1
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Olsson TB, Abariute L, Hrachowina L, Barrigón E, Volpati D, Limpert S, Otnes G, Borgström MT, Prinz CN. Photovoltaic nanowires affect human lung cell proliferation under illumination conditions. Nanoscale 2020; 12:14237-14244. [PMID: 32608415 DOI: 10.1039/c9nr07678f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
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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Affiliation(s)
- Therese B Olsson
- Division of Solid State Physics and NanoLund, Lund University, 221 00 Lund, Sweden.
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2
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McKibbin S, Colvin J, Troian A, Knutsson JV, Webb JL, Otnes G, Dirscherl K, Sezen H, Amati M, Gregoratti L, Borgström MT, Mikkelsen A, Timm R. Operando Surface Characterization of InP Nanowire p-n Junctions. Nano Lett 2020; 20:887-895. [PMID: 31891513 PMCID: PMC7025757 DOI: 10.1021/acs.nanolett.9b03529] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Revised: 12/10/2019] [Indexed: 05/21/2023]
Abstract
We present an in-depth analysis of the surface band alignment and local potential distribution of InP nanowires containing a p-n junction using scanning probe and photoelectron microscopy techniques. The depletion region is localized to a 15 nm thin surface region by scanning tunneling spectroscopy and an electronic shift of up to 0.5 eV between the n- and p-doped nanowire segments was observed and confirmed by Kelvin probe force microscopy. Scanning photoelectron microscopy then allowed us to measure the intrinsic chemical shift of the In 3d, In 4d, and P 2p core level spectra along the nanowire and the effect of operating the nanowire diode in forward and reverse bias on these shifts. Thanks to the high-resolution techniques utilized, we observe fluctuations in the potential and chemical energy of the surface along the nanowire in great detail, exposing the sensitive nature of nanodevices to small scale structural variations.
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Affiliation(s)
- Sarah
R. McKibbin
- Department
of Physics and NanoLund, Lund University, 22100 Lund, Sweden
| | - Jovana Colvin
- Department
of Physics and NanoLund, Lund University, 22100 Lund, Sweden
| | - Andrea Troian
- Department
of Physics and NanoLund, Lund University, 22100 Lund, Sweden
| | - Johan V. Knutsson
- Department
of Physics and NanoLund, Lund University, 22100 Lund, Sweden
| | - James L. Webb
- Department
of Physics and NanoLund, Lund University, 22100 Lund, Sweden
| | - Gaute Otnes
- Department
of Physics and NanoLund, Lund University, 22100 Lund, Sweden
| | - Kai Dirscherl
- Danish
National Metrology Institute, 2970 Hørsholm, Denmark
| | - Hikmet Sezen
- Elettra
− Sincrotrone Trieste S.C.p.A. di Interesse Nazionale, 34149 Trieste, Italy
| | - Matteo Amati
- Elettra
− Sincrotrone Trieste S.C.p.A. di Interesse Nazionale, 34149 Trieste, Italy
| | - Luca Gregoratti
- Elettra
− Sincrotrone Trieste S.C.p.A. di Interesse Nazionale, 34149 Trieste, Italy
| | | | - Anders Mikkelsen
- Department
of Physics and NanoLund, Lund University, 22100 Lund, Sweden
| | - Rainer Timm
- Department
of Physics and NanoLund, Lund University, 22100 Lund, Sweden
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3
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Espinet-Gonzalez P, Barrigón E, Otnes G, Vescovi G, Mann C, France RM, Welch AJ, Hunt MS, Walker D, Kelzenberg MD, Åberg I, Borgström MT, Samuelson L, Atwater HA. Radiation Tolerant Nanowire Array Solar Cells. ACS Nano 2019; 13:12860-12869. [PMID: 31626535 DOI: 10.1021/acsnano.9b05213] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
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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Affiliation(s)
