| 1. |
- Barrigón, Enrique, et al.
(author)
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Light current-voltage measurements of single, as-grown, nanowire solar cells standing vertically on a substrate
- 2020
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In: Nano Energy. - : Elsevier BV. - 2211-2855. ; 78
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Journal article (peer-reviewed)abstract
- Nanowire based solar cells hold promise for terrestrial and space photovoltaic applications. However, to speed-up and further continue with nanowire solar cell development, quick and reliable characterization tools capable of evaluating single nanowire performance of nanowires still standing on the substrate are necessary. Here, we present the use of a light emitting diode (LED) based setup, which combined with a nanoprobe system inside a scanning electron microscope, enables on-wafer, single, nanowire solar cell optoelectronic characterization. In particular, we study the I–V characteristics of single nanowire solar cells under in situ illumination and correlate the results with those of electron beam induced current measurements. Further, the LED setup enables the study of nanowire solar cell under varied incident power. We believe that this approach will enable rapid development of single and tandem nanowire based solar cells as well as other nanowire based optoelectronic devices.
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| 2. |
- Barrigón, Enrique, et al.
(author)
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Unravelling processing issues of nanowire-based solar cell arrays by use of electron beam induced current measurements
- 2020
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In: Nano Energy. - : Elsevier BV. - 2211-2855. ; 71
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Journal article (peer-reviewed)abstract
- III-V vertical nanowire arrays have great potential for next generation photovoltaics. Development towards high performing nanowire solar cells, which consist of a parallel connection of millions of single nanowire solar cells, requires a fast characterization technique that establishes a link between device performance and device processing. In this work, we use electron beam induced current measurements to characterize fully processed InP nanowire array solar cells at the nanoscale. Non-functional areas on fully processed devices can be quickly identified and processing induced effects on device performance can be clearly distinguished from those arising from nanowire growth. We identify how limiting factors on device performance are related to the processing procedures and provide a path to improve device performance further. In this way, electron beam induced current measurements become an essential tool for nanowire solar cell efficiency optimization, providing fast and useful information at the nanoscale and thus enabling up-scaling of the technology.
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| 3. |
- Barrutia, Laura, et al.
(author)
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Impact of the III-V/Ge nucleation routine on the performance of high efficiency multijunction solar cells
- 2020
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In: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248. ; 207
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Journal article (peer-reviewed)abstract
- This paper addresses the influence of III-V nucleation routines on Ge substrates for the growth of high efficiency multijunction solar cells. Three exemplary nucleation routines with differences in thickness and temperature were evaluated. The resulting open circuit voltage of triple-junction solar cells with these designs is significantly affected (up to 50 mV for the best optimization routine), whereas minimal differences in short circuit current are observed. Electroluminescence measurements show that both the Ge bottom cell and the Ga(In)As middle cell present a VOC gain of 25 mV each. This result indicates that the first stages of the growth not only affect the Ge subcell itself but also to subsequent subcells. This study highlights the impact of the nucleation routine design in the performance of high efficiency multijunction solar cell based on Ge substrates.
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| 4. |
- Espinet-Gonzalez, Pilar, et al.
(author)
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Nanowire Solar Cells : A New Radiation Hard PV Technology for Space Applications
- 2020
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In: IEEE Journal of Photovoltaics. - 2156-3381. ; 10:2, s. 502-507
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Journal article (peer-reviewed)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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| 5. |
- Fast, Jonatan, et al.
(author)
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Hot-carrier separation in heterostructure nanowires observed by electron-beam induced current
- 2020
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In: Nanotechnology. - : IOP Publishing. - 1361-6528 .- 0957-4484. ; 31:39
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Journal article (peer-reviewed)abstract
- The separation of hot carriers in semiconductors is of interest for applications such asthermovoltaic photodetection and third-generation photovoltaics. Semiconductor nanowiresoffer several potential advantages for effective hot-carrier separation such as: a high degree ofcontrol and flexibility in heterostructure-based band engineering, increased hot-carriertemperatures compared to bulk, and a geometry well suited for local control of light absorption.Indeed, InAs nanowires with a short InP energy barrier have been observed to produce electricpower under global illumination, with an open-circuit voltage exceeding the Shockley-Queisserlimit. To understand this behaviour in more detail, it is necessary to establish control over theprecise location of electron-hole pair-generation in the nanowire. In this work we performelectron-beam induced current measurements with high spatial resolution, and demonstrate therole of the InP barrier in extracting energetic electrons.We interprete the results in terms ofhot-carrier separation, and extract estimates of the hot carriers’ mean free path.
