| 1. |
- Espinet-Gonzalez, Pilar, et al.
(författare)
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Nanowire Solar Cells : A New Radiation Hard PV Technology for Space Applications
- 2020
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Ingår i: IEEE Journal of Photovoltaics. - 2156-3381. ; 10:2, s. 502-507
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Tidskriftsartikel (refereegranskat)abstract
- Radiation hard thin-film solar cell technologies are necessary in order to achieve a step forward in the specific power of solar arrays for space applications. In this article, we analyze the degradation of nanowire (NW) solar cells under high energy particles. GaAs NW solar cells have been irradiated with protons of 100 and 350 keV at different fluences. The radiation hardness of the NW solar cells in all the cases is remarkable in comparison with GaAs planar solar cells and prior literature. Design guidelines to optimize the specific power of NW solar cells for space applications by jointly increasing their efficiency and radiation hardness are presented.
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| 2. |
- Espinet-Gonzalez, Pilar, et al.
(författare)
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Radiation Tolerant Nanowire Array Solar Cells
- 2019
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 13:11, s. 12860-12869
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Tidskriftsartikel (refereegranskat)abstract
- Space power systems require photovoltaics that are lightweight, efficient, reliable, and capable of operating for years or decades in space environment. Current solar panels use planar multijunction, III-V based solar cells with very high efficiency, but their specific power (power to weight ratio) is limited by the added mass of radiation shielding (e.g., coverglass) required to protect the cells from the high-energy particle radiation that occurs in space. Here, we demonstrate that III-V nanowire-array solar cells have dramatically superior radiation performance relative to planar solar cell designs and show this for multiple cell geometries and materials, including GaAs and InP. Nanowire cells exhibit damage thresholds ranging from ∼10-40 times higher than planar control solar cells when subjected to irradiation by 100-350 keV protons and 1 MeV electrons. Using Monte Carlo simulations, we show that this improvement is due in part to a reduction in the displacement density within the wires arising from their nanoscale dimensions. Radiation tolerance, combined with the efficient optical absorption and the improving performance of nanowire photovoltaics, indicates that nanowire arrays could provide a pathway to realize high-specific-power, substrate-free, III-V space solar cells with substantially reduced shielding requirements. More broadly, the exceptional reduction in radiation damage suggests that nanowire architectures may be useful in improving the radiation tolerance of other electronic and optoelectronic devices.
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| 3. |
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| 4. |
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| 5. |
- Stankevič, Tomaš, et al.
(författare)
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Fast Strain Mapping of Nanowire Light-Emitting Diodes Using Nanofocused X-ray Beams.
- 2015
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 9:7, s. 6978-6984
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Tidskriftsartikel (refereegranskat)abstract
- X-ray nanobeams are unique nondestructive probes that allow direct measurements of the nanoscale strain distribution and composition inside the micrometer thick layered structures that are found in most electronic device architectures. However, the method is usually extremely time-consuming, and as a result, data sets are often constrained to a few or even single objects. Here we demonstrate that by special design of a nanofocused X-ray beam diffraction experiment we can (in a single 2D scan with no sample rotation) measure the individual strain and composition profiles of many structures in an array of upright standing nanowires. We make use of the observation that in the generic nanowire device configuration, which is found in high-speed transistors, solar cells, and light-emitting diodes, each wire exhibits very small degrees of random tilts and twists toward the substrate. Although the tilt and twist are very small, they give a new contrast mechanism between different wires. In the present case, we image complex nanowires for nanoLED fabrication and compare to theoretical simulations, demonstrating that this fast method is suitable for real nanostructured devices.
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| 6. |
- Stankevic, Tomas, et al.
(författare)
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Measurement of strain in InGaN/GaN nanowires and nanopyramids
- 2015
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Ingår i: Journal of Applied Crystallography. - 1600-5767. ; 48, s. 344-349
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Tidskriftsartikel (refereegranskat)abstract
- The growth and optoelectronic properties of core-shell nanostructures are influenced by the strain induced by the lattice mismatch between core and shell. In contrast with planar films, nanostructures contain multiple facets that act as independent substrates for shell growth, which enables different relaxation mechanisms. In this study, X-ray diffraction data are presented that show that InGa1-N shells grown on GaN cores are strained along each of the facets independently. Reciprocal space maps reveal multiple Bragg peaks, corresponding to different parts of the shell being strained along the individual facet planes. The strained lattice constants were found from the positions of the Bragg peaks. Vegard's law and Hooke's law for an anisotropic medium were applied in order to find the composition and strain in the InGaN shells. A range of nanowire samples with different InGaN shell thicknesses were measured and it is concluded that, with an In concentration of around 30%, major strain relaxation takes place when the thickness reaches 23nm. InGaN shells of 6 and 9nm thickness remain nearly fully strained biaxially along each of the facets of the nanowires and the facets of the nanopyramids.
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