- Pilar Espinet-Gonzalez
- Department of Applied Physics and Materials Science , California Institute of Technology , Pasadena , California 91125 , United States
| | - Enrique Barrigón
- Division of Solid State Physics , Lund University , Lund , SE-221 00 , Sweden
| | - Gaute Otnes
- Division of Solid State Physics , Lund University , Lund , SE-221 00 , Sweden
| | | | - Colin Mann
- The Aerospace Corporation , El Segundo , California 90245-4609 , United States
| | - Ryan M France
- National Renewable Energy Laboratory , Golden , Colorado 80401 , United States
| | - Alex J Welch
- Department of Applied Physics and Materials Science , California Institute of Technology , Pasadena , California 91125 , United States
| | - Matthew S Hunt
- The Kavli Nanoscience Institute , California Institute of Technology , Pasadena , California 91125 , United States
| | - Don Walker
- The Aerospace Corporation , El Segundo , California 90245-4609 , United States
| | - Michael D Kelzenberg
- Department of Applied Physics and Materials Science , California Institute of Technology , Pasadena , California 91125 , United States
| | | | - Magnus T Borgström
- Division of Solid State Physics , Lund University , Lund , SE-221 00 , Sweden
| | - Lars Samuelson
- Division of Solid State Physics , Lund University , Lund , SE-221 00 , Sweden
- Sol Voltaics AB , Lund , SE-223 63 , Sweden
| | - Harry A Atwater
- Department of Applied Physics and Materials Science , California Institute of Technology , Pasadena , California 91125 , United States
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4
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Harberts J, Zierold R, Fendler C, Koitmäe A, Bayat P, Fernandez-Cuesta I, Loers G, Diercks BP, Fliegert R, Guse AH, Ronning C, Otnes G, Borgström M, Blick RH. Culturing and patch clamping of Jurkat T cells and neurons on Al2O3 coated nanowire arrays of altered morphology. RSC Adv 2019; 9:11194-11201. [PMID: 35520244 PMCID: PMC9063011 DOI: 10.1039/c8ra05320k] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 05/02/2019] [Accepted: 03/30/2019] [Indexed: 01/19/2023] Open
Abstract
Report on electrophysiologically intact cell cultures on vertically arranged nanowires as a tool for next generation cell/nanowire stimulation studies.
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5
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Chayanun L, Otnes G, Troian A, Hammarberg S, Salomon D, Borgström MT, Wallentin J. Nanoscale mapping of carrier collection in single nanowire solar cells using X-ray beam induced current. J Synchrotron Radiat 2019; 26:102-108. [PMID: 30655474 PMCID: PMC6337893 DOI: 10.1107/s1600577518015229] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Accepted: 10/28/2018] [Indexed: 05/22/2023]
Abstract
Here it is demonstrated how nanofocused X-ray beam induced current (XBIC) can be used to quantitatively map the spatially dependent carrier collection probability within nanostructured solar cells. The photocurrent generated by a 50 nm-diameter X-ray beam was measured as a function of position, bias and flux in single p-i-n doped solar-cell nanowires. The signal gathered mostly from the middle segment decays exponentially toward the p- and n-segments, with a characteristic decay length that varies between 50 nm and 750 nm depending on the flux and the applied bias. The amplitude of the XBIC shows saturation at reverse bias, which indicates that most carriers are collected. At forward bias, the relevant condition for solar cells, the carrier collection is only efficient in a small region. Comparison with finite element modeling suggests that this is due to unintentional p-doping in the middle segment. It is expected that nanofocused XBIC could be used to investigate carrier collection in a wide range of nanostructured solar cells.
