to answer the following: (1) What is the developmental response of non-transformed and transformed tobacco to red LED light? and (2) Can tomato plants that grow tall and spindly in red LED light be made to grow short by increasing the amount of phytochrome-A? The short phenotype of transformed tobacco was not evident when plants were grown in LED light. Addition of photons of far-red or blue light to red light resulted in short transformed tobacco. Tomato plants grew three times as tall and lacked leaf development in LED versus white light, but transformed tomato remained short and produced fruit under LED light. I have determined that the LED photons are useful for photosynthesis and that the photon efficiency of photosynthesis is the same in pulsed as in continuous light. From responses of tobacco, I concluded that the P_{ rm r} form of phytochrome-A and the phytochrome cycling rate mediate responses. In tomato, increased amounts of Phytochrome-A prevented stem elongation and caused chlorophyll accumulation in LED light.

  9. Luminescence properties of novel single-host white-light-emitting phosphor KBaBP2O8:Dy3+

    Science.gov (United States)

    Han, Bing; Zhang, Jie; Li, Pengju; Shi, Hengzhen

    2015-01-01

    A series of white-light-emitting KBaBP2O8:Dy3+ phosphors were synthesized by using a solid state reaction technique at high-temperature. X-ray diffraction and fluorescence spectroscopy measurements were utilized to characterize the structure and luminescence characteristics including excitation and emission spectra, decay curves, chromaticity coordinates of the assprepared phosphors. The influence of the doping concentration of Dy3+ on the relative emission intensity of Dy3+ was investigated. The critical distance as well as concentration quenching mechanism was calculated and confirmed. The as-prepared phosphors can be effectively excited with near ultraviolet, and exhibit white light emission with short decay time of milliseconds. The above work indicates these phosphors could be potential candidates as single-host white-light-emitting phosphors for application in white light-emitting-diodes.

  10. Evaluation of light-emitting diode beacon light fixtures.

    Science.gov (United States)

    2009-12-01

    Rotating beacons containing filament light sources have long been used on highway maintenance trucks : to indicate the presence of the truck to other drivers. Because of advances in light-emitting diode (LED) : technologies, flashing lights containin...

  11. Efficient semiconductor light-emitting device and method

    Science.gov (United States)

    Choquette, Kent D.; Lear, Kevin L.; Schneider, Jr., Richard P.

    1996-01-01

    A semiconductor light-emitting device and method. The semiconductor light-emitting device is provided with at least one control layer or control region which includes an annular oxidized portion thereof to channel an injection current into the active region, and to provide a lateral refractive index profile for index guiding the light generated within the device. A periodic composition grading of at least one of the mirror stacks in the device provides a reduced operating voltage of the device. The semiconductor light-emitting device has a high efficiency for light generation, and may be formed either as a resonant-cavity light-emitting diode (RCLED) or as a vertical-cavity surface-emitting laser (VCSEL).

  12. Organic light emitting diode with light extracting electrode

    Energy Technology Data Exchange (ETDEWEB)

    Bhandari, Abhinav; Buhay, Harry

    2017-04-18

    An organic light emitting diode (10) includes a substrate (20), a first electrode (12), an emissive active stack (14), and a second electrode (18). At least one of the first and second electrodes (12, 18) is a light extracting electrode (26) having a metallic layer (28). The metallic layer (28) includes light scattering features (29) on and/or in the metallic layer (28). The light extracting features (29) increase light extraction from the organic light emitting diode (10).

  13. Organic light emitting diode with surface modification layer

    Energy Technology Data Exchange (ETDEWEB)

    Basil, John D.; Bhandari, Abhinav; Buhay, Harry; Arbab, Mehran; Marietti, Gary J.

    2017-09-12

    An organic light emitting diode (10) includes a substrate (12) having a first surface (14) and a second surface (16), a first electrode (32), and a second electrode (38). An emissive layer (36) is located between the first electrode (32) and the second electrode (38). The organic light emitting diode (10) further includes a surface modification layer (18). The surface modification layer (18) includes a non-planar surface (30, 52).

  14. Doping Asymmetry Problem in ZnO: Current Status and Outlook. A Review of Experimental and Theoretical Efforts Focused on Achieving P-Type ZnO Suitable for Light-Emitting Optoelectronic Devices for the Blue/Ultraviolet Spectral Range

    Science.gov (United States)

    2009-04-24

    have a low valence-band maximum or a high conduction-band minimum [12] [13]. Some semiconductors such as ZnTe, CdTe , and diamond in which the...Y. Segawa, H. Ohno, H. Koinuma, and M. Kawasaki, “Repeated temperature modulation epitaxy for p-type doping and light-emitting diode based on ZnO

  15. Experimental investigations into the physics of light emitting conjugated polymers

    CERN Document Server

    Whitelegg, S A

    2001-01-01

    chloroprecursor MEH-PPV in-situ of ITO results in a reaction of the polymer with ITO, which significantly shift the emission to high energies. Electroabsorption spectroscopy is used to probe the internal electric fields within operating polymer light emitting devices. When a PPV based LED in an oxygen/water atmosphere, degradation of the device occurs whereby an electric field develops, which opposes the applied electric field. This opposing electric field subsequently decays when the device is turned to its off state. Operating lifetimes and emission efficiencies of polymer light emitting devices are now approaching values suitable for the manufacture and sale of polymer light emitting based products. However, degradation and device performance still continues to be of chief concern and in order for these to be improved the underlying physical processes have to be identified. This thesis aims to identify some of these processes. An investigation in to the optical absorption and emission properties of insolub...

  16. Close-packed array of light emitting devices

    Science.gov (United States)

    Ivanov, Ilia N.; Simpson, John T.

    2013-04-09

    A close-packed array of light emitting diodes includes a nonconductive substrate having a plurality of elongate channels extending therethrough from a first side to a second side, where each of the elongate channels in at least a portion of the substrate includes a conductive rod therein. The conductive rods have a density over the substrate of at least about 1,000 rods per square centimeter and include first conductive rods and second conductive rods. The close-packed array further includes a plurality of light emitting diodes on the first side of the substrate, where each light emitting diode is in physical contact with at least one first conductive rod and in electrical contact with at least one second conductive rod.

  17. Light emitting ceramic device and method for fabricating the same

    Science.gov (United States)

    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.

  18. Semiconductor Nanomembrane-Based Light-Emitting and Photodetecting Devices

    Directory of Open Access Journals (Sweden)

    Dong Liu

    2016-06-01

    Full Text Available Heterogeneous integration between silicon (Si, III-V group material and Germanium (Ge is highly desirable to achieve monolithic photonic circuits. Transfer-printing and stacking between different semiconductor nanomembranes (NMs enables more versatile combinations to realize high-performance light-emitting and photodetecting devices. In this paper, lasers, including vertical and edge-emitting structures, flexible light-emitting diode, photodetectors at visible and infrared wavelengths, as well as flexible photodetectors, are reviewed to demonstrate that the transfer-printed semiconductor nanomembrane stacked layers have a large variety of applications in integrated optoelectronic systems.

  19. Electrically driven surface plasmon light-emitting diodes

    DEFF Research Database (Denmark)

    Fadil, Ahmed; Ou, Yiyu; Iida, Daisuke

    We investigate device performance of GaN light-emitting diodes (LEDs) with a 30-nm p-GaN layer. The metallization used to separate the p-contact from plasmonic metals, reveals limitations on current spreading which reduces surface plasmonic enhancement.......We investigate device performance of GaN light-emitting diodes (LEDs) with a 30-nm p-GaN layer. The metallization used to separate the p-contact from plasmonic metals, reveals limitations on current spreading which reduces surface plasmonic enhancement....

  20. Hybrid Light-Emitting Diode Enhanced With Emissive Nanocrystals

    DEFF Research Database (Denmark)

    Kopylov, Oleksii

    This thesis investigates a new type of white light emitting hybrid diode, composed of a light emitting GaN/InGaN LED and a layer of semiconductor nanocrystals for color conversion. Unlike standard white LEDs, the device is configured to achieve high color conversion efficiency via non...... was less than 10nm. Analysis of the results shows that in order to achieve sufficient for the white LED color conversion, better surface passivation and nanocrystals with shorter exciton lifetimes and weaker Auger recombination and needed....

  1. Fabrication of organic light-emitting devices comprising stacked light-emitting units by solution-based processes.

    Science.gov (United States)

    Pu, Yong-Jin; Chiba, Takayuki; Ideta, Kazushige; Takahashi, Shogo; Aizawa, Naoya; Hikichi, Tatsuya; Kido, Junji

    2015-02-25

    Multi-organic light-emitting devices comprising two light-emitting units stacked in series through a charge-generation layer are fabricated by solution processes. A zinc oxide nanoparticles/polyethylene-imine bilayer is used as the electron-injection layer and phosphomolybdic acid is used as the charge-generation layer. Appropriate choice of solvents during spin-coating of each layer ensures the nine-layered structure fabricated by solution processes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Toward inkjet printing of small molecule organic light emitting diodes

    NARCIS (Netherlands)

    Gorter, H.; Coenen, M.J.J.; Slaats, M.W.L.; Ren, M.; Lu, W.; Kuijpers, C.J.; Groen, W.A.

    2013-01-01

    Thermal evaporation is the current standard for the manufacture of small molecule organic light emitting diodes (smOLEDs), but it requires vacuum process, complicated shadow masks and is inefficient in material utilization, resulting in high cost of ownership. As an alternative, wet solution

  3. Gallium-Nitride-Based Light-Emitting Diodes

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 20; Issue 7. Gallium-Nitride-Based Light-Emitting Diodes: 2014 Nobel Prize in Physics. Kota V R M Murali Vinayak Bharat Naik Deepanjan Datta. General Article Volume 20 Issue 7 July 2015 pp 605-616 ...

  4. Transient Behavior of Light-Emitting Electrochemical Cells

    Science.gov (United States)

    2011-06-01

    Triflate Lithium Trifluoromethanesulfonate NVG Night Vision Goggles OIF Operation Iraqi Freedom OLED Organic Light Emitting Diode Opamp Operational...xii R Resistance TTI OSD Technology Transition Initiative Z Impedance ZI Imaginary Impedance ZR Real Impedance xiii...response to questions arising from these studies the IFF LEC patch will be used to make measurements of the device’s capacitance, resistance , current and

  5. Organic light emitting diodes with spin polarized electrodes

    NARCIS (Netherlands)

    Arisi, E.; Bergenti, I.; Dediu, V.; Loi, M.A.; Muccini, M.; Murgia, M.; Ruani, G.; Taliani, C.; Zamboni, R.

    2003-01-01

    Electrical and optical properties of Alq3 based organic light emitting diodes with normal and spin polarized electrodes are presented. Epitaxial semitransparent highly spin polarized La0.7Sr0.3MnO3 were used as hole injector, substituting the traditional indium tin oxide electrode. A comparison of

  6. Tuning the colour of white polymer light emitting diodes

    NARCIS (Netherlands)

    Kok, M.M. de; Sarfert, W.; Paetzold, R.

    2010-01-01

    Colour tuning of white polymer light emitting diode (LED) light sources can be attained by various methods at various stages in the production process of the lamps and/or by the design of the active material incorporated in the LEDs. In this contribution we will describe the methods and discuss the

  7. The Light-Emitting Diode as a Light Detector

    Science.gov (United States)

    Baird, William H.; Hack, W. Nathan; Tran, Kiet; Vira, Zeeshan; Pickett, Matthew

    2011-01-01

    A light-emitting diode (LED) and operational amplifier can be used as an affordable method to provide a digital output indicating detection of an intense light source such as a laser beam or high-output LED. When coupled with a microcontroller, the combination can be used as a multiple photogate and timer for under $50. A similar circuit is used…

  8. Determination of illuminants representing typical white light emitting diodes sources

    DEFF Research Database (Denmark)

    Jost, S.; Ngo, M.; Ferrero, A.

    2017-01-01

    Solid-state lighting (SSL) products are already in use by consumers and are rapidly gaining the lighting market. Especially, white Light Emitting Diode (LED) sources are replacing banned incandescent lamps and other lighting technologies in most general lighting applications. The aim of this work...

  9. Operation of AC Adapters Visualized Using Light-Emitting Diodes

    Science.gov (United States)

    Regester, Jeffrey

    2016-01-01

    A bridge rectifier is a diamond-shaped configuration of diodes that serves to convert alternating current(AC) into direct current (DC). In our world of AC outlets and DC electronics, they are ubiquitous. Of course, most bridge rectifiers are built with regular diodes, not the light-emitting variety, because LEDs have a number of disadvantages. For…

  10. Silicon light-emitting diode antifuse: properties and devices

    NARCIS (Netherlands)

    Le Minh, P.; Holleman, J.

    2006-01-01

    This paper reviews our research on the silicon light-emitting diode antifuse, a tiny source featuring a full white-light spectrum. Optical and electrical properties of the device are discussed together with the modelling of the spectral emission, explaining the emitting mechanism of the device. An

  11. Device Physics of White Polymer Light-Emitting Diodes

    NARCIS (Netherlands)

    Nicolai, Herman T.; Hof, Andre; Blom, Paul W. M.

    2012-01-01

    The charge transport and recombination in white-emitting polymer light- emitting diodes (PLEDs) are studied. The PLED investigated has a single emissive layer consisting of a copolymer in which a green and red dye are incorporated in a blue backbone. From single-carrier devices the effect of the

  12. Admittance spectroscopy on polymer light-emitting diodes

    NARCIS (Netherlands)

    Blom, PWM; Martens, HCF; Brom, HB; Huiberts, JN; Jabbour, GE; Sariciftci, NS

    2002-01-01

    From admittance spectroscopy measurements on poly(p-phenylene vinylene) based light-emitting diodes various relaxation processes can be observed. At low bias inductive contributions due to the transit of charge carriers dominate, at high bias capacitive contributions as a result of charge

  13. Device physics of white polymer light-emitting diodes

    NARCIS (Netherlands)

    Nicolai, H.T.; Hof, A.; Blom, P.W.M.

    2012-01-01

    The charge transport and recombination in white-emitting polymer light- emitting diodes (PLEDs) are studied. The PLED investigated has a single emissive layer consisting of a copolymer in which a green and red dye are incorporated in a blue backbone. From single-carrier devices the effect of the

  14. Defining the light emitting area for displays in the unipolar regime of highly efficient light emitting transistors

    Science.gov (United States)

    Ullah, Mujeeb; Armin, Ardalan; Tandy, Kristen; Yambem, Soniya D.; Burn, Paul L.; Meredith, Paul; Namdas, Ebinazar B.

    2015-01-01

    Light-emitting field effect transistors (LEFETs) are an emerging class of multifunctional optoelectronic devices. It combines the light emitting function of an OLED with the switching function of a transistor in a single device architecture. The dual functionality of LEFETs has the potential applications in active matrix displays. However, the key problem of existing LEFETs thus far has been their low EQEs at high brightness, poor ON/OFF and poorly defined light emitting area - a thin emissive zone at the edge of the electrodes. Here we report heterostructure LEFETs based on solution processed unipolar charge transport and an emissive polymer that have an EQE of up to 1% at a brightness of 1350 cd/m2, ON/OFF ratio > 104 and a well-defined light emitting zone suitable for display pixel design. We show that a non-planar hole-injecting electrode combined with a semi-transparent electron-injecting electrode enables to achieve high EQE at high brightness and high ON/OFF ratio. Furthermore, we demonstrate that heterostructure LEFETs have a better frequency response (fcut-off = 2.6 kHz) compared to single layer LEFETs. The results presented here therefore are a major step along the pathway towards the realization of LEFETs for display applications. PMID:25743444

  15. All-Quantum-Dot Infrared Light-Emitting Diodes

    KAUST Repository

    Yang, Zhenyu

    2015-12-22

    © 2015 American Chemical Society. Colloidal quantum dots (CQDs) are promising candidates for infrared electroluminescent devices. To date, CQD-based light-emitting diodes (LEDs) have employed a CQD emission layer sandwiched between carrier transport layers built using organic materials and inorganic oxides. Herein, we report the infrared LEDs that use quantum-tuned materials for each of the hole-transporting, the electron-transporting, and the light-emitting layers. We successfully tailor the bandgap and band position of each CQD-based component to produce electroluminescent devices that exhibit emission that we tune from 1220 to 1622 nm. Devices emitting at 1350 nm achieve peak external quantum efficiency up to 1.6% with a low turn-on voltage of 1.2 V, surpassing previously reported all-inorganic CQD LEDs.

  16. Light-emitting diodes in dermatology: stimulation of wound healing

    Directory of Open Access Journals (Sweden)

    Justyna Fryc

    2016-05-01

    Full Text Available Low-level light therapy (LLLT, which is sometimes included in phototherapy, is an effective therapeutic strategy to improve wound healing and reduce pain, inflammation and swelling. Nowadays, new sources of light, such as light-emitting diodes (LEDs with a broad range of wavelengths, are widely available. The biological effects promoted by LEDs are dependent on irradiation parameters, mainly wavelength and dose. This review article focuses on recent clinical trials using light-emitting diode low-level light therapy (LED-LLLT for enhancing wound healing. In this article, we also cover the mechanisms of action of LLLT on cells and tissues and highlight the importance of defining optimum LLLT parameters for stimulation of wound healing.

  17. Organic light-emitting diodes from homoleptic square planar complexes

    Science.gov (United States)

    Omary, Mohammad A

    2013-11-12

    Homoleptic square planar complexes [M(N.LAMBDA.N).sub.2], wherein two identical N.LAMBDA.N bidentate anionic ligands are coordinated to the M(II) metal center, including bidentate square planar complexes of triazolates, possess optical and electrical properties that make them useful for a wide variety of optical and electrical devices and applications. In particular, the complexes are useful for obtaining white or monochromatic organic light-emitting diodes ("OLEDs"). Improved white organic light emitting diode ("WOLED") designs have improved efficacy and/or color stability at high brightness in single- or two-emitter white or monochrome OLEDs that utilize homoleptic square planar complexes, including bis[3,5-bis(2-pyridyl)-1,2,4-triazolato]platinum(II) ("Pt(ptp).sub.2").

  18. The heating effect on different light emitting diodes chips materials

    Science.gov (United States)

    Chu, K. K.; Hambali, N. A. M. A.; Ariffin, S. N.; Wahid, M. H. A.; Shahimin, M. M.; Ali, Norshamsuri

    2017-09-01

    In this paper, simulation of non-radiative recombination heating and Joule heating effects based on different material of a light emitting diodes chip for Gallium Nitride, Indium Nitride, Zinc Oxide, Zinc Selenide and Titanium Dioxide are demonstrated. Among the light emitting diodes chips materials, Indium Nitride, Zinc Oxide and Zinc Selenide has the capability to produce the highest non-radiative recombination heating which the heating value is potential up to ×1012 to ×1013 W/m3. Meanwhile, Titanium Dioxide has the capability to generate higher value of non-radiative recombination heating with lowest value of electron carriers concentration. For the joule heating effect, the Titanium Dioxide shows the fast heating behavior as compared with other materials.

  19. Concave-hemisphere-patterned organic top-light emitting device

    Science.gov (United States)

    Forrest, Stephen R.; Slootsky, Michael; Lunt, Richard

    2015-06-09

    A first device is provided. The first device includes an organic light emitting device, which further comprises a first electrode, a second electrode, and an organic emissive layer disposed between the first and second electrode. Preferably, the second electrode is more transparent than the first electrode. The organic emissive layer has a first portion shaped to form an indentation in the direction of the first electrode, and a second portion shaped to form a protrusion in the direction of the second electrode. The first device may include a plurality of organic light emitting devices. The indentation may have a shape that is formed from a partial sphere, a partial cylinder, a pyramid, or a pyramid with a mesa, among others. The protrusions may be formed between adjoining indentations or between an indentation and a surface parallel to the substrate.

  20. Cubic-phase GaN light-emitting diodes

    Science.gov (United States)

    Yang, Hui; Zheng, L. X.; Li, J. B.; Wang, X. J.; Xu, D. P.; Wang, Y. T.; Hu, X. W.; Han, P. D.

    1999-04-01

    The feasibility of growing device-quality cubic GaN/GaAs(001) films by metal organic chemical vapor deposition has been demonstrated. The optical quality of the GaN films was characterized by room-temperature photoluminescence measurements, which shows a full width at half maximum of 46 meV. The structural quality of the films was investigated by transmission electron microscopy. There are submicron-size grains free from threading dislocations and stacking faults. More importantly, a cubic-phase GaN blue light-emitting diode has been fabricated. The device process, which is very simple and compatible with current GaAs technology, indicates a promising future for the blue light-emitting diode.

  1. ZnO-nanowires/PANI inorganic/organic heterostructure light-emitting diode.

    Science.gov (United States)

    He, Ying; Wang, Jun-an; Zhang, Wenfei; Song, Jizhong; Pei, Changlong; Chen, Xiaoban

    2010-11-01

    In this paper, we report a flexible inorganic/organic heterostructure light-emitting diode, in which inorganic ZnO nanowires are the optically active components and organic polyaniline (PANI) is the hole-transporting layer. The fabrication of the hybrid LED is as follows, the ordered single-crystalline ZnO nanowires were uniformly distributed on flexible polyethylene terephthalate (PET)-based indium-tin-oxide-coated substrates by our polymer-assisted growth method, and proper materials were chosen as electrode and carrier. In this construction, an array of ZnO nanowires grown on PET substrate is successfully embedded in a polyaniline thin film. The performance of the hybrid device of organic-inorganic hetero-junction of ITO/(ZnO nanowires-PANI) for LED application in the blue and UV ranges are investigated, and tunable electroluminescence has been demonstrated by contacting the upper tips of ZnO nanowires and the PET substrate. The effect of surface capping with polyvinyl alcohol (PANI) on the photocarrier relaxation of the aqueous chemically grown ZnO nanowires has been investigated. The photoluminescence spectrum shows an enhanced ultraviolet emission and reduced defect-related emission in the capped ZnO NWs compared to bare ZnO. The results of our study may offer a fundamental understanding in the field of inorganic/organic heterostructure light-emitting diode, which may be useful for potential applications of hybrid ZnO nanowires with conductive polymers.

  2. Laterally injected light-emitting diode and laser diode

    Science.gov (United States)

    Miller, Mary A.; Crawford, Mary H.; Allerman, Andrew A.

    2015-06-16

    A p-type superlattice is used to laterally inject holes into an III-nitride multiple quantum well active layer, enabling efficient light extraction from the active area. Laterally-injected light-emitting diodes and laser diodes can enable brighter, more efficient devices that impact a wide range of wavelengths and applications. For UV wavelengths, applications include fluorescence-based biological sensing, epoxy curing, and water purification. For visible devices, applications include solid state lighting and projection systems.

  3. Active targeting of tumor cells using light emitting bacteria

    Energy Technology Data Exchange (ETDEWEB)

    Moon, Sung Min; Min, Jung Joon; Hong, Yeong Jin; Kim, Hyun Ju; Le, Uuenchi N.; Rhee, Joon Haeng; Song, Ho Chun; Heo, Young Jun; Bom, Hee Seung; Choy, Hyon E [School of Medicine, Chonnam National University, Gwangju (Korea, Republic of)

    2004-07-01

    The presence of bacteria and viruses in human tumors has been recognized for more than 50 years. Today, with the discovery of bacterial strains that specifically target tumors, and aided by genomic sequencing and genetic engineering, there is new interest in the use of bacteria as tumor vectors. Here, we show that bacteria injected intravenously into live animals entered and replicated in solid tumors and metastases using the novel imaging technology of biophotonics. Bioluminescence operon (LuxCDABE) or fluorescence protein, GFP) has been cloned into pUC19 plasmid to engineer pUC19lux or pUC19gfp. Engineered plasmid was transformed into different kinds of wild type (MG1655) or mutant E. coli (DH5, ppGpp, fnr, purE, crpA, flagella, etc.) strains to construct light emitting bacteria. Xenograft tumor model has been established using CT26 colon cancer cell line. Light emitting bacteria was injected via tail vein into tumor bearing mouse. In vivo bioluminescence imaging has been done after 20 min to 14 days of bacterial injection. We observed localization of tumors by light-emitting E. coli in tumor (CT-26) bearing mice. We confirmed the presence of light-emitting bacteria under the fluorescence microscope with E. coli expressing GFP. Althoug varying mutants strain with deficient invading function has been found in tumor tissues, mutant strains of movement (flagella) couldn't show any light signal from the tumor tissue under the cooled CCD camera, indicating bacteria may actively target the tumor cells. Based on their 'tumor-finding' nature, bacteria may be designed to carry multiple genes or drugs for detection and treatment of cancer, such as prodrug-converting enzymes, toxins, angiogenesis inhibitors and cytokines.

  4. Fabrication of natural DNA-containing organic light emitting diodes

    Science.gov (United States)

    Gomez, Eliot F.; Spaeth, Hans D.; Steckl, Andrew J.; Grote, James G.

    2011-09-01

    The process of creating natural DNA-containing bio-organic light emitting diodes is a fascinating journey from salmon fish to the highly-efficient BiOLED. DNA from salmon sperm is used as a high-performance electron blocking layer, to enhance the efficiency of the BiOLED over its conventional OLED counterpart. An overview of the BiOLED fabrication process and its key steps are presented in this paper.

  5. Absorbance based light emitting diode optical sensors and sensing devices

    OpenAIRE

    Dermot Diamond; Martina O’Toole

    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 i...

  6. DNA electron injection interlayers for polymer light-emitting diodes.

    Science.gov (United States)

    Zalar, Peter; Kamkar, Daniel; Naik, Rajesh; Ouchen, Fahima; Grote, James G; Bazan, Guillermo C; Nguyen, Thuc-Quyen

    2011-07-27

    Introduction of a DNA interlayer adjacent to an Al cathode in a polymer light-emitting diode leads to lower turn-on voltages, higher luminance efficiencies, and characteristics comparable to those observed using a Ba electrode. The DNA serves to improve electron injection and also functions as a hole-blocking layer. The temporal characteristics of the devices are consistent with an interfacial dipole layer adjacent to the electrode being responsible for the reduction of the electron injection barrier.

  7. Light-emitting diode technology in vitreoretinal surgery.

    Science.gov (United States)

    Dithmar, Stefan; Hoeh, Alexandra E; Amberger, Roman; Ruppenstein, Mira; Ach, Thomas

    2011-05-01

    Systems for vitreoretinal illumination during surgery usually consist of an external light source and a light fiber. We introduce a new illumination system for vitreoretinal surgery based on the light-emitting diode technology, with an embedded light source in the handle of the light fiber, making a separate light source unnecessary. A prototype of a new illumination system for vitreoretinal surgery (ocuLED; Geuder, Heidelberg, Germany) was tested. This system consists of a handle with a built-in light-emitting diode, supported by an external power source. The OcuLED was analyzed in regards to wavelength, maximum radiant power, and maximum irradiance and was compared with three commercially available vitreoretinal illumination systems. Furthermore, the first intraoperative application and handling were evaluated. The ocuLED system works with a cool white or a neutral white light-emitting diode and is powered externally. The wavelength spectrum shows a maximum at 565 nm and a second peak at 455 nm. Compared with other light sources, the proportion of potentially harmful blue light is low. Maximum radiant power and irradiance are in line with xenon and mercury vapor light sources. The intrasurgical light is bright and offers good visibility. The handle of ocuLED is slightly wider than commonly used light fiber handles, which do not affect its use during surgery. Technical progress in light-emitting diode technology allows minimizing the equipment for vitreoretinal illumination. The OcuLED provides bright illumination without an external light source. Wavelength spectrum, maximum radiant power, and irradiance are safe from the risk of phototoxic damage. Intrasurgical handling is identical to conventional light fibers.

  8. Organic light emitting device having multiple separate emissive layers

    Science.gov (United States)

    Forrest, Stephen R [Ann Arbor, MI

    2012-03-27

    An organic light emitting device having multiple separate emissive layers is provided. Each emissive layer may define an exciton formation region, allowing exciton formation to occur across the entire emissive region. By aligning the energy levels of each emissive layer with the adjacent emissive layers, exciton formation in each layer may be improved. Devices incorporating multiple emissive layers with multiple exciton formation regions may exhibit improved performance, including internal quantum efficiencies of up to 100%.

  9. Light emitting diodes as a plant lighting source

    Energy Technology Data Exchange (ETDEWEB)

    Bula, R.J.; Tennessen, D.J.; Morrow, R.C. [Wisconsin Center for Space Automation and Robotics, Madison, WI (United States); Tibbitts, T.W. [Univ. of Wisconsin, Madison, WI (United States)

    1994-12-31

    Electroluminescence in solid materials is defined as the generation of light by the passage of an electric current through a body of solid material under an applied electric field. A specific type of electroluminescence, first noted by Lossew in 1923, involves the generation of photons when electrons are passed through a p-n junction of certain solid materials (junction of a n-type semiconductor, an electron donor, and a p-type semiconductor, an electron acceptor). Development efforts to translate these observations into visible light emitting devices, however, was not undertaken until the 1950s. The term, light emitting diode (LEDs), was first used in a report by Wolfe, et al., in 1955. The development of this light emitting semiconductor technology dates back less than 30 years. During this period of time, the LED has evolved from a rare and expensive light generating device to one of the most widely used electronic components. The most popular applications of the LED are as indicators or as optoelectronic switches. However, several recent advances in LED technology have made possible the utilization of LEDs for applications that require a high photon flux, such as for plant lighting in controlled environments. The new generation of LEDs based on a gallium aluminum arsenide (GaAlAS) semiconductor material fabricated as a double heterostructure on a transparent substrate has opened up many new applications for these LEDs.

  10. Si light-emitting device in integrated photonic CMOS ICs

    Science.gov (United States)

    Xu, Kaikai; Snyman, Lukas W.; Aharoni, Herzl

    2017-07-01

    The motivation for integrated Si optoelectronics is the creation of low-cost photonics for mass-market applications. Especially, the growing demand for sensitive biochemical sensors in the environmental control or medicine leads to the development of integrated high resolution sensors. Here CMOS-compatible Si light-emitting device structures are presented for investigating the effect of various depletion layer profiles and defect engineering on the photonic transition in the 1.4-2.8 eV. A novel Si device is proposed to realize both a two-terminal Si-diode light-emitting device and a three-terminal Si gate-controlled diode light-emitting device in the same device structure. In addition to the spectral analysis, differences between two-terminal and three-terminal devices are discussed, showing the light emission efficiency change. The proposed Si optical source may find potential applications in micro-photonic systems and micro-optoelectro-mechanical systems (MOEMS) in CMOS integrated circuitry.

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

    Science.gov (United States)

    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.

  12. Employment of gold-coated silver nanowires as transparent conductive electrode for organic light emitting diodes

    Science.gov (United States)

    Kim, Sunho; Kim, Bongsung; Im, Inseob; Kim, Dongjae; Lee, Haeseong; Nam, Jaewook; Chung, Ho Kyoon; Lee, Hoo-Jeong; Cho, Sung Min

    2017-08-01

    This study proposes a simple method of Au coating on silver nanowires (Ag NWs) transparent conductive films as the anode of organic light emitting diodes (OLED) to increase the work function of the film and thus enhance hole transport. We carefully engineer the process conditions (pretreatment, solution concentrations, and coating number) of the coating using a diluted HAuCl4 solution on the Ag NWs film to minimize etching damage on Ag NWs accompanying the galvanic replacement reaction. Ultraviolet photoelectron spectroscopy and Kelvin probe force microscopy show work function increase of Ag NWs upon Au coating. OLED devices based on Au-coated Ag NWs show a lower turn-on voltage and higher luminance, compared with pristine Ag NWs device. Although the Ag NWs device displays poor efficiencies in the low luminance range due to a high leakage, some of the Au-coated Ag NWs devices showed efficiencies higher than those of the ITO device in a high luminance.

  13. The Electric and Optical Properties of Doped Small Molecular Organic Light-Emitting Devices

    CERN Document Server

    Kwang Ohk Cheo

    2003-01-01

    Organic light-emitting devices (OLEDs) constitute a new and exciting emissive display technology. In general, the basic OLED structure consists of a stack of fluorescent organic layers sandwiched between a transparent conducting-anode and metallic cathode. When an appropriate bias is applied to the device, holes are injected from the anode and electrons from the cathode; some of the recombination events between the holes and electrons result in electroluminescence (EL). Until now, most of the efforts in developing OLEDs have focused on display applications, hence on devices within the visible range. However some organic devices have been developed for ultraviolet or infrared emission. Various aspects of the device physics of doped small molecular OLEDs were described and discussed. The doping layer thickness and concentration were varied systematically to study their effects on device performances, energy transfer, and turn-off dynamics. Low-energy-gap DCM2 guest molecules, in either alpha-NPD or DPVBi host l...

  14. Fabrication of Flexible White Light-Emitting Diodes from Photoluminescent Polymer Materials with Excellent Color Quality.

    Science.gov (United States)

    Lin, Huang-Yu; Sher, Chin-Wei; Lin, Chih-Hao; Tu, Hsien-Hao; Chen, Xin Yin; Lai, Yi-Chun; Lin, Chien-Chung; Chen, Huang-Ming; Yu, Peichen; Meng, Hsin-Fei; Chi, Gou-Chung; Honjo, Keiji; Chen, Teng-Ming; Kuo, Hao-Chung

    2017-10-11

    This study developed flexible light-emitting diodes (LEDs) with warm white and neutral white light. A simple ultraviolet flip-chip sticking process was adopted for the pumping source and combined with polymer and quantum dot (QD) films technology to yield white light. The polymer-blended flexible LEDs exhibited higher luminous efficiency than the QD-blended flexible LEDs. Moreover, the polymer-blended LEDs achieved excellent color-rendering index (CRI) values (Ra = 96 and R9 = 96), with high reliability, demonstrating high suitability for special applications like accent, down, or retrofit lights in the future. In places such as a museum, kitchen, or surgery room, its high R9 and high CRI characteristics can provide high-quality services.

  15. Fluorescent Silicon Carbide and its Applications in White Light-Emitting Diodes

    DEFF Research Database (Denmark)

    Ou, Yiyu

    This thesis focuses on the optical properties analysis of Donor-Acceptor-Pair (DAP) co-doped Fluorescent Silicon Carbide (f-SiC) as a wavelengthconversion material in white Light-Emitting Diodes (LEDs). Different methods of fabricating surface Antireflective Structures (ARS) on f-SiC to enhance its...... light extraction efficiency are presented. White LEDs are the most promising techniques to replace the conventional lighting sources. A typical white LED consists of a Gallium Nitride (GaN) blue or Ultraviolet (UV) LED stack and a wavelengthconversion material. Silicon Carbide (SiC) has a wide optical...... bandgap and could be tailored to emit light at different wavelength by introducing different dopants. Combined emitting spectra of two types of DAP co-doped f-SiC could cover the whole visible spectral range and make f-SiC as a good candidate of wavelength-conversion material. It has a better color...

  16. Unraveled Face-Dependent Effects of Multilayered Graphene Embedded in Transparent Organic Light-Emitting Diodes.

    Science.gov (United States)

    Lim, Jong Tae; Kim, Jaesu; Lee, Hyunkoo; Moon, Jaehyun; Kwon, Byoung-Hwa; Ahn, Seongdeok; Cho, Nam Sung; Ahn, Byung-Wook; Lee, Jeong-Ik; Ihm, Kyuwook; Lim, Seong Chu

    2017-12-13

    With increasing demand for transparent conducting electrodes, graphene has attracted considerable attention, owing to its high electrical conductivity, high transmittance, low reflectance, flexibility, and tunable work function. Two faces of single-layer graphene are indistinguishable in its nature, and this idea has not been doubted even in multilayered graphene (MLG) because it is difficult to separately characterize the front (first-born) and the rear face (last-born) of MLG by using conventional analysis tools, such as Raman and ultraviolet spectroscopy, scanning probe microscopy, and sheet resistance. In this paper, we report the striking difference of the emission pattern and performance of transparent organic light-emitting diodes (OLEDs) depending on the adopted face of MLG and show the resolved chemical and physical states of both faces by using depth-selected absorption spectroscopy. Our results strongly support that the interface property between two different materials rules over the bulk property in the driving performance of OLEDs.

  17. Pseudomorphic Bipolar Quantum Resonant-Tunneling Transistor

    National Research Council Canada - National Science Library

    Seabaugh, Alan C; Frensley, William R; Randall, John N; Reed, Mark A; Farrington, Dewey L; Matyi, Richard J

    1989-01-01

    ...+ InGaAs quantum well of a double-barrier resonant-tunneling structure. The heterojunction transistor consists of an n-GaAs emitter and collector, undoped AlAs tunnel barriers, and a pseudomorphic p...

  18. Top-emitting organic light-emitting diodes.

    Science.gov (United States)

    Hofmann, Simone; Thomschke, Michael; Lüssem, Björn; Leo, Karl

    2011-11-07

    We review top-emitting organic light-emitting diodes (OLEDs), which are beneficial for lighting and display applications, where non-transparent substrates are used. The optical effects of the microcavity structure as well as the loss mechanisms are discussed. Outcoupling techniques and the work on white top-emitting OLEDs are summarized. We discuss the power dissipation spectra for a monochrome and a white top-emitting OLED and give quantitative reports on the loss channels. Furthermore, the development of inverted top-emitting OLEDs is described.

  19. Light outcoupling enhanced flexible organic light-emitting diodes.

    Science.gov (United States)

    Ou, Qing-Dong; Xu, Lu-Hai; Zhang, Wen-Yue; Li, Yan-Qing; Zhang, Yi-Bo; Zhao, Xin-Dong; Chen, Jing-De; Tang, Jian-Xin

    2016-03-21

    Flexible organic light-emitting diodes (OLEDs) are emerging as a leading technology for rollable and foldable display applications. For the development of high-performance flexible OLEDs on plastic substrate, we report a transparent nanocomposite electrode with superior mechanical, electrical, and optical properties, which is realized by integrating the nanoimprinted quasi-random photonic structures into the ultrathin metal/dielectric stack to collectively optimize the electrical conduction and light outcoupling capabilities. The resulting flexible OLEDs with green emission yield the enhanced device efficiency, reaching the maximum external quantum efficiency of 43.7% and luminous efficiency of 154.9 cd/A, respectively.

  20. Capturing triplet emission in white organic light emitting devices

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Jai [Faculty of EHSE, School of Engineering and IT, B-purple-12, Charles Darwin University, Darwin, NT 0909 (Australia)

    2011-08-15

    The state-of-the art in the white organic light emitting devices (WOLEDs) is reviewed for further developments with a view to enhance the capture of triplet emission. In particular, applying the new exciton-spin-orbit-photon interaction operator as a perturbation, rates of spontaneous emission are calculated in a few phosphorescent materials and compared with experimental results. For iridium based phosphorescent materials the rates agree quite well with the experimental results. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Organimetallic Fluorescent Complex Polymers For Light Emitting Applications

    Science.gov (United States)

    Shi, Song Q.; So, Franky

    1997-10-28

    A fluorescent complex polymer with fluorescent organometallic complexes connected by organic chain spacers is utilized in the fabrication of light emitting devices on a substantially transparent planar substrate by depositing a first conductive layer having p-type conductivity on the planar surface of the substrate, depositing a layer of a hole transporting and electron blocking material on the first conductive layer, depositing a layer of the fluorescent complex polymer on the layer of hole transporting and electron blocking material as an electron transporting emissive layer and depositing a second conductive layer having n-type conductivity on the layer of fluorescent complex polymer.

  2. Efficiency droop in nitride-based light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Piprek, Joachim [NUSOD Institute LLC, Newark, Delaware 19714-7204 (United States)

    2010-10-15

    Nitride-based light-emitting diodes (LEDs) suffer from a reduction (droop) of the internal quantum efficiency with increasing injection current. This droop phenomenon is currently the subject of intense research worldwide, as it delays general lighting applications of GaN-based LEDs. Several explanations of the efficiency droop have been proposed in recent years, but none is widely accepted. This feature article provides a snapshot of the present state of droop research, reviews currently discussed droop mechanisms, contextualizes them, and proposes a simple yet unified model for the LED efficiency droop. Illustration of LED efficiency droop. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  3. High efficiency III-nitride light-emitting diodes

    Science.gov (United States)

    Crawford, Mary; Koleske, Daniel; Cho, Jaehee; Zhu, Di; Noemaun, Ahmed; Schubert, Martin F; Schubert, E. Fred

    2013-05-28

    Tailored doping of barrier layers enables balancing of the radiative recombination among the multiple-quantum-wells in III-Nitride light-emitting diodes. This tailored doping enables more symmetric carrier transport and uniform carrier distribution which help to reduce electron leakage and thus reduce the efficiency droop in high-power III-Nitride LEDs. Mitigation of the efficiency droop in III-Nitride LEDs may enable the pervasive market penetration of solid-state-lighting technologies in high-power lighting and illumination.

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

    Science.gov (United States)

    O'Toole, Martina; Diamond, Dermot

    2008-04-07

    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.

  5. Using high-power light emitting diodes for photoacoustic imaging

    DEFF Research Database (Denmark)

    Hansen, René Skov

    The preliminary result of using a high-power light emitting diode, LED, for photoacoustic imaging is presented. The pulsed light source is created by a 1Watt red Luxeon LED. The LED delivers light pulses with 25W peak power when supplied by 40A peak, 60ns wide current pulses. The phantom used...... for the experiment consists of a 3mm high x 5mm wide slice of green colored gelatine overlaid by a 3cm layer of colorless gelatine. The light pulses from the LED is focused on the green gelatine. The photoacoustic response from the green gelatine is detected by a single transducer on the opposite (top) surface...

  6. Fabrication and characterization of a germanium nanowire light emitting diode

    Science.gov (United States)

    Greil, Johannes; Bertagnolli, Emmerich; Salem, Bassem; Baron, Thierry; Gentile, Pascal; Lugstein, Alois

    2017-12-01

    In this letter, we demonstrate the feasibility of a germanium nanowire light emitting diode as a reasonable approach for downscaling of CMOS compatible light sources. We show room-temperature direct bandgap electroluminescence from axial p-n junction nanowire devices. The electron population in the Γ valley, necessary for direct bandgap emission, is achieved by high injection current densities. Carrier temperature is consistently found to be higher than the lattice temperature, indicating inhibited carrier cooling in small diameter wires. Strong polarization of the emission parallel to the nanowire axis is observed and attributed to dielectric contrast phenomena.

  7. Camera vibration measurement using blinking light-emitting diode array.

    Science.gov (United States)

    Nishi, Kazuki; Matsuda, Yuichi

    2017-01-23

    We present a new method for measuring camera vibrations such as camera shake and shutter shock. This method successfully detects the vibration trajectory and transient waveforms from the camera image itself. We employ a time-varying pattern as the camera test chart over the conventional static pattern. This pattern is implemented using a specially developed blinking light-emitting-diode array. We describe the theoretical framework and pattern analysis of the camera image for measuring camera vibrations. Our verification experiments show that our method has a detection accuracy and sensitivity of 0.1 pixels, and is robust against image distortion. Measurement results of camera vibrations in commercial cameras are also demonstrated.