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| 6. |
- Jafari Jam, Reza, et al.
(author)
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Template-assisted vapour-liquid-solid growth of InP nanowires on (001) InP and Si substrates
- 2020
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In: Nanoscale. - Cambridge : Royal Society of Chemistry. - 2040-3364 .- 2040-3372. ; 12:2, s. 888-894
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Journal article (peer-reviewed)abstract
- We report on the synthesis of vertical InP nanowire arrays on (001) InP and Si substrates using template-assisted vapour-liquid-solid growth. A thick silicon oxide layer was first deposited on the substrates. The samples were then patterned by electron beam lithography and deep dry etching through the oxide layer down to the substrate surface. Gold seed particles were subsequently deposited in the holes of the pattern by the use of pulse electrodeposition. The subsequent growth of nanowires by the vapour-liquid-solid method was guided towards the [001] direction by the patterned oxide template, and displayed a high growth yield with respect to the array of holes in the template. In order to confirm the versatility and robustness of the process, we have also demonstrated guided growth of InP nanowire p-n junctions and InP/InAs/InP nanowire heterostructures on (001) InP substrates. Our results show a promising route to monolithically integrate III-V nanowire heterostructure devices with commercially viable (001) silicon platforms.
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| 7. |
- Olsson, Therese B, et al.
(author)
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Photovoltaic nanowires affect human lung cell proliferation under illumination conditions
- 2020
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In: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 12, s. 14237-14244
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Journal article (peer-reviewed)abstract
- Using light to interact with cells is a promising way to steer cell behavior with minimal perturbation. Besides optogenetics, photovoltaic nanostructures such as nanowires can be used to interact with cells using light as a switch. Photovoltaic nanowires have, for instance, been used to stimulate neurons. However, the effects of the photovoltaic activity on cells are still poorly understood and characterized. Here, we investigate the effects of the photovoltaic activity of p-i-n nanowire arrays on A549 human lung adenocarcinoma cells. We have cultured A549 cells on top of vertical arrays of indium phosphide p-i-n nanowires (photovoltaic nanowires), with and without illumination to assess the effects of the nanowire photovoltaic activity on cells. We show that there is a higher proportion of dormant cells when the p-i-n nanowire arrays are illuminated. However, there is no difference in the proportion of dormant cells when the p-i-n nanowires are coated with oxide, which suggests that carrier injection in the cell medium (in this case, the release of electrons from the tip of the nanowires) is an important factor for modulating cell proliferation on photovoltaic nanowires. The results open up for interesting applications of photovoltaic nanowires in biomedicine, such as using them as a dormancy switch.
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| 8. |
- Zhang, Yuwei, et al.
(author)
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Self-Limiting Polymer Exposure for Vertical Processing of Semiconductor Nanowire-Based Flexible Electronics
- 2020
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In: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 3:8, s. 7743-7749
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Journal article (peer-reviewed)abstract
- In this work, we demonstrate a vertical processing method to fabricate nanowire (NW)-based devices. This method combines the strong light absorption ability caused by the NW geometry and exposure to dose-dependent clearance properties of a photo-sensitive polymer. By embedding NW arrays in a polymer, the NW light absorption leads to self-limited exposure and selective removal of the polymer. This optical and self-limited exposure pattern definition method can replace more expensive processing equipment, such as reactive ion etching and the use of a mask aligner. Excitingly, this method can be used to enable peel-off of NW arrays from their parent substrate, opening up opportunities to fabricate flexible NW array devices.
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