| 1. |
- Kishwar, S, et al.
(författare)
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Electro-optical and Cathodoluminescence properties of low temperature grown ZnO nanorods/p-GaN white light emitting diodes
- 2010
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Ingår i: PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE. - : Wiley. - 1862-6300. ; 207:1, s. 67-72
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Tidskriftsartikel (refereegranskat)abstract
- Vertically aligned ZnO nanorods (NRs) with a diameter in the range of 160-200 nm were grown on p-GaN/sapphire substrates by aqueous chemical growth technique and white light emitting I diodes (LEDs) are fabricated. The properties of this LED were investigated by parameter analyzer, cathodoluminescence (CL), electroluminescence (EL), and photoluminescence (PL). The I-V characteristics of the fabricated ZnO/GaN heterojunction revealed rectifying behavior and the LED emits visible EL when bias is applied. From the CL it was confirmed that both the ZnO NRs and the p-GaN are contributing to the observed peaks. The observed EL measurements showed two emission hands centered at 450 nm and a second broad deep level defect related emission centered at 630 nm and extending from 500 rim and up to over 700 rim. Moreover, the room temperature PL spectrum of the ZnO NRs/p-GaN reveals an extra peak at the green color wavelength centered at 550 nm. Comparison of the PL, CL, and EL data suggest that the blue and near red emissions in the EL spectra are originating from Mg acceptor levels in the p-GaN and from the deep levels defects present in the ZnO NRs, respectively. The mixture of high and low energy colors, i.e., blue, green, and red, has led to the white observed luminescence.
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| 2. |
- Tzamalis, G., et al.
(författare)
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Fluorescence light emission at 1 eV from a conjugated polymer
- 2010
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 489:1-3, s. 92-95
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Tidskriftsartikel (refereegranskat)abstract
- While polymer light-emitting diodes are currently finding commercial applications in displays and lighting, the development of low bandgap polymers emitting in the infrared has received much less attention in spite of potential applications for instance in the field of communication technologies. We report here a light emission at 1 eV from a low bandgap polymer made of an alternation of dialkoxy-phenylene units and a low bandgap monomer composed of an electron accepting 2-thia-1,3,5,8-tetraaza-cyclopenta[b]naphthalene group fenced with electron donating thiophene units. The electronic structure of the polymer chains has been characterized at a quantum-chemical level to shed light into the experimental results. (C) 2010 Published by Elsevier B.V.
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| 3. |
- Ul Hassan Alvi, Naveed, et al.
(författare)
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Junction temperature in n-ZnO nanorods/(p-4H-SiC, p-GaN, and p-Si) heterojunction light emitting diodes
- 2010
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Ingår i: Solid-State Electronics. - : Elsevier Science B.V., Amsterdam.. - 0038-1101 .- 1879-2405. ; 54:5, s. 536-540
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Tidskriftsartikel (refereegranskat)abstract
- The junction temperature of n-ZnO nanorods/(p-4H-SiC, p-GaN, and p-Si) heterojunction light emitting diodes (LEDs) at built-in potential was modeled and experiments were performed at various temperatures (15-65 degrees C) to validate the model. As the LEDs operate near the built-in potential thats why it is interesting to investigate the temperature coefficient of forward voltage near the built-in potential (similar to V-o). The model and experimental values of the temperature coefficient of forward voltage near the built-in potential (similar to V-o) were compared. We measured the experimental temperature coefficient of the series resistance. By including the temperature coefficient of the series resistance in the model, the theoretical and experimental values become very close to each other. It was found that the series resistance has the main contribution in the junction temperature of our devices. We also measured the junction temperature above the built-in potential and found that the model deviates at higher forward voltage. From this observation we concluded that the model is applicable for low power devices, operated near the built-in potential.
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| 4. |
- Wadeasa, Amal, et al.
(författare)
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Solution processed ZnO nanorods/polyfluorene semiconductor heterojunctions with white light photoluminescence
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Hybrid inorganic-organic semiconductor heterojunctions are nowadays scrutinized for optoelectronic devices, such as solar cells and light emitting diodes. Here, ZnOnanorods/ polyfluorene heterojunctions have been entirely fabricated from solution by wet chemistry and low temperature processes. The morphology of the polyfluorene film appears to be an important parameter to control the growth of the ZnO nanorods and affects their optical properties. The visible emission of the conjugated polymer and the ZnO are complementary and provide a broad emission in the visible. Because of its solution processability and broad emission, the ZnO/polyfluorene heterojunction is promising for large area white lightning applications.
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| 5. |
- Wadeasa, Amal, et al.
(författare)
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Solution processed ZnO nanowires/polyfluorene heterojunctions for large area lightening
- 2010
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Ingår i: Chemical Physics Letters. - : Elsevier Science B.V., Amsterdam.. - 0009-2614 .- 1873-4448. ; 490:4-6, s. 200-204
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid inorganic-organic semiconductor heterojunctions are nowadays scrutinized for optoelectronic devices, such as solar cells and light emitting diodes. Here, ZnO nanowires/polyfluorene heterojunctions have been entirely fabricated from solution by wet chemistry and low temperature processes. The transparent plastic electrode PEDOT injects holes in the polyfluorene, while the electrons are injected via the ZnO-Au contact, thus avoiding the use of air sensitive low work function metals. The hybrid inorganic-organic light emitting diode emits almost white light. Because of its solution processability, stable cathode, low cost and low temperature process, the ZnO/polymer heterojunction devices are promising for large area lightening applications.
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