  8. Broadband mid-infrared superlattice light-emitting diodes

    Science.gov (United States)

    Ricker, R. J.; Provence, S. R.; Norton, D. T.; Boggess, T. F.; Prineas, J. P.

    2017-05-01

    InAs/GaSb type-II superlattice light-emitting diodes were fabricated to form a device that provides emission over the entire 3-5 μm mid-infrared transmission window. Variable bandgap emission regions were coupled together using tunnel junctions to emit at peak wavelengths of 3.3 μm, 3.5 μm, 3.7 μm, 3.9 μm, 4.1 μm, 4.4 μm, 4.7 μm, and 5.0 μm. Cascading the structure recycles the electrons in each emission region to emit several wavelengths simultaneously. At high current densities, the light-emitting diode spectra broadened into a continuous, broadband spectrum that covered the entire mid-infrared band. When cooled to 77 K, radiances of over 1 W/cm2 sr were achieved, demonstrating apparent temperatures above 1000 K over the 3-5 μm band. InAs/GaSb type-II superlattices are capable of emitting from 3 μm to 30 μm, and the device design can be expanded to include longer emission wavelengths.

  9. New Optoelectronic Technology Simplified for Organic Light Emitting Diode (OLED

    Directory of Open Access Journals (Sweden)

    Andre F. S. Guedes

    2014-06-01

    Full Text Available The development of Organic Light Emitting Diode (OLED, using an optically transparent substrate material and organic semiconductor materials, has been widely utilized by the electronic industry when producing new technological products. The OLED are the base Poly (3,4-ethylenedioxythiophene, PEDOT, and Polyaniline, PANI, were deposited in Indium Tin Oxide, ITO, and characterized by UV-Visible Spectroscopy (UV-Vis, Optical Parameters (OP and Scanning Electron Microscopy (SEM. In addition, the thin film obtained by the deposition of PANI, prepared in perchloric acid solution, was identified through PANI-X1. The result obtained by UV-Vis has demonstrated that the Quartz/ITO/PEDOT/PANI-X1 layer does not have displacement of absorption for wavelengths greaters after spin-coating and electrodeposition. Thus, the spectral irradiance of the OLED informed the irradiance of 100 W/m2, and this result, compared with the standard Light Emitting Diode (LED, has indicated that the OLED has higher irradiance. After 1000 hours of electrical OLED tests, the appearance of nanoparticles visible for images by SEM, to the migration process of organic semiconductor materials, was present, then. Still, similar to the phenomenon of electromigration observed in connections and interconnections of microelectronic devices, the results have revealed a new mechanism of migration, which raises the passage of electric current in OLED.

  10. Blue Light Emitting Polyphenylene Dendrimers with Bipolar Charge Transport Moieties

    Directory of Open Access Journals (Sweden)

    Guang Zhang

    2016-10-01

    Full Text Available Two light-emitting polyphenylene dendrimers with both hole and electron transporting moieties were synthesized and characterized. Both molecules exhibited pure blue emission solely from the pyrene core and efficient surface-to-core energy transfers when characterized in a nonpolar environment. In particular, the carbazole- and oxadiazole-functionalized dendrimer (D1 manifested a pure blue emission from the pyrene core without showing intramolecular charge transfer (ICT in environments with increasing polarity. On the other hand, the triphenylamine- and oxadiazole-functionalized one (D2 displayed notable ICT with dual emission from both the core and an ICT state in highly polar solvents. D1, in a three-layer organic light emitting diode (OLED by solution processing gave a pure blue emission with Commission Internationale de l’Éclairage 1931 CIE xy = (0.16, 0.12, a peak current efficiency of 0.21 cd/A and a peak luminance of 2700 cd/m2. This represents the first reported pure blue dendrimer emitter with bipolar charge transport and surface-to-core energy transfer in OLEDs.

  11. Organic light-emitting devices using spin-dependent processes

    Science.gov (United States)

    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.

  12. Doping of nanostructures for light emitting diode applications

    Energy Technology Data Exchange (ETDEWEB)

    Han, S. U.; Jeon, J. S.; Park, C. I.; Kim, B. H. [Chonbuk National University, Jeonju (Korea, Republic of)

    2009-04-15

    Lighting Emitting Diodes have been widely studied and developed for practical applications and the LED market in the world has been dramatically expended. GaN-based materials are mostly used for LED applications. However, for diverse application, we should first solved several problems in the GaN-based LEDs, thermal heating effects and low light emitting efficiency. In this project, we studied the possibility of ZnO nanomaterials as LEDs. We have developed a technique to fabricate ZnO nanorods on various substrates with a ZnO homo-buffer layer. We also systematically studied the doping of ZnO nanorods with the implantation method of protons and nitrogen ions. After the protons and N+ ions with various energy of 50-90 keV were implanted to pre-grown ZnO nanorods, the ZnO nanorods were analyzed with various techniques, XRD, EXAFS, SEM, TEM, PL, EDS, and others. Any strong impurity peak were observed in the PL spectra. This strongly suggests that the implanted ions capture the excitons.

  13. 53% Efficient Red Emissive Carbon Quantum Dots for High Color Rendering and Stable Warm White-Light-Emitting Diodes.

    Science.gov (United States)

    Wang, Zifei; Yuan, Fanglong; Li, Xiaohong; Li, Yunchao; Zhong, Haizheng; Fan, Louzhen; Yang, Shihe

    2017-10-01

    Red emissive carbon quantum dots (R-CQDs) with quantum yield of 53% is successfully prepared. An ultraviolet (UV)-pumped CQD phosphors-based warm white light-emitting diode (WLED) is realized for the first time and achieves a color rendering index of 97. This work provides a new avenue for the exploration of low cost, environment-friendly, and high-performance CQD phosphors-based warm WLEDs. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Vacuum-Deposited Organometallic Halide Perovskite Light-Emitting Devices.

    Science.gov (United States)

    Chiang, Kai-Ming; Hsu, Bo-Wei; Chang, Yi-An; Yang, Lin; Tsai, Wei-Lun; Lin, Hao-Wu

    2017-11-22

    In this work, a sequential vacuum deposition process of bright, highly crystalline, and smooth methylammonium lead bromide and phenethylammonium lead bromide perovskite thin films are investigated and the first vacuum-deposited organometallic halide perovskite light-emitting devices (PeLEDs) are demonstrated. Exceptionally low refractive indices and extinction coefficients in the emission wavelength range are obtained for these films, which contributed to a high light out-coupling efficiency of the PeLEDs. By utilizing these perovskite thin films as emission layers, the vacuum-deposited PeLEDs exhibit a very narrow saturated green electroluminescence at 531 nm, with a spectral full width at half-maximum bandwidth of 18.6 nm, a promising brightness of up to 6200 cd/m2, a current efficiency of 1.3 cd/A, and an external quantum efficiency of 0.36%.

  15. Resonance Raman measurements of carotenoids using light emitting diodes

    CERN Document Server

    Bergeson, S D; Eyring, N J; Fralick, J F; Stevenson, D N; Ferguson, S B

    2008-01-01

    We report on the development of a compact commercial instrument for measuring carotenoids in skin tissue. The instrument uses two light emitting diodes (LEDs) for dual-wavelength excitation and four photomultiplier tubes for multichannel detection. Bandpass filters are used to select the excitation and detection wavelengths. The f/1.3 optical system has high optical throughput and single photon sensitivity, both of which are crucial in LED-based Raman measurements. We employ a signal processing technique that compensates for detector drift and error. The sensitivity and reproducibility of the LED Raman instrument compares favorably to laser-based Raman spectrometers. This compact, portable instrument is used for non-invasive measurement of carotenoid molecules in human skin with a repeatability better than 10%.

  16. Chemically Addressable Perovskite Nanocrystals for Light-Emitting Applications

    KAUST Repository

    Sun, Haizhu

    2017-07-10

    Whereas organic–inorganic hybrid perovskite nanocrystals (PNCs) have remarkable potential in the development of optoelectronic materials, their relatively poor chemical and colloidal stability undermines their performance in optoelectronic devices. Herein, this issue is addressed by passivating PNCs with a class of chemically addressable ligands. The robust ligands effectively protect the PNC surfaces, enhance PNC solution processability, and can be chemically addressed by thermally induced crosslinking or radical-induced polymerization. This thin polymer shield further enhances the photoluminescence quantum yields by removing surface trap states. Crosslinked methylammonium lead bromide (MAPbBr3) PNCs are applied as active materials to build light-emitting diodes that have low turn-on voltages and achieve a record luminance of over 7000 cd m−2, around threefold better than previous reported MA-based PNC devices. These results indicate the great potential of this ligand passivation approach for long lifespan, highly efficient PNC light emitters.

  17. Electroluminescence property of organic light emitting diode (OLED)

    Energy Technology Data Exchange (ETDEWEB)

    Özdemir, Orhan; Kavak, Pelin; Saatci, A. Evrim; Gökdemir, F. Pınar; Menda, U. Deneb; Can, Nursel; Kutlu, Kubilay [Yıldız Technical University, Department of Physics, Esenler, Istanbul (Turkey); Tekin, Emine; Pravadalı, Selin [National Metrology Instıtute of Turkey (TUBİTAK-UME), Kocaeli (Turkey)

    2013-12-16

    Transport properties of electrons and holes were investigated not only in a anthracene-containing poly(p-phenylene-ethynylene)- alt - poly(p-phenylene-vinylene) (PPE-PPV) polymer (AnE-PVstat) light emitting diodes (OLED) but also in an ITO/Ag/polymer/Ag electron and ITO/PEDOT:PSS/polymer/Au hole only devices. Mobility of injected carriers followed the Poole-Frenkel type conduction mechanism and distinguished in the frequency range due to the difference of transit times in admittance measurement. Beginning of light output took place at the turn-on voltage (or flat band voltage), 1.8 V, which was the difference of energy band gap of polymer and two barrier offsets between metals and polymer.

  18. LIGHT-EMITTING DIODE TECHNOLOGY IMPROVES INSECT TRAPPING

    Science.gov (United States)

    GILLEN, JONATHON I.; MUNSTERMANN, LEONARD E.

    2008-01-01

    In a climate of increased funding for vaccines, chemotherapy, and prevention of vector-borne diseases, fewer resources have been directed toward improving disease and vector surveillance. Recently developed light-emitting diode (LED) technology was applied to standard insect-vector traps to produce a more effective lighting system. This approach improved phlebotomine sand fly capture rates by 50%, and simultaneously reduced the energy consumption by 50–60%. The LEDs were incorporated into 2 lighting designs, 1) a LED combination bulb for current light traps and 2) a chip-based LED design for a modified Centers for Disease Control and Prevention light trap. Detailed descriptions of the 2 designs are presented. PMID:18666546

  19. Smartphone-Driven Low-Power Light-Emitting Device

    Directory of Open Access Journals (Sweden)

    Hea-Ja An

    2017-01-01

    Full Text Available Low-level light (laser therapy (LLLT has been widely researched in the recent past. Existing LLLT studies were performed based on laser. Recently, studies using LED have increased. This study presents a smartphone-driven low-power light-emitting device for use in colour therapy as an alternative medicine. The device consists of a control unit and a colour probe. The device is powered by and communicates with a smartphone using USB On-The-Go (OTG technology. The control unit controls emitting time and intensity of illumination with the configuration value of a smartphone application. Intensity is controlled by pulse width modulation (PWM without feedback. A calibration is performed to resolve a drawback of no feedback. To calibrate, intensity is measured in every 10 percent PWM output. PWM value is linearly calibrated to obtain accurate intensity. The device can control the intensity of illumination, and so, it can find application in varied scenarios.

  20. Electroformed silicon nitride based light emitting memory device

    Science.gov (United States)

    Anutgan, Tamila; Anutgan, Mustafa; Atilgan, Ismail; Katircioglu, Bayram

    2017-07-01

    The resistive memory switching effect of an electroformed nanocrystal silicon nitride thin film light emitting diode (LED) is demonstrated. For this purpose, current-voltage (I-V) characteristics of the diode were systematically scanned, paying particular attention to the sequence of the measurements. It was found that when the voltage polarity was changed from reverse to forward, the previously measured reverse I-V behavior was remembered until some critical forward bias voltage. Beyond this critical voltage, the I-V curve returns to its original state instantaneously, and light emission switches from the OFF state to the ON state. The kinetics of this switching mechanism was studied for different forward bias stresses by measuring the corresponding time at which the switching occurs. Finally, the switching of resistance and light emission states was discussed via energy band structure of the electroformed LED.

  1. Color tunable organic light emitting diodes using Eu complex doping

    Science.gov (United States)

    Li, W. X.; Hagen, J.; Jones, R.; Heikenfeld, J.; Steckl, A. J.

    2007-03-01

    A voltage-controlled color tunable organic light emitting device has been demonstrated by using a co-evaporated emissive layer of NPB [( N, N'-bis(naphthalene-1-yl)- N, N'-bis(phenyl)benzidine)] and an organic Eu complex. As a result of minimized energy transfer from the host (NPB) to the guest emitter (Eu complex), this device can vary the light emission from vivid red to deep blue with increasing bias. Optimal device performance is obtained for a 20 wt.% Eu doping in NPB. This doping concentration is able to yield x and y chromaticity coordinates in the range of 0.61-0.17 and 0.31-0.12, respectively.

  2. High mobility solution-processed hybrid light emitting transistors

    Science.gov (United States)

    Walker, Bright; Ullah, Mujeeb; Chae, Gil Jo; Burn, Paul L.; Cho, Shinuk; Kim, Jin Young; Namdas, Ebinazar B.; Seo, Jung Hwa

    2014-11-01

    We report the design, fabrication, and characterization of high-performance, solution-processed hybrid (inorganic-organic) light emitting transistors (HLETs). The devices employ a high-mobility, solution-processed cadmium sulfide layer as the switching and transport layer, with a conjugated polymer Super Yellow as an emissive material in non-planar source/drain transistor geometry. We demonstrate HLETs with electron mobilities of up to 19.5 cm2/V s, current on/off ratios of >107, and external quantum efficiency of 10-2% at 2100 cd/m2. These combined optical and electrical performance exceed those reported to date for HLETs. Furthermore, we provide full analysis of charge injection, charge transport, and recombination mechanism of the HLETs. The high brightness coupled with a high on/off ratio and low-cost solution processing makes this type of hybrid device attractive from a manufacturing perspective.

  3. Application of Surface Plasmonics for Semiconductor Light-Emitting Diodes

    DEFF Research Database (Denmark)

    Fadil, Ahmed

    This thesis addresses the lack of an efficient semiconductor light source at green emission colours. Considering InGaN based quantum-well (QW) light-emitters and light-emitting diodes (LEDs), various ways of applying surface plasmonics and nano-patterning to improve the efficiency, are investigated....... By placing metallic thin films or nanoparticles (NPs) in the near-field of QW light-emitters, it is possible to improve their internal quantum efficiency (IQE) through the Purcell enhancement effect. It has been a general understanding that in order to achieve surface plasmon (SP) coupling with QWs...... is presented to obtain light extraction efficiency (LEE) improvement through nano-patterning, and IQE improvement through SP-QW coupling. Considering the fabrication process aspect, dry-etching damage on the semiconductor light-emitters from the nano-patterning is also addressed. Different ion-damage treatment...

  4. Oxycarbonitride phosphors and light emitting devices using the same

    Science.gov (United States)

    Li, Yuanqiang; Romanelli, Michael Dennis; Tian, Yongchi

    2013-10-08

    Disclosed herein is a novel family of oxycarbidonitride phosphor compositions and light emitting devices incorporating the same. Within the sextant system of M--Al--Si--O--N--C--Ln and quintuplet system of M--Si--O--N--C--Ln (M=alkaline earth element, Ln=rare earth element), the phosphors are composed of either one single crystalline phase or two crystalline phases with high chemical and thermal stability. In certain embodiments, the disclosed phosphor of silicon oxycarbidonitrides emits green light at wavelength between 530-550 nm. In further embodiments, the disclosed phosphor compositions emit blue-green to yellow light in a wavelength range of 450-650 nm under near-UV and blue light excitation.

  5. Thermal resistance of light emitting diode PCB with thermal vias.

    Science.gov (United States)

    Lee, Hyo Soo; Shin, Hyung Won; Jung, Seung Boo

    2012-04-01

    Light emitting diodes (LEDs) are already familiar for use as lighting sources in various electronic devices and displays. LEDs have many advantages such as long life, low power consumption, and high reliability. In the future, as an alternative to fluorescent lighting, LEDs are certain to receive much attention. However, in components related to advanced LED packages or modules there has been an issue regarding the heat from the LED chip. The LED chip is still being developed for use in high-power devices which generate more heat. In this study, we investigate the variation of thermal resistance in LED modules embedded with thermal vias. Through the analysis of thermal resistance with various test vehicles, we obtained the concrete relationship between thermal resistance and the thermal via structure.

  6. Indoor localization system utilizing two visible light emitting diodes

    Science.gov (United States)

    Mousa, Farag I. K.; Le-Minh, Hoa; Ghassemlooy, Zabih; Dai, Xuewu; Tran, Son T.; Boucouvalas, Anthony C.; Liaw, Shien-Kuei

    2016-11-01

    Indoor positioning or localization based on visible light communications (VLC) is an emerging technology with wide applications. In conventional localization schemes, the trilateration technique is widely used with at least three separate lighting sources to determine the user's location. An indoor VLC positioning scheme based on the optical power distributions of only two light emitting diodes (LEDs) is reported for different environments. We have used two received signal strength indications to determine the user's position based on the LEDs configuration offering less complexity. We propose comprehensive mathematical models for the VLC localization system considering the noise and its impact on the user's location, and numerically evaluated it over a range of signal-to-noise ratios (SNRs). In addition, it is compared to the results with the exiting trilateration technique. The performance of the proposed system is evaluated with a reported accuracy of 13 dB.

  7. Quantum key distribution with an entangled light emitting diode

    Energy Technology Data Exchange (ETDEWEB)

    Dzurnak, B.; Stevenson, R. M.; Nilsson, J.; Dynes, J. F.; Yuan, Z. L.; Skiba-Szymanska, J.; Shields, A. J. [Toshiba Research Europe Limited, 208 Science Park, Milton Road, Cambridge CB4 0GZ (United Kingdom); Farrer, I.; Ritchie, D. A. [Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE (United Kingdom)

    2015-12-28

    Measurements performed on entangled photon pairs shared between two parties can allow unique quantum cryptographic keys to be formed, creating secure links between users. An advantage of using such entangled photon links is that they can be adapted to propagate entanglement to end users of quantum networks with only untrusted nodes. However, demonstrations of quantum key distribution with entangled photons have so far relied on sources optically excited with lasers. Here, we realize a quantum cryptography system based on an electrically driven entangled-light-emitting diode. Measurement bases are passively chosen and we show formation of an error-free quantum key. Our measurements also simultaneously reveal Bell's parameter for the detected light, which exceeds the threshold for quantum entanglement.

  8. III-nitride based light emitting diodes and applications

    CERN Document Server

    Han, Jung; Amano, Hiroshi; Morkoç, Hadis

    2013-01-01

    Light emitting diodes (LEDs) are already used in traffic signals, signage lighting, and automotive applications. However, its ultimate goal is to replace traditional illumination through LED lamps since LED lighting significantly reduces energy consumption and cuts down on carbon-dioxide emission. Despite dramatic advances in LED technologies (e.g., growth, doping and processing technologies), however, there remain critical issues for further improvements yet to be achieved for the realization of solid-state lighting. This book aims to provide the readers with some contemporary LED issues, which have not been comprehensively discussed in the published books and, on which the performance of LEDs is seriously dependent. For example, most importantly, there must be a breakthrough in the growth of high-quality nitride semiconductor epitaxial layers with a low density of dislocations, in particular, in the growth of Al-rich and and In-rich GaN-based semiconductors. The materials quality is directly dependent on th...

  9. Light-emitting diodes enhanced by localized surface plasmon resonance.

    Science.gov (United States)

    Gu, Xuefeng; Qiu, Teng; Zhang, Wenjun; Chu, Paul K

    2011-03-08

    Light-emitting diodes [LEDs] are of particular interest recently as their performance is approaching fluorescent/incandescent tubes. Moreover, their energy-saving property is attracting many researchers because of the huge energy crisis we are facing. Among all methods intending to enhance the efficiency and intensity of a conventional LED, localized surface plasmon resonance is a promising way. The mechanism is based on the energy coupling effect between the emitted photons from the semiconductor and metallic nanoparticles fabricated by nanotechnology. In this review, we describe the mechanism of this coupling effect and summarize the common fabrication techniques. The prospect, including the potential to replace fluorescent/incandescent lighting devices as well as applications to flat panel displays and optoelectronics, and future challenges with regard to the design of metallic nanostructures and fabrication techniques are discussed.

  10. Light-emitting diodes enhanced by localized surface plasmon resonance

    Directory of Open Access Journals (Sweden)

    Zhang Wenjun

    2011-01-01

    Full Text Available Abstract Light-emitting diodes [LEDs] are of particular interest recently as their performance is approaching fluorescent/incandescent tubes. Moreover, their energy-saving property is attracting many researchers because of the huge energy crisis we are facing. Among all methods intending to enhance the efficiency and intensity of a conventional LED, localized surface plasmon resonance is a promising way. The mechanism is based on the energy coupling effect between the emitted photons from the semiconductor and metallic nanoparticles fabricated by nanotechnology. In this review, we describe the mechanism of this coupling effect and summarize the common fabrication techniques. The prospect, including the potential to replace fluorescent/incandescent lighting devices as well as applications to flat panel displays and optoelectronics, and future challenges with regard to the design of metallic nanostructures and fabrication techniques are discussed.

  11. Cooling analysis of a light emitting diode automotive fog lamp

    Directory of Open Access Journals (Sweden)

    Zadravec Matej

    2017-01-01

    Full Text Available Efficiency of cooling fins inside of a light emitting diode fog lamp is studied using computational fluid dynamics. Diffusion in heat sink, natural convection and radiation are the main principles of the simulated heat transfer. The Navier-Stokes equations were solved by the computational fluid dynamics code, including Monte Carlo radiation model and no additional turbulence model was needed. The numerical simulation is tested using the existing lamp geometry and temperature measurements. The agreement is excellent inside of few degrees at all measured points. The main objective of the article is to determine the cooling effect of various heat sink parts. Based on performed simulations, some heat sink parts are found to be very ineffective. The geometry and heat sink modifications are proposed. While radiation influence is significant, compressible effects are found to be minor.

  12. Wireless Low Power Light Emitting Device with RGB LED

    Directory of Open Access Journals (Sweden)

    Mi-So Lee

    2017-06-01

    Full Text Available Color therapy is a type of alternative medicine. It utilizes the emission of a specific wavelength of light to treat diseased areas. This study presents a wireless, low-power light-emitting device with RGB LED to conduct color therapy. The device is small-sized, adhesive to the skin, and without a tether line for power or communication. Aided by the property of skin adhesiveness, the device provides a therapeutic effect comparable to that of available devices, over a short radiation distance and consumes low power. The therapeutic dosage parameters including color wavelength combination, LED brightness, and illumination time can be regulated through the smartphone application. The wavelength consistency over intensities and the intensity accuracy were validated. With effective calibration, the emission of light by the LED can be effectively regulated to ensure therapeutic effects.

  13. Hybrid perovskites: Approaches towards light-emitting devices

    KAUST Repository

    Alias, Mohd Sharizal

    2016-10-06

    The high optical gain and absorption of organic-inorganic hybrid perovskites have attracted extensive research for photonic device applications. Using the bromide halide as an example, we present key approaches of our work towards realizing efficient perovskites based light-emitters. The approaches involved determination of optical constants for the hybrid perovskites thin films, fabrication of photonic nanostructures in the form of subwavelength grating reflector patterned directly on the hybrid perovskites as light manipulation layer, and enhancing the emission property of the hybrid perovskites by using microcavity structure. Our results provide a platform for realization of hybrid perovskites based light-emitting devices for solid-state lighting and display applications. © 2016 IEEE.

  14. Light-emitting diodes enhanced by localized surface plasmon resonance

    Science.gov (United States)

    Gu, Xuefeng; Qiu, Teng; Zhang, Wenjun; Chu, Paul K.

    2011-12-01

    Light-emitting diodes [LEDs] are of particular interest recently as their performance is approaching fluorescent/incandescent tubes. Moreover, their energy-saving property is attracting many researchers because of the huge energy crisis we are facing. Among all methods intending to enhance the efficiency and intensity of a conventional LED, localized surface plasmon resonance is a promising way. The mechanism is based on the energy coupling effect between the emitted photons from the semiconductor and metallic nanoparticles fabricated by nanotechnology. In this review, we describe the mechanism of this coupling effect and summarize the common fabrication techniques. The prospect, including the potential to replace fluorescent/incandescent lighting devices as well as applications to flat panel displays and optoelectronics, and future challenges with regard to the design of metallic nanostructures and fabrication techniques are discussed.

  15. Combinational light emitting diode-high frequency focused ultrasound treatment for HeLa cell.

    Science.gov (United States)

    Choe, Se-Woon; Park, Kitae; Park, Chulwoo; Ryu, Jaemyung; Choi, Hojong

    2017-12-01

    Light sources such as laser and light emitting diode or ultrasound devices have been widely used for cancer therapy and regenerative medicines, since they are more cost-effective and less harmful than radiation therapy, chemotherapy or magnetic treatment. Compared to laser and low intensity ultrasound techniques, light emitting diode and high frequency focused ultrasound shows enhanced therapeutic effects, especially for small tumors. We propose combinational light emitting diode-high frequency focused ultrasound treatment for human cervical cancer HeLa cells. Individual red, green, and blue light emitting diode light only, high frequency focused ultrasound only, or light emitting diode light combined with high frequency focused ultrasound treatments were applied in order to characterize the responses of HeLa cells. Cell density exposed by blue light emitting diode light combined with high frequency focused ultrasound (2.19 ± 0.58%) was much lower than that of cells exposed by red and green light emitting diode lights (81.71 ± 9.92% and 61.81 ± 4.09%), blue light emitting diode light (11.19 ± 2.51%) or high frequency focused ultrasound only (9.72 ± 1.04%). We believe that the proposed combinational blue light emitting diode-high frequency focused ultrasound treatment could have therapeutic benefits to alleviate cancer cell proliferation.

  16. Multicolor light-emitting devices with Tb2O3 on silicon.

    Science.gov (United States)

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

    2017-02-21

    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.

  17. Environmental barrier material for organic light emitting device and method of making

    Science.gov (United States)

    Graff, Gordon L [West Richland, WA; Gross, Mark E [Pasco, WA; Affinito, John D [Kennewick, WA; Shi, Ming-Kun [Richland, WA; Hall, Michael [West Richland, WA; Mast, Eric [Richland, WA

    2003-02-18

    An encapsulated organic light emitting device. The device includes a first barrier stack comprising at least one first barrier layer and at least one first polymer layer. There is an organic light emitting layer stack adjacent to the first barrier stack. A second barrier stack is adjacent to the organic light emitting layer stack. The second barrier stack has at least one second barrier layer and at least one second polymer layer. A method of making the encapsulated organic light emitting device is also provided.

  18. Disinfection of Spacecraft Potable Water Systems by Photocatalytic Oxidation Using UV-A Light Emitting Diodes

    Science.gov (United States)

    Birmele, Michele N.; O'Neal, Jeremy A.; Roberts, Michael S.

    2011-01-01

    Ultraviolet (UV) light has long been used in terrestrial water treatment systems for photodisinfection and the removal of organic compounds by several processes including photoadsorption, photolysis, and photocatalytic oxidation/reduction. Despite its effectiveness for water treatment, UV has not been explored for spacecraft applications because of concerns about the safety and reliability of mercury-containing UV lamps. However, recent advances in ultraviolet light emitting diodes (UV LEDs) have enabled the utilization of nanomaterials that possess the appropriate optical properties for the manufacture of LEDs capable of producing monochromatic light at germicidal wavelengths. This report describes the testing of a commercial-off-the-shelf, high power Nichia UV-A LED (250mW A365nnJ for the excitation of titanium dioxide as a point-of-use (POD) disinfection device in a potable water system. The combination of an immobilized, high surface area photocatalyst with a UV-A LED is promising for potable water system disinfection since toxic chemicals and resupply requirements are reduced. No additional consumables like chemical biocides, absorption columns, or filters are required to disinfect and/or remove potentially toxic disinfectants from the potable water prior to use. Experiments were conducted in a static test stand consisting of a polypropylene microtiter plate containing 3mm glass balls coated with titanium dioxide. Wells filled with water were exposed to ultraviolet light from an actively-cooled UV-A LED positioned above each well and inoculated with six individual challenge microorganisms recovered from the International Space Station (ISS): Burkholderia cepacia, Cupriavidus metallidurans, Methylobacterium fujisawaense, Pseudomonas aeruginosa, Sphingomonas paucimobilis and Wautersia basilensis. Exposure to the Nichia UV-A LED with photocatalytic oxidation resulted in a complete (>7-log) reduction of each challenge bacteria population in <180 minutes of contact

  19. Active Matrix Organic Light Emitting Diode (AMOLED) Environmental Test Report

    Science.gov (United States)

    Salazar, George A.

    2013-01-01

    This report focuses on the limited environmental testing of the AMOLED display performed as an engineering evaluation by The NASA Johnson Space Center (JSC)-specifically. EMI. Thermal Vac, and radiation tests. The AMOLED display is an active-matrix Organic Light Emitting Diode (OLED) technology. The testing provided an initial understanding of the technology and its suitability for space applications. Relative to light emitting diode (LED) displays or liquid crystal displays (LCDs), AMOLED displays provide a superior viewing experience even though they are much lighter and smaller, produce higher contrast ratio and richer colors, and require less power to operate than LCDs. However, AMOLED technology has not been demonstrated in a space environment. Therefore, some risks with the technology must be addressed before they can be seriously considered for human spaceflight. The environmental tests provided preliminary performance data on the ability of the display technology to handle some of the simulated induced space/spacecraft environments that an AMOLED display will see during a spacecraft certification test program. This engineering evaluation is part of a Space Act Agreement (SM) between The NASA/JSC and Honeywell International (HI) as a collaborative effort to evaluate the potential use of AMOLED technology for future human spaceflight missions- both government-led and commercial. Under this SM, HI is responsible for doing optical performance evaluation, as well as temperature and touch screen studies. The NASA/JSC is responsible for performing environmental testing comprised of EMI, Thermal Vac, and radiation tests. Additionally, as part of the testing, limited optical data was acquired to assess performance as the display was subjected to the induced environments. The NASA will benefit from this engineering evaluation by understanding AMOLED suitability for future use in space as well as becoming a smarter buyer (or developer) of the technology. HI benefits

  20. Diffusion-Driven Charge Transport in Light Emitting Devices

    Directory of Open Access Journals (Sweden)

    Iurii Kim

    2017-12-01

    Full Text Available Almost all modern inorganic light-emitting diode (LED designs are based on double heterojunctions (DHJs whose structure and current injection principle have remained essentially unchanged for decades. Although highly efficient devices based on the DHJ design have been developed and commercialized for energy-efficient general lighting, the conventional DHJ design requires burying the active region (AR inside a pn-junction. This has hindered the development of emitters utilizing nanostructured ARs located close to device surfaces such as nanowires or surface quantum wells. Modern DHJ III-N LEDs also exhibit resistive losses that arise from the DHJ device geometry. The recently introduced diffusion-driven charge transport (DDCT emitter design offers a novel way to transport charge carriers to unconventionally placed ARs. In a DDCT device, the AR is located apart from the pn-junction and the charge carriers are injected into the AR by bipolar diffusion. This device design allows the integration of surface ARs to semiconductor LEDs and offers a promising method to reduce resistive losses in high power devices. In this work, we present a review of the recent progress in gallium nitride (GaN based DDCT devices, and an outlook of potential DDCT has for opto- and microelectronics.

  1. Applications of Transparent Conducting Oxides in Organic Light Emitting Devices.

    Science.gov (United States)

    Yan, Meng; Zhang, Qiaoxia; Zhao, Yanghua; Yang, Jianping; Yang, Tao; Zhang, Jian; Li, Xing'ao

    2015-09-01

    Organic light emitting devices (OLEDs) have received great attention in the field of flat panel display. The transparent metal oxide semiconductor materials play crucial roles in the applications of OLEDs and have strong influence on the performance of OLEDs. In this review, we mainly pay attention to the application of transparent conducting oxides (TCOs) as anodes and buffer layers in OLEDs. Currently indium tin oxide (ITO) is the most widely used anode material in OLEDs owing to the advantage on electrical and optical properties, such as high work function, low resistivity and high transparency. TCO materials, such as ZnO et al., as the anode candidates also have been discussed and analyzed. The energy level can be controlled by semiconductor doping which improve the carrier density and Hall mobility. Interfacial engineering between the anodes and the overlying organic layers is an important process to obtain the high performance of the devices. Physical, chemical and the combined treatment methods to modify the TCO/organic interfaces are reviewed. The property of anode/organic interfaces can be modified and enhanced by introducing the buffer layers between anodes and hole transport layers.

  2. Enhanced Phycocyanin Production from Spirulina platensis using Light Emitting Diode

    Science.gov (United States)

    Bachchhav, Manisha Bhanudas; Kulkarni, Mohan Vinayak; Ingale, Arun G.

    2017-06-01

    This work investigates the performance of different cultivation conditions using Light Emitting Diode (LED) as a light source for the production of phycocyanin from Spirulina platensis. With LEDs under autotrophic conditions, red LED produced maximum amount of biomass (8.95 g/l). As compared to autotrophic cultivation with fluorescent lamp (control), cultivations using LEDs under autotrophic and mixotrophic mode significantly enhanced the phycocyanin content. For autotrophic conditions (with LED) phycocyanin content was in the range of 103-242 mg/g of dry biomass, whereas for mixotrophic conditions (0.1% glucose and LED) it was in the range of 254-380 mg/g of dry biomass. Spirulina cultivated with yellow LED under mixotrophic conditions had 5.4-fold more phycocyanin (380 mg/g of dry biomass) than control (70 mg/g of dry biomass). The present study demonstrates that the LEDs under mixotrophic conditions gave sixfold (2497 mg/l) higher yields of phycocyanin as compared to autotrophic condition under white light (415 mg/l).

  3. Light-emitting diodes as a radiation source for plants

    Science.gov (United States)

    Bula, R. J.; Morrow, R. C.; Tibbitts, T. W.; Barta, D. J.; Ignatius, R. W.; Martin, T. S.

    1991-01-01

    Development of a more effective radiation source for use in plant-growing facilities would be of significant benefit for both research and commercial crop production applications. An array of light-emitting diodes (LEDs) that produce red radiation, supplemented with a photosynthetic photon flux (PPF) of 30 micromoles s-1 m-2 in the 400- to 500-nm spectral range from blue fluorescent lamps, was used effectively as a radiation source for growing plants. Growth of lettuce (Lactuca sativa L. Grand Rapids') plants maintained under the LED irradiation system at a total PPF of 325 micromoles s-1 m-2 for 21 days was equivalent to that reported in the literature for plants grown for the same time under cool-white fluorescent and incandescent radiation sources. Characteristics of the plants, such as leaf shape, color, and texture, were not different from those found with plants grown under cool-white fluorescent lamps. Estimations of the electrical energy conversion efficiency of a LED system for plant irradiation suggest that it may be as much as twice that published for fluorescent systems.

  4. Green Fluorescent Organic Light Emitting Device with High Luminance

    Directory of Open Access Journals (Sweden)

    Ning YANG

    2014-06-01

    Full Text Available In this work, we fabricated the small molecule green fluorescent bottom-emission organic light emitting device (OLED with the configuration of glass substrate/indium tin oxide (ITO/Copper Phthalocyanine (CuPc 25 nm/ N,N’-di(naphthalen-1-yl-N,N’-diphenyl-benzidine (NPB 45 nm/ tris(8-hydroxyquinoline aluminium (Alq3 60 nm/ Lithium fluoride (LiF 1 nm/Aluminum (Al 100 nm where CuPc and NPB are the hole injection layer and the hole transport layer, respectively. CuPc is introduced in this device to improve carrier injection and efficiency. The experimental results indicated that the turn-on voltage is 2.8 V with a maximum luminance of 23510 cd/m2 at 12 V. The maximum current efficiency and power efficiency are 4.8 cd/A at 100 cd/m2 and 4.2 lm/W at 3 V, respectively. The peak of electroluminance (EL spectrum locates at 530 nm which is typical emission peak of green light. In contrast, the maximum current efficiency and power efficiency of the device without CuPc are only 4.0 cd/A at 100 mA/cm2 and 4.2 lm/W at 3.6 V, respectively.

  5. Flexible fluorescent white organic light emitting diodes with ALD encapsulation

    Science.gov (United States)

    Tsai, Yu-Sheng; Chittawanij, Apisit; Juang, Fuh-Shyang; Lin, Pen-Chu; Hong, Lin-Ann; Tsai, Feng-Yu; Tseng, Ming-Hong; Wang, Ching-Chiun; Chen, Chien-Chih; Lin, Kung-Liang; Chen, Szu-Hao

    2015-08-01

    In this paper, the flexible white organic light-emitting diodes (WOLED) was fabricated on polyethylene naphthalate (PEN) with structure of ITO/EHI608 (75 nm)/HTG-1 (10 nm)/3% EB502:0.8% EY53 (5 nm)/3% EB502 (35 nm)/Alq3 (10 nm)/LiF (0.8 nm)/Al (150 nm) and was compared with glass substrate the same structure. It was seen that the performances of flexible and glass substrate are almost the same. The luminance, current efficiency, and CIE coordinates of flexible device is 6351 cd/m2, 12.7 cd/A, and (0.31, 0.38) at 50 mA/cm2, respectively. Then, an Al2O3/HfO2 film on polyethylene terephthalate (PET) was deposited using atomic layer deposition (ALD) as a thin film encapsulation layer have been described and compared, such as the characteristics of water permeability and lifetime of flexible WOLED. The results show that the PET/ALD film low value of about 0.04 g/m2d, and the PET film shows WVTR of about 3.8 g/m2/d. The lifetimes of PET/ALD and PET encapsulations are 840 min and 140 min, respectively. Simultaneous deposition of ALD film on PET film gave the lifetime of flexible WOLED is six times longer than device without ALD encapsulation.

  6. Printable candlelight-style organic light-emitting diode

    Science.gov (United States)

    Jou, J. H.; Singh, M.; Song, W. C.; Liu, S. H.

    2017-06-01

    Candles or oil lamps are currently the most friendly lighting source to human eyes, physiology, ecosystems, artifacts, environment, and night skies due to their blue light-less emission. Candle light also exhibits high light-quality that provides visual comfort. However, they are relatively low in power efficacy (0.3 lm/W), making them energy-wasting, besides having problems like scorching hot, burning, catching fire, flickering, carbon blacking, oxygen consuming, and release of green house gas etc. In contrast, candlelight organic light-emitting diode (OLED) can be made blue-hazard free and energy-efficient. The remaining challenges are to maximize its light-quality and enable printing feasibility, the latter of which would pave a way to cost-effective manufacturing. We hence demonstrate herein the design and fabrication of a candlelight OLED via wet-process. From retina protection perspective, its emission is 13, 12 and 8 times better than those of the blue-enriched white CFL, LED and OLED. If used at night, it is 9, 6 and 4 times better from melatonin generation perspective.

  7. Quantum dot light emitting devices for photomedical applications.

    Science.gov (United States)

    Chen, Hao; He, Juan; Lanzafame, Raymond; Stadler, Istvan; Hamidi, Hamid El; Liu, Hui; Celli, Jonathan; Hamblin, Michael R; Huang, Yingying; Oakley, Emily; Shafirstein, Gal; Chung, Ho-Kyoon; Wu, Shin-Tson; Dong, Yajie

    2017-03-01

    While OLEDs have struggled to find a niche lighting application that can fully take advantage of their unique form factors as thin, flexible, lightweight and uniformly large-area luminaire, photomedical researchers have been in search of low-cost, effective illumination devices with such form factors that could facilitate widespread clinical applications of photodynamic therapy (PDT) or photobiomodulation (PBM). Although existing OLEDs with either fluorescent or phosphorescent emitters cannot achieve the required high power density at the right wavelength windows for photomedicine, the recently developed ultrabright and efficient deep red quantum dot light emitting devices (QLEDs) can nicely fit into this niche. Here, we report for the first time the in-vitro study to demonstrate that this QLED-based photomedical approach could increase cell metabolism over control systems for PBM and kill cancerous cells efficiently for PDT. The perspective of developing wavelength-specific, flexible QLEDs for two critical photomedical fields (wound repair and cancer treatment) will be presented with their potential impacts summarized. The work promises to generate flexible QLED-based light sources that could enable the widespread use and clinical acceptance of photomedical strategies including PDT and PBM.

  8. White organic light-emitting diodes with fluorescent tube efficiency.

    Science.gov (United States)

    Reineke, Sebastian; Lindner, Frank; Schwartz, Gregor; Seidler, Nico; Walzer, Karsten; Lüssem, Björn; Leo, Karl

    2009-05-14

    The development of white organic light-emitting diodes (OLEDs) holds great promise for the production of highly efficient large-area light sources. High internal quantum efficiencies for the conversion of electrical energy to light have been realized. Nevertheless, the overall device power efficiencies are still considerably below the 60-70 lumens per watt of fluorescent tubes, which is the current benchmark for novel light sources. Although some reports about highly power-efficient white OLEDs exist, details about structure and the measurement conditions of these structures have not been fully disclosed: the highest power efficiency reported in the scientific literature is 44 lm W(-1) (ref. 7). Here we report an improved OLED structure which reaches fluorescent tube efficiency. By combining a carefully chosen emitter layer with high-refractive-index substrates, and using a periodic outcoupling structure, we achieve a device power efficiency of 90 lm W(-1) at 1,000 candelas per square metre. This efficiency has the potential to be raised to 124 lm W(-1) if the light outcoupling can be further improved. Besides approaching internal quantum efficiency values of one, we have also focused on reducing energetic and ohmic losses that occur during electron-photon conversion. We anticipate that our results will be a starting point for further research, leading to white OLEDs having efficiencies beyond 100 lm W(-1). This could make white-light OLEDs, with their soft area light and high colour-rendering qualities, the light sources of choice for the future.

  9. Engineering of Semiconductor Nanocrystals for Light Emitting Applications

    Directory of Open Access Journals (Sweden)

    Francesco Todescato

    2016-08-01

    Full Text Available Semiconductor nanocrystals are rapidly spreading into the display and lighting markets. Compared with liquid crystal and organic LED displays, nanocrystalline quantum dots (QDs provide highly saturated colors, wide color gamut, resolution, rapid response time, optical efficiency, durability and low cost. This remarkable progress has been made possible by the rapid advances in the synthesis of colloidal QDs and by the progress in understanding the intriguing new physics exhibited by these nanoparticles. In this review, we provide support to the idea that suitably engineered core/graded-shell QDs exhibit exceptionally favorable optical properties, photoluminescence and optical gain, while keeping the synthesis facile and producing QDs well suited for light emitting applications. Solid-state laser emitters can greatly profit from QDs as efficient gain materials. Progress towards fabricating low threshold, solution processed DFB lasers that are optically pumped using one- and two-photon absorption is reviewed. In the field of display technologies, the exploitation of the exceptional photoluminescence properties of QDs for LCD backlighting has already advanced to commercial levels. The next big challenge is to develop the electroluminescence properties of QD to a similar state. We present an overview of QLED devices and of the great perspectives for next generation display and lighting technologies.

  10. Emerging Transparent Conducting Electrodes for Organic Light Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Tze-Bin Song

    2014-03-01

    Full Text Available Organic light emitting diodes (OLEDs have attracted much attention in recent years as next generation lighting and displays, due to their many advantages, including superb performance, mechanical flexibility, ease of fabrication, chemical versatility, etc. In order to fully realize the highly flexible features, reduce the cost and further improve the performance of OLED devices, replacing the conventional indium tin oxide with better alternative transparent conducting electrodes (TCEs is a crucial step. In this review, we focus on the emerging alternative TCE materials for OLED applications, including carbon nanotubes (CNTs, metallic nanowires, conductive polymers and graphene. These materials are selected, because they have been applied as transparent electrodes for OLED devices and achieved reasonably good performance or even higher device performance than that of indium tin oxide (ITO glass. Various electrode modification techniques and their effects on the device performance are presented. The effects of new TCEs on light extraction, device performance and reliability are discussed. Highly flexible, stretchable and efficient OLED devices are achieved based on these alternative TCEs. These results are summarized for each material. The advantages and current challenges of these TCE materials are also identified.

  11. The development of monolithic alternating current light-emitting diode

    Science.gov (United States)

    Yeh, Wen-Yung; Yen, Hsi-Hsuan; Chan, Yi-Jen

    2011-02-01

    The monolithic alternating current light emitting diode (ACLED) has been revealed for several years and was regarded as a potential device for solid state lighting. In this study, we will discuss the characteristics, development status, future challenges, and ITRI's development strategy about ACLED, especially focusing on the development progress of the monolithic GaN-based Schottky barrier diodes integrated ACLED (SBD-ACLED). The SBD-ACLED design can not only improve the chip area utilization ratio but also provide much higher reverse breakdown voltage by integrating four SBDs with the micro-LEDs array in a single chip, which was regarded as a good on-chip ACLED design. According to the experimental results, higher chip efficiency can be reached through SBD-ACLED design since the chip area utilization ratio was increased. Since the principle and the operation condition of ACLED is quite different from those of the typical DCLED, critical issues for ACLED like the current droops, the flicker phenomenon, the safety regulations, the measurement standards and the power fluctuation have been studied for getting a practical and reliable ACLED design. Besides, the "AC LED application and research alliance" (AARA) lead by ITRI in Taiwan for the commercialization works of ACLED has also been introduced.

  12. Infrared Organic Light-Emitting Diodes with Carbon Nanotube Emitters.

    Science.gov (United States)

    Graf, Arko; Murawski, Caroline; Zakharko, Yuriy; Zaumseil, Jana; Gather, Malte C

    2018-01-30

    While organic light-emitting diodes (OLEDs) covering all colors of the visible spectrum are widespread, suitable organic emitter materials in the near-infrared (nIR) beyond 800 nm are still lacking. Here, the first OLED based on single-walled carbon nanotubes (SWCNTs) as the emitter is demonstrated. By using a multilayer stacked architecture with matching charge blocking and charge-transport layers, narrow-band electroluminescence at wavelengths between 1000 and 1200 nm is achieved, with spectral features characteristic of excitonic and trionic emission of the employed (6,5) SWCNTs. Here, the OLED performance is investigated in detail and it is found that local conduction hot-spots lead to pronounced trion emission. Analysis of the emissive dipole orientation shows a strong horizontal alignment of the SWCNTs with an average inclination angle of 12.9° with respect to the plane, leading to an exceptionally high outcoupling efficiency of 49%. The SWCNT-based OLEDs represent a highly attractive platform for emission across the entire nIR. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Highly efficient light-emitting diodes based on intramolecular rotation

    CERN Document Server

    Di, Dawei; Yang, Le; Jones, Saul; Friend, Richard H; Linnolahti, Mikko; Bochmann, Manfred; Credgington, Dan

    2016-01-01

    The efficiency of an organic light-emitting diode (OLED) is fundamentally governed by the spin of recombining electron-hole pairs (singlet and triplet excitons), since triplets cannot usually emit light. The singlet-triplet energy gap, a key factor for efficient utilization of triplets, is normally positive. Here we show that in a family of materials with amide donor and carbene acceptor moieties linked by a metal, this energy gap for singlet and triplet excitons with charge-transfer character can be tuned from positive to negative values via the rotation of donor and acceptor about the metal-amide bond. When the gap is close to zero, facile intersystem crossing is possible, enabling efficient emission from singlet excitons. We demonstrate solution-processed LEDs with exceptionally high quantum efficiencies (near-100% internal and >27% external quantum efficiencies), and current and power efficiencies (87 cd/A and 75 lm/W) comparable to, or exceeding, those of state-of-the-art vacuum-processed OLEDs and quant...

  14. Light Emitting, Photovoltaic or Other Electronic Apparatus and System

    Science.gov (United States)

    Ray, William Johnstone (Inventor); Lowenthal, Mark D. (Inventor); Shotton, Neil O. (Inventor); Blanchard, Richard A. (Inventor); Lewandowski, Mark Allan (Inventor); Fuller, Kirk A. (Inventor); Frazier, Donald Odell (Inventor)

    2016-01-01

    The present invention provides an electronic apparatus, such as a lighting device comprised of light emitting diodes (LEDs) or a power generating apparatus comprising photovoltaic diodes, which may be created through a printing process, using a semiconductor or other substrate particle ink or suspension and using a lens particle ink or suspension. An exemplary apparatus comprises a base; at least one first conductor; a plurality of diodes coupled to the at least one first conductor; at least one second conductor coupled to the plurality of diodes; and a plurality of lenses suspended in a polymer deposited or attached over the diodes. The lenses and the suspending polymer have different indices of refraction. In some embodiments, the lenses and diodes are substantially spherical, and have a ratio of mean diameters or lengths between about 10:1 and 2:1. The diodes may be LEDs or photovoltaic diodes, and in some embodiments, have a junction formed at least partially as a hemispherical shell or cap.

  15. Thin film Encapsulations of Flexible Organic Light Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Tsai Fa-Ta

    2016-01-01

    Full Text Available Various encapsulated films for flexible organic light emitting diodes (OLEDs were studied in this work, where gas barrier layers including inorganic Al2O3 thin films prepared by atomic layer deposition, organic Parylene C thin films prepared by chemical vapor deposition, and their combination were considered. The transmittance and water vapor transmission rate of the various organic and inorgabic encapsulated films were tested. The effects of the encapsulated films on the luminance and current density of the OLEDs were discussed, and the life time experiments of the OLEDs with these encapsulated films were also conducted. The results showed that the transmittance are acceptable even the PET substrate were coated two Al2O3 and Parylene C layers. The results also indicated the WVTR of the PET substrate improved by coating the barrier layers. In the encapsulation performance, it indicates the OLED with Al2O3 /PET, 1 pair/PET, and 2 pairs/PET presents similarly higher luminance than the other two cases. Although the 1 pair/PET encapsulation behaves a litter better luminance than the 2 pairs/PET encapsulation, the 2 pairs/PET encapsulation has much better life time. The OLED with 2 pairs/PET encapsulation behaves near double life time to the 1 pair encapsulation, and four times to none encapsulation.

  16. Microtube Light-Emitting Diode Arrays with Metal Cores.

    Science.gov (United States)

    Tchoe, Youngbin; Lee, Chul-Ho; Park, Jun Beom; Baek, Hyeonjun; Chung, Kunook; Jo, Janghyun; Kim, Miyoung; Yi, Gyu-Chul

    2016-03-22

    We report the fabrication and characteristics of vertical microtube light-emitting diode (LED) arrays with a metal core inside the devices. To make the LEDs, gallium nitride (GaN)/indium gallium nitride (In(x)Ga(1-x)N)/zinc oxide (ZnO) coaxial microtube LED arrays were grown on an n-GaN/c-aluminum oxide (Al2O3) substrate. The microtube LED arrays were then lifted-off the substrate by wet chemical etching of the sacrificial ZnO microtubes and the silicon dioxide (SiO2) layer. The chemically lifted-off LED layer was then transferred upside-down on other supporting substrates. To create the metal cores, titanium/gold and indium tin oxide were deposited on the inner shells of the microtubes, forming n-type electrodes inside the metal-cored LEDs. The characteristics of the resulting devices were determined by measuring electroluminescence and current-voltage characteristic curves. To gain insights into the current-spreading characteristics of the devices and understand how to make them more efficient, we modeled them computationally.

  17. Carrier Modulation Layer-Enhanced Organic Light-Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Jwo-Huei Jou

    2015-07-01

    Full Text Available Organic light-emitting diode (OLED-based display products have already emerged in the market and their efficiencies and lifetimes are sound at the comparatively low required luminance. To realize OLED for lighting application sooner, higher light quality and better power efficiency at elevated luminance are still demanded. This review reveals the advantages of incorporating a nano-scale carrier modulation layer (CML, also known as a spacer, carrier-regulating layer, or interlayer, among other terms, to tune the chromaticity and color temperature as well as to markedly improve the device efficiency and color rendering index (CRI for numerous OLED devices. The functions of the CML can be enhanced as multiple layers and blend structures are employed. At proper thickness, the employment of CML enables the device to balance the distribution of carriers in the two emissive zones and achieve high device efficiencies and long operational lifetime while maintaining very high CRI. Moreover, we have also reviewed the effect of using CML on the most significant characteristics of OLEDs, namely: efficiency, luminance, life-time, CRI, SRI, chromaticity, and the color temperature, and see how the thickness tuning and selection of proper CML are crucial to effectively control the OLED device performance.

  18. Diffusion-Driven Charge Transport in Light Emitting Devices.

    Science.gov (United States)

    Kim, Iurii; Kivisaari, Pyry; Oksanen, Jani; Suihkonen, Sami

    2017-12-12

    Almost all modern inorganic light-emitting diode (LED) designs are based on double heterojunctions (DHJs) whose structure and current injection principle have remained essentially unchanged for decades. Although highly efficient devices based on the DHJ design have been developed and commercialized for energy-efficient general lighting, the conventional DHJ design requires burying the active region (AR) inside a pn-junction. This has hindered the development of emitters utilizing nanostructured ARs located close to device surfaces such as nanowires or surface quantum wells. Modern DHJ III-N LEDs also exhibit resistive losses that arise from the DHJ device geometry. The recently introduced diffusion-driven charge transport (DDCT) emitter design offers a novel way to transport charge carriers to unconventionally placed ARs. In a DDCT device, the AR is located apart from the pn-junction and the charge carriers are injected into the AR by bipolar diffusion. This device design allows the integration of surface ARs to semiconductor LEDs and offers a promising method to reduce resistive losses in high power devices. In this work, we present a review of the recent progress in gallium nitride (GaN) based DDCT devices, and an outlook of potential DDCT has for opto- and microelectronics.

  19. Transparent Perovskite Light-Emitting Touch-Responsive Device.

    Science.gov (United States)

    Chou, Shu-Yu; Ma, Rujun; Li, Yunfei; Zhao, Fangchao; Tong, Kwing; Yu, Zhibin; Pei, Qibing

    2017-11-28

    A light-emitting touch-responsive device (LETD) for instantaneous visualization of pressure mapping is reported. The LETD integrates an organometal halide perovskite polymer composite emissive layer and a flexible silver nanowire polyurethane composite transparent electrode. The composite emissive layer contains methylammonium lead bromide nanocrystals uniformly dispersed in a poly(ethylene oxide) (PEO) matrix and emits an intense green luminescence that peaks at 529 nm. The PEO matrix promotes the formation of small perovskite grains (∼20 nm) and a pinhole-free composite film with surface roughness of only 2.96 nm. The composite transparent electrode is separated from the emissive layer with a 100 μm thick spacer. When a local pressure is applied, a Schottky contact is formed instantaneously between the metal and the emissive layer, and electroluminescence is produced at voltages as low as 2.5 V and reaches 1030 cd/m2 at 6 V. The transparent LETD has approximately 68% transparency. It can be bent to a 6 mm radius when polyethylene terephthalate is used as the substrate. The perovskite LETD has fast response and can be pixelated to offer potential applications in robotics, motion detection, fingerprint devices, and interactive wallpapers.

  20. Using Organic Light-Emitting Electrochemical Thin-Film Devices to Teach Materials Science

    Science.gov (United States)

    Sevian, Hannah; Muller, Sean; Rudmann, Hartmut; Rubner, Michael F.

    2004-01-01

    Materials science can be taught by applying organic light-emitting electrochemical thin-film devices and in this method students were allowed to make a light-emitting device by spin coating a thin film containing ruthenium (II) complex ions onto a glass slide. Through this laboratory method students are provided with the opportunity to learn about…

  1. Recycling of guided mode light emission in planar microcavity light emitting diodes

    Science.gov (United States)

    De Neve, H.; Blondelle, J.; Van Daele, P.; Demeester, P.; Baets, R.; Borghs, G.

    1997-02-01

    Results are presented on planar microcavity light emitting diodes with different device diameters. A record external quantum efficiency of 20% is achieved for a 1.5 mm light emitting diode. The strong dependence of the quantum efficiency on current density and device size are compared with theoretical results. A good correspondence is obtained when spectral broadening and photon recycling are taken into account.

  2. 77 FR 75190 - Certain Light-Emitting Diodes and Products Containing Same; Commission Determination Not To...

    Science.gov (United States)

    2012-12-19

    ... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION Certain Light-Emitting Diodes and Products Containing Same; Commission Determination Not To Review... importation of certain light- emitting diodes and products containing same by reason of infringement of...

  3. 77 FR 55499 - Certain Light-Emitting Diodes and Products Containing Same; Commission Determination Not To...

    Science.gov (United States)

    2012-09-10

    ... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION Certain Light-Emitting Diodes and Products Containing Same; Commission Determination Not To Review... States after importation of certain light-emitting diodes and products containing same by reason of...

  4. p-i-n Homojunction in Organic Light-Emitting Transistors

    NARCIS (Netherlands)

    Bisri, Satria Zulkarnaen; Takenobu, Taishi; Sawabe, Kosuke; Tsuda, Satoshi; Yomogidao, Yohei; Yamao, Takeshi; Hotta, Shu; Adachi, Chihaya; Iwasa, Yoshihiro

    2011-01-01

    A new method for investigating light-emitting property in organic devices is demonstrated. We apply the ambipolar light-emitting transistors (LETS) to directly observe the recombination zone, and find a strong link between the transistor performance and the zone size. This finding unambiguously

  5. Process optimization of gravure printed light-emitting polymer layers by a neural network approach

    NARCIS (Netherlands)

    Michels, J.J.; Winter, S.H.P.M. de; Symonds, L.H.G.

    2009-01-01

    We demonstrate that artificial neural network modeling is a viable tool to predict the processing dependence of gravure printed light-emitting polymer layers for flexible OLED lighting applications. The (local) thickness of gravure printed light-emitting polymer (LEP) layers was analyzed using

  6. Spin-polarized light-emitting diodes based on organic bipolar spin valves

    Energy Technology Data Exchange (ETDEWEB)

    Vardeny, Zeev Valentine; Nguyen, Tho Duc; Ehrenfreund, Eitan Avraham

    2017-10-25

    Spin-polarized organic light-emitting diodes are provided. Such spin-polarized organic light-emitting diodes incorporate ferromagnetic electrodes and show considerable spin-valve magneto-electroluminescence and magneto-conductivity responses, with voltage and temperature dependencies that originate from the bipolar spin-polarized space charge limited current.

  7. Heat transfer and structure stress analysis of micro packaging component of high power light emitting diode

    Directory of Open Access Journals (Sweden)

    Hsu Chih-Neng

    2013-01-01

    Full Text Available This paper focuses on the heat transfer and structural stress analysis of the micro- scale packaging structure of a high-power light emitting diode. The thermal-effect and thermal-stress of light emitting diode are determined numerically. Light emitting diode is attached to the silicon substrate through the wire bonding process by using epoxy as die bond material. The silicon substrate is etched with holes at the bottom and filled with high conductivity copper material. The chip temperature and structure stress increase with input power consumption. The micro light emitting diode is mounted on the heat sink to increase the heat dissipation performance, to decrease chip temperature, to enhance the material structure reliability and safety, and to avoid structure failure as well. This paper has successfully used the finite element method to the micro-scale light emitting diode heat transfer and stress concentration at the edges through etched holes.

  8. Ultraviolet fire detector

    Science.gov (United States)

    Turnage, J. E.; Linford, R. M. F.; Cornish, S. D.

    1976-01-01

    System is capable of detecting ultraviolet light emitted by match size flame at distance of 10 ft. System is not affected by high energy or particulate radiation and is therefore particularly suited for applications around nuclear plants and X-ray equipment.

  9. A two-colour heterojunction unipolar nanowire light-emitting diode by tunnel injection

    Science.gov (United States)

    Zimmler, Mariano A.; Bao, Jiming; Shalish, Ilan; Yi, Wei; Narayanamurti, Venkatesh; Capasso, Federico

    2007-10-01

    We present a systematic study of the current-voltage characteristics and electroluminescence of gallium nitride (GaN) nanowire on silicon (Si) substrate heterostructures where both semiconductors are n-type. A novel feature of this device is that by reversing the polarity of the applied voltage the luminescence can be selectively obtained from either the nanowire or the substrate. For one polarity of the applied voltage, ultraviolet (and visible) light is generated in the GaN nanowire, while for the opposite polarity infrared light is emitted from the Si substrate. We propose a model, which explains the key features of the data, based on electron tunnelling from the valence band of one semiconductor into the conduction band of the other semiconductor. For example, for one polarity of the applied voltage, given a sufficient potential energy difference between the two semiconductors, electrons can tunnel from the valence band of GaN into the Si conduction band. This process results in the creation of holes in GaN, which can recombine with conduction band electrons generating GaN band-to-band luminescence. A similar process applies under the opposite polarity for Si light emission. This device structure affords an additional experimental handle to the study of electroluminescence in single nanowires and, furthermore, could be used as a novel approach to two-colour light-emitting devices.

  10. Fabrication Methods and Luminescent Properties of ZnO Materials for Light-Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Ching-Ting Lee

    2010-03-01

    Full Text Available Zinc oxide (ZnO is a potential candidate material for optoelectronic applications, especially for blue to ultraviolet light emitting devices, due to its fundamental advantages, such as direct wide band gap of 3.37 eV, large exciton binding energy of 60 meV, and high optical gain of 320 cm−1 at room temperature. Its luminescent properties have been intensively investigated for samples, in the form of bulk, thin film, or nanostructure, prepared by various methods and doped with different impurities. In this paper, we first review briefly the recent progress in this field. Then a comprehensive summary of the research carried out in our laboratory on ZnO preparation and its luminescent properties, will be presented, in which the involved samples include ZnO films and nanorods prepared with different methods and doped with n-type or p-type impurities. The results of ZnO based LEDs will also be discussed.

  11. Enhancing Carrier Injection Using Graded Superlattice Electron Blocking Layer for UVB Light-Emitting Diodes

    KAUST Repository

    Janjua, Bilal

    2014-12-01

    We have studied enhanced carrier injection by having an electron blocking layer (EBL) based on a graded superlattice (SL) design. Here, we examine, using a selfconsistent 6 × 6 k.p method, the energy band alignment diagrams under equilibrium and forward bias conditions while also considering carrier distribution and recombination rates (Shockley-Read-Hall, Auger, and radiative recombination rates). The graded SL is based on AlxGa1-xN (larger bandgap) Al0:5Ga0:5N (smaller bandgap) SL, where x is changed from 0.8 to 0.56 in steps of 0.06. Graded SL was found to be effective in reducing electron leakage and enhancing hole injection into the active region. Due to our band engineering scheme for EBL, four orders-of-magnitude enhancement were observed in the direct recombination rate, as compared with the conventional bulk EBL consisting of Al0:8Ga0:2N. An increase in the spatial overlap of carrier wavefunction was obtained due to polarization-induced band bending in the active region. An efficient single quantum-well ultraviolet-B light-emitting diode was designed, which emits at 280 nm. This is the effective wavelength for water disinfection application, among others.

  12. The Electric and Optical Properties of Doped Small Molecular Organic Light-Emitting Devices

    Energy Technology Data Exchange (ETDEWEB)

    Cheon, Kwang-Ohk [Iowa State Univ., Ames, IA (United States)

    2003-01-01

    Organic light-emitting devices (OLEDs) constitute a new and exciting emissive display technology. In general, the basic OLED structure consists of a stack of fluorescent organic layers sandwiched between a transparent conducting-anode and metallic cathode. When an appropriate bias is applied to the device, holes are injected from the anode and electrons from the cathode; some of the recombination events between the holes and electrons result in electroluminescence (EL). Until now, most of the efforts in developing OLEDs have focused on display applications, hence on devices within the visible range. However some organic devices have been developed for ultraviolet or infrared emission. Various aspects of the device physics of doped small molecular OLEDs were described and discussed. The doping layer thickness and concentration were varied systematically to study their effects on device performances, energy transfer, and turn-off dynamics. Low-energy-gap DCM2 guest molecules, in either α-NPD or DPVBi host layers, are optically efficient fluorophores but also generate deep carrier trap-sites. Since their traps reduce the carrier mobility, the current density decreases with increased doping concentration. At the same time, due to efficient energy transfer, the quantum efficiency of the devices is improved by light doping or thin doping thickness, in comparison with the undoped neat devices. However, heavy doping induces concentration quenching effects. Thus, the doping concentration and doping thickness may be optimized for best performance.

  13. Tuning the white light spectrum of light emitting diode lamps to reduce attraction of nocturnal arthropods.

    Science.gov (United States)

    Longcore, Travis; Aldern, Hannah L; Eggers, John F; Flores, Steve; Franco, Lesly; Hirshfield-Yamanishi, Eric; Petrinec, Laina N; Yan, Wilson A; Barroso, André M

    2015-05-05

    Artificial lighting allows humans to be active at night, but has many unintended consequences, including interference with ecological processes, disruption of circadian rhythms and increased exposure to insect vectors of diseases. Although ultraviolet and blue light are usually most attractive to arthropods, degree of attraction varies among orders. With a focus on future indoor lighting applications, we manipulated the spectrum of white lamps to investigate the influence of spectral composition on number of arthropods attracted. We compared numbers of arthropods captured at three customizable light-emitting diode (LED) lamps (3510, 2704 and 2728 K), two commercial LED lamps (2700 K), two commercial compact fluorescent lamps (CFLs; 2700 K) and a control. We configured the three custom LEDs to minimize invertebrate attraction based on published attraction curves for honeybees and moths. Lamps were placed with pan traps at an urban and two rural study sites in Los Angeles, California. For all invertebrate orders combined, our custom LED configurations were less attractive than the commercial LED lamps or CFLs of similar colour temperatures. Thus, adjusting spectral composition of white light to minimize attracting nocturnal arthropods is feasible; not all lights with the same colour temperature are equally attractive to arthropods. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  14. Performance improvement of indoor positioning using light-emitting diodes and an image sensor for light-emitting diode communication

    Science.gov (United States)

    Hossen, Md. Sazzad; Park, Youngil; Kim, Ki-Doo

    2015-04-01

    Light-emitting diodes (LEDs) are expected to replace existing lighting technologies in the near future because of the potential dual function of LED light (i.e., wireless communication and lighting) in the context of visible light communication (VLC). We propose a highly precise indoor positioning algorithm using lighting LEDs, an image sensor, and VLC. In the proposed algorithm, three LEDs transmit their three-dimensional coordinate information, which is received and demodulated by a single image sensor at an unknown position. The unknown position is then calculated from the geometrical relations of the LED images created on the image sensor plane. We describe the algorithm in detail. A simulation of the proposed algorithm is presented in this paper. We also compare the performance of this algorithm with that of our previously proposed algorithm. The comparison indicates significant improvement in positioning accuracy because of the simple algorithmic structure and low computational complexity. This technique does not require any angular measurement, which is needed in the contemporary positioning algorithms using LEDs and image sensor. The simulation results show that the proposed system can estimate the unknown position to an accuracy of 0.001 m inside the approximate positioning area when the pixel value is >3000.

  15. A standardized light-emitting diode device for photoimmunotherapy.

    Science.gov (United States)

    de Boer, Esther; Warram, Jason M; Hartmans, Elmire; Bremer, Peter J; Bijl, Ben; Crane, Lucia M A; Nagengast, Wouter B; Rosenthal, Eben L; van Dam, Gooitzen M

    2014-11-01

    Antibody-based photodynamic therapy-photoimmunotherapy (PIT)-is an ideal modality to improve cancer treatment because of its selective and tumor-specific mode of therapy. Because the use of PIT for cancer treatment is continuing to be described, there is great need to characterize a standardized light source for PIT application. In this work, we designed and manufactured a light-emitting diode (LED)/PIT device and validated the technical feasibility, applicability, safety, and consistency of the system for cancer treatment. To outline the characteristics and photobiologic safety of the LED device, multiple optical measurements were performed in accordance with a photobiologic safety standard. A luciferase-transfected breast cancer cell line (2LMP-Luc) in combination with panitumumab-IRDye 700DX (pan-IR700) was used to validate the in vitro and in vivo performance of our LED device. Testing revealed the light source to be safe, easy to use, and independent of illumination and power output (mW cm(-2)) variations over time. For in vitro studies, an LED dose (2, 4, 6 J cm(-2))-dependent cytotoxicity was observed using propidium iodide exclusion and annexin V staining. Dose-dependent blebbing was also observed during microscopic analysis. Bioluminescence signals of tumors treated with 0.3 mg of pan-IR700 and 50 J cm(-2) decreased significantly (>80%) compared with signals of contralateral nontreated sites at 4 h and at 1 d after PIT. To our knowledge, a normalized and standardized LED device has not been explicitly described or developed. In this article, we introduce a standardized light source and validate its usability for PIT applications. © 2014 by the Society of Nuclear Medicine and Molecular Imaging, Inc.

  16. Carbonitride based phosphors and light emitting devices using the same

    Science.gov (United States)

    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

  17. Multicolor white light-emitting diodes for illumination applications

    Science.gov (United States)

    Chi, Solomon W. S.; Chen, Tzer-Perng; Tu, Chuan-Cheng; Chang, Chih-Sung; Tsai, Tzong-Liang; Hsieh, Mario C. C.

    2004-01-01

    Semiconductor light emitting diode (LED) has become a promising device for general-purpose illumination applications. LED has the features of excellent durability, long operation life, low power consumption, no mercury containing and potentially high efficiency. Several white LED technologies appear capable of meeting the technical requirements of illumination. In this paper we present a new multi-color white (MCW) LED as a high luminous efficacy, high color rendering index and low cost white illuminator. The device consists of two LED chips, one is AlInGaN LED for emitting shorter visible spectra, another is AlInGaP LED for emitting longer visible spectra. At least one chip in the MCW-LED has two or more transition energy levels used for emitting two or more colored lights. The multiple colored lights generated from the MCW-LED can be mixed into a full-spectral white light. Besides, there is no phosphors conversion layer used in the MCW-LED structure. Therefore, its color rendering property and illumination efficiency are excellent. The Correlated Color Temperature (CCT) of the MCW-LED may range from 2,500 K to over 10,000 K. The theoretical General Color Rendering Index (Ra) could be as high as 94, which is close to the incandescent and halogen sources, while the Ra of binary complementary white (BCW) LED is about 30 ~ 45. Moreover, compared to the expensive ternary RGB (Red AlInGaP + Green AlInGaN + Blue AlInGaN) white LED sources, the MCW-LED uses only one AlInGaN chip in combination with one cheap AlInGaP chip, to form a low cost, high luminous performance white light source. The MCW-LED is an ideal light source for general-purpose illumination applications.

  18. Chip-scale white flip-chip light-emitting diode containing indium phosphide/zinc selenide quantum dots

    Science.gov (United States)

    Fan, Bingfeng; Yan, Linchao; Lao, Yuqin; Ma, Yanfei; Chen, Zimin; Ma, Xuejin; Zhuo, Yi; Pei, Yanli; Wang, Gang

    2017-08-01

    A method for preparing a quantum dot (QD)-white light-emitting diode (WLED) is reported. Holes were etched in the SiO2 layer deposited on the sapphire substrate of the flip-chip LED by inductively coupled plasma, and these holes were then filled with QDs. An ultraviolet-curable resin was then spin-coated on top of the QD-containing SiO2 layer, and the resin was cured to act as a protecting layer. The reflective sidewall structure minimized sidelight leakage. The fabrication of the QD-WLED is simple in preparation and compatible with traditional LED processes, which was the minimum size of the WLED chip-scale integrated package. InP/ZnS core-shell QDs were used as the converter in the WLED. A blue light-emitting diode with a flip-chip structure was used as the excitation source. The QD-WLED exhibited color temperatures from 5900 to 6400 K and Commission Internationale De L'Elcairage color coordinates from (0.315, 0.325) to (0.325, 0.317), under drive currents from 100 to 400 mA. The QD-WLED exhibited stable optoelectronic properties.

  19. Single crystalline ZnO radial homojunction light-emitting diodes fabricated by metalorganic chemical vapour deposition

    Science.gov (United States)

    Yoo, Jinkyoung; Ahmed, Towfiq; Tang, Wei; Kim, Yong-Jin; Hong, Young Joon; Lee, Chul-Ho; Yi, Gyu-Chul

    2017-09-01

    ZnO radial p-n junction architecture has the potential for forward-leap of light-emitting diode (LED) technology in terms of higher efficacy and economical production. We report on ZnO radial p-n junction-based light emitting diodes prepared by full metalorganic chemical vapour deposition (MOCVD) with hydrogen-assisted p-type doping approach. The p-type ZnO(P) thin films were prepared by MOCVD with the precursors of dimethylzinc, tert-butanol, and tertiarybutylphosphine. Controlling the precursor flow for dopant results in the systematic change of doping concentration, Hall mobility, and electrical conductivity. Moreover, the approach of hydrogen-assisted phosphorous doping in ZnO expands the understanding of doping behaviour in ZnO. Ultraviolet and visible electroluminescence of ZnO radial p-n junction was demonstrated through a combination of position-controlled nano/microwire and crystalline p-type ZnO(P) radial shell growth on the wires. The reported research opens a pathway of realisation of production-compatible ZnO p-n junction LEDs.

  20. White light emitting silicon nano-crystals-polymeric hybrid films prepared by single batch solution based method

    Energy Technology Data Exchange (ETDEWEB)

    Balci, Mustafa H. [Department of Materials Science and Engineering, NTNU, 7491 Trondheim (Norway); Aas, Lars Martin Sandvik; Kildemo, Morten; Sæterli, Ragnhild; Holmestad, Randi; Lindgren, Mikael [Department of Physics, NTNU, 7491 Trondheim (Norway); Grande, Tor [Department of Materials Science and Engineering, NTNU, 7491 Trondheim (Norway); Einarsrud, Mari-Ann, E-mail: Mari-Ann.Einarsrud@ntnu.no [Department of Materials Science and Engineering, NTNU, 7491 Trondheim (Norway)

    2016-03-31

    Silicon nano-crystals have been studied intensively due to their photoluminescence properties and possible applications in new generation opto-electronic devices. Their importance in lightning and display technologies is increasing due to the abundance and non-toxicity of silicon. Here we report a single batch solution based synthesis route to silicon nano-crystal organic hybrid films exhibiting white light photoluminescence at room temperature upon excitation by ultraviolet light. Films prepared by ethylene glycol terminated Si nano-crystals showed maximum 240 nm red shift in photoluminescence response upon excitation at 350 nm. The shift was found to decrease in order for hybrid films fabricated using acrylic acid, 1-octanol acid and oleic acid terminated Si nano-crystals. The mean size of the Si nano-crystals (~ 2–10 nm) estimated by Raman spectroscopy were smallest for the ethylene glycol capped Si nano-crystal films. The calculated Tauc bandgaps of the hybrid films varied between 1.51 and 2.35 eV. - Highlights: • White light emitting Si nanocrystal hybrid films were synthesized at low temperature • The effect of the surface termination of the Si nano-crystals is reported • A red shift in photoluminescence response was observed • The hybrid films are new candidate white light emitting diodes • The hybrid films can be used in solar cell applications for spectral-shifting control.

  1. Efficient and bright organic light-emitting diodes on single-layer graphene electrodes

    Science.gov (United States)

    Li, Ning; Oida, Satoshi; Tulevski, George S.; Han, Shu-Jen; Hannon, James B.; Sadana, Devendra K.; Chen, Tze-Chiang

    2013-08-01

    Organic light-emitting diodes are emerging as leading technologies for both high quality display and lighting. However, the transparent conductive electrode used in the current organic light-emitting diode technologies increases the overall cost and has limited bendability for future flexible applications. Here we use single-layer graphene as an alternative flexible transparent conductor, yielding white organic light-emitting diodes with brightness and efficiency sufficient for general lighting. The performance improvement is attributed to the device structure, which allows direct hole injection from the single-layer graphene anode into the light-emitting layers, reducing carrier trapping induced efficiency roll-off. By employing a light out-coupling structure, phosphorescent green organic light-emitting diodes exhibit external quantum efficiency >60%, while phosphorescent white organic light-emitting diodes exhibit external quantum efficiency >45% at 10,000 cd m-2 with colour rendering index of 85. The power efficiency of white organic light-emitting diodes reaches 80 lm W-1 at 3,000 cd m-2, comparable to the most efficient lighting technologies.

  2. Benzoporphyrin derivative and light-emitting diode for use in photodynamic therapy: Applications of space light-emitting diode technology

    Science.gov (United States)

    Whelan, Harry T.; Houle, John M.; Bajic, Dawn M.; Schmidt, Meic H.; Reichert, Kenneth W.; Meyer, Glenn A.

    1998-01-01

    Photodynamic therapy (PDT) is a cancer treatment modality that recently has been applied as adjuvant therapy for brain tumors. PDT consists of intravenously injecting a photosensitizer, which preferentially accumulates in tumor cells, into a patient and then activating the photosensitizer with a light source. This results in free radical generation followed by cell death. The development of more effective light sources for PDT of brain tumors has been facilitated by applications of space light-emitting diode array technology; thus permitting deeper tumor penetration of light and use of better photosensitizers. Currently, the most commonly used photosensitizer for brain tumor PDT is Photofrin®. Photofrin® is a heterogeneous mixture of compounds derived from hematoporphyrin. Photofrin® is activated with a 630 nm laser light and does destroy tumor cells in animal models and humans. However, treatment failure does occur using this method. Most investigators attribute this failure to the limited penetration of brain tissue by a 630 nm laser light and to the fact that Photofrin® has only a minor absorption peak at 630 nm, meaning that only a small fraction of the chemical is activated. Benzoporphyrin Derivative Monoacid Ring A (BPD) is a new, second generation photosensitizer that can potentially improve PDT for brain tumors. BPD has a major absorption peak at 690 nm, which gives it two distinct advantages over Photofrin®. First, longer wavelengths of light penetrate brain tissue more easily so that larger tumors could be treated, and second, the major absorption peak means that a larger fraction of the drug is activated upon exposure to light. In the first part of this project we have studied the tumoricidal effects of BPD in vitro using 2A9 canine glioma and U373 human glioblastoma cell cultures. Using light emitting diodes (LED) with a peak emission of 688 nm as a light source, cell kill of up to 86 percent was measured in these cell lines by tumor DNA synthesis

  3. Device physics of polymer light-emitting diodes

    Science.gov (United States)

    Crone, Brian Keith

    Organic light emitting diodes have the structure metal_A/organic/metal_B. The physical processes which determine the operating characteristics of these devices are carrier injection into the organic material from the metal contacts, carrier transport through the organic, and carrier recombination in the organic layer. The philosophy employed here is to study these processes in simple situations where they can be studied independently to as large a degree as possible, and then to apply the understanding gained from simple systems to successively more complex systems. This is done by using experiments in parallel with a device model to describe the experimental results. First single carrier single layer devices are considered. Current voltage characteristics are measured for series of electron and hole only devices both as a function of device thickness and of energy barrier to carrier injection. These measurements were described by a device model and carrier mobilities were extracted. The energy barriers to injection were measured independently. Then the current voltage characteristics were measured for series of bipolar single layer devices both as a function of device thickness and energy barrier to carrier injection. These measurements were described by the carrier mobilities and energy barriers determined from single carrier experiments with no additional fitting parameters. The device model also gave a qualitative description of single layer device luminances. The calculated current voltage characteristics were found to be relatively insensitive to the magnitude of the recombination rate used in the device model. Organic materials which have desirable electroluminescence properties may not have the necessary physical characteristics to make an efficient single layer LED. Device model results are presented which show that if the injection or transport of one carrier is lacking in a material, an efficient device can be made by introducing a second material which

  4. Magnetic field effect in organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Niedermeier, Ulrich

    2009-12-14

    The discovery of a magnetic field dependent resistance change of organic light emitting diodes (OLEDs) in the year 2003 has attracted considerable scientific and industrial research interest. However, despite previous progress in the field of organic spin-electronics, the phenomenon of the ''organic magnetoresistance (OMR) effect'' is not yet completely understood. In order to improve the understanding of the microscopic mechanisms which ultimately cause the OMR effect, experimental investigations as well as theoretical considerations concerning the OMR are addressed in this thesis. In polymer-based OLED devices the functional dependencies of the OMR effect on relevant parameters like magnetic field, operating voltage, operating current and temperature are investigated. Based on these results, previously published models for potential OMR mechanisms are critically analyzed and evaluated. Finally, a concept for the OMR effect is favored which suggests magnetic field dependent changes of the spin state of electron-hole pairs as being responsible for changes in current flow and light emission in OLEDs. In the framework of this concept it is possible to explain all results from own measurements as well as results from literature. Another important finding made in this thesis is the fact that the value of the OMR signal in the investigated OLED devices can be enhanced by appropriate electrical and optical conditioning processes. In particular, electrical conditioning causes a significant enhancement of the OMR values, while at the same time it has a negative effect on charge carrier transport and optical device characteristics. These results can be explained by additional results from charge carrier extraction measurements which suggest that electrical conditioning leads to an increase in the number of electronic trap states inside the emission layer of the investigated OLED devices. The positive influence of trap states on the OMR effect is

  5. Resonant-cavity light-emitting diodes for optical interconnects

    Science.gov (United States)

    Jin, Xu

    This dissertation addresses the issues related to external quantum efficiencies and light coupling efficiency of novel 1.3 mum Resonant-cavity light-emitting diodes (RCLEDs) on GaAs substrates. External quantum efficiency (QE) is defined as the number of extracted photons per injected electrons, i.e., the product of injection efficiency, internal QE, and light extraction efficiency. This study focuses on the latter two terms. Internal QE mainly depends on the properties of the active region quantum wells (QWs) used in the RCLEDs, such as composition, thickness, and strain compensation. GaAsSb/GaAs QW edge-emitting (EE) lasers are characterized experimentally to extract key parameters, such as internal QE and internal loss. With optimized QWs and a novel self-aligned EE lasers process, room temperature continuous wave (CW) operation of GaAsSb EE lasers has been demonstrated for the first time. The highest operational temperature for the EE lasers is 48°C at a wavelength as long as 1260 nm. This result is the best ever reported by a university group. In conventional LEDs, very little light generated by the active region, succeeds in escaping from the semiconductor material due to the small critical angle of total internal reflection. With the use of a resonant cavity, the light extraction efficiency of RCLEDs is significantly improved. Front and back reflectivities, detuning (offset) between resonant-cavity peak and electroluminescence, and electroluminescence linewidth have been identified as key factors influencing light extraction efficiency. Numerical simulations indicate that the fraction of luminescence transmitted through the top mirror of an optimized RCLED is around 9%, which is more than double that of conventional LEDs. This number will be larger when multiple reflections and photon recycling are considered; which are not included in the current model since they are structure dependent. The best GaAsSb/GaAs QW RCLEDs demonstrated in this work have shown

  6. Surface Plasmon Enhanced Phosphorescent Organic Light Emitting Diodes

    Energy Technology Data Exchange (ETDEWEB)

    Guillermo Bazan; Alexander Mikhailovsky

    2008-08-01

    The objective of the proposed work was to develop the fundamental understanding and practical techniques for enhancement of Phosphorescent Organic Light Emitting Diodes (PhOLEDs) performance by utilizing radiative decay control technology. Briefly, the main technical goal is the acceleration of radiative recombination rate in organometallic triplet emitters by using the interaction with surface plasmon resonances in noble metal nanostructures. Increased photonic output will enable one to eliminate constraints imposed on PhOLED efficiency by triplet-triplet annihilation, triplet-polaron annihilation, and saturation of chromophores with long radiative decay times. Surface plasmon enhanced (SPE) PhOLEDs will operate more efficiently at high injection current densities and will be less prone to degradation mechanisms. Additionally, introduction of metal nanostructures into PhOLEDs may improve their performance due to the improvement of the charge transport through organic layers via multiple possible mechanisms ('electrical bridging' effects, doping-like phenomena, etc.). SPE PhOLED technology is particularly beneficial for solution-fabricated electrophosphorescent devices. Small transition moment of triplet emitters allows achieving a significant enhancement of the emission rate while keeping undesirable quenching processes introduced by the metal nanostructures at a reasonably low level. Plasmonic structures can be introduced easily into solution-fabricated PhOLEDs by blending and spin coating techniques and can be used for enhancement of performance in existing device architectures. This constitutes a significant benefit for a large scale fabrication of PhOLEDs, e.g. by roll-to-roll fabrication techniques. Besides multieexciton annihilation, the power efficacy of PhOLEDs is often limited by high operational bias voltages required for overcoming built-in potential barriers to injection and transport of electrical charges through a device. This problem is

  7. GaN doped with beryllium—An effective light converter for white light emitting diodes

    Science.gov (United States)

    Teisseyre, Henryk; Bockowski, Michal; Grzegory, Izabella; Kozanecki, Adrian; Damilano, Benjamin; Zhydachevskii, Yaroslav; Kunzer, Michael; Holc, Katarzyna; Schwarz, Ulrich T.

    2013-07-01

    So far, most of the studies on GaN doped with beryllium have mainly concentrated on possible p-type doping. Unfortunately, realization of p-type conductivity in such a way appeared to be very difficult. It seems, however, that bulk crystals doped with beryllium can be used as white light converters in the monolithic white light emitting diodes. To realize monolithic white light emitting diode, we used blue light emitting diodes and a single GaN:Be crystal as converter. High value of the Color Rendering Index gives hope for obtaining an effective light converter based on gallium nitride doped with beryllium.

  8. Influence of constant current stress on the conduction mechanisms of reverse leakage current in UV-A light emitting diodes

    Science.gov (United States)

    Wang, Yingzhe; Zheng, Xuefeng; Dai, Feng; Zhu, Jiaduo; Li, Peixian; Ma, Xiaohua; Hao, Yue

    2017-12-01

    The influence of constant current stress on the conduction mechanism of reverse leakage current in ultraviolet (UV) light emitting diodes (LEDs) in the UV-A spectral range has been investigated for the first time using temperature-dependent current-voltage measurement from 370 K to 55 K. Below 220 K, variable range hopping mechanism dominates in UV-A LEDs. While, above 220 K, the leakage current is attributed to Poole-Frenkel emission mechanism within the bias range of -3 ∼ -6 V. With the increasing of the reverse bias, the conduction mechanism transforms from Poole-Frenkel emission to space-charge-limited conduction mechanism. In particular, applying electrical stress yields an alteration of the transition voltage from -7.5 V to -6.5 V. We propose that stress could lead to a reduction of the thermal activation energy, and therefore alters the transition voltage.

  9. Voltage Reduction and Lifetime Elongation of Organic Light-Emitting Diodes Using Photopolymerization for Fluorizated Polyxylylene Hole Injection Layer

    Science.gov (United States)

    Jiang, Meng-Dan; Chiu, Tien-Lung; Lee, Pei-Yu; Yang, Shun-Po; Lin, Hong-Cheu

    2012-03-01

    This study describes a novel method for manufacturing a hole injection layer of an organic light-emitting diode (OLED), comprising an ultraviolet (UV) reactive Br-fluorocarbon precursor (Br-CF2-C6F4-CF2-Br). The proposed method can be used to form a fluorizated polyxylylene film, demonstrating high repeatability on the anode as the hole injection layer of organic electroluminescent devices to enhance the hole injection, reduce the operating voltage of 1.2 V, and extend the operational lifetime by more than 150 times under a high current density of 125 mA/cm2. Using a spin-coating process, the remaining precursor can be recycled to prevent wasting materials. UV curing without the solvent-removing process shortens manufacturing time. Hence, fabricating a high performance OLED using a simple, low-cost process is the aim of this study.

  10. Effect of Electron Blocking Layer Doping and Composition on the Performance of 310 nm Light Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Tim Kolbe

    2017-12-01

    Full Text Available The effects of composition and p-doping profile of the AlGaN:Mg electron blocking layer (EBL in 310 nm ultraviolet B (UV-B light emitting diodes (LEDs have been investigated. The carrier injection and internal quantum efficiency of the LEDs were simulated and compared to electroluminescence measurements. The light output power depends strongly on the temporal biscyclopentadienylmagnesium (Cp 2 Mg carrier gas flow profile during growth as well as on the aluminum profile of the AlGaN:Mg EBL. The highest emission power has been found for an EBL with the highest Cp 2 Mg carrier gas flow and a gradually decreasing aluminum content in direction to the p-side of the LED. This effect is attributed to an improved carrier injection and confinement that prevents electron leakage into the p-doped region of the LED with a simultaneously enhanced carrier injection into the active region.

  11. Luminescent carbon quantum dots with high quantum yield as a single white converter for white light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Feng, X. T.; Zhang, Y.; Liu, X. G., E-mail: liuxuguang@tyut.edu.cn [Key Laboratory of Interface Science and Engineering in Advanced Materials, Taiyuan University of Technology, Taiyuan 030024 (China); College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024 (China); Zhang, F.; Wang, Y. L.; Yang, Y. Z., E-mail: yyztyut@126.com [Key Laboratory of Interface Science and Engineering in Advanced Materials, Taiyuan University of Technology, Taiyuan 030024 (China); Research Center on Advanced Materials Science and Technology, Taiyuan University of Technology, Taiyuan 030024 (China)

    2015-11-23

    Carbon quantum dots (CQDs) with high quantum yield (51.4%) were synthesized by a one-step hydrothermal method using thiosalicylic acid and ethylenediamine as precursor. The CQDs have the average diameter of 2.3 nm and possess excitation-independent emission wavelength in the range from 320 to 440 nm excitation. Under an ultraviolet (UV) excitation, the CQDs aqueous solutions emit bright blue fluorescence directly and exhibit broad emission with a high spectral component ratio of 67.4% (blue to red intensity to total intensity). We applied the CQDs as a single white-light converter for white light emitting diodes (WLEDs) using a UV-LED chip as the excitation light source. The resulted WLED shows superior performance with corresponding color temperature of 5227 K and the color coordinates of (0.34, 0.38) belonging to the white gamut.

  12. On the photosynthetic responses of crops to intracanopy lighting with light emitting diodes

    NARCIS (Netherlands)

    Trouwborst, G.

    2011-01-01

    Key words: Cucumis sativus, intracanopy lighting, light-emitting diodes (LEDs), light distribution, light interception, light quality, photosynthesis, photosynthetic acclimation Assimilation lighting is a production factor of increasing importance in Dutch greenhouse horticulture. Assimilation

  13. Highly efficient inverted polymer light-emitting diodes using surface modifications of ZnO layer

    National Research Council Canada - National Science Library

    Lee, Bo Ram; Jung, Eui Dae; Park, Ji Sun; Nam, Yun Seok; Min, Sa Hoon; Kim, Byeong-Su; Lee, Kyung-Min; Jeong, Jong-Ryul; Friend, Richard H; Kim, Ji-Seon; Kim, Sang Ouk; Song, Myoung Hoon

    2014-01-01

    .... Here, we improve the efficiency of inverted polymer light-emitting diodes by introducing a spontaneously formed ripple-shaped nanostructure of ZnO and applying an amine-based polar solvent treatment...

  14. Evaluation of light-emitting diode beacon light fixtures : final report.

    Science.gov (United States)

    2009-12-01

    Rotating beacons containing filament light sources have long been used on highway maintenance trucks : to indicate the presence of the truck to other drivers. Because of advances in light-emitting diode (LED) : technologies, flashing lights containin...

  15. Robust Visible and Infrared Light Emitting Devices Using Rare-Earth-Doped GaN

    National Research Council Canada - National Science Library

    Steckl, Andrew

    2006-01-01

    Rare earth (RE) dopants (such as Er, Eu, Tm) in the wide bandgap semiconductor (WBGS) GaN are investigated for the fabrication of robust visible and infrared light emitting devices at a variety of wavelengths...

  16. A Device Model for Polymer Light-Emitting Diodes with Mobile Ions

    NARCIS (Netherlands)

    Jong, M.J.M. de; Blom, P.W.M.

    1996-01-01

    A model is presented for the device operation of a polymer light-emitting diode (PLED) with mobile ions. It is calculated that the low efficiency of a PLED with a high injection barrier increases as the ions migrate.

  17. The power conversion efficiency of visible light emitting devices in standard BiCMOS processes

    NARCIS (Netherlands)

    Kuindersma, P.; Hoang, T.; Schmitz, Jurriaan; Vijayaraghavan, M.N.; Dijkstra, Mindert; Dijkstra, M.; van Noort, W.A.; Vanhoucke, T.; Peters, W.C.M.; Kramer, M.C.J.C.M.

    2008-01-01

    We present experimental and theoretical proof for a single and unique relationship between the breakdown voltage and power efficiency of visible light emitting devices fabricated in standard BiCMOS processes.

  18. Method and apparatus for improving the performance of light emitting diodes

    Science.gov (United States)

    Lowery, Christopher H.; McElfresh, David K.; Burchet, Steve; Adolf, Douglas B.; Martin, James

    1996-01-01

    A method for increasing the resistance of a light emitting diode and other semiconductor devices to extremes of temperature is disclosed. During the manufacture of the light emitting diode, a liquid coating is applied to the light emitting die after the die has been placed in its lead frame. After the liquid coating has been placed on the die and its lead frames, a thermosetting encapsulant material is placed over the coating. The operation that cures the thermosetting material leaves the coating liquid intact. As the die and the encapsulant expand and contract at different rates with respect to changes in temperature, and as in known light emitting diodes the encapsulating material adheres to the die and lead frames, this liquid coating reduces the stresses that these different rates of expansion and contraction normally cause by eliminating the adherence of the encapsulating material to the die and frame.

  19. Fabrication of InGaN/GaN nanopillar light-emitting diode arrays

    DEFF Research Database (Denmark)

    Ou, Yiyu; Fadil, Ahmed; Ou, Haiyan

    Nanopillar InGaN/GaN green light-emitting diode arrays were fabricated by using self-assembled nanopatterning and dry etching process. Both internal and external quantum efficiency were increased due to strain relaxation and enhanced light extraction.......Nanopillar InGaN/GaN green light-emitting diode arrays were fabricated by using self-assembled nanopatterning and dry etching process. Both internal and external quantum efficiency were increased due to strain relaxation and enhanced light extraction....

  20. Thermally evaporated hybrid perovskite for hetero-structured green light-emitting diodes

    Science.gov (United States)

    Mariano, Fabrizio; Listorti, Andrea; Rizzo, Aurora; Colella, Silvia; Gigli, Giuseppe; Mazzeo, Marco

    2017-10-01

    Thermal evaporation of green-light emitting perovskite (MaPbBr3) films is reported. Morphological studies show that a soft thermal treatment is needed to induce an outstanding crystal growth and film organization. Hetero-structured light-emitting diodes, embedding as-deposited and annealed MAPbBr3 films as active layers, are fabricated and their performances are compared, highlighting that the perovskite evolution is strongly dependent on the growing substrate, too.

  1. Novel Biomedical Device Utilizing Light-Emitting Nanostructures Developed

    Science.gov (United States)

    Scardelletti, Maximilian C.; Goldman, Rachel

    2004-01-01

    and viruses in fluids. A novel sample preparation technique that exploits micromembrane filtration and centrifugation methods has been developed for this device. The technique greatly reduces the time required to prepare the sample and the amount of sample needed to perform an accurate and comprehensive analysis. Last, and probably most important, because of the nano-light-emitting source and the novel sample preparation technique, the overall size of the device could be reduced dramatically. This device will serve as a nanoscale lab-on-a-chip for in situ microorganism detection and will enable tests to be performed on a time scale of minutes rather than days. Thus, it is ideally suited for monitoring the environmental conditions onboard the International Space Station and the space shuttles, thereby enhancing the safety of the astronauts. In addition, the device has important commercial applications, such as detecting the presence of bacteria and viruses in water at food- and beverage-processing centers, water treatment plants, and restaurants. Also, this technology has the potential to be used to detect bacteria and viruses in more complex fluids, such as blood--which in all likelihood would revolutionize blood analysis as it is performed today. This project was made possible through the Director's Discretionary Fund and is ongoing. In addition, this project provides funding to Dr. Rachel Goldman of the University of Michigan for the research and development of nanostructured quantum dots.

  2. Light-Emitting Photon-Upconversion Nanoparticles in the Generation of Transdermal Reactive-Oxygen Species.

    Science.gov (United States)

    Prieto, Martin; Rwei, Alina Y; Alejo, Teresa; Wei, Tuo; Lopez-Franco, Maria Teresa; Mendoza, Gracia; Sebastian, Victor; Kohane, Daniel S; Arruebo, Manuel

    2017-12-06

    Common photosensitizers used in photodynamic therapy do not penetrate the skin effectively. In addition, the visible blue and red lights used to excite such photosensitizers have shallow penetration depths through tissue. To overcome these limitations, we have synthesized ultraviolet- and visible-light-emitting, energy-transfer-based upconversion nanoparticles and coencapsulated them inside PLGA-PEG (methoxy poly(ethylene glycol)-b-poly(lactic-co-glycolic acid)) nanoparticles with the photosensitizer protoporphyrin IX. Nd3+ has been introduced as a sensitizer in the upconversion nanostructure to allow its excitation at 808 nm. The subcytotoxic doses of the hybrid nanoparticles have been evaluated on different cell lines (i.e., fibroblasts, HaCaT, THP-1 monocytic cell line, U251MG (glioblastoma cell line), and mMSCs (murine mesenchymal stem cells). Upon NIR (near infrared)-light excitation, the upconversion nanoparticles emitted UV and VIS light, which consequently activated the generation of reactive-oxygen species (ROS). In addition, after irradiating at 808 nm, the resulting hybrid nanoparticles containing both upconversion nanoparticles and protoporphyrin IX generated 3.4 times more ROS than PLGA-PEG nanoparticles containing just the same dose of protoporphyrin IX. Their photodynamic effect was also assayed on different cell cultures, demonstrating their efficacy in selectively killing treated and irradiated cells. Compared to the topical application of the free photosensitizer, enhanced skin permeation and penetration were observed for the nanoparticulate formulation, using an ex vivo human-skin-permeation experiment. Whereas free protoporphyrin IX remained located at the outer layer of the skin, nanoparticle-encapsulated protoporphyrin IX was able to penetrate through the epidermal layer slightly into the dermis.

  3. Multi-solution processes of small molecule for flexible white organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, Yu-Sheng, E-mail: ystsai@nfu.edu.tw [Institute of Electro-optical and Materials Science, National Formosa University, Yunlin 63201, Taiwan, ROC (China); Chittawanij, Apisit; Hong, Lin-Ann; Guo, Siou-Wei [Institute of Electro-optical and Materials Science, National Formosa University, Yunlin 63201, Taiwan, ROC (China); Wang, Ching-Chiun [Department of Solid State Lighting Technology, Mechanical and Systems Research Laboratories, Industrial Technology Research Institute, Hsinchu 31040, Taiwan, ROC (China); Juang, Fuh-Shyang [Institute of Electro-optical and Materials Science, National Formosa University, Yunlin 63201, Taiwan, ROC (China); Lai, Shih-Hsiang [Department of Solid State Lighting Technology, Mechanical and Systems Research Laboratories, Industrial Technology Research Institute, Hsinchu 31040, Taiwan, ROC (China); Lin, Yang-Ching [Institute of Electro-optical and Materials Science, National Formosa University, Yunlin 63201, Taiwan, ROC (China)

    2016-04-01

    Most small molecule organic light emitting diode (SM-OLED) device structures are made in one layer using solution-based processing because the solution is usually a high dissolvent material that easily attacks the layer below it. We demonstrate a simple and reliable stamping technique for fabricating multi-solution process flexible white SM-OLEDs. The structure is anode/spin-hole injection layer/spin-emitting layer/stamping-electron transport layer/cathode. Poly(di-methyl silane) (PDMS) stamp is used for transferring electron transport layer. An intermediate ultraviolet-ozone surface treatment is introduced to temporarily modify the PDMS stamp surface. Then, the solution-based electron transport layer film can therefore be uniformly formed on top of the PDMS surface. After that the electron transport layer film on the PDMS stamp is transfer-printed onto the emitting layer with suitable heating and pressing. A solution-based processing is successfully established to efficiently fabricate flexible white SM-OLEDs. The SM-OLEDs were obtained at the current density of 20 mA/cm{sup 2}, luminance of 1062 cd/m{sup 2}, current efficiency of 5.57 cd/A, and Commission internationale de l'éclairage coordinate of (0.32, 0.35). - Highlights: • All solution-processed small molecule materials (emitting layer, electron transport layer). • Poly(di-methylsilane) (PDMS) stamp is subsequently used for stamping transfer. • The flexible white SM-OLEDs are based on solution-processes with a low-cost method.

  4. Hole injection enhancement in organic light emitting devices using plasma treated graphene oxide

    Energy Technology Data Exchange (ETDEWEB)

    Jesuraj, P. Justin; Parameshwari, R. [Centre for Nanoscience and Nanotechnology, School of Physics, Bharathidasan University, Tiruchirappalli, 620 024, Tamil Nadu (India); Kanthasamy, K.; Koch, J. [Institut für Festkörperphysik, ATMOS, Appelstr. 2, D-30167, Hannover (Germany); Pfnür, H. [Institut für Festkörperphysik, ATMOS, Appelstr. 2, D-30167, Hannover (Germany); Laboratorium für Nano- und Quantene$ngineering, Schneiderberg 30, D-30167, Hannover (Germany); Jeganathan, K., E-mail: kjeganathan@yahoo.com [Centre for Nanoscience and Nanotechnology, School of Physics, Bharathidasan University, Tiruchirappalli, 620 024, Tamil Nadu (India)

    2017-03-01

    Graphical abstract: Plasma treated Graphene oxide for hole injection enhancement in OLEDs. - Highlights: • Oxygen (O{sub 2}) and hydrogen (H{sub 2}) plasma exposed graphene oxide (GO) sheets have been demonstrated as hole buffer layers in OLEDs. • O{sub 2} plasma exposure induces assimilation of oxygen contents in GO lattice resulting in improved work function that reduced the hole injection barrier further. Whereas, H{sub 2} plasma contrastingly reduced the GO by excluding oxygen which ensuing lower work function. • X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy investigations reveal the capricious amount of oxygen in GO lattice and its corresponding work function variations. • GO and O{sub 2} plasma treated GO significantly improves the current efficiency of OLEDs more than one order with notable reduction in turn on voltage. - Abstract: The hole injection layer (HIL) with high work function (WF) is desirable to reduce the injection barrier between anode and hole transport layer in organic light emitting devices (OLED). Here, we report a novel approach to tune the WF of graphene oxide (GO) using oxygen and hydrogen plasma treatment and its hole injection properties in OLEDs. The mild exposure of oxygen plasma on GO (O{sub 2}-GO) significantly reduces the injection barrier by increasing the WF of anode (4.98 eV) through expansion of C−O bonds. In contrast, the hole injection barrier was drastically increased for hydrogen plasma treated GO (H{sub 2}-GO) layers as the WF is lowered by the contraction of C−O bond. By employing active O{sub 2}-GO as HIL in OLEDs found to exhibit superior current efficiency of 4.2 cd/A as compared to 3.3 cd/A for pristine GO. Further, the high injection efficiency of O{sub 2}-GO infused hole only device can be attributed to the improved energy level matching. Ultraviolet and X-ray photoelectron spectroscopy were used to correlate the WF of HIL infused anode towards the enhanced performance of

  5. Nanocrystalline silicon as the light emitting material of a field emission display device.

    Science.gov (United States)

    Biaggi-Labiosa, A; Solá, F; Resto, O; Fonseca, L F; González-Berríos, A; De Jesús, J; Morell, G

    2008-06-04

    A nanocrystalline Si-based paste was successfully tested as the light emitting material in a field emission display test device that employed a film of carbon nanofibers as the electron source. Stable emission in the 550-850 nm range was obtained at 16 V µm(-1). This relatively low field required for intense cathodoluminescence (CL) from the PSi paste may lead to longer term reliability of both the electron emitting and the light emitting materials, and to lower power consumption. Here we describe the synthesis, characterization, and analyses of the light emitting nanostructured Si paste and the electron emitting C nanofibers used for building the device, including x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. The corresponding spectra and field emission curves are also shown and discussed.

  6. Characteristics of organic light emitting diodes with copper iodide as injection layer

    Energy Technology Data Exchange (ETDEWEB)

    Stakhira, P., E-mail: stakhira@polynet.lviv.u [Lviv Polytechnic National University, S. Bandera, 12, Lviv, 79013 (Ukraine); Cherpak, V.; Volynyuk, D.; Ivastchyshyn, F. [Lviv Polytechnic National University, S. Bandera, 12, Lviv, 79013 (Ukraine); Hotra, Z. [Lviv Polytechnic National University, S. Bandera, 12, Lviv, 79013 (Ukraine); Rzeszow University of Technology, W. Pola 2, Rzeszow, 35-959 (Poland); Tataryn, V. [Lviv Polytechnic National University, S. Bandera, 12, Lviv, 79013 (Ukraine); Luka, G. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland)

    2010-09-30

    We have studied the use of a thin copper iodide (CuI) film as an efficient injection layer of holes from indium tin oxide (ITO) anode in a light-emitting diode structure based on tris-8-hydroxyquinoline aluminium (Alq3). The results of impedance analysis of two types of diode structures, ITO/CuI/Alq3/poly(ethylene glycol) dimethyl ether/Al and ITO/Alq3/poly(ethylene glycol) dimethyl ether/Al, are presented. Comparative analysis of their current density-voltage, luminance-voltage and impedance characteristics shows that presence of CuI layer facilitates injection of holes from ITO anode into the light-emitting layer Alq3 and increases electroluminescence efficiency of the organic light emitting diodes.

  7. Light emitting diode with high aspect ratio submicron roughness for light extraction and methods of forming

    Science.gov (United States)

    Li, Ting [Ventura, CA

    2011-04-26

    The surface morphology of an LED light emitting surface is changed by applying a reactive ion etch (RIE) process to the light emitting surface. High aspect ratio, submicron roughness is formed on the light emitting surface by transferring a thin film metal hard-mask having submicron patterns to the surface prior to applying a reactive ion etch process. The submicron patterns in the metal hard-mask can be formed using a low cost, commercially available nano-patterned template which is transferred to the surface with the mask. After subsequently binding the mask to the surface, the template is removed and the RIE process is applied for time duration sufficient to change the morphology of the surface. The modified surface contains non-symmetric, submicron structures having high aspect ratio which increase the efficiency of the device.

  8. Light emitting diode with high aspect ratio submicron roughness for light extraction and methods of forming

    Science.gov (United States)

    Li, Ting

    2013-08-13

    The surface morphology of an LED light emitting surface is changed by applying a reactive ion etch (RIE) process to the light emitting surface. High aspect ratio, submicron roughness is formed on the light emitting surface by transferring a thin film metal hard-mask having submicron patterns to the surface prior to applying a reactive ion etch process. The submicron patterns in the metal hard-mask can be formed using a low cost, commercially available nano-patterned template which is transferred to the surface with the mask. After subsequently binding the mask to the surface, the template is removed and the RIE process is applied for time duration sufficient to change the morphology of the surface. The modified surface contains non-symmetric, submicron structures having high aspect ratio which increase the efficiency of the device.

  9. Silicon light-emitting diodes and lasers photon breeding devices using dressed photons

    CERN Document Server

    Ohtsu, Motoichi

    2016-01-01

    This book focuses on a novel phenomenon named photon breeding. It is applied to realizing light-emitting diodes and lasers made of indirect-transition-type silicon bulk crystals in which the light-emission principle is based on dressed photons. After presenting physical pictures of dressed photons and dressed-photon phonons, the principle of light emission by using dressed-photon phonons is reviewed. A novel phenomenon named photon breeding is also reviewed. Next, the fabrication and operation of light emitting diodes and lasers are described The role of coherent phonons in these devices is discussed. Finally, light-emitting diodes using other relevant crystals are described and other relevant devices are also reviewed.

  10. Phototoxic action of light emitting diode in the in vitro viability of Trichophyton rubrum.

    Science.gov (United States)

    Amorim, José Cláudio Faria; Soares, Betania Maria; Alves, Orley Araújo; Ferreira, Marcus Vinícius Lucas; Sousa, Gerdal Roberto; Silveira, Lívio de Barros; Piancastelli, André Costa Cruz; Pinotti, Marcos

    2012-01-01

    Trichophyton rubrum is the most common agent of superficial mycosis of the skin and nails causing long lasting infections and high recurrence rates. Current treatment drawbacks involve topical medications not being able to reach the nail bed at therapeutic concentrations, systemic antifungal drugs failing to eradicate the fungus before the nails are renewed, severe side effects and selection of resistant fungal isolates. Photodynamic therapy (PDT) has been a promising alternative to conventional treatments. This study evaluated the in vitro effectiveness of toluidine blue O (TBO) irradiated by Light emitting diode (LED) in the reduction of T. rubrum viability. The fungal inoculums' was prepared and exposed to different TBO concentrations and energy densities of Light emitting diode for evaluate the T. rubrum sensibility to PDT and production effect fungicidal after photodynamic treatment. In addition, the profiles of the area and volume of the irradiated fungal suspensions were also investigated. A small reduction, in vitro, of fungal cells was observed after exposition to 100 µM toluidine blue O irradiated by 18 J/cm² Light emitting diode. Fungicidal effect occurred after 25 µM toluidine blue O irradiation by Light emitting diode with energy density of 72 J/cm². The analysis showed that the area and volume irradiated by the Light emitting diode were 52.2 mm² and 413.70 mm³, respectively. The results allowed to conclude that Photodynamic therapy using Light emitting diode under these experimental conditions is a possible alternative approach to inhibit in vitro T. rubrum and may be a promising new treatment for dermatophytosis caused by this fungus.

  11. Efficient light emitting devices based on phosphorescent partially doped emissive layers

    KAUST Repository

    Yang, Xiaohui

    2013-05-29

    We report efficient organic light emitting devices employing an ultrathin phosphor emissive layer. The electroluminescent spectra of these devices can be tuned by introducing a low-energy emitting phosphor layer into the emission zone. Devices with the emissive layer consisting of multiple platinum-complex/spacer layer cells show a peak external quantum efficiency of 18.1%, which is among the best EQE values for platinum-complex based light emitting devices. Devices with an ultrathin phosphor emissive layer show stronger luminance decay with the operating time compared to the counterpart devices having a host-guest emissive layer.

  12. Organic light emitting diode with a DNA biopolymer electron blocking layer

    Science.gov (United States)

    Hagen, Joshua A.; Grote, James G.; Li, Wayne X.; Steckl, Andrew J.; Diggs, Darnell E.; Zetts, John S.; Nelson, Robert L.; Hopkins, F. Kenneth

    2006-08-01

    Enhanced electroluminescent efficiency using a deoxyribonucleic acid (DNA)-based biopolymer complex as an electron blocking layer has been demonstrated in both green- and blue-emitting organic light emitting diodes. The resulting bio organic light emitting diodes, or BioLEDs, achieved a maximum luminous efficiency of 8.2 and 0.8 cd/A, respectively, resulting in as much as 10× higher efficiency, 30× brighter output and 3× longer lifetime than their OLED counterparts. In this paper we describe the device fabrication and present the performance of these new structures.

  13. Investigations of thin p-GaN light-emitting diodes

    DEFF Research Database (Denmark)

    Fadil, Ahmed; Ou, Yiyu; Iida, Daisuke

    2016-01-01

    We investigate device performance of InGaN light-emitting diodes with a 30-nm p-GaN layer. The metallization used to separate the p-contact from plasmonic metals, reveals limitations on current spreading which reduces surface plasmonic enhancement.......We investigate device performance of InGaN light-emitting diodes with a 30-nm p-GaN layer. The metallization used to separate the p-contact from plasmonic metals, reveals limitations on current spreading which reduces surface plasmonic enhancement....

  14. Investigations of thin p-GaN light-emitting diodes with surface plasmon compatible metallization

    DEFF Research Database (Denmark)

    Fadil, Ahmed; Ou, Yiyu; Iida, Daisuke

    2016-01-01

    We investigate device performance of InGaN light-emitting diodes with a 30-nm p-GaN layer. The metallization used to separate the p-contact from plasmonic metals, reveals limitations on current spreading which reduces surface plasmonic enhancement.......We investigate device performance of InGaN light-emitting diodes with a 30-nm p-GaN layer. The metallization used to separate the p-contact from plasmonic metals, reveals limitations on current spreading which reduces surface plasmonic enhancement....

  15. Molecular-scale simulation of electroluminescence in a multilayer white organic light-emitting diode

    DEFF Research Database (Denmark)

    Mesta, Murat; Carvelli, Marco; de Vries, Rein J

    2013-01-01

    In multilayer white organic light-emitting diodes the electronic processes in the various layers--injection and motion of charges as well as generation, diffusion and radiative decay of excitons--should be concerted such that efficient, stable and colour-balanced electroluminescence can occur. Here...... we show that it is feasible to carry out Monte Carlo simulations including all of these molecular-scale processes for a hybrid multilayer organic light-emitting diode combining red and green phosphorescent layers with a blue fluorescent layer. The simulated current density and emission profile...

  16. High efficiency and brightness fluorescent organic light emitting diode by triplet-triplet fusion

    Science.gov (United States)

    Forrest, Stephen; Zhang, Yifan

    2015-02-10

    A first device is provided. The first device further comprises an organic light emitting device. The organic light emitting device further comprises an anode, a cathode, and an emissive layer disposed between the anode and the cathode. The emissive layer may include an organic host compound and at least one organic emitting compound capable of fluorescent emission at room temperature. Various configurations are described for providing a range of current densities in which T-T fusion dominates over S-T annihilation, leading to very high efficiency fluorescent OLEDs.

  17. Room-temperature fabrication of light-emitting thin films based on amorphous oxide semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Junghwan, E-mail: JH.KIM@lucid.msl.titech.ac.jp; Miyokawa, Norihiko; Ide, Keisuke [Materials and Structures Laboratory, Tokyo Institute of Technology, Mailbox R3-4, 4259 Nagatsuta, Midori-ku, Yokohama (Japan); Toda, Yoshitake [Materials Research Center for Element Strategy, Tokyo Institute of Technology, Mailbox SE-6, 4259 Nagatsuta, Midori-ku, Yokohama (Japan); Hiramatsu, Hidenori; Hosono, Hideo; Kamiya, Toshio [Materials and Structures Laboratory, Tokyo Institute of Technology, Mailbox R3-4, 4259 Nagatsuta, Midori-ku, Yokohama (Japan); Materials Research Center for Element Strategy, Tokyo Institute of Technology, Mailbox SE-6, 4259 Nagatsuta, Midori-ku, Yokohama (Japan)

    2016-01-15

    We propose a light-emitting thin film using an amorphous oxide semiconductor (AOS) because AOS has low defect density even fabricated at room temperature. Eu-doped amorphous In-Ga-Zn-O thin films fabricated at room temperature emitted intense red emission at 614 nm. It is achieved by precise control of oxygen pressure so as to suppress oxygen-deficiency/excess-related defects and free carriers. An electronic structure model is proposed, suggesting that non-radiative process is enhanced mainly by defects near the excited states. AOS would be a promising host for a thin film phosphor applicable to flexible displays as well as to light-emitting transistors.

  18. Printed assemblies of ultrathin, microscale inorganic light emitting diodes for deformable and semitransparent displays

    Science.gov (United States)

    Rogers, John A.; Nuzzo, Ralph; Kim, Hoon-sik; Brueckner, Eric; Park, Sang Il; Kim, Rak Hwan

    2017-05-09

    Described herein are printable structures and methods for making, assembling and arranging electronic devices. A number of the methods described herein are useful for assembling electronic devices where one or more device components are embedded in a polymer which is patterned during the embedding process with trenches for electrical interconnects between device components. Some methods described herein are useful for assembling electronic devices by printing methods, such as by dry transfer contact printing methods. Also described herein are GaN light emitting diodes and methods for making and arranging GaN light emitting diodes, for example for display or lighting systems.

  19. Measuring the Photocatalytic Breakdown of Crystal Violet Dye using a Light Emitting Diode Approach

    Science.gov (United States)

    Ryan, Robert E.; Underwood, Lauren W.; O'Neal, Duane; Pagnutti, Mary; Davis, Bruce A.

    2009-01-01

    A simple method to estimate the photocatalytic reactivity performance of spray-on titanium dioxide coatings for transmissive glass surfaces was developed. This novel technique provides a standardized method to evaluate the efficiency of photocatalytic material systems over a variety of illumination levels. To date, photocatalysis assessments have generally been conducted using mercury black light lamps. Illumination levels for these types of lamps are difficult to vary, consequently limiting their use for assessing material performance under a diverse range of simulated environmental conditions. This new technique uses an ultraviolet (UV) gallium nitride (GaN) light emitting diode (LED) array instead of a traditional black light to initiate and sustain photocatalytic breakdown. This method was tested with a UV-resistant dye (crystal violet) applied to a titanium dioxide coated glass slide. Experimental control is accomplished by applying crystal violet to both titanium dioxide coated slides and uncoated control slides. A slide is illuminated by the UV LED array, at various light levels representative of outdoor and indoor conditions, from the dye side of the slide. To monitor degradation of the dye over time, a temperature-stabilized white light LED, whose emission spectrum overlaps with the dye absorption spectrum, is used to illuminate the opposite side of the slide. Using a spectrometer, the amount of light from the white light LED transmitted through the slide as the dye degrades is monitored as a function of wavelength and time and is subsequently analyzed. In this way, the rate of degradation for photocatalytically coated versus uncoated slide surfaces can be compared. Results demonstrate that the dye absorption decreased much more rapidly on the photocatalytically coated slides than on the control uncoated slides, and that dye degradation is dependent on illumination level. For photocatalytic activity assessment purposes, this experimental configuration and

  20. Efficient polymer light-emitting diode with air-stable aluminum cathode

    NARCIS (Netherlands)

    Abbaszadeh, Davood; Wetzelaer, G.A.H.; Doumon, Nutifafa Y.; Blom, P.W.M

    2016-01-01

    The fast degradation of polymer light-emitting diodes (PLEDs) in ambient conditions is primarily due to the oxidation of highly reactive metals, such as barium or calcium, which are used as cathode materials. Here, we report the fabrication of PLEDs using an air-stable partially oxidized aluminum

  1. Efficient electron injection from solution-processed cesium stearate interlayers in organic light-emitting diodes

    NARCIS (Netherlands)

    Wetzelaer, G. A. H.; Najafi, A.; Kist, R. J. P.; Kuik, M.; Blom, P. W. M.

    2013-01-01

    The electron-injection capability of solution-processed cesium stearate films in organic light-emitting diodes is investigated. Cesium stearate, which is expected to exhibit good solubility and film formation due to its long hydrocarbon chain, is synthesized using a straightforward procedure.

  2. Hyperbranched red light-emitting phosphorescent polymers based on iridium complex as the core

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Ting; Yu, Lei; Yang, Yong; Li, Yanhu; Tao, Yun [Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640 (China); Hou, Qiong [School of Chemistry & Environment, South China Normal University, Guangzhou 510006 (China); Ying, Lei, E-mail: msleiying@scut.edu.cn [Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640 (China); Yang, Wei; Wu, Hongbin; Cao, Yong [Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640 (China)

    2015-11-15

    A series of hyperbranched π-conjugated light-emitting polymers containing an iridium complex as the branched core unit and polyfluorene or poly(fluorene-alt-carbazole) as the branched segments were synthesized via a palladium catalyzed Suzuki polymerization. Apparent Förster energy transfer in the photoluminescent spectra as thin films was observed, while no discernible characteristic absorbance and photoluminescence of the iridium complex can be realized in dilute solutions. Copolymers based on poly(fluorene-alt-carbazole) as the branched segments demonstrated enhanced highest occupied molecular orbital energy levels relative to those based on polyfluorene. The electroluminescent spectra of these copolymers exclusively showed the characteristic emission of the iridium complex, with corresponding CIE coordinates of (0.67±0.01, 0.31). All devices exhibited relatively slow roll-off of efficiency, and the best device performance with the maximum luminous efficiency of 5.33 cd A{sup −1} was attained by using PFCzTiqIr3 as the emissive layer. These results indicated that the hyperbranched conjugated architectures can be a promising molecular design strategy for efficient electrophosphorescent light-emitting polymers. - Highlights: • Hyperbranched red light-emitting polymers are synthesized. • Red light-emitting iridium complex is used as the branched core unit. • Hyperbranched polymers based on PFCz exhibit higher luminescence. • The highest luminous efficiency of 5.33 cd A{sup −1} is attained.

  3. Topology optimisation of passive coolers for light-emitting diode lamps

    DEFF Research Database (Denmark)

    Alexandersen, Joe

    2015-01-01

    This work applies topology optimisation to the design of passive coolers for light-emitting diode (LED) lamps. The heat sinks are cooled by the natural convection currents arising from the temperature difference between the LED lamp and the surrounding air. A large scale parallel computational...

  4. Hand-Drawn Resistors and a Simple Tester Using a Light-Emitting Diode

    Science.gov (United States)

    Kamata, Masahiro; Abe, Mayumi

    2012-01-01

    A thick line drawn on a sheet of paper with a 6B pencil is electrically conductive and its resistance can be roughly estimated using a simple tester made of a light-emitting diode (LED) and a lithium coin-type cell. Using this hand-drawn resistor and the LED tester, we developed teaching materials that help students to understand how electrical…

  5. Charge transport and recombination in polyspirobifluorene blue light-emitting diodes

    NARCIS (Netherlands)

    Nicolai, H.T.; Hof, A.; Oosthoek, J.L.M.; Blom, P.W.M.

    2011-01-01

    The charge transport in blue light-emitting polyspirobifluorene is investigated by both steady-state current-voltage measurements and transient electroluminescence. Both measurement techniques yield consistent results and show that the hole transport is space-charge limited. The electron current is

  6. Charge Transport and Recombination in Polyspirobifluorene Blue Light-Emitting Diodes

    NARCIS (Netherlands)

    Nicolai, Herman T.; Hof, Andre; Oosthoek, Jasper L. M.; Blom, Paul W. M.

    2011-01-01

    The charge transport in blue light-emitting polyspirobifluorene is investigated by both steady-state current-voltage measurements and transient electroluminescence. Both measurement techniques yield consistent results and show that the hole transport is space-charge limited. The electron current is

  7. Monolithically integrated Si gate-controlled light-emitting device: science and properties

    Science.gov (United States)

    Xu, Kaikai

    2018-02-01

    The motivation of this study is to develop a p–n junction based light emitting device, in which the light emission is conventionally realized using reverse current driving, by voltage driving. By introducing an additional terminal of insulated gate for voltage driving, a novel three-terminal Si light emitting device is described where both the light intensity and spatial light pattern of the device are controlled by the gate voltage. The proposed light emitting device employs injection-enhanced Si in avalanche mode where electric field confinement occurs in the corner of a reverse-biased p+n junction. It is found that, depending on the bias conditions, the light intensity is either a linear or a quadratic function of the applied gate voltage or the reverse-bias. Since the light emission is based on the avalanching mode, the Si light emitting device offers the potential for very large scale integration-compatible light emitters for inter- or intra-chip signal transmission and contactless functional testing of wafers.

  8. Medical applications of space light-emitting diode technology-space station and beyond

    Science.gov (United States)

    Whelan, Harry T.; Houle, John M.; Donohoe, Deborah L.; Bajic, Dawn M.; Schmidt, Meic H.; Reichert, Kenneth W.; Weyenberg, George T.; Larson, David L.; Meyer, Glenn A.; Caviness, James A.

    1999-01-01

    Space light-emitting diode (LED) technology has provided medicine with a new tool capable of delivering light deep into tissues of the body, at wavelengths which are biologically optimal for cancer treatment and wound healing. This LED technology has already flown on Space Shuttle missions, and shows promise for wound healing applications of benefit to Space Station astronauts.

  9. Red for LED : New narrow band red phosphors for white light emitting diodes

    NARCIS (Netherlands)

    Senden, T.|info:eu-repo/dai/nl/37060217X

    2018-01-01

    White light emitting diodes (LEDs) are nowadays widely applied in general lighting and consumer electronics. Due to their superior energy efficiency and long operation lifetime, white LEDs are considered to be the light sources of the future, and it is anticipated that white LEDs will largely

  10. Finding the Average Speed of a Light-Emitting Toy Car with a Smartphone Light Sensor

    Science.gov (United States)

    Kapucu, Serkan

    2017-01-01

    This study aims to demonstrate how the average speed of a light-emitting toy car may be determined using a smartphone's light sensor. The freely available Android smartphone application, "AndroSensor," was used for the experiment. The classroom experiment combines complementary physics knowledge of optics and kinematics to find the…

  11. Medical Applications of Space Light-Emitting Diode Technology--Space Station and Beyond

    Energy Technology Data Exchange (ETDEWEB)

    Whelan, H.T.; Houle, J.M.; Donohoe, D.L.; Bajic, D.M.; Schmidt, M.H.; Reichert, K.W.; Weyenberg, G.T.; Larson, D.L.; Meyer, G.A.; Caviness, J.A.

    1999-06-01

    Space light-emitting diode (LED) technology has provided medicine with a new tool capable of delivering light deep into tissues of the body, at wavelengths which are biologically optimal for cancer treatment and wound healing. This LED technology has already flown on Space Shuttle missions, and shows promise for wound healing applications of benefit to Space Station astronauts.

  12. Bias-dependent current efficiency in polymer light-emitting diodes

    NARCIS (Netherlands)

    van Woudenbergh, T; Wildeman, J; Blom, PWM

    The current efficiency (CE) of single-layer poly-p-phenylene vinylene-based light-emitting diodes (PLEDs) at low voltages is poor and strongly bias dependent, which has been attributed to the quenching of excitons at the metallic cathode. In the absence of exciton quenching the CE is expected to be

  13. Two-phase cooling of light emitting diode for higher light output and increased efficiency

    NARCIS (Netherlands)

    Ye, H.; Mihailovic, M.; Wong, C.K.Y.; Zeijl, H.W. van; Gielen, A.W.J.; Zhang, G.Q.; Sarro, P.M.

    2013-01-01

    High Power Light Emitting Diode (HP LED) is one of the promising candidates for future lighting systems with efficient energy consumption. However, around 70% of the input power will be still transferred to heat. Recently, to obtain more light output, the increased electrical currents consequently

  14. Electron-enhanced hole injection in blue polyfluorene-based polymer light-emitting diodes

    NARCIS (Netherlands)

    Woudenbergh, T. van; Wildeman, J.; Blom, P.W.M.; Bastiaansen, J.J.A.M.; Langeveld-Voss, B.M.W.

    2004-01-01

    It has recently been reported that, after electrical conditioning, an ohmic hole contact is formed in poly(9,9-dioctylfluorene) (PFO)-based polymer light-emitting diodes (PLED), despite the large hole-injection barrier obtained with a poly(styrene sulfonic acid)-doped

  15. Hole-enhanced electron injection from ZnO in inverted polymer light-emitting diodes

    NARCIS (Netherlands)

    Lu, Mingtao; de Bruyn, Paul; Nicolai, Herman T.; Wetzelaer, Gert-Jan A. H.; Blom, Paul W. M.

    Metal oxides as ZnO provide an interesting alternative for conventional low work function metals as electron injection layer in organic light-emitting diodes (OLEDs). However, for most state-of-the-art OLED materials the high work function of ZnO leads to a large injection barrier for electrons. As

  16. Novel integration of a microchannel with a silicon light emitting diode antifuse

    NARCIS (Netherlands)

    Le Minh, P.; Holleman, J.; Wallinga, Hans; Berenschot, Johan W.; Tas, Niels Roelof; van den Berg, Albert

    Light emitting diode antifuses have been integrated into a microfluidic device that is realized with extended standard IC-compatible technological steps. The device comprises a microchannel sandwiched between a photodiode detector and a nanometre-scale diode antifuse light emitter. In this paper,

  17. Investigating Bandgap Energies, Materials, and Design of Light-Emitting Diodes

    Science.gov (United States)

    Wagner, Eugene P., II

    2016-01-01

    A student laboratory experiment to investigate the intrinsic and extrinsic bandgaps, dopant materials, and diode design in light-emitting diodes (LEDs) is presented. The LED intrinsic bandgap is determined by passing a small constant current through the diode and recording the junction voltage variation with temperature. A second visible…

  18. Optimization of light quality from color mixing light-emitting diode systems for general lighting

    DEFF Research Database (Denmark)

    Thorseth, Anders

    2012-01-01

    To address the problem of spectral light quality from color mixing light-emitting diode systems, a method for optimizing the spectral output of multicolor LED system with regards to standardized quality parameters has been developed. The composite spectral power distribution from the LEDs...... boundaries mapping the capabilities of the simulated lighting system....

  19. Monolithic integration of a novel microfluidic device with silicon light emitting diode-antifuse and photodetector

    NARCIS (Netherlands)

    Le Minh, P.; Holleman, J.; Berenschot, Johan W.; Tas, Niels Roelof; van den Berg, Albert

    2002-01-01

    Light emitting diode antifuse has been integrated into a microfluidic device that is realized with extended standard CMOS technological steps. The device comprises of a microchannel sandwiched between a photodiode detector and a nanometer-scale diode antifuse light emitter. Within this contribution,

  20. Patterning of Flexible Organic Light Emitting Diode (FOLED) stack using an ultrafast laser

    NARCIS (Netherlands)

    Mandamparambil, R.; Fledderus, H.; Steenberge, G.V.; Dietzel, A.H.

    2010-01-01

    A femtosecond laser has been successfully utilized for patterning thin Flexible Organic Light Emitting Diode (FOLED) structures of individual layer thickness around 100nm. The authors report in this paper a step-like ablation behavior at the layer interfaces which accounts for a local removal of

  1. Integration of a novel microfluidic device with silicon light emitting diode-antifuse and photodetector

    NARCIS (Netherlands)

    Le Minh, P.; Holleman, J.; Berenschot, Johan W.; Tas, Niels Roelof; van den Berg, Albert

    2002-01-01

    Light emitting diode antifuse has been integrated into a microfluidic device that is realized with extended standard CMOS technological steps. The device comprises of a microchannel sandwiched between a photodiode detector and a nanometer-scale diode antifuse light emitter. Within this contribution,

  2. Photodynamic effect of light-emitting diode light on cell growth ...

    Indian Academy of Sciences (India)

    The aim of this study was to propose the use of red light-emitting diode (LED) as an alternative light source for methylene blue (MB) photosensitizing effect in photodynamic therapy (PDT). Its effectiveness was tested against Staphylococcus aureus (ATCC 26923), Escherichia coli (ATCC 26922), Candida albicans (ATCC ...

  3. Hole transport in poly(p-phenylene vinylene) based light-emitting diodes revisited

    NARCIS (Netherlands)

    Tanase, C; Blom, PWM; de Leeuw, DM; Kafafi, ZH; Lane, PA

    2004-01-01

    Understanding of the charge transport properties is of great importance for the operation and the efficiency of polymer based light-emitting diodes (LEDs). We investigate the charge transport in hole-only diodes based on poly(p-phenylene vinylene) (PPV) as function of temperature T, charge carrier

  4. Deep blue polymer light emitting diodes based on easy to synthesize, non-aggregating polypyrene

    NARCIS (Netherlands)

    Trattnig, Roman; Figueira-Duarte, Teresa M.; Lorbach, Dominik; Wiedemair, Wolfgang; Sax, Stefan; Winkler, Stefanie; Vollmer, Antje; Koch, Norbert; Manca, Marianna; Loi, Maria Antonietta; Baumgarten, Martin; List, Emil J. W.; Muellen, Klaus; Müllen, Klaus

    2011-01-01

    Thorough analyses of the photo- and devicephysics of poly-7-tert-butyl-1,3-pyrenylene (PPyr) by the means of absorption and photoluminescence emission, time resolved photoluminescence and photoinduced absorption spectroscopy as well as organic light emitting devices (OLEDs) are presented in this

  5. Indium contamination from the indium-tin-oxide electrode in polymer light-emitting diodes

    NARCIS (Netherlands)

    Schlatmann, A.R.; Floet, D.W.; Hilberer, A; Garten, F; Smulders, P.J M; Klapwijk, T.M; Hadziioannou, G

    1996-01-01

    We have found that polymer light-emitting diodes (LEDs) contain high concentrations of metal impurities prior to operation. Narrow peaks in the electroluminescence spectrum unambiguously demonstrate the presence of atomic indium and aluminum. Rutherford backscattering spectroscopy (RBS) and x-ray

  6. Exciton quenching at PEDOT:PSS anode in polymer blue-light-emitting diodes

    NARCIS (Netherlands)

    Abbaszadeh, D.; Wetzelaer, G.A.H.; Nicolai, H.T.; Blom, P.W.M.

    2014-01-01

    The quenching of excitons at the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) PEDOT:PSS) anode in blue polyalkoxyspirobifluorene-arylamine polymer light-emitting diodes is investigated. Due to the combination of a higher electron mobility and the presence of electron traps, the

  7. Exciton quenching at PEDOT : PSS anode in polymer blue-light-emitting diodes

    NARCIS (Netherlands)

    Abbaszadeh, D.; Wetzelaer, G. A. H.; Nicolai, H. T.; Blom, P. W. M.

    2014-01-01

    The quenching of excitons at the poly(3,4-ethylenedioxythiophene): poly(styrenesulfonic acid) (PEDOT:PSS) anode in blue polyalkoxyspirobifluorene-arylamine polymer light-emitting diodes is investigated. Due to the combination of a higher electron mobility and the presence of electron traps, the

  8. Influence of interface recombination in light emission from lateral Si-based light emitting devices

    NARCIS (Netherlands)

    Le Minh, P.; Hoang, T.; Holleman, J.; Schmitz, Jurriaan

    2006-01-01

    The influence of interface recombination on the electroluminescence profile of a lateral p+/p/n+ light emitting diode fabricated on Silicon On Insulator (SOI) materials has been experimentally investigated. Our device resembles a MOSFET fabricated on SOI, except that the source region has opposite

  9. Color Shift Modeling of Light-Emitting Diode Lamps in Step-Loaded Stress Testing

    NARCIS (Netherlands)

    Cai, Miao; Yang, Daoguo; Huang, J.; Zhang, Maofen; Chen, Xianping; Liang, Caihang; Koh, S.W.; Zhang, G.Q.

    2017-01-01

    The color coordinate shift of light-emitting diode (LED) lamps is investigated by running three stress-loaded testing methods, namely step-up stress accelerated degradation testing, step-down stress accelerated degradation testing, and constant stress accelerated degradation testing. A power

  10. All-solution processed polymer light-emitting diodes with air stable metal-oxide electrodes

    NARCIS (Netherlands)

    de Bruyn, P.; Moet, D. J. D.; Blom, P. W. M.

    We present an all-solution processed polymer light-emitting diode (PLED) using spincoated zinc oxide (ZnO) and vanadium pentoxide (V2O5) as electron and hole injecting contact, respectively. We compare the performance of these devices to the standard PLED design using PEDOT:PSS as anode and Ba/Al as

  11. Outsmarting waveguide losses in thin-film light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Meerholz, K.; Mueller, D.C. [Muenchen Univ. (Germany). Chemistry Dept.

    2001-08-01

    Several attempts to overcome the problem of waveguide losses in light-emitting diodes (LEDs) have been made over past few years. This article summarizes the most important developments in this area and specifically highlights one attempt, achieved by Tsutsui et al. and published in the latest issue of Advanced Materials. (orig.)

  12. Bright infrared quantum-dot light-emitting diodes through inter-dot spacing control

    KAUST Repository

    Sun, Liangfeng

    2012-05-06

    Infrared light-emitting diodes are currently fabricated from direct-gap semiconductors using epitaxy, which makes them expensive and difficult to integrate with other materials. Light-emitting diodes based on colloidal semiconductor quantum dots, on the other hand, can be solution-processed at low cost, and can be directly integrated with silicon. However, so far, exciton dissociation and recombination have not been well controlled in these devices, and this has limited their performance. Here, by tuning the distance between adjacent PbS quantum dots, we fabricate thin-film quantum-dot light-emitting diodes that operate at infrared wavelengths with radiances (6.4 W sr \\'1 m \\'2) eight times higher and external quantum efficiencies (2.0%) two times higher than the highest values previously reported. The distance between adjacent dots is tuned over a range of 1.3 nm by varying the lengths of the linker molecules from three to eight CH 2 groups, which allows us to achieve the optimum balance between charge injection and radiative exciton recombination. The electroluminescent powers of the best devices are comparable to those produced by commercial InGaAsP light-emitting diodes. By varying the size of the quantum dots, we can tune the emission wavelengths between 800 and 1,850 nm.© 2012 Macmillan Publishers Limited.

  13. All-solution processed polymer light-emitting diodes with air stable metal-oxide electrodes

    NARCIS (Netherlands)

    Bruyn, P. de; Moet, D.J.D.; Blom, P.W.M.

    2012-01-01

    We present an all-solution processed polymer light-emitting diode (PLED) using spincoated zinc oxide (ZnO) and vanadium pentoxide (V2O5) as electron and hole injecting contact, respectively. We compare the performance of these devices to the standard PLED design using PEDOT:PSS as anode and Ba/Al as

  14. Non-radiative recombination losses in polymer light-emitting diodes

    NARCIS (Netherlands)

    Kuik, M.; Koster, L.J.A.; Dijkstra, A.G.; Wetzelaer, G.A.H.; Blom, P.W.M.

    2012-01-01

    We present a quantitative analysis of the loss of electroluminescence in light-emitting diodes (LEDs) based on poly[2-methoxy-5-(2′-ethylhexyloxy)- p-phenylenevinylene] (MEH-PPV) due to the combination of non-radiative trap-assisted recombination and exciton quenching at the metallic cathode. It is

  15. Ultra-thin ohmic contacts for p-type nitride light emitting devices

    Science.gov (United States)

    Raffetto, Mark [Raleigh, NC; Bharathan, Jayesh [Cary, NC; Haberern, Kevin [Cary, NC; Bergmann, Michael [Chapel Hill, NC; Emerson, David [Chapel Hill, NC; Ibbetson, James [Santa Barbara, CA; Li, Ting [Ventura, CA

    2012-01-03

    A semiconductor based Light Emitting Device (LED) can include a p-type nitride layer and a metal ohmic contact, on the p-type nitride layer. The metal ohmic contact can have an average thickness of less than about 25 .ANG. and a specific contact resistivity less than about 10.sup.-3 ohm-cm.sup.2.

  16. Polymer solar cells and infrared light emitting diodes : Dual function low bandgap polymer

    NARCIS (Netherlands)

    Winder, C.; Mühlbacher, D.; Neugebauer, H.; Sariciftci, N.S.; Brabec, C.J.; Janssen, R.A.J.; Hummelen, J.C.

    2002-01-01

    Conjugated Polymers with a HOMO-LUMO transition <2eV, i.e. a low bandgap, respectively, have interesting and desired properties for some thin film optoelectronic devices like light emitting diodes and solar cells. In this contribution we present the implementation of the novel copolymer PTPTB,

  17. Determination of the trap-assisted recombination strength in polymer light emitting diodes

    NARCIS (Netherlands)

    Kuik, M.; Nicolai, H.T.; Lenes, M.; Wetzelaer, G.-J.A.H.; Lu, M.; Blom, P.W.M.

    2011-01-01

    The recombination processes in poly(p -phenylene vinylene) based polymer light-emitting diodes (PLEDs) are investigated. Photogenerated current measurements on PLED device structures reveal that next to the known Langevin recombination also trap-assisted recombination is an important recombination

  18. Trap-assisted and Langevin-type recombination in organic light-emitting diodes

    NARCIS (Netherlands)

    Wetzelaer, G. A. H.; Kuik, M.; Nicolai, H. T.; Blom, P. W. M.

    2011-01-01

    Trapping of charges is known to play an important role in the charge transport of organic semiconductors, but the role of traps in the recombination process has not been addressed. Here we show that the ideality factor of the current of organic light-emitting diodes (OLEDs) in the

  19. Electrical-thermal-luminous-chromatic model of phosphor-converted white light-emitting diodes

    NARCIS (Netherlands)

    Ye, H.; Koh, S.W.; Yuan, C.; Zeijl, H. van; Gielen, A.W.J.; Lee, S.W.R.; Zhang, G.

    2014-01-01

    The drive of increased electrical currents to achieve high luminous output for phosphor-converted white light-emitting diodes (PW-LED) has led to a series of thermal problems. The light performance of PW-LED is affected by the heat generated by the two major sources in a package/module: chip(s) and

  20. Finding the Acceleration and Speed of a Light-Emitting Object on an Inclined Plane with a Smartphone Light Sensor

    Science.gov (United States)

    Kapucu, Serkan

    2017-01-01

    This study investigates how the acceleration and speed of a light-emitting object on an inclined plane may be determined using a smartphone's light sensor. A light-emitting object was released from the top of an inclined plane and its illuminance values were detected by a smartphone's light sensor during its subsequent motion down the plane. Using…

  1. 76 FR 51396 - Certain Light-Emitting Diodes and Products Containing Same; Notice of Institution of Investigation

    Science.gov (United States)

    2011-08-18

    ... COMMISSION Certain Light-Emitting Diodes and Products Containing Same; Notice of Institution of Investigation... importation, and the sale within the United States after importation of certain light-emitting diodes and...- emitting diodes and products containing same that infringe one or more of claims 1, 3, 5-10, and 13-16 of...

  2. 77 FR 807 - Certain Light-Emitting Diodes and Products Containing the Same; Determination Not To Review...

    Science.gov (United States)

    2012-01-06

    ... COMMISSION Certain Light-Emitting Diodes and Products Containing the Same; Determination Not To Review... importation, sale for importation, and sale within the United States after importation of certain light-emitting diodes and products containing same by ] reason of infringement of certain claims of U.S. Patent...

  3. 76 FR 52348 - Certain Light-Emitting Diodes and Products Containing Same; Corrected Notice of Institution of...

    Science.gov (United States)

    2011-08-22

    ... COMMISSION Certain Light-Emitting Diodes and Products Containing Same; Corrected Notice of Institution of... importation, or the sale within the United States after importation of certain light- emitting diodes and...-emitting diodes and products containing same by reason of infringement of certain claims of U.S. Patent No...

  4. 76 FR 77552 - Certain Light-Emitting Diodes and Products Containing Same; Determination Not To Review an...

    Science.gov (United States)

    2011-12-13

    ... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION Certain Light-Emitting Diodes and Products Containing Same; Determination Not To Review an Initial... importation of certain light-emitting diodes and products containing same by reason of infringement of certain...

  5. 77 FR 56672 - Certain Light-Emitting Diodes and Products Containing the Same; Determination To Review a Final...

    Science.gov (United States)

    2012-09-13

    ... Light-Emitting Diodes and Products Containing the Same; Determination To Review a Final Initial... importation of certain light-emitting diodes and products containing same by reason of infringement of certain... Office (see RX-118) and USPTO (see RX-10002), show that JP 609 teaches a ``partial conversion'' of light...

  6. 77 FR 75446 - Certain Light-Emitting Diodes and Products Containing the Same; Commission Determination To Grant...

    Science.gov (United States)

    2012-12-20

    ... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION Certain Light-Emitting Diodes and Products Containing the Same; Commission Determination To Grant... importation of certain light-emitting diodes and products containing same by reason of infringement of certain...

  7. Preliminary evaluation of discomfort glare from organic light-emitting diode and edge-lit light-emitting diode lighting panels.

    Science.gov (United States)

    Mou, Xi; Freyssinier, Jean Paul; Narendran, Nadarajah; Bullough, John D

    2017-05-01

    The organic light-emitting diode (OLED) is an area light source, and its primary competing technology is the edge-lit light-emitting diode (LED) panel. Both technologies are similar in shape and appearance, but there is little understanding of how people perceive discomfort glare (DG) from area sources. The objective of this study was to evaluate the DG of these two technologies under similar operating conditions. Additionally, two existing DG models were compared to evaluate the correlation between predicted values and observed values. In an earlier study, we found no statistically significant difference in human response in terms of DG between OLED and edge-lit LED panels when the two sources produced the same luminous stimulus. The range of testing stimulus was expanded to test different panel luminances at three background illuminations. The results showed no difference in perceived glare between the panels, and, as the background illumination increased, the perceived glare decreased. In other words, both appeared equally glary beyond a certain luminance and background illumination. We then compared two existing glare models with the observed values and found that one model showed a good estimation of how humans perceive DG. That model was further modified to increase its power.

  8. Effect of heterostructure design on carrier injection and emission characteristics of 295 nm light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Mehnke, Frank, E-mail: mehnke@physik.tu-berlin.de; Kuhn, Christian; Stellmach, Joachim; Rothe, Mark-Antonius; Reich, Christoph; Ledentsov, Nikolay; Pristovsek, Markus; Wernicke, Tim [Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstr. 36, EW 6-1, 10623 Berlin (Germany); Kolbe, Tim; Lobo-Ploch, Neysha; Rass, Jens [Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin (Germany); Kneissl, Michael [Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstr. 36, EW 6-1, 10623 Berlin (Germany); Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin (Germany)

    2015-05-21

    The effects of the heterostructure design on the injection efficiency and external quantum efficiency of ultraviolet (UV)-B light emitting diodes (LEDs) have been investigated. It was found that the functionality of the Al{sub x}Ga{sub 1−x}N:Mg electron blocking layer is strongly influenced by its aluminum mole fraction x and its magnesium doping profile. By comparing LED electroluminescence, quantum well photoluminescence, and simulations of LED heterostructure, we were able to differentiate the contributions of injection efficiency and internal quantum efficiency to the external quantum efficiency of UV LEDs. For the optimized heterostructure using an Al{sub 0.7}Ga{sub 0.3}N:Mg electron blocking layer with a Mg to group III ratio of 4% in the gas phase the electron leakage currents are suppressed without blocking the injection of holes into the multiple quantum well active region. Flip chip mounted LED chips have been processed achieving a maximum output power of 3.5 mW at 290 mA and a peak external quantum efficiency of 0.54% at 30 mA.

  9. Improved efficiency of organic light-emitting diodes with self-assembled molybdenum oxide hole injection layers

    Science.gov (United States)

    Liu, Chia-Wei; Tsai, Ming-Chih; Cheng, Tsung-Chin; Ho, Yu-Hsuan; You, Huang-kuo; Li, Chia-Shuo; Chen, Chin-Ti; Wu, Chih-I.

    2017-05-01

    In this paper, we demonstrate the use of self-assembly to fabricate solution-processed molybdenum oxide (MoO3) films by simply casting a metal oxide solution onto an indium tin oxide substrate. The self-assembled MoO3 (SA-MoO3) films were used as hole injection layers (HILs) in green phosphorescent organic light-emitting diodes. The devices with SA-MoO3 HILs exhibited nearly double the efficiency of the one made with commonly used evaporated MoO3 (e-MoO3) HILs. This improvement was attributed to the much smoother surface and smaller grains of the SA-MoO3 films to reduce the leakage currents, as shown by monitoring the surface morphology via atomic force microscopy and scanning electron microscopy. The work function and Mo 3d core level characteristics were determined via ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy. The e-MoO3 film offered better conductivity and hole injection ability; however, the increased device current may not enhance electroluminance proportionally. As a result, the efficiencies of SA-MoO3 devices were better than those of e-MoO3 devices.

  10. A Systematic Review of Light Emitting Diode (LED) Phototherapy for Treatment of Psoriasis: An Emerging Therapeutic Modality.

    Science.gov (United States)

    Ho, Derek; Koo, Eugene; Mamalis, Andrew; Jagdeo, Jared

    2017-05-01

    Background: Psoriasis is a chronic, inflammatory skin condition. The economic burden of psoriasis is approximately $35.2 billion in the United States per year, and treatment costs are increasing at a higher rate than general inflation. Light emitting diode (LED) phototherapy may represent a cost-effective, efficacious, safe, and portable treatment modality for psoriasis. Objective: The goal of our manuscript is to review the published literature and provide evidence-based recommendations on LED phototherapy for the treatment of psoriasis. Methods & Materials: A search of the databases Pubmed, EMBASE, Web of Science, and CINAHL was performed on April 5, 2016. Key search terms were related to psoriasis and LED-based therapies. Results: A total of 7,793 articles were generated from the initial search and 5 original articles met inclusion criteria for our review. Grade of recommendation: B for LED-blue light. Grade of recommendation: C for LED-ultraviolet B, LED-red light, and combination LED-near-infrared and LED-red light. Conclusion: We envision further characterizing the effects of LED phototherapy to treat psoriasis in patients may increase adoption of LED-based modalities and provide clinicians and patients with new therapeutic options that balance safety, efficacy, and cost. J Drugs Dermatol. 2017;16(5):482-488..

  11. Efficient deep-blue organic light-emitting diodes with a 1,4-(dinaphthalen-2-yl)-naphthalene.

    Science.gov (United States)

    Seo, Ji Hoon; Lee, Seok Jae; Hyung, Gun Woo; Lee, Kum Hee; Park, Jung Keun; Yoon, Seung Soo; Kim, Young Kwan

    2011-07-01

    Deep-blue organic light-emitting diodes (OLEDs) with nearly 5% external quantum efficiency were demonstrated using a 1,4-(dinaphthalen-2-yl)-naphthalene (DNN) host. The 4,4'-bis(9-ethyl-3-carbazovinylene)-1,1'-biphenyl (BCzVBi) dopant that was used in this experiment effectively accepted energy from the DNN host via Förster energy transfer because the photoluminescence spectrum of the DNN host showed better spectra overlap with the ultraviolet-visible (UV-vis) absorption spectrum of the BCzVBi dopant than the photoluminescence spectrum of the 2-methyl-9,10-bis(naphthalen-2-yl)anthracene host did. Moreover, the DNN host had a higher energy bandgap (3.5 eV) than the BCzVBi dopant did (3.0 eV), while the MADN host had the same energy bandgap as the BCzVBi dopant. The optimized deep-blue device also had ETL of bis-(2-methyl-8-quinolinolate)-4-(phenylphenolato)aluminium which showed smoother sigma of 0.6 nm and higher Tg of 92 degrees than those of 4,7-diphenyl-1,10-phenanthroline (14.8 nm and 62 degrees C). The deep-blue device exhibited a peak current efficiency of 5.68 cd/A, a peak external quantum efficiency of 4.89%, and Commission Internationale d' Eclairage coordinates of (0.15, 0.13).

  12. Rapid microwave-assisted synthesis of highly luminescent nitrogen-doped carbon dots for white light-emitting diodes

    Science.gov (United States)

    Wang, Yaling; Zheng, Jingxia; Wang, Junli; Yang, Yongzhen; Liu, Xuguang

    2017-11-01

    Highly luminescent nitrogen-doped carbon dots (N-CDs) were synthesized rapidly by one-step microwave-assisted hydrothermal method using citric acid as carbon source and ethylenediamine as dopant. The influences of reaction temperature, reaction time and raw material ratio on the fluorescence performance of N-CDs were investigated. Then N-CDs with the highest quantum yield were selected as fluorescent materials for fabricating white light-emitting diodes (LEDs). Highly luminescent N-CDs with the quantum yield of 75.96% and blue-to-red spectral composition of 51.48% were obtained at the conditions of 180 °C, 8 min and the molar ratio of citric acid to ethylenediamine 2:1. As-prepared highly luminescent N-CDs have an average size of 6.06 nm, possess extensive oxygen- and nitrogen-containing functional groups on their surface, and exhibit strong absorption in ultraviolet region. White LEDs based on the highly luminescent N-CDs emit warm white light with color coordinates of (0.42, 0.40) and correlated color temperature of 3416 K.

  13. Zinc silicates with tunable morphology by surfactant assisted sonochemical route suitable for NUV excitable white light emitting diodes.

    Science.gov (United States)

    Basavaraj, R B; Nagabhushana, H; Daruka Prasad, B; Vijayakumar, G R

    2017-01-01

    The cationic surfactants assisted ultrasound route was used to prepare Dy(3+) doped Zn2SiO4 nanophosphors. The final products were characterized by powder X-ray diffraction (PXRD), ultraviolet visible spectroscopy, scanning electron microscopy, transmission electron microscopy and photoluminescence. Orthorhombic phase of Zn2SiO4:Dy(3+) (JCPDS card No. 35-1485) was confirmed from PXRD. It was evident that the morphology of spherical and broom like structures were obtained with epigallocatechin gallate (EGCG) and cetyltrimethylammonium bromide (CTAB) surfactants respectively. Further the size and agglomeration of the products were varied with surfactants concentration, sonication time, pH and sonication power. The probable formation mechanisms to obtain various micro/nano superstructures were discussed. The characteristic PL peaks were observed at 484, 574 and 666nm due to the electronic transitions (4)F9/2→(6)Hj (j=15/2, 13/2, 11/2) of Dy(3+) ions upon excited at NUV pumping wavelength of 350nm [(6)H15/2→(6)P7/2 ((4)M15/2)]. The Judd-Ofelt intensity parameters and radiative properties were estimated by using PL emission data. The photometric studies indicated that the obtained phosphors could be promising materials in white light emitting diodes (wLED's). The present synthesis route was rapid, environmentally benign, cost-effective and useful for industrial applications such as solid state lighting and display devices. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Semiconductor Nanowire Light-Emitting Diodes Grown on Metal: A Direction Toward Large-Scale Fabrication of Nanowire Devices.

    Science.gov (United States)

    Sarwar, A T M Golam; Carnevale, Santino D; Yang, Fan; Kent, Thomas F; Jamison, John J; McComb, David W; Myers, Roberto C

    2015-10-28

    Bottom-up nanowires are attractive for realizing semiconductor devices with extreme heterostructures because strain relaxation through the nanowire sidewalls allows the combination of highly lattice mismatched materials without creating dislocations. The resulting nanowires are used to fabricate light-emitting diodes (LEDs), lasers, solar cells, and sensors. However, expensive single crystalline substrates are commonly used as substrates for nanowire heterostructures as well as for epitaxial devices, which limits the manufacturability of nanowire devices. Here, nanowire LEDs directly grown and electrically integrated on metal are demonstrated. Optical and structural measurements reveal high-quality, vertically aligned GaN nanowires on molybdenum and titanium films. Transmission electron microscopy confirms the composition variation in the polarization-graded AlGaN nanowire LEDs. Blue to green electroluminescence is observed from InGaN quantum well active regions, while GaN active regions exhibit ultraviolet emission. These results demonstrate a pathway for large-scale fabrication of solid state lighting and optoelectronics on metal foils or sheets. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Quantum-Dot Light-Emitting Diodes with Nitrogen-Doped Carbon Nanodot Hole Transport and Electronic Energy Transfer Layer

    Science.gov (United States)

    Park, Young Ran; Jeong, Hu Young; Seo, Young Soo; Choi, Won Kook; Hong, Young Joon

    2017-04-01

    Electroluminescence efficiency is crucial for the application of quantum-dot light-emitting diodes (QD-LEDs) in practical devices. We demonstrate that nitrogen-doped carbon nanodot (N-CD) interlayer improves electrical and luminescent properties of QD-LEDs. The N-CDs were prepared by solution-based bottom up synthesis and were inserted as a hole transport layer (HTL) between other multilayer HTL heterojunction and the red-QD layer. The QD-LEDs with N-CD interlayer represented superior electrical rectification and electroluminescent efficiency than those without the N-CD interlayer. The insertion of N-CD layer was found to provoke the Förster resonance energy transfer (FRET) from N-CD to QD layer, as confirmed by time-integrated and -resolved photoluminescence spectroscopy. Moreover, hole-only devices (HODs) with N-CD interlayer presented high hole transport capability, and ultraviolet photoelectron spectroscopy also revealed that the N-CD interlayer reduced the highest hole barrier height. Thus, more balanced carrier injection with sufficient hole carrier transport feasibly lead to the superior electrical and electroluminescent properties of the QD-LEDs with N-CD interlayer. We further studied effect of N-CD interlayer thickness on electrical and luminescent performances for high-brightness QD-LEDs. The ability of the N-CD interlayer to improve both the electrical and luminescent characteristics of the QD-LEDs would be readily exploited as an emerging photoactive material for high-efficiency optoelectronic devices.

  16. A comparison of commercial light-emitting diode baited suction traps for surveillance of Culicoides in northern Europe.

    Science.gov (United States)

    Hope, Andrew; Gubbins, Simon; Sanders, Christopher; Denison, Eric; Barber, James; Stubbins, Francesca; Baylis, Matthew; Carpenter, Simon

    2015-04-22

    The response of Culicoides biting midges (Diptera: Ceratopogonidae) to artificial light sources has led to the use of light-suction traps in surveillance programmes. Recent integration of light emitting diodes (LED) in traps improves flexibility in trapping through reduced power requirements and also allows the wavelength of light used for trapping to be customized. This study investigates the responses of Culicoides to LED light-suction traps emitting different wavelengths of light to make recommendations for use in surveillance. The abundance and diversity of Culicoides collected using commercially available traps fitted with Light Emitting Diode (LED) platforms emitting ultraviolet (UV) (390 nm wavelength), blue (430 nm), green (570 nm), yellow (590 nm), red (660 nm) or white light (425 nm - 750 nm with peaks at 450 nm and 580 nm) were compared. A Centre for Disease Control (CDC) UV light-suction trap was also included within the experimental design which was fitted with a 4 watt UV tube (320-420 nm). Generalised linear models with negative binomial error structure and log-link function were used to compare trap abundance according to LED colour, meteorological conditions and seasonality. The experiment was conducted over 49 nights with 42,766 Culicoides caught in 329 collections. Culicoides obsoletus Meigen and Culicoides scoticus Downes and Kettle responded indiscriminately to all wavelengths of LED used with the exception of red which was significantly less attractive. In contrast, Culicoides dewulfi Goetghebuer and Culicoides pulicaris Linnaeus were found in significantly greater numbers in the green LED trap than in the UV LED trap. The LED traps collected significantly fewer Culicoides than the standard CDC UV light-suction trap. Catches of Culicoides were reduced in LED traps when compared to the standard CDC UV trap, however, their reduced power requirement and small size fulfils a requirement for trapping in logistically challenging areas or where many

  17. Manufacturing polymer light emitting diode with high luminance efficiency by solution process

    Science.gov (United States)

    Kim, Miyoung; Jo, SongJin; Yang, Ho Chang; Yoon, Dang Mo; Kwon, Jae-Taek; Lee, Seung-Hyun; Choi, Ju Hwan; Lee, Bum-Joo; Shin, Jin-Koog

    2012-06-01

    While investigating polymer light emitting diodes (polymer-LEDs) fabricated by solution process, surface roughness influences electro-optical (E-O) characteristics. We expect that E-O characteristics such as luminance and power efficiency related to surface roughness and layer thickness of emitting layer with poly-9-Vinylcarbazole. In this study, we fabricated polymer organic light emitting diodes by solution process which guarantees easy, eco-friendly and low cost manufacturing for flexible display applications. In order to obtain high luminescence efficiency, E-O characteristics of these devices by varying parameters for printing process have been investigated. Therefore, we optimized process condition for polymer-LEDs by adjusting annealing temperatures of emission, thickness of emission layer showing efficiency (10.8 cd/A) at 10 mA/cm2. We also checked wavelength dependent electroluminescence spectrum in order to find the correlation between the variation of efficiency and the thickness of the layer.

  18. Novel organic electron injection layer for efficient and stable organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Grover, Rakhi [Center for Organic Electronics, CSIR-National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi 110012 (India); Instrument Design Development Center, Indian Institute of Technology Delhi, New Delhi 110016 (India); Srivastava, Ritu, E-mail: ritu@mail.nplindia.ernet.in [Center for Organic Electronics, CSIR-National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi 110012 (India); Kamalasanan, M.N. [Center for Organic Electronics, CSIR-National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi 110012 (India); Mehta, D.S. [Instrument Design Development Center, Indian Institute of Technology Delhi, New Delhi 110016 (India)

    2014-02-15

    The efficiency of organic light-emitting diodes (OLEDs) was significantly improved by introducing a novel organic composition (4,7-diphyenyl-1,10-phenanthroline (BPhen): 20 wt% tetracyanoquinodimethane (TCNQ)) as an electron injection layer which could be uniformly deposited over a range of thicknesses. A highly injecting contact was obtained using 1.5 nm thick film of 20 wt% TCNQ mixed BPhen as the electron injection layer. High efficiency and stability of organic light emitting device are ascribed to improved electron injection and hence better charge carrier balance inside the OLEDs. -- Highlights: • • Highly conducting mixed BPhen films were used as electron injection layer in OLEDs for the first time. • Thickness of the proposed film has been optimized for best efficiency of OLEDs. • Proposed layer being organic could be deposited at relatively low temperatures. • TCNQ mixed BPhen films prove to be an efficient n-type layer in OLEDs.

  19. Emitter Orientation as a Key Parameter in Organic Light-Emitting Diodes

    Science.gov (United States)

    Schmidt, Tobias D.; Lampe, Thomas; Sylvinson, Daniel M. R.; Djurovich, Peter I.; Thompson, Mark E.; Brütting, Wolfgang

    2017-09-01

    The distinct preferential alignment, i.e., horizontal orientation with respect to the substrate plane, of the optical transition dipole moment vectors (TDMVs) of organic dye molecules is of paramount importance for extracting the internally generated power of organic light-emitting diodes (OLEDs) to the outside world. This feature is one of the most promising approaches for the enhancement of the electrical efficacy in state-of-the-art OLEDs, as their internal quantum efficiencies are already close to the ultimate limit. If one can achieve complete horizontal orientation of the TDMVs, it is possible to increase the efficiency by at least 50% because alignment strongly influences the power dissipation into the different optical modes present in such a thin-film device. Thus, this feature of organic light-emitting molecules can lead to advanced performance for future applications. Therefore, we present here a review of recent achievements, ongoing research, and future tasks in this particular area of organic electronics.

  20. Color stable white phosphorescent organic light emitting diodes with red emissive electron transport layer

    Energy Technology Data Exchange (ETDEWEB)

    Wook Kim, Jin; Yoo, Seung Il; Sung Kang, Jin [Department of Green Energy & Semiconductor Engineering, Hoseo University, Asan 336-795 (Korea, Republic of); Eun Lee, Song; Kwan Kim, Young [Department of Information Display, Hongik University, Seoul 121-791 (Korea, Republic of); Hwa Yu, Hyeong; Turak, Ayse [Department of Engineering Physics, McMaster University, Hamilton, Ontario L8S 4L7 (Canada); Young Kim, Woo, E-mail: wykim@hoseo.edu [Department of Green Energy & Semiconductor Engineering, Hoseo University, Asan 336-795 (Korea, Republic of); Department of Engineering Physics, McMaster University, Hamilton, Ontario L8S 4L7 (Canada)

    2015-06-28

    We analyzed the performance of multi-emissive white phosphorescent organic light-emitting diodes (PHOLEDs) in relation to various red emitting sites of hole and electron transport layers (HTL and ETL). The shift of the recombination zone producing stable white emission in PHOLEDs was utilized as luminance was increased with red emission in its electron transport layer. Multi-emissive white PHOLEDs including the red light emitting electron transport layer yielded maximum external quantum efficiency of 17.4% with CIE color coordinates (−0.030, +0.001) shifting only from 1000 to 10 000 cd/m{sup 2}. Additionally, we observed a reduction of energy loss in the white PHOLED via Ir(piq){sub 3} as phosphorescent red dopant in electron transport layer.

  1. The influence of melt purification and structure defects on mid-infrared light emitting diodes

    CERN Document Server

    Krier, A

    2003-01-01

    Mid-infrared light emitting diodes which exhibit more than 7 mW (pulsed) and 0.35 mW dc output power at 3.3 mu m and at room temperature have been fabricated by liquid phase epitaxy using Pb as a neutral solvent. Using Pb solution an increase in pulsed output power of between two and three times was obtained compared with InAs light emitting diodes (LEDs) made using rare-earth gettering. The performance improvements were attributed to a reduction in residual carrier concentration arising from the removal of un-intentional donors and structure defects in the InAs active region material. These LEDs are well matched to the CH sub 4 absorption spectrum and potentially could form the basis of a practical infrared CH sub 4 gas sensor.

  2. Morphology control of perovskite light-emitting diodes by using amino acid self-assembled monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Nana; Cheng, Lu; Wang, Jianpu, E-mail: iamjpwang@njtech.edu.cn [Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials - SICAM, Nanjing Tech University - NanjingTech, 30 South Puzhu Road, Nanjing 211816 (China); Si, Junjie; Liang, Xiaoyong [State Key Laboratory of Silicon Materials, Center for Chemistry of High-Performance and Novel Materials, and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Jin, Yizheng [Center for Chemistry of High-Performance and Novel Materials, State Key Laboratory of Silicon Materials, and Department of Chemistry, Zhejiang University, Hangzhou 310027 (China); Huang, Wei [Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials - SICAM, Nanjing Tech University - NanjingTech, 30 South Puzhu Road, Nanjing 211816 (China); Key Laboratory for Organic Electronics and Information Displays and Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing University of Posts & Telecommunications, 9 Wenyuan Road, Nanjing 210023 (China)

    2016-04-04

    Amino acid self-assembled monolayers are used in the fabrication of light-emitting diodes based on organic-inorganic halide perovskites. The monolayers of amino acids provide modified interfaces by anchoring to the surfaces of ZnO charge-transporting layers using carboxyl groups, leaving the amino groups to facilitate the nucleation of MAPbBr{sub 3} perovskite films. This surface-modification strategy, together with chlorobenzene-assisted fast crystallization method, results in good surface coverage and reduced defect density of the perovskite films. These efforts lead to green perovskite light emitting diodes with a low turn-on voltage of 2 V and an external quantum efficiency of 0.43% at a brightness of ∼5000 cd m{sup −2}.

  3. Magnetoluminescence of light-emitting field-effect transistors based on alpha sexithiophene

    Science.gov (United States)

    Pham, Song-Toan; Tada, Hirokazu

    2014-03-01

    We demonstrated the effect of a magnetic field on the luminous intensity and electric current of light-emitting field-effect transistors (LEFETs) based on alpha sexithiophene (α-6T). Sublimate-grade α-6T was thermally deposited on an n+-Si/300 nm-SiO2 substrate with patterned asymmetric gold-aluminum electrodes to fabricate a bottom-contact LEFET. We observed an increase in luminous intensity of approximately 1.3% under a magnetic field of 100 mT. A possible explanation for this is that the magnetic field increased the probability of singlet formation at the α-6T/Al interface. While the magneto-electroluminescence (MEL) was reported to be derived from the magneto-conductance (MC) in ordinary light emitting diodes, the MEL in LEFET was independent with MC. This indicates that the luminous efficiency can be improved by optimizing the magnetic field effect.

  4. Organic Light-Emitting Diodes on Solution-Processed Graphene Transparent Electrodes

    KAUST Repository

    Wu, Junbo

    2010-01-26

    Theoretical estimates indicate that graphene thin films can be used as transparent electrodes for thin-film devices such as solar cells and organic light-emitting diodes, with an unmatched combination of sheet resistance and transparency. We demonstrate organic light-emitting diodes with solution-processed graphene thin film transparent conductive anodes. The graphene electrodes were deposited on quartz substrates by spincoating of an aqueous dispersion of functionalized graphene, followed by a vacuum anneal step to reduce the sheet resistance. Small molecular weight organic materials and a metal cathode were directly deposited on the graphene anodes, resulting in devices with a performance comparable to control devices on indium-tin-oxide transparent anodes. The outcoupling efficiency of devices on graphene and indium-tin-oxide is nearly identical, in agreement with model predictions. © 2010 American Chemical Society.

  5. Metal-halide perovskites for photovoltaic and light-emitting devices.

    Science.gov (United States)

    Stranks, Samuel D; Snaith, Henry J

    2015-05-01

    Metal-halide perovskites are crystalline materials originally developed out of scientific curiosity. Unexpectedly, solar cells incorporating these perovskites are rapidly emerging as serious contenders to rival the leading photovoltaic technologies. Power conversion efficiencies have jumped from 3% to over 20% in just four years of academic research. Here, we review the rapid progress in perovskite solar cells, as well as their promising use in light-emitting devices. In particular, we describe the broad tunability and fabrication methods of these materials, the current understanding of the operation of state-of-the-art solar cells and we highlight the properties that have delivered light-emitting diodes and lasers. We discuss key thermal and operational stability challenges facing perovskites, and give an outlook of future research avenues that might bring perovskite technology to commercialization.

  6. Tailor-made directional emission in nanoimprinted plasmonic-based light-emitting devices.

    Science.gov (United States)

    Lozano, G; Grzela, G; Verschuuren, M A; Ramezani, M; Rivas, J Gómez

    2014-08-07

    We demonstrate an enhanced and tailor-made directional emission of light-emitting devices using nanoimprinted hexagonal arrays of aluminum nanoparticles. Fourier microscopy reveals that the luminescence of the device is not only determined by the material properties of the organic dye molecules but is also strongly influenced by the coherent scattering resulting from periodically arranged metal nanoparticles. Emitters can couple to lattice-induced hybrid plasmonic-photonic modes sustained by plasmonic arrays. Such modes enhance the spatial coherence of an emitting layer, allowing the efficient beaming of the emission along narrow angular and spectral ranges. We show that tailoring the separation of the nanoparticles in the array yields an accurate angular distribution of the emission. This combination of large-area metal nanostructures fabricated by nanoimprint lithography and light-emitting devices is beneficial for the design and optimization of solid-state lighting systems.

  7. High-performance light-emitting diodes based on carbene-metal-amides

    Science.gov (United States)

    Di, Dawei; Romanov, Alexander S.; Yang, Le; Richter, Johannes M.; Rivett, Jasmine P. H.; Jones, Saul; Thomas, Tudor H.; Abdi Jalebi, Mojtaba; Friend, Richard H.; Linnolahti, Mikko; Bochmann, Manfred; Credgington, Dan

    2017-04-01

    Organic light-emitting diodes (OLEDs) promise highly efficient lighting and display technologies. We introduce a new class of linear donor-bridge-acceptor light-emitting molecules, which enable solution-processed OLEDs with near-100% internal quantum efficiency at high brightness. Key to this performance is their rapid and efficient utilization of triplet states. Using time-resolved spectroscopy, we establish that luminescence via triplets occurs within 350 nanoseconds at ambient temperature, after reverse intersystem crossing to singlets. We find that molecular geometries exist at which the singlet-triplet energy gap (exchange energy) is close to zero, so that rapid interconversion is possible. Calculations indicate that exchange energy is tuned by relative rotation of the donor and acceptor moieties about the bridge. Unlike other systems with low exchange energy, substantial oscillator strength is sustained at the singlet-triplet degeneracy point.

  8. Reduced Graphene Oxide/Single-Walled Carbon Nanotube Hybrid Film Using Various p-Type Dopants and Its Application to GaN-Based Light-Emitting Diodes.

    Science.gov (United States)

    Lee, Byeong Ryong; Kim, Tae Geun

    2016-06-01

    This paper reports the electrical and optical properties of the reduced graphene oxide (RGO)/single-walled carbon nanotube (SWNT) films using various p-type dopants and its application to GaN-based light-emitting diodes. To enhance the current injection and spreading of the RGO/SWNT films on the light-emitting diodes (LEDs), we increased the work function (φ) of the films using chemical doping with AuCl3, poly(3,4-ethylenedioxythiophene) oxidized with poly(4-styrenesulfonate) ( PSS) and MoO3; thereby reduced the Schottky barrier height between the RGO/SWNT films and p-GaN. By comparison, LEDs fabricated with work-function-tuned RGO/SWNT film doped with MoO3 exhibited the decrease of the forward voltage from 5.3 V to 5.02 V at 20 mA and the increase of the output power up to 1.26 times. We also analyzed the current injection mechanism using ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy.

  9. Carbon Nanotube Driver Circuit for 6 ? 6 Organic Light Emitting Diode Display

    OpenAIRE

    Jianping Zou; Kang Zhang; Jingqi Li; Yongbiao Zhao; Yilei Wang; Suresh Kumar Raman Pillai; Hilmi Volkan Demir; Xiaowei Sun; Chan-Park, Mary B.; Qing Zhang

    2015-01-01

    Single-walled carbon nanotube (SWNT) is expected to be a very promising material for flexible and transparent driver circuits for active matrix organic light emitting diode (AM OLED) displays due to its high field-effect mobility, excellent current carrying capacity, optical transparency and mechanical flexibility. Although there have been several publications about SWNT driver circuits, none of them have shown static and dynamic images with the AM OLED displays. Here we report on the first s...

  10. Amber light-emitting diode comprising a group III-nitride nanowire active region

    Science.gov (United States)

    Wang, George T.; Li, Qiming; Wierer, Jr., Jonathan J.; Koleske, Daniel

    2014-07-22

    A temperature stable (color and efficiency) III-nitride based amber (585 nm) light-emitting diode is based on a novel hybrid nanowire-planar structure. The arrays of GaN nanowires enable radial InGaN/GaN quantum well LED structures with high indium content and high material quality. The high efficiency and temperature stable direct yellow and red phosphor-free emitters enable high efficiency white LEDs based on the RGYB color-mixing approach.

  11. Continuous light-emitting Diode (LED) lighting for improving food quality

    OpenAIRE

    Lu, C.; Bian, Z.

    2016-01-01

    Lighting-emitting diodes (LEDs) have shown great potential for plant growth and development, with higher luminous efficiency and positive impact compared with other artificial lighting. The combined effects of red/blue or/and green, and white LED light on plant growth and physiology, including chlorophyll fluorescence, nitrate content and phytochemical concentration before harvest, were investigated. The results showed that continuous light (CL)\\ud exposure at pre-harvest can effectively redu...

  12. Near-infrared organic light-emitting diodes for biosensing with high operating stability

    Science.gov (United States)

    Yamanaka, Takahiko; Nakanotani, Hajime; Hara, Shigeo; Hirohata, Toru; Adachi, Chihaya

    2017-07-01

    We demonstrate highly stable NIR organic light-emitting diodes (OLEDs) based on a system using excitonic energy transfer from thermally activated delay fluorescence molecules to NIR fluorophores. The NIR OLEDs showed an electroluminescence peak at 780 nm and robust operational stability with 2% loss of the initial radiant flux after 1000 h under a constant current density of 10 mA/cm2. The variation of hemoglobin oxygen saturation can be detected using the NIR OLEDs as a light source.

  13. All-silicon light-emitting diodes waveguide-integrated with superconducting single-photon detectors

    Science.gov (United States)

    Buckley, Sonia; Chiles, Jeffrey; McCaughan, Adam N.; Moody, Galan; Silverman, Kevin L.; Stevens, Martin J.; Mirin, Richard P.; Nam, Sae Woo; Shainline, Jeffrey M.

    2017-10-01

    We demonstrate cryogenic, electrically injected, waveguide-coupled Si light-emitting diodes (LEDs) operating at 1.22 μm. The active region of the LED consists of W centers implanted in the intrinsic region of a p-i-n diode. The LEDs are integrated on waveguides with superconducting nanowire single-photon detectors (SNSPDs). We demonstrate the scalability of this platform with an LED coupled to eleven SNSPDs in a single integrated photonic device.

  14. Analysis of photon recycling in light emitting diodes with nonuniform injection

    Science.gov (United States)

    Tsutsui, N.; Khmyrova, I.; Ryzhii, V.; Ikegami, T.

    2000-09-01

    We studied the effect of photon recycling in double heterostructure light emitting diodes (LEDs) with relatively small area contact providing nonuniform injection of electrons. A simple phenomenological model of the electron and photon transport in the LED is used to calculate the spatial distributions of electrons and output radiation as well as the external quantum efficiency as functions of device parameters. It is shown that photon recycling is the governing factor of the operation of LEDs with nonuniform injection.

  15. Efficient GaAs light-emitting diodes by photon recycling

    Science.gov (United States)

    Dupont, E.; Liu, H. C.; Buchanan, M.; Chiu, S.; Gao, M.

    2000-01-01

    Heterostructure AlGaAs/GaAs light-emitting diodes (LEDs) with a thick active region have shown high external efficiencies, thanks to reabsorption in the active region. For high injection currents and low temperature, we report a 22% efficiency which corresponds to a 98% efficiency internally. We discuss the application of such LED when integrated with a quantum-well infrared photodetector for pixelless thermal imaging systems.

  16. Highly Efficient Perovskite-Quantum-Dot Light-Emitting Diodes by Surface Engineering

    KAUST Repository

    Pan, Jun

    2016-08-16

    A two-step ligand-exchange strategy is developed, in which the long-carbon-chain ligands on all-inorganic perovskite (CsPbX3, X = Br, Cl) quantum dots (QDs) are replaced with halide-ion-pair ligands. Green and blue light-emitting diodes made from the halide-ion-paircapped quantum dots exhibit high external quantum efficiencies compared with the untreated QDs.

  17. DNA Bases Thymine and Adenine in Bio-Organic Light Emitting Diodes

    OpenAIRE

    Eliot F. Gomez; Venkatraman, Vishak; Grote, James G.; Steckl, Andrew J.

    2014-01-01

    We report on the use of nucleic acid bases (NBs) in organic light emitting diodes (OLEDs). NBs are small molecules that are the basic building blocks of the larger DNA polymer. NBs readily thermally evaporate and integrate well into the vacuum deposited OLED fabrication. Adenine (A) and thymine (T) were deposited as electron-blocking/hole-transport layers (EBL/HTL) that resulted in increases in performance over the reference OLED containing the standard EBL material NPB. A-based OLEDs reached...

  18. Electrical and Optical Enhancement in Internally Nanopatterned Organic Light-Emitting Diodes

    Science.gov (United States)

    Fina, Michael Dane

    Organic light-emitting diodes (OLEDs) have made tremendous technological progress in the past two decades and have emerged as a top competitor for next generation light-emitting displays and lighting. State-of-the-art OLEDs have been reported in literature to approach, and even surpass, white fluorescent tube efficiency. However, despite rapid technological progress, efficiency metrics must be improved to compete with traditional inorganic light-emitting diode (LED) technology. Organic materials possess specialized traits that permit manipulations to the light-emitting cavity. Overall, as demonstrated within, these modifications can be used to improve electrical and optical device efficiencies. This work is focused at analyzing the effects that nanopatterned geometric modifications to the organic active layers play on device efficiency. In general, OLED efficiency is complicated by the complex, coupled processes which contribute to spontaneous dipole emission. A composite of three sub-systems (electrical, exciton and optical) ultimately dictate the OLED device efficiency. OLED electrical operation is believed to take place via a low-mobility-modified Schottky injection process. In the injection-limited regime, geometric effects are expected to modify the local electric field leading to device current enhancement. It is shown that the patterning effect can be used to enhance charge carrier parity, thereby enhancing overall recombination. Current density and luminance characteristics are shown to be improved by OLED nanopatterning from both the model developed within and experimental techniques. Next, the optical enhancement effects produced by the nanopatterned array are considered. Finite-difference time-domain (FDTD) simulations are used to determine positional, spectral optical enhancement for the nanopatterned device. The results show beneficial effects to the device performance. The optical enhancements are related to the reduction in internal radiative

  19. Solution processed, white emitting tandem organic light-emitting diodes with inverted device architecture.

    Science.gov (United States)

    Höfle, Stefan; Schienle, Alexander; Bernhard, Christoph; Bruns, Michael; Lemmer, Uli; Colsmann, Alexander

    2014-08-13

    Fully solution processed monochromatic and white-light emitting tandem or multi-photon polymer OLEDs with an inverted device architecture have been realized by employing WO3 /PEDOT:PSS/ZnO/PEI charge carrier generation layers. The luminance of the sub-OLEDs adds up in the stacked device indicating multi-photon emission. The white OLEDs exhibit a CRI of 75. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Light emitting diodes (LED): applications in forest and native plant nurseries

    Science.gov (United States)

    Thomas D. Landis; Jeremiah R. Pinto; R. Kasten Dumroese

    2013-01-01

    It was quotes like this that made us want to learn more about light emitting diodes (LED). Other than knowing that LEDs were the latest innovation in artificial lighting, we knew that we had a lot to learn. So we started by reviewing some of the basics. The following review is a brief synopsis of how light affects plants and some discussion about LED lighting. If you...

  1. Investigation of Light-Emitting Diode (LED) Point Light Source Color Visibility against Complex Multicolored Backgrounds

    Science.gov (United States)

    2017-11-01

    sent from light-emitting diodes (LEDs) of 5 colors (green, red, white , amber, and blue). Experiment 1 involved controlled laboratory measurements of...for operation at 12 VDC. Specifications for colored and white LEDs are in Table 1. * A picture of...520 nm Blue 15 mA 1000 mcd 465 nm White LED specifications Color Current draw Output Effective color temperature Cool white 20 mA 4100 mcd 6000 K

  2. Organic light-emitting device with a phosphor-sensitized fluorescent emission layer

    Science.gov (United States)

    Forrest, Stephen [Ann Arbor, MI; Kanno, Hiroshi [Osaka, JP

    2009-08-25

    The present invention relates to organic light emitting devices (OLEDs), and more specifically to OLEDS that emit light using a combination of fluorescent emitters and phosphorescent emitters. The emissive region of the devices of the present invention comprise at least one phosphor-sensitized layer which has a combined emission from a phosphorescent emitter and a fluorescent emitter. In preferred embodiments, the invention relates to white-emitting OLEDS (WOLEDs).

  3. First examples of organophosphorus-containing materials for light-emitting diodes.

    Science.gov (United States)

    Fave, Claire; Cho, Ting-Yi; Hissler, Muriel; Chen, Chieh-Wei; Luh, Tien-Yau; Wu, Chung-Chih; Réau, Régis

    2003-08-06

    Exploiting the reactivity of the P-atom of phosphole-based oligomers, we have achieved access to the first organophosphorus-containing organic light-emitting diode (OLED) materials. The versatility of these P-materials is demonstrated with the synthesis of a corresponding gold complex that has also been used as an OLED material. Optimization of the OLED devices by doping the phosphole layer with a red fluorescent dye is described.

  4. Photo thermal efficacy of green light emitting diode and gold nano spheres for malignancy

    Science.gov (United States)

    Gananathan, Poorani; Prakasa Rao, Aruna; Ganesan, Singaravelu; Manickan, Elanchezhiyan

    2016-03-01

    The effect of 30nm Gold Nanoparticles (GNP) based on concentration and incubation time with respect to their cellular uptake kinetics was studied with Vero and HeLa cells . Photoirradiation effect of GNPs in combination with light emitting diode(LED) found to be remarkable and this work concentrates on optimizing concentration and light source. The effect of Gold nanoparticles alone and in combination with LED in malignant and normal cells lines were studied.

  5. Reversible tuning luminescent color and emission intensity: a dipeptide-based light-emitting material.

    Science.gov (United States)

    Teng, Ming-Jun; Jia, Xin-Ru; Yang, Shuang; Chen, Xiao-Fang; Wei, Yen

    2012-03-02

    A smart luminescent material whose emission color and emission intensity can be separately modulated by external force is demonstrated. The rational manipulation of rich noncovalent interactions and fluorophore packing style promotes an in-depth understanding between supramolecular structure and photophysical property and offers an effective strategy to modulate the light-emitting property in a predicative way. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. White organic light emitting diodes based on fluorene-carbazole dendrimers

    Energy Technology Data Exchange (ETDEWEB)

    Usluer, Özlem, E-mail: usluerozlem@yahoo.com.tr [Department of Chemistry, Muğla Sıtkı Koçman University, 48000 Muğla (Turkey); Demic, Serafettin [Department of Materials Science and Engineering, Izmir Katip Çelebi University, 35620 Çiğli, Izmir (Turkey); Kus, Mahmut, E-mail: mahmutkus1@gmail.com [Chemical Engineering Department and Advanced Technology R and D Center, Selçuk University, Konya (Turkey); Özel, Faruk [Chemical Engineering Department and Advanced Technology R and D Center, Selçuk University, Konya (Turkey); Serdar Sariciftci, Niyazi [Linz Institute for Organic Solar Cells (LIOS), Physical Chemistry, Johannes Kepler University, Altenbergerstr. 69, A-4040 Linz (Austria)

    2014-02-15

    In this paper, we report on theProd. Type: FTP fabrication and characterization of blue and white light emitting devices based on two fluorene-carbazole containing dendrimers and para-sexiphenyl (6P) oligomers. Blue light emitting diodes were fabricated using 9′,9″-(9,9-dioctyl-9H-fluorene-2,7-diyl)bis-9′H-9,3′:6′,9″-tercarbazole (OFC-G2) and 9′,9″-(9,9′-spirobi[fluorene]-2,7-diyl)bis-9′H-9,3′:6′,9″-tercarbazole (SBFC-G2) dendrimers as a hole transport and emissive layer (EML) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) as an electron transport layer. White light emitting diodes were fabricated using 6P and these two dendrimers as an EML. OLED device with the structure of ITO/PEDOT:PSS (50 nm)/OFC-G2 (40 nm)/6P (20 nm)/LiF:Al (0.5:100 nm) shows maximum luminance of nearly 1400 cd/m{sup 2} and a Commission Internationale de l'Eclairage chromaticity coordinates of (0.27, 0.30) at 12 V. -- Highlights: • White organic light emitting diodes have been fabricated using two fluorene-carbazole dendrimers and para-sexiphenyl (6P) oligomers. • When only these two dendrimers are used as EML, OLED devices are emitted blue light. • The emission colors of OLED devices change from blue to white when 6P is coated on dendrimer films.

  7. Enhanced light extraction from organic light-emitting devices using a sub-anode grid

    Science.gov (United States)

    Qu, Yue; Slootsky, Michael; Forrest, Stephen R.

    2015-11-01

    We demonstrate the highly effective extraction of waveguided light from the active region of organic light-emitting devices using a non-diffractive dielectric grid layer placed between the transparent anode and the substrate. The sub-anode grid couples out all waveguide mode power into the substrate without changing the device electrical properties, resulting in an increase in both the external quantum efficiency and luminous efficacy for green phosphorescent organic light-emitting devices from 15 ± 1% and 36 ± 2 lm W-1 to 18 ± 1% and 43 ± 2 lm W-1. These characteristics are further increased to 40 ± 2% and 95 ± 4 lm W-1 when all glass modes are also extracted. The use of a thick electron transport layer further reduces surface plasmon modes, resulting in an increase in the substrate and air modes by 50 ± 8% compared with devices lacking the grids. The sub-anode grid has minimal impact on organic light-emitting device emission wavelength and viewing angle, and is likely to prove beneficial for a broad range of display and lighting applications.

  8. Highly efficient non-doped blue organic light emitting devices based on anthracene–pyridine derivatives

    Energy Technology Data Exchange (ETDEWEB)

    Haykir, Gulcin; Tekin, Emine; Atalar, Taner; Türksoy, Figen

    2013-12-02

    Four different 2-(10-aryl)anthracen-9-yl)pyridine derivatives 5a–d were synthesized via the Suzuki cross-coupling reaction. Photo-physical characteristics of these materials having strong electron donating or electron withdrawing groups were explored. Multilayer small molecule organic light emitting diodes without any dopant were fabricated in the following sequence: Indium tin oxide/4,4′-bis(N-(1-naphthyl)-N-phenylamino)biphenyl (50 nm)/5a–d (30 nm)/4,7-diphenyl-1,10-phenanthroline (30 nm)/LiF/Al. The electroluminescent property of the device fabricated with 5d as an emitter exhibited a high external quantum efficiency of 3.80% (at around 1 mA/cm{sup 2}) with Commission Internationale De L'Eclairage coordinates of (0.14, 0.25). - Highlights: • Synthesis and characterization of 2-(10-aryl)anthracen-9-yl)pyridine derivatives • Thermal, photophysical and electrochemical properties of anthracene derivatives • Emitters from blue to greenish blue for organic light emitting device applications • Organic light emitting device fabrication and characterization of 2-(10-aryl)anthracen-9-yl)pyridine derivatives.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  10. Light-emitting diode-generated red light inhibits keloid fibroblast proliferation.

    Science.gov (United States)

    Mamalis, Andrew; Jagdeo, Jared

    2015-01-01

    Red light is part of the visible light spectrum that does not generate DNA adducts associated with skin cancer and photoaging and may represent a safer therapeutic modality for treatment of keloid scars and other fibrotic skin diseases. Our laboratory previously demonstrated that light-emitting diode-generated red light (LED-RL) inhibits proliferation of skin fibroblasts. The effects of LED-RL on keloidal skin are not well characterized. To determine the effect of LED-RL on keloid-derived fibroblast proliferation and viability in vitro. Irradiation of primary keloid-derived human skin fibroblasts using LED-RL panels was performed in vitro, and modulation of proliferation and viability was quantified using trypan blue dye exclusion assay. Statistical analysis was performed using analysis of variance to compare treatment arms and the Student t-test to compare each treatment arm with the paired bench control arm. Keloid fibroblasts treated with LED-RL 240, 320, and 480 J/cm demonstrated statistically significant dose-dependent decreases in relative proliferation rate of 12.4%, 16.5%, and 28.9%, respectively, compared with matched nonirradiated controls (p Light-emitting diode-generated red light can inhibit keloid fibroblast proliferation in a dose-dependent manner without altering viability. Light-emitting diode-generated red light has the potential to contribute to the treatment of keloids and other fibrotic skin diseases and is worthy of further translational and clinical investigation.

  11. Solution-processable organic light emitting diode on glass fibers for textile applications

    Energy Technology Data Exchange (ETDEWEB)

    Gruber, Bjoern; Kerstin, Schulze; Silvia, Janietz [Fraunhofer Institute for Applied Polymer Research, Geiselbergstr. 69, 14476 Potsdam-Golm (Germany)

    2011-07-01

    Electronic devices based on organic materials offers the possibility to be a low-cost production technology on large area in several years. As a special application organic devices could be used in the field of electronic-textiles in future, for example for safety applications or as smart textiles. Therefore the direct integration of the electronic devices on the textile fibers is interesting. In this work, organic light emitting diodes (OLEDs) have been manufactured and investigated on cylindrical and flexible substrates. Especially the cylindrical geometry of the substrate hinders a homogeneous deposition of organic layers. Here, we present first results using solution processes for the preparation of the organic materials of an organic light emitting diode on glass fibers. The OLEDs were prepared on thin glass fibers using thermally evaporated metals and dip-coated polymeric layers. We focus on the challenging preparation steps of these layers on cylindrical substrates resulting in working devices. Additionally a current density-voltage-characteristic of a light emitting device on a glass fiber is presented and analyzed.

  12. Printing Smart Designs of Light Emitting Devices with Maintained Textile Properties.

    Science.gov (United States)

    Verboven, Inge; Stryckers, Jeroen; Mecnika, Viktorija; Vandevenne, Glen; Jose, Manoj; Deferme, Wim

    2018-02-13

    To maintain typical textile properties, smart designs of light emitting devices are printed directly onto textile substrates. A first approach shows improved designs for alternating current powder electroluminescence (ACPEL) devices. A configuration with the following build-up, starting from the textile substrate, was applied using the screen printing technique: silver (10 µm)/barium titanate (10 µm)/zinc-oxide (10 µm) and poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate) (10 µm). Textile properties such as flexibility, drapability and air permeability are preserved by implementing a pixel-like design of the printed layers. Another route is the application of organic light emitting devices (OLEDs) fabricated out of following layers, also starting from the textile substrate: polyurethane or acrylate (10-20 µm) as smoothing layer/silver (200 nm)/poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate) (35 nm)/super yellow (80 nm)/calcium/aluminum (12/17 nm). Their very thin nm-range layer thickness, preserving the flexibility and drapability of the substrate, and their low working voltage, makes these devices the possible future in light-emitting wearables.

  13. Highly Efficient Soluble Blue Delayed Fluorescent and Hyperfluorescent Organic Light-Emitting Diodes by Host Engineering.

    Science.gov (United States)

    Jeon, Sang Kyu; Park, Hee-Jun; Lee, Jun Yeob

    2018-01-30

    Solution-processed high-efficiency fluorescent organic light-emitting diodes with an external quantum efficiency over 18% were developed by engineering a host material and device structure designed for solution process. A high triplet energy host material designed for the solution process, (oxybis(3-(tert-butyl)-6,1-phenylene))bis(diphenylphosphine oxide) (DPOBBPE), worked efficiently as the host of blue fluorescent devices because of good solubility, high photoluminescence quantum yield, and good film properties. The DPOBBPE host enabled a high external quantum efficiency of 18.8% in the fluorescent organic light-emitting diodes by the solution process. Moreover, 25.8% external quantum efficiency in the soluble blue thermally activated delayed fluorescent devices was also realized. The 25.8% external quantum efficiency of the DPOBBPE delayed fluorescent device and 18.8% external quantum efficiency of the fluorescent device are the highest efficiency values achieved in the solution-processed blue fluorescent organic light-emitting diodes. Moreover, the solution-processed fluorescent device showed an improved blue color coordinate of (0.14, 0.20) compared to (0.17, 0.31) of the delayed fluorescent device.

  14. Charge carrier trapping and enhanced electroluminescent efficiency of blue light emitting polymer with gold nanoparticles.

    Science.gov (United States)

    Park, Jong Hyeok; Choi, Yu-Ri; Chin, Byung Doo

    2009-12-01

    We investigated the current injection, transport, and luminous efficiency behavior of organic light emitting diode (OLED) containing the 5-10 nm-sized gold particles mixed in the polyfluorene-type copolymer. This nanoparticle-conjugated polymer mixture layer was used as hole injection, transport, and light emitting layer for various structures of OLED based on the phosphorescent and fluorescent emitters. Due to the hole trapping at the nanopaticle, carrier injection is significantly reduced while the hole transport behavior is found to be barely affected. Hole trapping of nanoparticle in light emitting layer (at 4.7 approximately 9.4 x 10(-5) w/w fraction) resulted in an enhancement of efficiency (from 5.23 cd/A to 6.50 cd/A). The existence of the outcoupling effect also supports the carrier trapping behavior, which is amended mechanism of the improved efficiency compared to previously reported mechanism of enhanced photoluminescent stability by a hindrance of photo-oxidation.

  15. Efficient Sky-Blue Perovskite Light-Emitting Devices Based on Ethylammonium Bromide Induced Layered Perovskites.

    Science.gov (United States)

    Wang, Qi; Ren, Jie; Peng, Xue-Feng; Ji, Xia-Xia; Yang, Xiao-Hui

    2017-09-06

    Low-dimensional organometallic halide perovskites are actively studied for the light-emitting applications due to their properties such as solution processability, high luminescence quantum yield, large exciton binding energy, and tunable band gap. Introduction of large-group ammonium halides not only serves as a convenient and versatile method to obtain layered perovskites but also allows the exploitation of the energy-funneling process to achieve a high-efficiency light emission. Herein, we investigate the influence of the addition of ethylammonium bromide on the morphology, crystallite structure, and optical properties of the resultant perovskite materials and report that the phase transition from bulk to layered perovskite occurs in the presence of excess ethylammonium bromide. On the basis of this strategy, we report green perovskite light-emitting devices with the maximum external quantum efficiency of ca. 3% and power efficiency of 9.3 lm/W. Notably, blue layered perovskite light-emitting devices with the Commission Internationale de I'Eclairage coordinates of (0.16, 0.23) exhibit the maximum external quantum efficiency of 2.6% and power efficiency of 1 lm/W at 100 cd/m2, representing a large improvement over the previously reported analogous devices.

  16. Ag nanocluster-based color converters for white organic light-emitting devices

    Science.gov (United States)

    Nishikitani, Yoshinori; Takizawa, Daisuke; Uchida, Soichi; Lu, Yue; Nishimura, Suzushi; Oyaizu, Kenichi; Nishide, Hiroyuki

    2017-11-01

    The authors present Ag nanocluster-based color converters (Ag NC color converters), which convert part of the blue light from a light source to yellow light so as to create white organic light-emitting devices that could be suitable for lighting systems. Ag NCs synthesized by poly(methacrylic acid) template methods have a statistical size distribution with a mean diameter of around 4.5 nm, which is larger than the Fermi wavelength of around 2 nm. Hence, like free electrons in metals, the Ag NC electrons are thought to form a continuous energy band, leading to the formation of surface plasmons by photoexcitation. As for the fluorescence emission mechanism, the fact that the photoluminescence is excitation wavelength dependent suggests that the fluorescence originates from surface plasmons in Ag NCs of different sizes. By using Ag NC color converters and suitable blue light sources, white organic light-emitting devices can be fabricated based on the concept of light-mixing. For our blue light sources, we used polymer light-emitting electrochemical cells (PLECs), which, like organic light-emitting diodes, are area light sources. The PLECs were fabricated with a blue fluorescent π-conjugated polymer, poly[(9,9-dihexylfluoren-2,7-diyl)-co-(anthracen-9,10-diyl)] (PDHFA), and a polymeric solid electrolyte composed of poly(ethylene oxide) and KCF3SO3. In this device structure, the Ag NC color converter absorbs blue light from the PDHFA-based PLEC (PDHFA-PLEC) and then emits yellow light. When the PDHFA-PLEC is turned on by applying an external voltage, pure white light emission can be produced with Commission Internationale de l'Eclairage coordinates of (x = 0.32, y = 0.33) and a color rendering index of 93.6. This study shows that utilization of Ag NC color converters and blue PLECs is a very promising and highly effective method for realizing white organic light-emitting devices.

  17. Analytical devices based on light-emitting diodes--a review of the state-of-the-art.

    Science.gov (United States)

    Bui, Duy Anh; Hauser, Peter C

    2015-01-01

    A general overview of the development of the uses of light-emitting diodes in analytical instrumentation is given. Fundamental aspects of light-emitting diodes, as far as relevant for this usage, are covered in the first part. The measurement of light intensity is also discussed, as this is an essential part of any device based on light-emitting diodes as well. In the second part, applications are discussed, which cover liquid and gas-phase absorbance measurements, flow-through detectors for chromatography and capillary electrophoresis, sensors, as well as some less often reported methods such as photoacoustic spectroscopy. Copyright © 2014 Elsevier B.V. All rights reserved.

  18. Measurement of the water content in oil and oil products using IR light-emitting diode-photodiode optrons

    Science.gov (United States)

    Bogdanovich, M. V.; Kabanau, D. M.; Lebiadok, Y. V.; Shpak, P. V.; Ryabtsev, A. G.; Ryabtsev, G. I.; Shchemelev, M. A.; Andreev, I. A.; Kunitsyna, E. V.; Ivanov, E. V.; Yakovlev, Yu. P.

    2017-02-01

    The feasibility of using light-emitting devices, the radiation spectrum of which has maxima at wavelengths of 1.7, 1.9, and 2.2 μm for determining the water concentration in oil and oil products (gasoline, kerosene, diesel fuel) has been demonstrated. It has been found that the measurement error can be lowered if (i) the temperature of the light-emitting diode is maintained accurate to 0.5-1.0°C, (ii) by using a cell through which a permanently stirred analyte is pumped, and (iii) by selecting the repetition rate of radiation pulses from the light-emitting diodes according to the averaging time. A meter of water content in oil and oil products has been developed that is built around IR light-emitting device-photodiode optrons. This device provides water content on-line monitoring accurate to 1.5%.

  19. Comparison of intensive light-emitting diode and intensive compact fluorescent phototherapy in non-hemolytic jaundice

    National Research Council Canada - National Science Library

    Takcı, Sahin; Yiğit, Sule; Bayram, Gülperi; Korkmaz, Ayşe; Yurdakök, Murat

    2013-01-01

    ...: intensive compact fluorescent tube (CFT) and intensive light-emitting diode (LED) phototherapy. Forty-three infants over 35 weeks of gestation with severe non-hemolytic hyperbilirubinemia were enrolled in the prospective study...

  20. Design rules for light-emitting electrochemical cells delivering bright luminance at 27.5 percent external quantum efficiency

    National Research Council Canada - National Science Library

    Shi Tang; Andreas Sandström; Petter Lundberg; Thomas Lanz; Christian Larsen; Stephan van Reenen; Martijn Kemerink; Ludvig Edman

    2017-01-01

    The light-emitting electrochemical cell promises cost-efficient, large-area emissive applications, as its characteristic in-situ doping enables use of air-stabile electrodes and a solution-processed...

  1. Usability of light-emitting diodes in precision approach path indicator systems by individuals with marginal color vision.

    Science.gov (United States)

    2014-05-01

    To save energy, the FAA is planning to convert from incandescent lights to light-emitting diodes (LEDs) in : precision approach path indicator (PAPI) systems. Preliminary work on the usability of LEDs by color vision-waivered pilots (Bullough, Skinne...

  2. Improving Light Distribution by Zoom Lens for Electricity Savings in a Plant Factory with Light-Emitting Diodes

    National Research Council Canada - National Science Library

    Li, Kun; Li, Zhipeng; Yang, Qichang

    2016-01-01

    The high energy consumption of a plant factory is the biggest issue in its rapid expansion, especially for lighting electricity, which has been solved to a large extent by light-emitting diodes (LED...

  3. Effect of gold wire bonding process on angular correlated color temperature uniformity of white light-emitting diode

    National Research Council Canada - National Science Library

    Wu, Bulong; Luo, Xiaobing; Zheng, Huai; Liu, Sheng

    2011-01-01

    Gold wire bonding is an important packaging process of lighting emitting diode (LED). In this work, we studied the effect of gold wire bonding on the angular uniformity of correlated color temperature...

  4. Ambient fabrication of flexible and large-area organic light-emitting devices using slot-die coating

    National Research Council Canada - National Science Library

    Sandström, Andreas; Dam, Henrik F; Krebs, Frederik C; Edman, Ludvig

    2012-01-01

    The grand vision of manufacturing large-area emissive devices with low-cost roll-to-roll coating methods, akin to how newspapers are produced, appeared with the emergence of the organic light-emitting...

  5. Wearable red-green-blue quantum dot light-emitting diode array using high-resolution intaglio transfer printing

    National Research Council Canada - National Science Library

    Choi, Moon Kee; Yang, Jiwoong; Kang, Kwanghun; Kim, Dong Chan; Choi, Changsoon; Park, Chaneui; Kim, Seok Joo; Chae, Sue In; Kim, Tae-Ho; Kim, Ji Hoon; Hyeon, Taeghwan; Kim, Dae-Hyeong

    2015-01-01

    Deformable full-colour light-emitting diodes with ultrafine pixels are essential for wearable electronics, which requires the conformal integration on curvilinear surface as well as retina-like high-definition displays...

  6. AlGaInN-based light emitting diodes with a transparent p-contact based on thin ITO films

    Energy Technology Data Exchange (ETDEWEB)

    Smirnova, I. P., E-mail: irina@quantum.ioffe.ru; Markov, L. K.; Pavlyuchenko, A. S. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation); Kukushkin, M. V. [ZAO Innovation Company ' TETIS' (Russian Federation)

    2012-03-15

    A method for obtaining transparent conductive ITO (indium-tin oxide) films aimed for use in light emitting diodes of the blue spectral range is developed. The peak external quantum efficiency of light-emitting diodes with a p-contact based on the obtained films reaches 25%, while for similar light-emitting diodes with a standard semitransparent metal contact, it is <10%. An observed increase in the direct voltage drop from 3.15 to 3.37 V does not significantly affect the possibility of applying these films in light-emitting diodes since the optical power of light-emitting diodes with a transparent p-contact based on ITO films exceeds that of chips with metal semitransparent p-contacts with a working current of 20 mA by a factor of almost 2.5. Light-emitting diodes with p-contacts based on ITO films successfully withstand a pumping current that exceeds their calculated working current by a factor of 5 without the appearance of any signs of degradation.

  7. All-inorganic white light emitting devices based on ZnO nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Nannen, Ekaterina

    2012-09-21

    Semiconductor nanaocrystals (NCs) are very promising candidates for lightweight large-area rollable displays and light emitting devices (LEDs). They are expected to combine the efficiency, robustness and color tunability of conventional semiconductor LEDs with the flexible fabrication techniques known from OLED technology, since the NCs are compatible with solution processing and therefore can be deposited on virtually any substrates including glass and plastic. Today, NC-LEDs consist of chemically synthesized QDs embedded in organic charge injection and transport layers. The organic layers limit the robustness of the NC-LEDs and result in significant constrictions within the device fabrication procedure, such as organic evaporation steps, inert (i.e. humidity and oxygen free) atmosphere and obligatory encapsulation. These limitations during the production process as well as complex chemical synthesis route of the implemented NCs and organic components lead to high fabrication costs and low turnover. So far, only prototype devices have been introduced by several research groups and industrial companies. Still, the main concern retarding NC-LEDs from market launch is the high content of toxic heavy metals like Cd in the active nanocrystalline light emitting material. Within this work, possible environmentally safe and ambient-air-compatible alternatives to conventional QDs and organics were explored, with the main focus on design and fabrication of completely inorganic white NC-LEDs with commercial ZnO nanoparticles as an active light emitting material. While the electrical transport properties through the NC-network of the commercially available VP AdNano {sup registered} ZnO2O particles were already to some extent explored, their optical properties and therefore suitability as an active light emitter in NC-LEDs were not studied so far. (orig.)

  8. Single cavity Fabry-Perot modulator enhancements and integrated vertically coupled cavity light-emitting diode

    Science.gov (United States)

    Liu, Daxin

    Fabry-Perot modulators with Multi-Quantum Wells (MQWs) cavities have been studied with great interest during recent years. Usually operating as intensity modulators, these devices have very high modulation contrast ratios, can be operated at very high speed, can be easily made into two dimensional arrays and can be integrated with silicon ICs. They are thus very promising for optical interconnects, optical switching and image processing applications. But before these modulators are to be used in real applications, there are several issues that need to be solved, including the parasitic phase modulation, the bandwidth of such modulators and the alignment of modulator operation wavelength with the wavelength of lasers or light emitting diodes. In this work, the phase properties of Fabry-Perot reflection modulators will be discussed first and an experimental method using a modified Michelson interferometer to characterize the exact phase change will be demonstrated. It is demonstrated that the phase of the reflection light beam from a Fabry-Perot modulator is determined not only by the refractive index change inside the cavity but also by the absorption change inside the cavity. With the purpose of expanding the limited bandwidth of such modulator, devices with short passive cavities are designed and fabricated, the results are described and trade-offs between modulation depth and bandwidth will be discussed. In order to solve the problem of alignment and expand the functionality of Fabry-Perot modulators further, vertically coupled cavity devices with each cavity being electrically controlled independently have been developed. Both a coupled cavity modulator and an integrated light emitting diode with a transmission Fabry-Perot modulator are demonstrated; the first device enhances the modulation bandwidth while the second device has the potential of combining the advantage of high speed operation of MQWs modulators with the long lifetime and low cost of light

  9. POWER, METALLURGICAL AND CHEMICAL MECHANICAL ENGINEERING THERMOELECTRIC EVENTS IN LIGHT-EMITTING BIPOLAR SEMICONDUCTOR STRUCTURES

    Directory of Open Access Journals (Sweden)

    P. A. Magomedova

    2017-01-01

    Full Text Available Objective. The development of light-emitting bipolar semiconductor structures having a low level of parasitic heat release.Methods. A method for converting thermoelectric heat in bipolar semiconductor structures into optical radiation to divert the excess energy into the environment was developed. At the same time, the cooling effect on thermoelectric junctions remains. Instead of an inertial process of conductive or convective heat transfer, practically instantaneous heat removal from electronic components to the environment takes place.Results. As a result, light-emitting bipolar semiconductor structures will allow more powerful devices with greater speed and degree of integration to be created. It is possible to produce transparent LED matrices with a two-way arrangement of transparent solar cells and mirror metal electrodes along the perimeter. When current is applied, the LED matrix on one of the transitions will absorb thermal energy; on other electrodes, it will emit radiation that is completely recovered into electricity by means of transparent solar cells following repeated reflection between the mirror electrodes. The low efficiency of solar cells will be completely compensated for with the multiple passages of photons through these batteries.Conclusion. Light-emitting bipolar semiconductor structures will not only improve the reliability of electronic components in a wide range of performance characteristics, but also improve energy efficiency through the use of optical radiation recovery. Semiconductor thermoelectric devices using optical phenomena in conjunction with the Peltier effect allow a wide range of energy-efficient components of radio electronic equipment to be realised, both for discrete electronics and for microsystem techniques. Systems for obtaining ultra-low temperatures in order to achieve superconductivity are of particular value. 

  10. Molecular beam epitaxial growth and characterization of AlN nanowall deep UV light emitting diodes

    Science.gov (United States)

    Liu, Xianhe; Zhao, Songrui; Le, Binh Huy; Mi, Zetian

    2017-09-01

    We have demonstrated large area AlN nanowall light emitting diodes grown on a sapphire substrate, which operate at 214 nm. Through detailed temperature-dependent and power-dependent photoluminescence measurements and rate equation analysis, a relatively high internal quantum efficiency (˜60%) was derived for AlN nanowall structures at room-temperature. A consistent blueshift in the emission wavelengths was measured with decreasing nanowall widths due to the reduced tensile strain distribution. The devices exhibit excellent current-voltage characteristics, including a turn-on voltage of 7 V and current densities of >170 A/cm2 at 12 V.

  11. Towards developing a tandem of organic solar cell and light emitting diode

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Jai [School of Engineering and IT, B-purple-12, Faculty of EHS, Charles Darwin University, Darwin, NT 0909 (Australia)

    2011-01-15

    It is proposed here to design a tandem of organic solar cell (OSC) and white organic light emitting diode (WOLED) which can generate power in the day time from the sun and provide lighting at night. With the advancement of chemical technology, such device is expected to be very-cost effective and reasonably efficient. A device thus fabricated has the potential of meeting the world's sustainable domestic and commercial power and lighting needs (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Effects of gamma radiation on superluminescent light emitting diodes (SLEDs) for fibre optic gyroscope applications

    Science.gov (United States)

    Occhi, L.; Rezzonico, R.; Vélez, C.; van Uffelen, M.; Berghmans, F.

    2017-11-01

    In this work we present a study on teh Super Luminescent LIght Emitting Diodes (SLEDs) performance under high doses of gamma radiation. We investigate GaAs SLEDs with emission wavelengths around 830 nm. The devices were exposed to ionising radiation at a dose rate of about 4.7 Gy/s, up to a cumulated dose of 10.1 MGy in the CMF facility of the Belgian nuclear research centre SCK•CEN. We measured the device characteristics before adn after irradiation. We show that the SLED performance is only marginally affected.

  13. Transparent Heat-Resistant PMMA Copolymers for Packing Light-Emitting Diode Materials

    Directory of Open Access Journals (Sweden)

    Shu-Ling Yeh

    2015-07-01

    Full Text Available Transparent and heat-resistant poly(methyl methacrylate copolymers were synthesized by bulk polymerizing methyl methacrylate (MMA, isobornyl methacrylate (IBMA, and methacrylamide (MAA monomers. Copolymerization was performed using a chain transfer agent to investigate the molecular weight changes of these copolymers, which exhibited advantages including a low molecular weight distribution, excellent optical properties, high transparency, high glass transition temperature, low moisture absorption, and pellets that can be readily mass produced by using extrusion or jet injection for packing light-emitting diode materials.

  14. Development of cyclometallated iridium(III) complexes for light-emitting electrochemical cells

    OpenAIRE

    Housecroft, Catherine E.; Constable, Edwin C.

    2017-01-01

    This chapter gives an overview of the development of cyclometallated iridium(III) complexes for application in light-emitting electrochemical cells (LECs) and highlights the ligand-design strategies employed to enhance device stability, operating efficiency and (critically for LECs in which the ion mobilities are typically low) turn-on times. Typical iridium-containing ionic transtion metal complexes (Ir-iTMCs) belong to the family of [Ir(C^N) 2 (N^N)] + complexes in which H(C^N) is a cyclome...

  15. Light-emitting nanocomposites and novel amorphous polymers for optical applications

    Science.gov (United States)

    Gipson, Kyle Garrod

    Polymeric optical materials generally are comprised of amorphous polymers that are transparent in at visible wavelengths but exhibit strong absorption bands in the near-infrared making them less useful for many optical applications. Attenuation, which is the absorption per unit length, largely results from the high vibrational energy associated with carbon-hydrogen bonds contained in the polymer backbone. Attenuation can be mitigated by optical amplification utilizing light emitting additives. Investigated in this dissertation are synthesis techniques for the fabrication of light-emitting polymer nanocomposites and their resultant thermal and rheological characteristics for potential use as polymer optical fibers or films. Inorganic nanocrystals doped with optically active rare-earth ions (Tb 3+:LaF3) treated with organic ligands were synthesized in water and methanol in order to produce polymethyl methacrylate (PMMA) light-emitting nanocomposites. Two different aromatic ligands (acetylsalicylic acid, ASA and 2-picolinic acid, PA) were employed to functionalize the surface of Tb 3+:LaF3 nanocrystals. We have used infrared spectroscopy, thermal analysis, elemental analysis, dynamic light scattering, rheological measurements and optical spectroscopy to investigate the nanoparticle structure and composition response of ligand-capped nanocrystals under various synthesis parameters. A theoretical interpretation of particle-to-particle interactions also was conducted which supported our study of the potential of agglomeration within the nanoparticle suspensions. Novel amorphous polymers (e.g. perfluorocyclobutyl aryl ethers, PFCB), which do not exhibit strong C-H vibrations, have been reported to possess excellent optical properties. Little is known of the intrinsic properties of PFCBs (e.g. biphenylvinyl ether, BPVE and hexafluoroisopropylidene vinyl ether, 6F) as well as the behavior of the polymer melt during extrusion. We preformed empirical and experimental thermal

  16. High light extraction efficiency in bulk-GaN based volumetric violet light-emitting diodes

    Science.gov (United States)

    David, Aurelien; Hurni, Christophe A.; Aldaz, Rafael I.; Cich, Michael J.; Ellis, Bryan; Huang, Kevin; Steranka, Frank M.; Krames, Michael R.

    2014-12-01

    We report on the light extraction efficiency of III-Nitride violet light-emitting diodes with a volumetric flip-chip architecture. We introduce an accurate optical model to account for light extraction. We fabricate a series of devices with varying optical configurations and fit their measured performance with our model. We show the importance of second-order optical effects like photon recycling and residual surface roughness to account for data. We conclude that our devices reach an extraction efficiency of 89%.

  17. Energy-recycling pixel for active-matrix organic light-emitting diode display

    Science.gov (United States)

    Yang, Che-Yu; Cho, Ting-Yi; Chen, Yen-Yu; Yang, Chih-Jen; Meng, Chao-Yu; Yang, Chieh-Hung; Yang, Po-Chuan; Chang, Hsu-Yu; Hsueh, Chun-Yuan; Wu, Chung-Chih; Lee, Si-Chen

    2007-06-01

    The authors report a pixel structure for active-matrix organic light-emitting diode (OLED) displays that has a hydrogenated amorphous silicon solar cell inserted between the driving polycrystalline Si thin-film transistor and the pixel OLED. Such an active-matrix OLED pixel structure not only exhibits a reduced reflection (and thus improved contrast) compared to conventional OLEDs but also is capable of recycling both incident photon energies and internally generated OLED radiation. Such a feature of energy recycling may be of use for portable/mobile electronics, which are particularly power aware.

  18. Laser pumped light emitting diodes as broad area sources of coherent radiation

    Science.gov (United States)

    Rahman, Faiz; Sorel, Marc

    2006-08-01

    This paper describes the use of large area light emitting diodes, pumped with various laser sources, as extended area emitters of coherent radiation. The photon recycling takes place through the intermediary of electron hole pair formation and subsequent stimulated recombination. It is possible to generate both spontaneous and stimulated emission together and the two channels are then independent of each other. This allows the generation of a mixture of coherent and non-coherent radiation in any desired proportion. The technique described is a broad-band resonant process with diffusive feedback and can be used for generating non-collimated laser radiation for a variety of applications.

  19. Spontaneous emission model of lateral light extraction from heterostructure light-emitting diodes

    Science.gov (United States)

    Ochoa, D.; Houdré, R.; Stanley, R. P.; Ilegems, M.; Benisty, H.; Hanke, C.; Borchert, B.

    2000-05-01

    We investigate the extraction of light from semiconductor light-emitting diodes made of dielectric multilayer stacks with quantum-well sources. The model is a combination of a rigorous vertical model of dipole emission and an in-plane ray-tracing model. The vertical model is shown to conveniently provide the relevant horizontal decay length of the various kinds of in-plane propagating modes. The proposed combination of the two models accounts for the lateral extraction as well as light recycling in the active layers.

  20. Color-tunable light emitting diodes based on quantum dot suspension.

    Science.gov (United States)

    Luo, Zhenyue; Chen, Haiwei; Liu, Yifan; Xu, Su; Wu, Shin-Tson

    2015-04-01

    We propose a color-tunable light emitting diode (LED) consisting of a blue LED as the light source and quantum dot (QD) suspension as the color-conversion medium. The LED color temperature can be controlled by varying the liquid volume of each QD suspension with different photoluminescence colors. We simulate and optimize the light efficiency and color quality of the color-tunable LED and also fabricated a prototype to prove concept. The proposed color-tunable LED exhibits several advantages such as excellent color-rendering property, simple structure and driving mechanism, as well as high energy efficiency. Its potential applications include circadian rhythm regulation and healthy lighting.

  1. Electroluminescence and impedance analyses of organic light emitting diodes using anhydride materials as cathode interfacial layers

    Energy Technology Data Exchange (ETDEWEB)

    Nam, Eunkyoung [Department of Physics, Brain Korea 21 Physics Research Division, Institute of Basic Science, Sungkyunkwan University, Suwon, 440-746 (Korea, Republic of); Park, Hyungjun [School of Information and Communication Engineering, Sungkyunkwan University, Suwon, 440-746 (Korea, Republic of); Park, Keunhee; Moon, Mi Ran [Department of Physics, Brain Korea 21 Physics Research Division, Institute of Basic Science, Sungkyunkwan University, Suwon, 440-746 (Korea, Republic of); Sohn, Sunyoung [Korea Basic Science Institute, Dukjin Dong 664-14, Jeonju 561-756 (Korea, Republic of); Jung, Donggeun [Department of Physics, Brain Korea 21 Physics Research Division, Institute of Basic Science, Sungkyunkwan University, Suwon, 440-746 (Korea, Republic of); Yi, Junsin [School of Information and Communication Engineering, Sungkyunkwan University, Suwon, 440-746 (Korea, Republic of); Chae, Heeyeop [Department of Chemical Engineering, Sungkyunkwan University, Suwon, 440-746 (Korea, Republic of); Kim, Hyoungsub, E-mail: hsubkim@skku.ed [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, 440-746 (Korea, Republic of)

    2009-05-29

    Pyromellitic dianhydride (PMDA) and trimellitic anhydride (TMA) were tried as cathode interfacial layers between tris-(8-hydroxyquinoline) aluminum (Alq{sub 3}) and Al in organic light emitting diodes (OLEDs). Both ultra-thin anhydride cathode interfacial layers improved the electroluminescence characteristics of OLEDs compared to those without any interfacial layer, and the PMDA interfacial layer showed the most significant enhancement of the device performance. According to impedance measurements and equivalent circuit analysis, the PMDA interfacial layer decreased the impedance, probably due to the increase in the injection efficiency of electrons from the Al cathode.

  2. A nearly ideal phosphor-converted white light-emitting diode

    Science.gov (United States)

    Allen, Steven C.; Steckl, Andrew J.

    2008-04-01

    A phosphor-converted light-emitting diode was obtained with nearly ideal blue-to-white conversion loss of only 1%. This is achieved using internal reflection to steer phosphor emission away from lossy surfaces, a reflector material with high reflectivity, and a remotely located organic phosphor having (1) unity quantum efficiency (ηq), (2) homogeneous refractive index to minimize scattering, and (3) refractive index-matched to the encapsulation to eliminate total internal reflection. An inorganic composite phosphor is also reported with a nearly homogeneous refractive index to minimize diffuse scattering of emitted light, thereby maximizing the effective phosphor ηq and light extraction.

  3. Red/blue electroluminescence from europium-doped organic light emitting diodes

    Science.gov (United States)

    Hagen, Joshua A.; Li, Wayne X.; Grote, James G.; Steckl, Andrew J.

    2006-02-01

    Red/Blue emitting organic light emitting diodes (OLED) devices have been obtained using a Europium-doped organic emitting layer (NPB:Eu). The Eu-doped OLEDs emit in 2 color ranges: a broad blue (~420-500nm) band due to NPB emission and a narrow red peak at 620nm due to Eu emission. The red/blue devices achieve a brightness ~13x more intense than a similarly structured green (Alq 3) emitting OLED. These NPB:Eu emitting structures also reach a maximum efficiency of 0.2 cd/A at brightnesses above 100 cd/m2.

  4. Surface recombination measurements on III-V candidate materials for nanostructure light-emitting diodes

    Science.gov (United States)

    Boroditsky, M.; Gontijo, I.; Jackson, M.; Vrijen, R.; Yablonovitch, E.; Krauss, T.; Cheng, Chuan-Cheng; Scherer, A.; Bhat, R.; Krames, M.

    2000-04-01

    Surface recombination is an important characteristic of an optoelectronic material. Although surface recombination is a limiting factor for very small devices it has not been studied intensively. We have investigated surface recombination velocity on the exposed surfaces of the AlGaN, InGaAs, and InGaAlP material systems by using absolute photoluminescence quantum efficiency measurements. Two of these three material systems have low enough surface recombination velocity to be usable in nanoscale photonic crystal light-emitting diodes.

  5. Enhanced Light Extraction From Triangular GaN-Based Light-Emitting Diodes

    OpenAIRE

    Kim, J. Y.; M. K. Kwon; Kim, J P; Park, S J

    2007-01-01

    This study investigated the characteristics of a triangular light-emitting diode (LED) and compared it to a standard quadrangular LED. The total radiant flux from the packaged triangular LED increased by 48% and 24% at input currents of 20 and 100 mA, respectively, compared to that of a quadrangular LED which was grown on patterned sapphire substrate. In light far-field beam distribution, the light extraction in the horizontal direction of the LED was much higher than that of the quadrangular...

  6. Device Fabrication of 60 μm Resonant Cavity Light-Emitting Diode

    Directory of Open Access Journals (Sweden)

    J. J. C. Reyes

    2004-12-01

    Full Text Available An array of 60-mm-diameter resonant cavity light-emitting diodes suited for coupling with fiber opticwere fabricated using standard device fabrication technique. I-V characterization was used to determinethe viability of the device fabricating process. Under forward bias, the turn-on voltage of the devices is1.95–2.45 V with a series resistance of 17–14 kW. Under reverse bias, the devices showed a breakdownvoltage of 35 V.

  7. InP/ZnS nanocrystals for colour conversion in white light emitting diodes

    DEFF Research Database (Denmark)

    Shirazi, Roza

    In this work a comprehensive study of a colloidal InP/ZnS nanocrystals (NC) as the colour conversion material for white light emitting diodes (WLED) is shown. Studied nanocrystals were synthesised by wet chemistry using one pot, hot injection method. A quantum efficiency (QE) of photoluminescence...... joined with a time resolved photoluminescence (TRPL) measurements of NCs covering the visible light spectrum range revealed a presence of a population of NCs that does not emit light upon photon absorption and it is significantly higher for a larger particles. By modifying local density of optical states...

  8. Efficient deep-blue organic light-emitting diodes using double-emitting layer.

    Science.gov (United States)

    Seo, Ji Hoon; Seo, Bo Min; Lee, Seok Jae; Lee, Kum Hee; Yoon, Seung Soo; Kim, Young Kwan

    2012-04-01

    Efficient deep-blue organic light-emitting diodes were demonstrated using 1,4-tetranaphthalene doped in double-emitting layers (D-EMLs) consisting of 2-methyl-9,10-di(2-naphthyl)anthracene and 4'-(dinaphthalen-2-yl)-1,1'-binaphthyl as blue hosts. The device with D-EML exhibits good confinement of holes and electrons, as well as a broad recombination zone. The optimized device showed a peak current efficiency of 3.67 cd/A, a peak external quantum efficiency of 3.97%, and Commission Internationale de L'Eclairage coordinates of (0.16, 0.10).

  9. Bigger, Brighter, Bluer-Better?Current light-emitting devices- adverse sleep properties and preventative strategies.

    OpenAIRE

    Paul eGringras; Benita eMiddleton; Debra eSkene; victoria erevell

    2015-01-01

    ObjectiveIn an effort to enhance the efficiency, brightness and contrast of light-emitting (LE) devices during the day, displays often generate substantial short-wavelength (blue-enriched) light emissions that can adversely affect sleep. We set out to verify the extent of such short-wavelength emissions, produced by a tablet (iPad Air), e-reader (Kindle Paperwhite 1st generation) and smartphone (iPhone 5s) and to determine the impact of strategies designed to reduce these light emissions. Set...

  10. Natural substrate lift-off technique for vertical light-emitting diodes

    Science.gov (United States)

    Lee, Chia-Yu; Lan, Yu-Pin; Tu, Po-Min; Hsu, Shih-Chieh; Lin, Chien-Chung; Kuo, Hao-Chung; Chi, Gou-Chung; Chang, Chun-Yen

    2014-04-01

    Hexagonal inverted pyramid (HIP) structures and the natural substrate lift-off (NSLO) technique were demonstrated on a GaN-based vertical light-emitting diode (VLED). The HIP structures were formed at the interface between GaN and the sapphire substrate by molten KOH wet etching. The threading dislocation density (TDD) estimated by transmission electron microscopy (TEM) was reduced to 1 × 108 cm-2. Raman spectroscopy indicated that the compressive strain from the bottom GaN/sapphire was effectively released through the HIP structure. With the adoption of the HIP structure and NSLO, the light output power and yield performance of leakage current could be further improved.

  11. A Substrate-Reclamation Technology for GaN-Based Lighting-Emitting Diodes Wafer

    Directory of Open Access Journals (Sweden)

    Shih-Yung Huang

    2017-03-01

    Full Text Available This study reports on the use of a substrate-reclamation technology for a gallium nitride (GaN-based lighting-emitting diode (LED wafer. There are many ways to reclaim sapphire substrates of scrap LED wafers. Compared with a common substrate-reclamation method based on chemical mechanical polishing, this research technology exhibits simple process procedures, without impairing the surface morphology and thickness of the sapphire substrate, as well as the capability of an almost unlimited reclamation cycle. The optical performances of LEDs on non-reclaimed and reclaimed substrates were consistent for 28.37 and 27.69 mcd, respectively.

  12. Efficient organic light-emitting devices with platinum-complex emissive layer

    KAUST Repository

    Yang, Xiaohui

    2011-01-18

    We report efficient organic light-emitting devices having a platinum-complex emissive layer with the peak external quantum efficiency of 17.5% and power efficiency of 45 lm W−1. Variation in the device performance with platinum-complex layer thickness can be attributed to the interplay between carrier recombination and intermolecular interactions in the layer. Efficient white devices using double platinum-complex layers show the external quantum efficiency of 10%, the Commission Internationale d’Énclairage coordinates of (0.42, 0.41), and color rendering index of 84 at 1000 cd m−2.

  13. Irreversible Thermodynamic Bound for the Efficiency of Light-Emitting Diodes

    Science.gov (United States)

    Xue, Jin; Li, Zheng; Ram, Rajeev J.

    2017-07-01

    A thermodynamic model for light-emitting diodes (LEDs) is developed by considering energy and entropy flows in the system. Thermodynamic constraints have previously been considered separately for the reversible process of electroluminescence in LEDs and for light extraction and collimation in other optical systems. By considering both processes in the LED model, an irreversible upper bound for the conversion of electrical energy to optical energy is derived and shown to be higher than unity, but tighter and more realistic than the reversible case. We also model a LED as an endoreversible heat engine where the carrier-transport processes can be directly connected to the elements of a thermodynamic cycle.

  14. Evaluation of light-emitting diodes as attractant for sandflies (Diptera: Psychodidae: Phlebotominae in northeastern Brazil

    Directory of Open Access Journals (Sweden)

    Francinaldo Soares Silva

    2015-09-01

    Full Text Available Hoover Pugedo light traps were modified for use with green and blue-light-emitting diodes to trap phlebotomine sandflies in northeastern Brazil. A total of 2,267 specimens belonging to eight genera and 15 species were sampled. The predominant species were Nyssomyia whitmani(34.41% and Micropygomyia echinatopharynx(17.25%.The green LED trap prevailed over the blue and control lights; however, no statistically significant difference could be detected among the three light sources. Even without statistical significance, we suggest using LEDs as an attractant for the capture of sandflies because of several advantages over the conventional method with incandescent lamps.

  15. Staining-free malaria diagnostics by multispectral and multimodality light-emitting-diode microscopy.

    Science.gov (United States)

    Merdasa, Aboma; Brydegaard, Mikkel; Svanberg, Sune; Zoueu, Jeremie T

    2013-03-01

    We report an accurate optical differentiation technique between healthy and malaria-infected erythrocytes by quasi-simultaneous measurements of transmittance, reflectance, and scattering properties of unstained blood smears using a multispectral and multimode light-emitting diode microscope. We propose a technique for automated imaging, identification, and counting of malaria-infected erythrocytes for real-time and cost-effective parasitaemia diagnosis as an effective alternative to the manual screening of stained blood smears, now considered to be the gold standard in malaria diagnosis. We evaluate the performance of our algorithm against manual estimations of an expert and show a spectrally resolved increased scattering from malaria-infected blood cells.

  16. Influence of dehydrated nanotubed titanic acid on polymer light-emitting diodes with phosphorescent dye

    Science.gov (United States)

    Qian, L.; Zhang, T.; Wang, Y. S.; Xu, X. R.; Jin, Z. S.; Du, Z. L.

    2006-01-01

    In this letter, we demonstrate that hole injection and transport in polymer light-emitting diodes with phosphorescent dye Ir(ppy)3 can be significantly enhanced by doping p-type conductive dehydrated nanotubed titanic acid into poly(vinylcarbazole) (PVK) films at 2wt.%. At the same time, both energy transfer and exciton recombination efficiency are improved because of the open and straight conformation of the PVK molecule in the nanocomposite. The performance of these devices was greatly improved, showing higher luminance, enhanced efficiency, and a lower turn-on voltage.

  17. Charge injection and transport properties of an organic light-emitting diode

    Directory of Open Access Journals (Sweden)

    Peter Juhasz

    2016-01-01

    Full Text Available The charge behavior of organic light emitting diode (OLED is investigated by steady-state current–voltage technique and impedance spectroscopy at various temperatures to obtain activation energies of charge injection and transport processes. Good agreement of activation energies obtained by steady-state and frequency-domain was used to analyze their contributions to the charge injection and transport. We concluded that charge is injected into the OLED device mostly through the interfacial states at low voltage region, whereas the thermionic injection dominates in the high voltage region. This comparison of experimental techniques demonstrates their capabilities of identification of major bottleneck of charge injection and transport.

  18. Interface modification and material synthesis of organic light-emitting diodes using plasma technology

    Science.gov (United States)

    Liang, Rongqing; Ou, Qiongrong; Yang, Cheng; He, Kongduo; Yang, Xilu; Zhong, Shaofeng; plasma application Team

    2015-09-01

    Organic light-emitting diodes (OLEDs), due to their unique properties of solution processability, compatibility with flexible substrates and with large-scale printing technology, attract huge interest in the field of lighting. The integration of plasma technology into OLEDs provides a new route to improve their performance. Here we demonstrate the modification of indium-tin-oxide (ITO) work function by plasma treatment, synthesis of thermally activated delayed fluorescence (TADF) materials using plasma grafting (polymerisation), and multi-layer solution processing achieved by plasma cross-linking.

  19. Solution-processed white phosphorescent tandem organic light-emitting devices.

    Science.gov (United States)

    Chiba, Takayuki; Pu, Yong-Jin; Kido, Junji

    2015-08-26

    Solution-processed phosphorescent tandem organic light-emitting devices (OLEDs) exhibit extremely high efficiencies (94 cd A(-1) ) and 26% external quantum efficiency (EQE) at 5000 cd m(-2) for green phosphorescent devices and 69 cd A(-1) and 28% EQE at 5000 cd m(-2) for white phosphorescent devices. Development of these highly efficient solution-processed tandem-OLEDs with inverted device structure paves the way to printable, low-cost, and large-area white lighting. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Unlocking the full potential of conducting polymers for high-efficiency organic light-emitting devices.

    Science.gov (United States)

    Huang, Yi-Hsiang; Tsai, Wei-Lung; Lee, Wei-Kai; Jiao, Min; Lu, Chun-Yang; Lin, Chun-Yu; Chen, Chien-Yu; Wu, Chung-Chih

    2015-02-04

    By carefully tuning the thicknesses of low-optical index PEDOT:PSS and high-index ITO layers in organic light-emitting devices (OLEDs), very high optical coupling efficiencies can be obtained through the generation of appropriate microcavity effects. These experiments result in an external quantum efficiency (EQE) of 33.7% for green phosphorescent OLEDs and even higher EQEs of 54.3% can be obtained by adopting an external out-coupling lens. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Two examples of organic opto-electronic devices: Light emitting diodes and solar cells

    Science.gov (United States)

    Maldonado, J. L.; Ramos-Ortíz, G.; Miranda, M. L.; Vázquez-Córdova, S.; Meneses-Nava, M. A.; Barbosa-García, O.; Ortíz-Gutiérrez, M.

    2008-12-01

    Organic and polymeric (plastic) opto-electronic devices have been developed over the past decade, and some of them have made the leap from the research laboratory to commercial use. We present a simple and inexpensive method of fabricating organic light emitting diodes and organic photovoltaic cells. The devices are fabricated by the deposition of solid films based on the fluorescent polymer MEH:PPV using the spin-coating technique. The films were sandwiched between electrodes, one of which was made of Bi-Pb-Cd-Sn alloy. An overview of these two devices is also provided.

  2. A non-doped phosphorescent organic light-emitting device with above 31% external quantum efficiency.

    Science.gov (United States)

    Wang, Qi; Oswald, Iain W H; Yang, Xiaolong; Zhou, Guijiang; Jia, Huiping; Qiao, Qiquan; Chen, Yonghua; Hoshikawa-Halbert, Jason; Gnade, Bruce E

    2014-12-23

    The demonstrated square-planar Pt(II)-complex has reduced triplet-triplet quenching and therefore a near unity quantum yield in the neat thin film. A non-doped phosphorescent organic light-emitting diode (PhOLED) based on this emitter achieves (31.1 ± 0.1)% external quantum efficiency without any out-coupling, which shows that a non-doped PhOLED can be comparable in efficiency to the best doped devices with very complicated device structures. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Design of a bike headlamp based on a power white-light-emitting diode

    Science.gov (United States)

    Lo, Yi-Chien; Chen, Cheng-Chien; Chou, Hung-Yu; Yang, Kai-Yu; Sun, Ching-Cherng

    2011-08-01

    In this letter, we present a new design for a light-emitting diode- based bike headlamp. The optical design contains two horizontal reflectors and a light pipe with two horizontal parallel mirrors. The designed illumination pattern in our simulations performs a contrast of 250 in the K-mark regulation, and it was measured to be 21 in the experiment with a not well-finished prototype, which was operated at 1 W. The contrast is higher than 5 as requested in the regulation.

  4. Noniterative algorithm for improving the accuracy of a multicolor-light-emitting-diode-based colorimeter

    Science.gov (United States)

    Yang, Pao-Keng

    2012-05-01

    We present a noniterative algorithm to reliably reconstruct the spectral reflectance from discrete reflectance values measured by using multicolor light emitting diodes (LEDs) as probing light sources. The proposed algorithm estimates the spectral reflectance by a linear combination of product functions of the detector's responsivity function and the LEDs' line-shape functions. After introducing suitable correction, the resulting spectral reflectance was found to be free from the spectral-broadening effect due to the finite bandwidth of LED. We analyzed the data for a real sample and found that spectral reflectance with enhanced resolution gives a more accurate prediction in the color measurement.

  5. Accuracy Improvement for Light-Emitting-Diode-Based Colorimeter by Iterative Algorithm

    Science.gov (United States)

    Yang, Pao-Keng

    2011-09-01

    We present a simple algorithm, combining an interpolating method with an iterative calculation, to enhance the resolution of spectral reflectance by removing the spectral broadening effect due to the finite bandwidth of the light-emitting diode (LED) from it. The proposed algorithm can be used to improve the accuracy of a reflective colorimeter using multicolor LEDs as probing light sources and is also applicable to the case when the probing LEDs have different bandwidths in different spectral ranges, to which the powerful deconvolution method cannot be applied.

  6. Design of an efficient light-emitting diode with 10 GHz modulation bandwidth

    Science.gov (United States)

    Fattal, D.; Fiorentino, M.; Tan, M.; Houng, D.; Wang, S. Y.; Beausoleil, Raymond G.

    2008-12-01

    We present a high-speed light-emitting-diode (LED) design for efficient modulation at speeds higher than 10 GHz. It relies on a tensile-strain GaAsP quantum well coupled with surface plasmon polaritons on a silver surface. We present optical pumping experiments showing a tenfold reduction in carrier lifetime when the quantum well is located 40 nm above the silver surface. We believe this represents the first step toward an efficient LED compatible with 10 GHz modulation speed for use in short distance optical communication systems.

  7. High-Efficiency Nitride-Based Light-Emitting Diodes with Moth-Eye Structure

    Science.gov (United States)

    Kasugai, Hideki; Miyake, Yasuto; Honshio, Akira; Mishima, Shunsuke; Kawashima, Takeshi; Iida, Kazuyoshi; Iwaya, Motoaki; Kamiyama, Satoshi; Amano, Hiroshi; Akasaki, Isamu; Kinoshita, Hiroyuki; Shiomi, Hiromu

    2005-10-01

    Nitride-based blue light-emitting diodes (LEDs) with a moth-eye structure on the back of a 6H-SiC substrate have been developed. The moth-eye LED has a roughness less than the optical wavelength at the back surface of the SiC substrate fabricated by reactive ion etching (RIE) with CF4 gas. The light extraction efficiency and corresponding output power have been increased to 3.8 times those of a LED with a conventional structure. The experimental findings agree with the results of a theoretical analysis of the effect of the moth-eye structure.

  8. Mobility balance in the light-emitting layer governs the polaron accumulation and operational stability of organic light-emitting diodes

    Science.gov (United States)

    Kim, Jae-Min; Lee, Chang-Heon; Kim, Jang-Joo

    2017-11-01

    Organic light-emitting diode (OLED) displays are lighter and more flexible, have a wider color gamut, and consume less power than conventional displays. Stable materials and the structural design of the device are important for OLED longevity. Control of charge transport and accumulation in the device is particularly important because the interaction of excitons and polarons results in material degradation. This research investigated the charge dynamics of OLEDs experimentally and by drift-diffusion modeling. Parallel capacitance-voltage measurements of devices provided knowledge of charge behavior at different driving voltages. A comparison of exciplex-forming co-host and single host structures established that the mobility balance in the emitting layers determined the amount of accumulated polarons in those layers. Consequently, an exciplex-forming co-host provides a superior structure in terms of device lifetime and efficiency because of its well-balanced mobility. Minimizing polaron accumulation is key to achieving long OLED device lifetimes. This is a crucial aspect of device physics that must be considered in the device design structure.

  9. Origin of the Electroluminescence from Annealed-ZnO/GaN Heterojunction Light-Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Kai-Chiang Hsu

    2015-11-01

    Full Text Available This paper addressed the effect of post-annealed treatment on the electroluminescence (EL of an n-ZnO/p-GaN heterojunction light-emitting diode (LED. The bluish light emitted from the 450 °C-annealed LED became reddish as the LED annealed at a temperature of 800 °C under vacuum atmosphere. The origins of the light emission for these LEDs annealed at various temperatures were studied using measurements of electrical property, photoluminescence, and Auger electron spectroscopy (AES depth profiles. A blue-violet emission located at 430 nm was associated with intrinsic transitions between the bandgap of n-ZnO and p-GaN, the green-yellow emission at 550 nm mainly originating from the deep-level transitions of native defects in the n-ZnO and p-GaN surfaces, and the red emission at 610 nm emerging from the Ga-O interlayer due to interdiffusion at the n-ZnO/p-GaN interface. The above-mentioned emissions also supported the EL spectra of LEDs annealed at 700 °C under air, nitrogen, and oxygen atmospheres, respectively.

  10. Flexible organic light-emitting diodes with transparent carbon nanotube electrodes: problems and solutions.

    Science.gov (United States)

    Hu, Liangbing; Li, Jianfeng; Liu, Jun; Grüner, George; Marks, Tobin

    2010-04-16

    We study in detail here the application of transparent, conductive carbon single-wall nanotube (SWNT) networks as electrodes in flexible organic light-emitting diodes (FOLEDs). Overall comparisons of these networks to the commonly used electrodes poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and indium tin oxide (ITO) are made, and SWNT networks are shown to have excellent optical and superior mechanical properties. The effects of protruding nanotubes, rough surface morphology, and SWNT network-adjacent layer dewetting are shown to be problematic, and approaches for addressing these issues are identified. The mechanical properties of SWNT networks and ITO are compared, and SWNT networks are shown to exhibit more durable sheet conductance under bending, which leads to bendable FOLEDs. We demonstrated FOLEDs with SWNT network anodes that exhibit outstanding light output and meet display requirements. SWNT-based FOLEDs show comparable lifetime performances to ITO-based devices. The promise and the remaining challenges for implementing SWNT networks in organic light-emitting diodes are discussed.

  11. Light emitting diode package element with internal meniscus for bubble free lens placement

    Science.gov (United States)

    Tarsa, Eric; Yuan, Thomas C.; Becerra, Maryanne; Yadev, Praveen

    2010-09-28

    A method for fabricating a light emitting diode (LED) package comprising providing an LED chip and covering at least part of the LED chip with a liquid encapsulant having a radius of curvature. An optical element is provided having a bottom surface with at least a portion having a radius of curvature larger than the liquid encapsulant. The larger radius of curvature portion of the optical element is brought into contact with the liquid encapsulant. The optical element is then moved closer to the LED chip, growing the contact area between said optical element and said liquid encapsulant. The liquid encapsulant is then cured. A light emitting diode comprising a substrate with an LED chip mounted to it. A meniscus ring is on the substrate around the LED chip with the meniscus ring having a meniscus holding feature. An inner encapsulant is provided over the LED chip with the inner encapsulant having a contacting surface on the substrate, with the meniscus holding feature which defines the edge of the contacting surface. An optical element is included having a bottom surface with at least a portion that is concave. The optical element is arranged on the substrate with the concave portion over the LED chip. A contacting encapsulant is included between the inner encapsulant and optical element.

  12. Comparison of organic light emitting diodes with different mixed layer structures

    Energy Technology Data Exchange (ETDEWEB)

    Kee, Y.Y.; Siew, W.O. [Faculty of Engineering, Multimedia University, 63100 Cyberjaya (Malaysia); Yap, S.S. [Faculty of Engineering, Multimedia University, 63100 Cyberjaya (Malaysia); Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia); Tou, T.Y., E-mail: tytou@mmu.edu.my [Faculty of Engineering, Multimedia University, 63100 Cyberjaya (Malaysia)

    2014-11-03

    A mixed-source thermal evaporation method was used to fabricate organic light emitting diodes (OLEDs) with uniformly mixed (UM), continuously graded mixed (CGM) and step-wise graded, mixed (SGM) light-emitting layers. N,N′-Bis(3-methylphenyl)-N,N′-diphenylbenzidine and Tris-(8-hydroxyquinoline)aluminum were used, respectively, as the hole- and electron-transport materials. As compared to the conventional, heterojunction OLED, the maximum brightness of UM-, CGM- and SGM-OLEDs without charge injection layers were improved by 2.2, 3.8 and 2.1 times, respectively, while the maximum power efficiencies improved by 1.5, 3.2 and 1.9 times. These improvements were discussed in terms of more distributed recombination zone and removal of interfacial barrier. - Highlights: • Fabrication of OLEDs using a mixed-source evaporation technique • Three different types of mixed-host OLEDs with better brightness • Improved electroluminescence and power efficiencies as compared to conventional OLED.

  13. Efficient inverted organic light-emitting devices by amine-based solvent treatment (Presentation Recording)

    Science.gov (United States)

    Song, Myoung Hoon; Choi, Kyoung-Jin; Jung, Eui Dae

    2015-10-01

    The efficiency of inverted polymer light-emitting diodes (iPLEDs) were remarkably enhanced by introducing spontaneously formed ripple-shaped nanostructure of ZnO (ZnO-R) and amine-based polar solvent treatment using 2-methoxyethanol and ethanolamine (2-ME+EA) co-solvents on ZnO-R. The ripple-shape nanostructure of ZnO layer fabricated by solution process with optimal rate of annealing temperature improves the extraction of wave guide modes inside the device structure, and 2-ME+EA interlayer enhances the electron injection and hole blocking and reduces exciton quenching between polar solvent treated ZnO-R and emissive layer. As a result, our optimized iPLEDs show the luminous efficiency (LE) of 61.6 cd A-1, power efficiency (PE) of 19.4 lm W-1 and external quantum efficiency (EQE) of 17.8 %. This method provides a promising method, and opens new possibilities for not only organic light-emitting diodes (OLEDs) but also other organic optoelectronic devices such as organic photovoltaics, organic thin film transistors, and electrically driven organic diode laser.

  14. Effect of the structure on luminescent characteristics of SRO-based light emitting capacitors

    Science.gov (United States)

    Palacios-Huerta, L.; Cabañas-Tay, S. A.; Luna-López, J. A.; Aceves-Mijares, M.; Coyopol, A.; Morales-Sánchez, A.

    2015-10-01

    In this paper, we study the structural, optical and electro-optical properties of silicon rich oxide (SRO) films, with 6.2 (SRO30) and 7.3 at.% (SRO20) of silicon excess thermally annealed at different temperatures and used as an active layer in light emitting capacitors (LECs). A typical photoluminescence (PL) red-shift is observed as the silicon content and annealing temperature are increased. Nevertheless, when SRO30 films are used in LECs, a resistance switching (RS) behavior from a high current state (HCS) to a low conduction state (LCS) is observed, enhancing the intense blue electroluminescence (EL). This RS produces a long spectral blue-shift (˜227 nm) between the EL and PL band, and it is related to structural defects created by a high current flow through preferential conductive paths breaking off Si-Si bonds from very small silicon nanoparticles (Si-nps) (Eδ (Si ↑ Si ≡ Si) centers). LECs with SRO20 films do not present the RS behavior and only exhibit a slight shift between PL and EL, both in red spectra. The carrier transport in these LEC devices is analyzed as being trap assisted tunnelling and Poole-Frenkel through a quasi ‘continuum’ of defect traps and quantum dots for the conduction mechanism in SRO30 and SRO20 films, respectively. The results prove the feasibility of obtaining light emitting devices by using simple panel structures with Si-nps embedded in the dielectric layer.

  15. Bigger, Brighter, Bluer-Better?Current light-emitting devices- adverse sleep properties and preventative strategies.

    Directory of Open Access Journals (Sweden)

    Paul eGringras

    2015-10-01

    Full Text Available ObjectiveIn an effort to enhance the efficiency, brightness and contrast of light-emitting (LE devices during the day, displays often generate substantial short-wavelength (blue-enriched light emissions that can adversely affect sleep. We set out to verify the extent of such short-wavelength emissions, produced by a tablet (iPad Air, e-reader (Kindle Paperwhite 1st generation and smartphone (iPhone 5s and to determine the impact of strategies designed to reduce these light emissions. SettingUniversity of Surrey dedicated chronobiology facility.MethodsFirstly, the spectral power of all the light-emitting (LE devices was assessed when displaying identical text. Secondly, we compared the text output with that of ‘Angry Birds’-a popular top 100 ‘App Store’ game. Finally we measured the impact of two strategies that attempt to reduce the output of short-wavelength light emissions. The first strategy employed an inexpensive commercially available pair of orange-tinted ‘blue-blocking’ glasses. The second tested an app designed to be ‘sleep-aware’ whose designers deliberately attempted to reduce blue-enriched light emissions.ResultsAll the LE devices shared very similar enhanced blue-light peaks when displaying text. This included the output from the backlit Kindle Paperwhite device. The spectra when comparing text to the Angry Birds game were also very similar, although the

  16. Polaron self-localization in white-light emitting hybrid perovskites

    KAUST Repository

    Cortecchia, Daniele

    2017-02-03

    Two-dimensional (2D) perovskites with the general formula APbX are attracting increasing interest as solution processable, white-light emissive materials. Recent studies have shown that their broadband emission is related to the formation of intra-gap colour centres. Here, we provide an in-depth description of the charge localization sites underlying the generation of such radiative centres and their corresponding decay dynamics, highlighting the formation of small polarons trapped within their lattice distortion field. Using a combination of spectroscopic techniques and first-principles calculations to study the white-light emitting 2D perovskites (EDBE)PbCl and (EDBE)PbBr, we infer the formation of Pb , Pb, and X (where X = Cl or Br) species confined within the inorganic perovskite framework. Due to strong Coulombic interactions, these species retain their original excitonic character and form self-trapped polaron-excitons acting as radiative colour centres. These findings are expected to be relevant for a broad class of white-light emitting perovskites with large polaron relaxation energy.

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

    CERN Document Server

    Li Juan Zo

    2003-01-01

    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 - sup 5 cm sup 2 /Vs and approx 10 sup - sup 4 cm sup 2 /Vs, respectively. Overshoot effects...

  18. Electron-hole capture in polymer heterojunction light-emitting diodes

    Science.gov (United States)

    Greenham, Neil

    2005-03-01

    Polymer light-emitting diodes based on blends of polyfluorene derivatives show very high efficiencies and low drive voltages. Electron-hole capture in these devices directly produces long-lived exciplex states where the electron and hole are predominantly localized on opposite sides of the heterojunction. The exciplex may then be thermally excited to form an intra-chain exciton, which can itself either emit, or be recycled to reform the exciplex. I will review the physics of exciplex formation and emission in these devices, and will show that exciplex formation rates are consistent with low free charge densities at the heterojunction. I will present evidence that the rate of charge transfer at polyfluorene heterojunctions can be modulated with an applied electric field, leading in some cases to an increase in photoluminescence efficiency with applied field. I will also present recent results showing enhanced triplet exciton formation after photoexcitation in polyfluorene blends, and will discuss the implications of the results for polymer light-emitting and photovoltaic devices.

  19. Transient measurement of light-emitting diode characteristic parameters for production lines.

    Science.gov (United States)

    Zhou, Shengjun; Liu, Sheng

    2009-09-01

    A new instrument has been developed for transient measurement of light-emitting diodes (LEDs), including photometric parameters, colorimetric parameters, and electrical parameters in a matter of milliseconds, by combining spectrometer with a human photopic vision detector and data acquisition card (DAQ). The instrument can provide communication interface for sorter to realize automatic sorting of measured LEDs samples. The light emitted from the measured LEDs, which are illuminated under pulse current operation condition, is captured by the spectrometer and the human photopic vision detector. The spectral power distributions of LEDs are recorded by spectrometer, and processed to provide colorimetric parameters. We employ two novel algorithms including look-up table method and curve fitting method to determine the dominant wavelength of LED. In combination with linear interpolation, the look-up table method can locate dominant wavelength with a resolution of 0.1 nm. A programmable constant current source/voltage source is designed for power supply to drive LED. The luminous intensity of LED can be derived by detecting the photocurrent of human photopic vision detector. We also describe the calibration of the human photopic vision detector. This calibration provides detector-specific correction factor that enables accurate extraction of luminous intensity of LED. The instrument has been used to measure and inspect the quality of packaging LED.

  20. Influence of electron transport layer thickness on optical properties of organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Guohong; Liu, Yong; Li, Baojun; Zhou, Xiang, E-mail: stszx@mail.sysu.edu.cn [State Key Lab of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China)

    2015-06-07

    We investigate experimentally and theoretically the influence of electron transport layer (ETL) thickness on properties of typical N,N′-diphenyl-N,N′-bis(1-naphthyl)-[1,1′-biphthyl]-4,4′-diamine (NPB)/tris-(8-hydroxyquinoline) aluminum (Alq{sub 3}) heterojunction based organic light-emitting diodes (OLEDs), where the thickness of ETL is varied to adjust the distance between the emitting zone and the metal electrode. The devices showed a maximum current efficiency of 3.8 cd/A when the ETL thickness is around 50 nm corresponding to an emitter-cathode distance of 80 nm, and a second maximum current efficiency of 2.6 cd/A when the ETL thickness is around 210 nm corresponding to an emitter-cathode distance of 240 nm. We adopt a rigorous electromagnetic approach that takes parameters, such as dipole orientation, polarization, light emitting angle, exciton recombination zone, and diffusion length into account to model the optical properties of devices as a function of varying ETL thickness. Our simulation results are accurately consistent with the experimental results with a widely varying thickness of ETL, indicating that the theoretical model may be helpful to design high efficiency OLEDs.

  1. Influence of electron transport layer thickness on optical properties of organic light-emitting diodes

    Science.gov (United States)

    Liu, Guohong; Liu, Yong; Li, Baojun; Zhou, Xiang

    2015-06-01

    We investigate experimentally and theoretically the influence of electron transport layer (ETL) thickness on properties of typical N,N'-diphenyl-N,N'-bis(1-naphthyl)-[1,1'-biphthyl]-4,4'-diamine (NPB)/tris-(8-hydroxyquinoline) aluminum (Alq3) heterojunction based organic light-emitting diodes (OLEDs), where the thickness of ETL is varied to adjust the distance between the emitting zone and the metal electrode. The devices showed a maximum current efficiency of 3.8 cd/A when the ETL thickness is around 50 nm corresponding to an emitter-cathode distance of 80 nm, and a second maximum current efficiency of 2.6 cd/A when the ETL thickness is around 210 nm corresponding to an emitter-cathode distance of 240 nm. We adopt a rigorous electromagnetic approach that takes parameters, such as dipole orientation, polarization, light emitting angle, exciton recombination zone, and diffusion length into account to model the optical properties of devices as a function of varying ETL thickness. Our simulation results are accurately consistent with the experimental results with a widely varying thickness of ETL, indicating that the theoretical model may be helpful to design high efficiency OLEDs.

  2. Efficient charge balance in blue phosphorescent organic light emitting diodes by two types of mixed layer

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Hyung Jin; Lee, Ho Won; Lee, Song Eun; Sun, Yong; Hwang, Kyo Min; Yoo, Han Kyu; Lee, Sung Kyu [Department of Information Display, Hongik University, Seoul 121-791 (Korea, Republic of); Kim, Woo Young, E-mail: wykim@hoseo.edu [Department of Green Energy & Semiconductor Engineering, Hoseo University, Asan 336-795 (Korea, Republic of); Kim, Young Kwan, E-mail: kimyk@hongik.ac.kr [Department of Information Display, Hongik University, Seoul 121-791 (Korea, Republic of)

    2015-07-31

    The authors have demonstrated a highly efficient and long-lifetime blue phosphorescent organic light emitting diode (PHOLED) that uses two types of mixed layers. The mixed layers play the role of carrier injection control and exciton generation zone extension. One of the layers is applied for mixing the hole transport layer (HTL) and host material at the HTL side for carrier injection control. The other works as a mixed electron transporting layer (ETL) and host material at the ETL side. The optimized blue PHOLED has been shown to achieve high performance owing to the mixed layer effects. It gave a maximum luminous efficiency of 25.55 cd/A, maximum external quantum efficiency of 13.05%, and lifetime of 7.24 h under 500 cd/m{sup 2}. These results indicate that applying mixed layers is a simple and efficient method that does not require significant structural change. - Highlights: • Highly efficient blue phosphorescent organic light-emitting diode (PHOLEDs) • Hole transporting layer consists with mixed layer for delayed hole injection • The blue PHOLEDs with long lifetime due to suppression of quenching process.

  3. Organic Light-Emitting Diodes with a Perylene Interlayer Between the Electrode-Organic Interface

    Science.gov (United States)

    Saikia, Dhrubajyoti; Sarma, Ranjit

    2018-01-01

    The performance of an organic light-emitting diode (OLED) with a vacuum-deposited perylene layer over a fluorine-doped tin oxide (FTO) surface is reported. To investigate the effect of the perylene layer on OLED performance, different thicknesses of perylene are deposited on the FTO surface and their current density-voltages (J-V), luminance-voltages (L-V) and device efficiency characteristics at their respective thickness are studied. Further analysis is carried out with an UV-visible light double-beam spectrophotometer unit, a four-probe resistivity unit and a field emission scanning electron microscope set up to study the optical transmittance, sheet resistance and surface morphology of the bilayer anode film. We used N,N'-bis(3-methyl phenyl)- N,N'(phenyl)-benzidine (TPD) as the hole transport layer, Tris(8-hydroxyquinolinato)aluminum (Alq3) as a light-emitting layer and lithium fluoride as an electron injection layer. The luminance efficiency of an OLED structure with a 9-nm-thick perylene interlayer is increased by 2.08 times that of the single-layer FTO anode OLED. The maximum value of current efficiency is found to be 5.25 cd/A.

  4. Low temperature solution process-based defect-induced orange-red light emitting diode

    Science.gov (United States)

    Biswas, Pranab; Baek, Sung-Doo; Hoon Lee, Sang; Park, Ji-Hyeon; Jeong Lee, Su; Il Lee, Tae; Myoung, Jae-Min

    2015-01-01

    We report low-temperature solution-processed p-CuO nanorods (NRs)/n-ZnO NRs heterojunction light emitting diode (LED), exploiting the native point defects of ZnO NRs. ZnO NRs were synthesized at 90 °C by using hydrothermal method while CuO NRs were synthesized at 100 °C by using microwave reaction system. The electrical properties of newly synthesized CuO NRs revealed a promising p-type nature with a hole concentration of 9.64 × 1018 cm−3. The current-voltage characteristic of the heterojunction showed a significantly high rectification ratio of 105 at 4 V with a stable current flow. A broad orange-red emission was obtained from the forward biased LED with a major peak at 610 nm which was attributed to the electron transition from interstitial zinc to interstitial oxygen point defects in ZnO. A minor shoulder peak was also observed at 710 nm, corresponding to red emission which was ascribed to the transition from conduction band of ZnO to oxygen vacancies in ZnO lattice. This study demonstrates a significant progress toward oxide materials based, defect-induced light emitting device with low-cost, low-temperature methods. PMID:26648420

  5. Improved heat dissipation in gallium nitride light-emitting diodes with embedded graphene oxide pattern.

    Science.gov (United States)

    Han, Nam; Cuong, Tran Viet; Han, Min; Ryu, Beo Deul; Chandramohan, S; Park, Jong Bae; Kang, Ji Hye; Park, Young-Jae; Ko, Kang Bok; Kim, Hee Yun; Kim, Hyun Kyu; Ryu, Jae Hyoung; Katharria, Y S; Choi, Chel-Jong; Hong, Chang-Hee

    2013-01-01

    The future of solid-state lighting relies on how the performance parameters will be improved further for developing high-brightness light-emitting diodes. Eventually, heat removal is becoming a crucial issue because the requirement of high brightness necessitates high-operating current densities that would trigger more joule heating. Here we demonstrate that the embedded graphene oxide in a gallium nitride light-emitting diode alleviates the self-heating issues by virtue of its heat-spreading ability and reducing the thermal boundary resistance. The fabrication process involves the generation of scalable graphene oxide microscale patterns on a sapphire substrate, followed by its thermal reduction and epitaxial lateral overgrowth of gallium nitride in a metal-organic chemical vapour deposition system under one-step process. The device with embedded graphene oxide outperforms its conventional counterpart by emitting bright light with relatively low-junction temperature and thermal resistance. This facile strategy may enable integration of large-scale graphene into practical devices for effective heat removal.

  6. A large-scale NEMS light-emitting array based on CVD graphene (Conference Presentation)

    Science.gov (United States)

    Kim, Hyungsik; Kim, Young Duck; Lee, Changhyuk; Lee, Sunwoo; Seo, Dong-jea; Jerng, Sahng-Kyoon; Chun, Seung-Hyun; Hone, James; Shepard, Kenneth L.

    2017-02-01

    Graphene has received much interest from optical communities largely owing to its photon-like linear energy band structure called Dirac cone. While majority of the recent research has dealt with plasmon and polariton of the two-dimensional material, a recently reported graphene light emitter could render a new dimension of applications, particularly in high-speed optical communication. Moreover chemical vapor deposition (CVD) growth technique for graphene is available today providing means for scalable high quality graphene. The reported graphene emitter provides broadband light emission from visible to mid-infrared which could be instrumental in multi-color display units and optical communications, however a truly large scale implementation has not previously been achieved. Here we demonstrate a CMOS-compatible 262,144 light-emitting pixels array (10 x 10 mm2) based on suspended CVD graphene nano-electro-mechanical systems (GNEMS). A single photoemission area is 19.6 µm2 and a unit pixel is consisting of 512 photoemission devices (16 x 16) where a multiplexer and a digital to analog converter (DAC) are used to control each pixel. This work clearly demonstrates scalability of multi-channel GNEMS light-emitting array, an atomically thin electro-optical module, and further paves a path for its commercial implementation transparent display or high-speed optical communication.

  7. Highly stable cesium lead iodide perovskite quantum dot light-emitting diodes

    Science.gov (United States)

    Zou, Chen; Huang, Chun-Ying; Sanehira, Erin M.; Luther, Joseph M.; Lin, Lih Y.

    2017-11-01

    Recently, all-inorganic perovskites such as CsPbBr3 and CsPbI3, have emerged as promising materials for light-emitting applications. While encouraging performance has been demonstrated, the stability issue of the red-emitting CsPbI3 is still a major concern due to its small tolerance factor. Here we report a highly stable CsPbI3 quantum dot (QD) light-emitting diode (LED) with red emission fabricated using an improved purification approach. The device achieved decent external quantum efficiency (EQE) of 0.21% at a bias of 6 V and outstanding operational stability, with a L 70 lifetime (EL intensity decreases to 70% of starting value) of 16 h and 1.5 h under a constant driving voltage of 5 V and 6 V (maximum EQE operation) respectively. Furthermore, the device can work under a higher voltage of 7 V (maximum luminance operation) and retain 50% of its initial EL intensity after 500 s. These findings demonstrate the promise of CsPbI3 QDs for stable red LEDs, and suggest the feasibility for electrically pumped perovskite lasers with further device optimizations.

  8. PEDOT:PSS/Graphene Nanocomposite Hole-Injection Layer in Polymer Light-Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Chun-Hsuan Lin

    2012-01-01

    Full Text Available We report on effects of doping graphene in poly(3,4-ethylenedioxythiophene: poly(styrene sulfonate, PEDOT:PSS, as a PEDOT:PSS/graphene nanocomposite hole injection layer on the performance enhancement of polymer light-emitting diodes (PLEDs. Graphene oxides were first synthesized and then mixed in the PEDOT:PSS solution with specifically various amounts. Graphenes were reduced in the PEDOT:PSS matrix through thermal reduction. PLED devices with hole-injection nanocomposite layer containing particular doping concentration were fabricated, and the influence of doping concentration on device performance was examined by systematically characterizations of various device properties. Through the graphene doping, the resistance in the hole-injection layer and the turn-on voltage could be effectively reduced that benefited the injection and transport of holes and resulted in a higher overall efficiency. The conductivity of the hole-injection layer was monotonically increased with the increase of doping concentration, performance indices from various aspects, however, did not show the same dependence because faster injected holes might alter not only the balance of holes and electrons but also their combination locations in the light-emitting layer. Results show that optimal doping concentration was the case with 0.03 wt% of graphene oxide.

  9. A Closed-Loop Smart Control System Driving RGB Light Emitting Diodes

    KAUST Repository

    Al-Saggaf, Abeer

    2015-05-01

    The demand for control systems that are highly capable of driving solid-state optoelectronic devices has significantly increased with the advancement of their efficiency and elevation of their current consumption. This work presents a closed-loop control system that is based on a microcontroller embedded system capable of driving high power optoelectronic devices. In this version of the system, the device in the center of control is a high-power red, green, and blue light emitting diode package. The system features a graphical user interface, namely an Android mobile phone application, in which the user can easily use to vary the light color and intensity of the light-emitting device wirelessly via Bluetooth. Included in the system is a feedback mechanism constituted by a red, green, and blue color sensor through which the user can use to observe feedback color information about the emitted light. The system has many commercial application including in-door lighting and research application including plant agriculture research fields.

  10. Real-time imaging of tumors using replication-competent light-emitting microorganisms.

    Science.gov (United States)

    Yu, Yong A; Weibel, Stephanie; Szalay, Aladar A

    2012-01-01

    Early detection of cancer and metastases is pivotal to the success of subsequent treatment intervention. In recent years, the use of live microorganisms, such as viruses and bacteria, has gained substantial research and clinical interest in both detection and therapy of cancer. Many of these live microorganisms have shown remarkable tumor-specific replication following systemic delivery. With the aid of modern molecular technologies, modified live microorganisms can be engineered to carry additional diagnostic and therapeutic capabilities. We have shown that when armed with light-emitting protein genes, such as genes for luciferase and green fluorescent protein, the entry and specific amplification of systemically-delivered vaccinia virus and bacteria in tumors can be visualized in real time using a low-light imager, or using macro- and micro-fluorescence microscopes. Therefore, through optical imaging, the location of tumors and metastases could be revealed by these light-emitting microorganisms. The tumor-colonization capability has been demonstrated in both immuno-competent as well as immuno-compromised rodent models with syngeneic and allogeneic tumors. Based on their "tumor-finding" nature, bacteria and viruses could be further designed as "vehicles" to carry multiple genes for detection and therapy of cancer.

  11. In Situ Preparation of Metal Halide Perovskite Nanocrystal Thin Films for Improved Light-Emitting Devices.

    Science.gov (United States)

    Zhao, Lianfeng; Yeh, Yao-Wen; Tran, Nhu L; Wu, Fan; Xiao, Zhengguo; Kerner, Ross A; Lin, YunHui L; Scholes, Gregory D; Yao, Nan; Rand, Barry P

    2017-04-25

    Hybrid organic-inorganic halide perovskite semiconductors are attractive candidates for optoelectronic applications, such as photovoltaics, light-emitting diodes, and lasers. Perovskite nanocrystals are of particular interest, where electrons and holes can be confined spatially, promoting radiative recombination. However, nanocrystalline films based on traditional colloidal nanocrystal synthesis strategies suffer from the use of long insulating ligands, low colloidal nanocrystal concentration, and significant aggregation during film formation. Here, we demonstrate a facile method for preparing perovskite nanocrystal films in situ and that the electroluminescence of light-emitting devices can be enhanced up to 40-fold through this nanocrystal film formation strategy. Briefly, the method involves the use of bulky organoammonium halides as additives to confine crystal growth of perovskites during film formation, achieving CH3NH3PbI3 and CH3NH3PbBr3 perovskite nanocrystals with an average crystal size of 5.4 ± 0.8 nm and 6.4 ± 1.3 nm, respectively, as confirmed through transmission electron microscopy measurements. Additive-confined perovskite nanocrystals show significantly improved photoluminescence quantum yield and decay lifetime. Finally, we demonstrate highly efficient CH3NH3PbI3 red/near-infrared LEDs and CH3NH3PbBr3 green LEDs based on this strategy, achieving an external quantum efficiency of 7.9% and 7.0%, respectively, which represent a 40-fold and 23-fold improvement over control devices fabricated without the additives.

  12. Recent Progress in Quantum Dot Based White Light-Emitting Devices.

    Science.gov (United States)

    Su, Liang; Zhang, Xiaoyu; Zhang, Yu; Rogach, Andrey L

    2016-08-01

    Colloidal semiconductor quantum dots (QDs) have been widely employed as components of white light-emitting diodes (WLEDs) due to their excellent optical properties (highly saturated emission color, high luminescence quantum yield) as well as thermal and chemical stability. Much effort has been devoted to realize efficient QD-based WLEDs, including the synthesis of superior luminescent nanomaterials with excellent stabilities, and the design of advanced devices structures. In this paper, after introducing photometric parameters of the contemporary QD-based WLEDs, we highlight the recent progress in these devices grouped according to three main mechanisms for white light generation: optical excitation, direct charge carrier injection, and Förster resonance energy transfer. The methods to generate white light, the design of QD emitters and QD-based devices, as well as their fabrication techniques are considered, and the key scientific and technological challenges in the QD-based WLEDs are highlighted. Novel light-emitting materials for WLEDs such as carbon-based nanoparticles are also considered.

  13. White polymer light-emitting devices for solid-state lighting: materials, devices, and recent progress.

    Science.gov (United States)

    Ying, Lei; Ho, Cheuk-Lam; Wu, Hongbin; Cao, Yong; Wong, Wai-Yeung

    2014-04-23

    White polymer light-emitting devices (WPLEDs) have become a field of immense interest in both scientific and industrial communities. They have unique advantages such as low cost, light weight, ease of device fabrication, and large area manufacturing. Applications of WPLEDs for solid-state lighting are of special interest because about 20% of the generated electricity on the earth is consumed by lighting. To date, incandescent light bulbs (with a typical power efficiency of 12-17 lm W(-1) ) and fluorescent lamps (about 40-70 lm W(-1) ) are the most widely used lighting sources. However, incandescent light bulbs convert 90% of their consumed power into heat while fluorescent lamps contain a small but significant amount of toxic mercury in the tube, which complicates an environmentally friendly disposal. Remarkably, the device performances of WPLEDs have recently been demonstrated to be as efficient as those of fluorescent lamps. Here, we summarize the recent advances in WPLEDs with special attention paid to the design of novel luminescent dopants and device structures. Such advancements minimize the gap (for both efficiency and stability) from other lighting sources such as fluorescent lamps, light-emitting diodes based on inorganic semiconductors, and vacuum-deposited small-molecular devices, thus rendering WPLEDs equally competitive as these counterparts currently in use for illumination purposes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Effect of light-emitting diode colour temperature on magnifier reading performance of the visually impaired.

    Science.gov (United States)

    Wolffsohn, James S; Palmer, Eshmael; Rubinstein, Martin; Eperjesi, Frank

    2012-09-01

    As light-emitting diodes become more common as the light source for low vision aids, the effect of illumination colour temperature on magnifier reading performance was investigated. Reading ability (maximum reading speed, critical print size, threshold near visual acuity) using Radner charts and subjective preference was assessed for 107 participants with visual impairment using three stand magnifiers with light emitting diode illumination colour temperatures of 2,700 K, 4,500 K and 6,000 K. The results were compared with distance visual acuity, prescribed magnification, age and the primary cause of visual impairment. Reading speed, critical print size and near visual acuity were unaffected by illumination colour temperature (p > 0.05). Reading metrics decreased with worsening acuity and higher levels of prescribed magnification but acuity was unaffected by age. Each colour temperature was preferred and disliked by a similar number of patients and was unrelated to distance visual acuity, prescribed magnification and age (p > 0.05). Patients had better near acuity (p = 0.002), critical print size (p = 0.034) and maximum reading speed (p colour temperature illumination. A range of colour temperature illuminations should be offered to all visually impaired individuals prescribed with an optical magnifier for near tasks to optimise subjective and objective benefits. © 2012 The Authors. Clinical and Experimental Optometry © 2012 Optometrists Association Australia.

  15. ZnO PN Junctions for Highly-Efficient, Low-Cost Light Emitting Diodes

    Energy Technology Data Exchange (ETDEWEB)

    David P. Norton; Stephen Pearton; Fan Ren

    2007-09-30

    By 2015, the US Department of Energy has set as a goal the development of advanced solid state lighting technologies that are more energy efficient, longer lasting, and more cost-effective than current technology. One approach that is most attractive is to utilize light-emitting diode technologies. Although III-V compound semiconductors have been the primary focus in pursuing this objective, ZnO-based materials present some distinct advantages that could yield success in meeting this objective. As with the nitrides, ZnO is a direct bandgap semiconductor whose gap energy (3.2 eV) can be tuned from 3.0 to 4 eV with substitution of Mg for higher bandgap, Cd for lower bandgap. ZnO has an exciton binding energy of 60 meV, which is larger than that for the nitrides, indicating that it should be a superior light emitting semiconductor. Furthermore, ZnO thin films can be deposited at temperatures on the order of 400-600 C, which is significantly lower than that for the nitrides and should lead to lower manufacturing costs. It has also been demonstrated that functional ZnO electronic devices can be fabricated on inexpensive substrates, such as glass. Therefore, for the large-area photonic application of solid state lighting, ZnO holds unique potential. A significant impediment to exploiting ZnO in light-emitting applications has been the absence of effective p-type carrier doping. However, the recent realization of acceptor-doped ZnO material overcomes this impediment, opening the door to ZnO light emitting diode development In this project, the synthesis and properties of ZnO-based pn junctions for light emitting diodes was investigated. The focus was on three issues most pertinent to realizing a ZnO-based solid state lighting technology, namely (1) achieving high p-type carrier concentrations in epitaxial and polycrystalline films, (2) realizing band edge emission from pn homojunctions, and (3) investigating pn heterojunction constructs that should yield efficient light

  16. Overcoming the limitations of silver nanowire electrodes for light emitting applications

    Science.gov (United States)

    Chen, Dustin Yuan

    The global lighting market is projected to exceed 100 billion dollars by 2020, undergoing rapid transitions driven by technological advancements. In conjunction with increased demand for new technology, global regulations have become increasingly stringent, mandating the development and implementation of more fuel-efficient light sources. As prior generations of lighting technology such as incandescent bulbs and florescent lighting progressively become phased out, newer technologies such as light emitting diodes (LEDs) and organic light emitting diodes (OLEDs) have become progressively popular and commonplace. Though they still lag behind LEDs in terms of market penetration, OLEDs have garnered increasing amounts of attention in recent years due to unique attributes such as their exotic and large scale form factors, mechanical flexibility, and potential for high volume, low-cost manufacturing. Unfortunately, the costs for OLED manufacturing are currently still prohibitively high for several applications, with the anode and substrate representing 20-25 percent of this total cost. Significant technical and processing improvements for OLED substrates are of utmost necessity for fiscal cost reduction and commercialization of OLED technology. Silver nanowires have gained traction as a potential replacement for the current status quo, indium tin oxide (ITO) due to attributes such as flexibility, low cost processing, and high optoelectronic properties. However, due to nanoscale size effects, the integration of silver nanowires in both process flows and operational use has proven to be problematic. This work makes several key contributions towards enabling the use of silver nanowires for practical and commercial applications within the lighting industry. First, a novel method for the fabrication of a high temperature-stable, flexible substrate with surface roughness (Ra) quantum dot light-emitting device exhibiting high flexibility. The use of quantum dots instead of

  17. Transparent ultraviolet photovoltaic cells.

    Science.gov (United States)

    Yang, Xun; Shan, Chong-Xin; Lu, Ying-Jie; Xie, Xiu-Hua; Li, Bing-Hui; Wang, Shuang-Peng; Jiang, Ming-Ming; Shen, De-Zhen

    2016-02-15

    Photovoltaic cells have been fabricated from p-GaN/MgO/n-ZnO structures. The photovoltaic cells are transparent to visible light and can transform ultraviolet irradiation into electrical signals. The efficiency of the photovoltaic cells is 0.025% under simulated AM 1.5 illumination conditions, while it can reach 0.46% under UV illumination. By connecting several such photovoltaic cells in a series, light-emitting devices can be lighting. The photovoltaic cells reported in this Letter may promise the applications in glass of buildings to prevent UV irradiation and produce power for household appliances in the future.

  18. Lithium hydroxide doped tris(8-hydroxyquinoline) aluminum as an effective interfacial layer in inverted bottom-emission organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Kao, Po-Ching, E-mail: pckao@mail.ncyu.edu.tw; Lu, Chia-Wen; Lin, Jie-Han; Lin, Yeh-Kai

    2014-11-03

    Lithium hydroxide doped tris(8-hydroxyquinoline) aluminum (Alq{sub 3}:LiOH) is used as an effective interfacial layer for the fabrication of efficient inverted bottom-emission organic light-emitting diodes (IBOLEDs). When 15% LiOH was doped into an Alq{sub 3} electron-transporting layer, the device properties such as the turn-on voltage, maximum luminance, and device efficiency improved, becoming better than those obtained with LiF doping and comparable to those of β-naphthylphenylbiphenyl diamine (NPB)/Alq{sub 3}-based OLEDs with conventional geometry. Electrical analysis reveals that LiOH-doped Alq{sub 3} layers have an enhanced electron injection and transport ability. X-ray and ultraviolet photoelectron spectroscopy results clearly show that the dipole layer formed at the indium tin oxide (ITO)/organic interface contributed to the reduction of the ITO work function, resulting in a decrease of the electron injection barrier. The enhanced electron injection and transport efficiency improves the charge carrier balance in IBOLEDs and leads to better device efficiency. Furthermore, improved morphology of the organic layer can be obtained by doping LiOH into Alq{sub 3}, which improves device operational stability under thermal stress. - Highlights: • Inverted bottom-emission organic light-emitting diodes with Alq{sub 3}:LiOH interfacial layer were investigated. • Alq{sub 3}:LiOH layers possess an enhanced electron injection and transporting ability. • The dipole layer is formed at the Alq{sub 3}:LiOH/indium tin oxide interface. • Alq{sub 3}:LiOH interfacial layer stabilizes the surface morphology of the Alq{sub 3} film.

  19. Extraction of Y2 O3 :Cr3+ nanophosphor by eco-friendly approach and its suitability for white light-emitting diode applications.

    Science.gov (United States)

    Prasanna Kumar, J B; Ramgopal, G; Sunitha, D V; Prasad, B Daruka; Nagabhushana, H; Vidya, Y S; Anantharaju, K S; Prashantha, S C; Sharma, S C; Prabhakara, K R

    2017-05-01

    Cr3+ -doped Y2 O3 (0.5-9 mol%) was synthesized by a simple solution combustion method using Aloe vera gel as a fuel/surfactant. The final obtained product was calcined at 750°C for 3 h, which is the lowest temperature reported so far for the synthesis of this compound. The calcined product was confirmed for its crystallinity and purity by powder X-ray diffraction (PXRD) studies which showed a single-phase nano cubic phosphor. The particles size estimated by Scherrer formula was in the range of 6-19 nm. The UV-vis spectra showed absorption bands at 198, 272 and 372 nm having band gap energy in the range 4.00-4.26 eV. In order to investigate the possibility of its use in white light emitting display applications, the photoluminescence properties of Cr3+ -doped Y2 O3 nanophosphors were studied at an excitation wavelength in the near ultraviolet (UV) light region (361 nm). The emission spectra consisted of emission peaks in the blue (4 F9/2  → 6 H15/2 ), orange (4 F9/2  → 6 H13/2 ) and red (4 F9/2  → 6 H11/2 ) regions. The CIE coordinates (0.33, 0.33) lie in the white light region. Hence Y2 O3 :Cr3+ can be used for white light-emitting diode (LED) applications. Copyright © 2016 John Wiley & Sons, Ltd.

  20. Low-cost photoacoustic imaging systems based on laser diode and light-emitting diode excitation

    Directory of Open Access Journals (Sweden)

    Qingkai Yao

    2017-07-01

    Full Text Available Photoacoustic imaging, an emerging biomedical imaging modality, holds great promise for preclinical and clinical researches. It combines the high optical contrast and high ultrasound resolution by converting laser excitation into ultrasonic emission. In order to generate photoacoustic signal efficiently, bulky Q-switched solid-state laser systems are most commonly used as excitation sources and hence limit its commercialization. As an alternative, the miniaturized semiconductor laser system has the advantages of being inexpensive, compact, and robust, which makes a significant effect on production-forming design. It is also desirable to obtain a wavelength in a wide range from visible to near-infrared spectrum for multispectral applications. Focussing on practical aspect, this paper reviews the state-of-the-art developments of low-cost photoacoustic system with laser diode and light-emitting diode excitation source and highlights a few representative installations in the past decade.

  1. Photonic effects in microstructured conjugated polymer films and light emitting diodes

    CERN Document Server

    Matterson, B J

    2002-01-01

    metal layers that are used as electrodes in the LED does not adversely affect the electrical properties of the LED. It is demonstrated that grating in the LED is able to substantially increase the light emission without using extra electrical power. The emission spectra from LEDs are observed to vary with angle, and exhibit considerable polarization. This thesis reports an investigation into the photonic effects caused by wavelength scale microstructure patterned onto films of conjugated polymers. The efficiency of light emitting diodes (LEDs) made from conjugated polymers is limited in part by the trapping of light into waveguide modes caused by the high refractive index of these materials. Waveguide modes in films of poly(p,-phenylene vinylene) (PPV) and poly(2-methoxy, 5-(2'ethylhexyloxy)-p-phenylene vinylene) (MEH-PPV) are analysed and the refractive index of these materials is calculated. The photoluminescence of conjugated polymer films that have been spun onto textured substrates is analysed. It is fou...

  2. Light extraction efficiency enhancement for fluorescent SiC based white light-emitting diodes

    DEFF Research Database (Denmark)

    Ou, Haiyan; Ou, Yiyu; Argyraki, Aikaterini

    Fluorescent SiC based white light-emitting diodes(LEDs) light source, as an innovative energy-efficient light source, would even have longer lifetime, better light quality and eliminated blue-tone effect, compared to the current phosphor based white LED light source. In this paper, the yellow....... At a device level, the focus is on improving the light extraction efficiency due to the rather high refractive index of SiC by nanostructuring the surface of SiC. Both periodic nanostructures made by e-beam lithography and nanosphere lithography and random nanostructures made by self-assembled Au nanosphere...... fluorescent Boron-Nitrogen co-doped 6H SiC is optimized in terms of source material, growth condition, dopant concentration, and carrier lifetime by using photoluminescence, pump-probe spectroscopy etc. The internal quantum efficiency is measured and the methods to increase the efficiency have been explored...

  3. Electroluminescent Characteristics of DBPPV–ZnO Nanocomposite Polymer Light Emitting Devices

    Directory of Open Access Journals (Sweden)

    Madhava Rao MV

    2009-01-01

    Full Text Available Abstract We have demonstrated that fabrication and characterization of nanocomposite polymer light emitting devices with metal Zinc Oxide (ZnO nanoparticles and 2,3-dibutoxy-1,4-poly(phenylenevinylene (DBPPV. The current and luminance characteristics of devices with ZnO nanoparticles are much better than those of device with pure DBPPV. Optimized maximum luminance efficiencies of DBPPV–ZnO (3:1 wt% before annealing (1.78 cd/A and after annealing (2.45 cd/A having a brightness 643 and 776 cd/m2at a current density of 36.16 and 31.67 mA/cm2are observed, respectively. Current density–voltage and brightness–voltage characteristics indicate that addition of ZnO nanoparticles can facilitate electrical injection and charge transport. The thermal annealing is thought to result in the formation of an interfacial layer between emissive polymer film and cathode.

  4. Carbon Nanotube Driver Circuit for 6 × 6 Organic Light Emitting Diode Display

    Science.gov (United States)

    Zou, Jianping; Zhang, Kang; Li, Jingqi; Zhao, Yongbiao; Wang, Yilei; Pillai, Suresh Kumar Raman; Volkan Demir, Hilmi; Sun, Xiaowei; Chan-Park, Mary B.; Zhang, Qing

    2015-06-01

    Single-walled carbon nanotube (SWNT) is expected to be a very promising material for flexible and transparent driver circuits for active matrix organic light emitting diode (AM OLED) displays due to its high field-effect mobility, excellent current carrying capacity, optical transparency and mechanical flexibility. Although there have been several publications about SWNT driver circuits, none of them have shown static and dynamic images with the AM OLED displays. Here we report on the first successful chemical vapor deposition (CVD)-grown SWNT network thin film transistor (TFT) driver circuits for static and dynamic AM OLED displays with 6 × 6 pixels. The high device mobility of ~45 cm2V-1s-1 and the high channel current on/off ratio of ~105 of the SWNT-TFTs fully guarantee the control capability to the OLED pixels. Our results suggest that SWNT-TFTs are promising backplane building blocks for future OLED displays.

  5. Charge injection and accumulation in organic light-emitting diode with PEDOT:PSS anode

    Science.gov (United States)

    Weis, Martin; Otsuka, Takako; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa

    2015-04-01

    Organic light-emitting diode (OLED) displays using flexible substrates have many attractive features. Since transparent conductive oxides do not fit the requirements of flexible devices, conductive polymer poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) has been proposed as an alternative. The charge injection and accumulation in OLED devices with PEDOT:PSS anodes are investigated and compared with indium tin oxide anode devices. Higher current density and electroluminescence light intensity are achieved for the OLED device with a PEDOT:PSS anode. The electric field induced second-harmonic generation technique is used for direct observation of temporal evolution of electric fields. It is clearly demonstrated that the improvement in the device performance of the OLED device with a PEDOT:PSS anode is associated with the smooth charge injection and accumulation.

  6. Strategies to Achieve High-Performance White Organic Light-Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Lirong Zhang

    2017-12-01

    Full Text Available As one of the most promising technologies for next-generation lighting and displays, white organic light-emitting diodes (WOLEDs have received enormous worldwide interest due to their outstanding properties, including high efficiency, bright luminance, wide viewing angle, fast switching, lower power consumption, ultralight and ultrathin characteristics, and flexibility. In this invited review, the main parameters which are used to characterize the performance of WOLEDs are introduced. Subsequently, the state-of-the-art strategies to achieve high-performance WOLEDs in recent years are summarized. Specifically, the manipulation of charges and excitons distribution in the four types of WOLEDs (fluorescent WOLEDs, phosphorescent WOLEDs, thermally activated delayed fluorescent WOLEDs, and fluorescent/phosphorescent hybrid WOLEDs are comprehensively highlighted. Moreover, doping-free WOLEDs are described. Finally, issues and ways to further enhance the performance of WOLEDs are briefly clarified.

  7. Current-voltage characteristics of light-emitting diodes under optical and electrical excitation

    Energy Technology Data Exchange (ETDEWEB)

    Wen Jing; Wen Yumei; Li Ping; Li Lian, E-mail: wenjing@cqu.edu.cn [Key Laboratory for Opto-Electronic Technologies and Systems of Ministry of Education, College of Opto-Electronic Engineering, Chongqing University, Chongqing 400044 (China)

    2011-08-15

    The factors influencing the current-voltage (I-V) characteristics of light-emitting diodes (LEDs) are investigated to reveal the connection of I-V characteristics under optical excitation and those under electrical excitation. By inspecting the I-V curves under optical and electrical excitation at identical injection current, it has been found that the I-V curves exhibit apparent differences in voltage values. Furthermore, the differences are found to originate from the junction temperatures in diverse excitation ways. Experimental results indicate that if the thermal effect of illuminating spot is depressed to an ignorable extent by using pulsed light, the junction temperature will hardly deflect from that under optical excitation, and then the I-V characteristics under two diverse excitation ways will be the same.

  8. Current-voltage characteristics of light-emitting diodes under optical and electrical excitation

    Science.gov (United States)

    Jing, Wen; Yumei, Wen; Ping, Li; Lian, Li

    2011-08-01

    The factors influencing the current—voltage (I—V) characteristics of light-emitting diodes (LEDs) are investigated to reveal the connection of I—V characteristics under optical excitation and those under electrical excitation. By inspecting the I—V curves under optical and electrical excitation at identical injection current, it has been found that the I—V curves exhibit apparent differences in voltage values. Furthermore, the differences are found to originate from the junction temperatures in diverse excitation ways. Experimental results indicate that if the thermal effect of illuminating spot is depressed to an ignorable extent by using pulsed light, the junction temperature will hardly deflect from that under optical excitation, and then the I—V characteristics under two diverse excitation ways will be the same.

  9. Design and Dynamic Analysis of a High-Speed Organic Light-Emitting Diode

    Science.gov (United States)

    Salehifar, Samira; Shayesteh, Mohammad Reza; Hashemian, Saeedeh

    2018-02-01

    We propose a structure of a high-speed multilayer organic light-emitting diode (OLED). The different organic materials have been chosen so that the barrier potential between two adjacent layers is smaller than 0.2 eV, which causes the charge carriers to move easily between layers to reach the emitting layer. The static and dynamic behaviors of the OLED have been analyzed numerically. The results from simulation show that the proposed OLED structure has an electroluminescence delay time of about 30 ns, and hence can respond to electrical pulses with a repetition rate of 2 MHz. Moreover, the device can provide good features such as high light emission efficiency, low voltage DC driving, and thermal stability.

  10. Emergence of White Organic Light-Emitting Diodes Based on Thermally Activated Delayed Fluorescence

    Directory of Open Access Journals (Sweden)

    Peng Xiao

    2018-02-01

    Full Text Available Recently, thermally activated delayed fluorescence (TADF organic light-emitting diodes (OLEDs have attracted both academic and industrial interest due to their extraordinary characteristics, such as high efficiency, low driving voltage, bright luminance, lower power consumption and potentially long lifetime. In this invited review, the fundamental concepts of TADF have been firstly introduced. Then, main approaches to realize WOLEDs based on TADF have been summarized. More specifically, the recent development of WOLEDs based on all TADF emitters, WOLEDs based on TADF and conventional fluorescence emitters, hybrid WOLEDs based on blue TADF and phosphorescence emitters and WOLEDs based on TADF exciplex host and phosphorescence dopants is highlighted. In particular, design strategies, device structures, working mechanisms and electroluminescent processes of the representative WOLEDs based on TADF are reviewed. Finally, challenges and opportunities for further enhancement of the performance of WOLEDs based on TADF are presented.

  11. A Flexible Blue Light-Emitting Diode Based on ZnO Nanowire/Polyaniline Heterojunctions

    Directory of Open Access Journals (Sweden)

    Y. Y. Liu

    2013-01-01

    Full Text Available An organic/inorganic light-emitting diode (LED consisting of n-type vertically aligned ZnO nanowires (NWs and p-type proton acid doped polyaniline (PANi is reported. The device was fabricated on flexible indium-tin-oxide (ITO coated polyethylene terephthalate (PET substrate. A broad blue light emission band ranging from 390 nm to 450 nm was observed in the electroluminescence (EL spectra of the device, which was related to the interface recombination of electrons in the conduction band of ZnO NWs and holes in the polaron level of PANi. The turn-on voltage of the device is ~3.5 V, lower than most of ZnO NWs based LED devices. In combination with the easy fabrication, flexibility, low power consumption, and mechanical robustness, this novel device is very promising in the application of blue LEDs.

  12. Organic semiconductor heterojunctions and its application in organic light-emitting diodes

    CERN Document Server

    Ma, Dongge

    2017-01-01

    This book systematically introduces the most important aspects of organic semiconductor heterojunctions, including the basic concepts and electrical properties. It comprehensively discusses the application of organic semiconductor heterojunctions as charge injectors and charge generation layers in organic light-emitting diodes (OLEDs). Semiconductor heterojunctions are the basis for constructing high-performance optoelectronic devices. In recent decades, organic semiconductors have been increasingly used to fabricate heterojunction devices, especially in OLEDs, and the subject has attracted a great deal of attention and evoked many new phenomena and interpretations in the field. This important application is based on the low dielectric constant of organic semiconductors and the weak non-covalent electronic interactions between them, which means that they easily form accumulation heterojunctions. As we know, the accumulation-type space charge region is highly conductive, which is an important property for high...

  13. White Electroluminescence Using ZnO Nanotubes/GaN Heterostructure Light-Emitting Diode.

    Science.gov (United States)

    Sadaf, J R; Israr, Mq; Kishwar, S; Nur, O; Willander, M

    2010-04-04

    We report the fabrication of heterostructure white light-emitting diode (LED) comprised of n-ZnO nanotubes (NTs) aqueous chemically synthesized on p-GaN substrate. Room temperature electroluminescence (EL) of the LED demonstrates strong broadband white emission spectrum consisting of predominating peak centred at 560 nm and relatively weak violet-blue emission peak at 450 nm under forward bias. The broadband EL emission covering the whole visible spectrum has been attributed to the large surface area and high surface states of ZnO NTs produced during the etching process. In addition, comparison of the EL emission colour quality shows that ZnO nanotubes have much better quality than that of the ZnO nanorods. The colour-rendering index of the white light obtained from the nanotubes was 87, while the nanorods-based LED emit yellowish colour.

  14. Thin copolymer-cased light-emitting display made with fluorine-foped tin oxide substrates

    Directory of Open Access Journals (Sweden)

    Rudolf Lessmann

    2004-09-01

    Full Text Available Seven-segment displays are used to show numerical quantities in electronic equipment, being present in most of the low-end electronics. In this work we describe a novel organic light emitting display made with poly(1,10 decanedioxy 2 methoxy - 1,2 phenylene - 1,2 ethenylene - 3,6 dimethoxy - 1,4 phenylene - 1,2 ethenylene 3 methoxy - 1,4 - phenylene (OPPVDBC, tris(8-hydroxyquinolinealuminum salt (Alq3 and a hole injection layer (PEDOT:PSS: poly(3,4 - ethylenedioxythiophene : poly(styrenesulfonate. The general device structure is FTO/PEDOT:PSS/OPPVDBC/Ca/Al or FTO/PEDOT:PSS/OPPVDBC/Alq3/Ca/Al. The FTO (fluorine-doped tin oxide thin films are transparent (transmittance > 80 % in the visible region of the spectrum, conductive (< 15 omega/º for 200 nm thick films, and present high chemical stability.

  15. A lamp light-emitting diode-induced fluorescence detector for capillary electrophoresis.

    Science.gov (United States)

    Xu, Jing; Xiong, Yan; Chen, Shiheng; Guan, Yafeng

    2008-07-15

    A light-emitting diode-induced fluorescence detector (LED-FD) for capillary electrophoresis was constructed and evaluated. A lamp LED with an enhanced emission spectrum and a band pass filter was used as the excitation light source. Refractive index matching fluid (RIMF) was used in the detection cell to reduce scattering light and the noise level. The limit of detection (LOD) for fluorescein was 1.5 nM (SNR=3). The system exhibited linear responses in the range of 1 x 10(-8) to 5 x 10(-6)M (R=0.999). Application of the lamp LED-FD for the analysis of FITC-labeled ephedra herb extract by capillary electrophoresis was demonstrated.

  16. Optical design of a light-emitting diode lamp for a maritime lighthouse.

    Science.gov (United States)

    Jafrancesco, D; Mercatelli, L; Sansoni, P; Fontani, D; Sani, E; Coraggia, S; Meucci, M; Francini, F

    2015-04-10

    Traffic signaling is an emerging field for light-emitting diode (LED) applications. This sustainable power-saving illumination technology can be used in maritime signaling thanks to the recently updated norms, where the possibility to utilize LED sources is explicitly cited, and to the availability of high-power white LEDs that, combined with suitable lenses, permit us to obtain well-collimated beams. This paper describes the optical design of a LED-based lamp that can replace a traditional lamp in an authentic marine lighthouse. This source recombines multiple separated LEDs realizing a quasi-punctual localized source. Advantages can be lower energy consumption, higher efficiency, longer life, fewer faults, slower aging, and minor maintenance costs. The proposed LED source allows us to keep and to utilize the old Fresnel lenses of the lighthouse, which very often have historical value.

  17. The efficiency challenge of nitride light-emitting diodes for lighting

    KAUST Repository

    Weisbuch, Claude

    2015-03-13

    © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. We discuss the challenges of light-emitting diodes in view of their application to solid-state lighting. The requirement is to at least displace the quite efficient fluorescent, sodium, and high intensity discharge lamps used today in the main energy consuming lighting sectors, industrial, commercial and outdoors, with more efficient and better light quality lamps. We show that both from the point of view of cost of ownership and carbon emissions reduction, the relevant metric is efficiency, more than the cost of lumens. Then, progress from present performance requires identification of the loss mechanisms in light emission from LEDs, and solutions competing with mainstream c-plane LEDS grown on sapphire need to be on par with these. Special attention is devoted to a discussion of the efficiency droop mechanisms, and of a recent direct measurement of Auger generated electrons which appear to be responsible for droop.

  18. White-Light-Emitting Lanthanide Metallogels with Tunable Luminescence and Reversible Stimuli-Responsive Properties.

    Science.gov (United States)

    Chen, Pangkuan; Li, Qiaochu; Grindy, Scott; Holten-Andersen, Niels

    2015-09-16

    We have developed model light-emitting metallogels functionalized with lanthanide metal-ligand coordination complexes via a terpyridyl-end-capped four-arm poly(ethylene glycol) polymer. The optical properties of these highly luminescent polymer networks are readily modulated over a wide spectrum, including white-light emission, simply by tuning of the lanthanide metal ion stoichiometry. Furthermore, the dynamic nature of the Ln-N coordination bonding leads to a broad variety of reversible stimuli-responsive properties (mechano-, vapo-, thermo-, and chemochromism) of both sol-gel systems and solid thin films. The versatile functional performance combined with the ease of assembly suggests that this lanthanide coordination polymer design approach offers a robust pathway for future engineering of multi-stimuli-responsive polymer materials.

  19. High-density G-centers, light-emitting point defects in silicon crystal

    Directory of Open Access Journals (Sweden)

    Koichi Murata

    2011-09-01

    Full Text Available We propose a new method of creating light-emitting point defects, or G-centers, by modifying a silicon surface with hexamethyldisilazane followed by laser annealing of the surface region. This laser annealing process has two advantages: creation of highly dense G-centers by incorporating carbon atoms into the silicon during heating; freezing in the created G-centers during rapid cooling. The method provides a surface region of up to 200 nm with highly dense carbon atoms of up to 4 × 1019 cm−3 to create G-centers, above the solubility limit of carbon atoms in silicon crystal (3 × 1017 cm−3. Photoluminescence measurement reveals that the higher-speed laser annealing produces stronger G-center luminescence. We demonstrate electrically-driven emission from the G-centers in samples made using our new method.

  20. High-power light-emitting diode based facility for plant cultivation

    Energy Technology Data Exchange (ETDEWEB)

    Tamulaitis, G [Institute of Materials Science and Applied Research, Vilnius University, Sauletekio al. 9-III, LT-10222 Vilnius (Lithuania); Duchovskis, P [Lithuanian Institute of Horticulture, Babtai, LT-54333 Kaunas District (Lithuania); Bliznikas, Z [Institute of Materials Science and Applied Research, Vilnius University, Sauletekio al. 9-III, LT-10222 Vilnius (Lithuania); Breive, K [Institute of Materials Science and Applied Research, Vilnius University, Sauletekio al. 9-III, LT-10222 Vilnius (Lithuania); Ulinskaite, R [Lithuanian Institute of Horticulture, Babtai, LT-54333 Kaunas District (Lithuania); Brazaityte, A [Lithuanian Institute of Horticulture, Babtai, LT-54333 Kaunas District (Lithuania); Novickovas, A [Institute of Materials Science and Applied Research, Vilnius University, Sauletekio al. 9-III, LT-10222 Vilnius (Lithuania); Zukauskas, A [Institute of Materials Science and Applied Research, Vilnius University, Sauletekio al. 9-III, LT-10222 Vilnius (Lithuania)

    2005-09-07

    Based on perspectives of the development of semiconductor materials systems for high-power light-emitting diodes (LEDs), an illumination facility for greenhouse plant cultivation was designed with the dominating 640 nm photosynthetically active component delivered by AlGaInP LEDs and supplementary components from AlGaN (photothropic action, 455 nm) and AlGaAs (photosynthetic 660 nm and photomorphogenetic 735 nm) LEDs. Photosynthesis intensity, photosynthetic productivity and growth morphology as well as chlorophyll and phytohormone concentrations were investigated in radish and lettuce grown in phytotron chambers under the LED-based illuminators and under high-pressure sodium (HPS) lamps with an equivalent photon flux density. Advantages of the high-power LED-based illuminators over conventional HPS lamps, applicability of AlGaInP LEDs for photosynthesis and control of plant growth by circadian manipulation of a relatively weak far-red component were demonstrated.