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Affiliation(s)
- Lert Chayanun
- Synchrotron Radiation Research and NanoLund, Lund University, Box 118, Lund 22100, Sweden
| | - Gaute Otnes
- Solid State Physics and NanoLund, Lund University, Box 118, Lund 22100, Sweden
| | - Andrea Troian
- Synchrotron Radiation Research and NanoLund, Lund University, Box 118, Lund 22100, Sweden
| | - Susanna Hammarberg
- Synchrotron Radiation Research and NanoLund, Lund University, Box 118, Lund 22100, Sweden
| | - Damien Salomon
- European Synchrotron Radiation Facility, 71 avenue des Martyrs, Grenoble 38043, France
| | - Magnus T. Borgström
- Solid State Physics and NanoLund, Lund University, Box 118, Lund 22100, Sweden
| | - Jesper Wallentin
- Synchrotron Radiation Research and NanoLund, Lund University, Box 118, Lund 22100, Sweden
- Correspondence e-mail:
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6
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Harberts J, Zierold R, Fendler C, Koitmäe A, Bayat P, Fernandez-Cuesta I, Loers G, Diercks BP, Fliegert R, Guse AH, Ronning C, Otnes G, Borgström M, Blick RH. Correction: Culturing and patch clamping of Jurkat T cells and neurons on Al 2O 3 coated nanowire arrays of altered morphology. RSC Adv 2019; 9:13614. [PMID: 35532444 PMCID: PMC9064027 DOI: 10.1039/c9ra90030f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Accepted: 04/15/2019] [Indexed: 11/30/2022] Open
Abstract
Correction for ‘Culturing and patch clamping of Jurkat T cells and neurons on Al2O3 coated nanowire arrays of altered morphology’ by Jann Harberts et al., RSC Adv., 2019, 9, 11194–11201.
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7
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Troian A, Otnes G, Zeng X, Chayanun L, Dagytė V, Hammarberg S, Salomon D, Timm R, Mikkelsen A, Borgström MT, Wallentin J. Nanobeam X-ray Fluorescence Dopant Mapping Reveals Dynamics of in Situ Zn-Doping in Nanowires. Nano Lett 2018; 18:6461-6468. [PMID: 30185034 DOI: 10.1021/acs.nanolett.8b02957] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The properties of semiconductors can be controlled using doping, making it essential for electronic and optoelectronic devices. However, with shrinking device sizes it becomes increasingly difficult to quantify doping with sufficient sensitivity and spatial resolution. Here, we demonstrate how X-ray fluorescence mapping with a nanofocused beam, nano-XRF, can quantify Zn doping within in situ doped III-V nanowires, by using large area detectors and high-efficiency focusing optics. The spatial resolution is defined by the focus size to 50 nm. The detection limit of 7 ppm (2.8 × 1017 cm-3), corresponding to about 150 Zn atoms in the probed volume, is bound by a background signal. In solar cell InP nanowires with a p-i-n doping profile, we use nano-XRF to observe an unintentional Zn doping of 5 × 1017 cm-3 in the middle segment. We investigated the dynamics of in situ Zn doping in a dedicated multisegment nanowire, revealing significantly sharper gradients after turning the Zn source off than after turning the source on. Nano-XRF could be used for quantitative mapping of a wide range of dopants in many types of nanostructures.
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Affiliation(s)
- Andrea Troian
- Synchrotron Radiation Research and NanoLund , Lund University , 22100 Lund , Sweden
| | - Gaute Otnes
- Solid State Physics and NanoLund , Lund University , 22100 Lund , Sweden
| | - Xulu Zeng
- Solid State Physics and NanoLund , Lund University , 22100 Lund , Sweden
| | - Lert Chayanun
- Synchrotron Radiation Research and NanoLund , Lund University , 22100 Lund , Sweden
| | - Vilgailė Dagytė
- Solid State Physics and NanoLund , Lund University , 22100 Lund , Sweden
| | - Susanna Hammarberg
- Synchrotron Radiation Research and NanoLund , Lund University , 22100 Lund , Sweden
| | - Damien Salomon
- European Synchrotron Radiation Facility , 38000 Grenoble , France
| | - Rainer Timm
- Synchrotron Radiation Research and NanoLund , Lund University , 22100 Lund , Sweden
| | - Anders Mikkelsen
- Synchrotron Radiation Research and NanoLund , Lund University , 22100 Lund , Sweden
| | - Magnus T Borgström
- Solid State Physics and NanoLund , Lund University , 22100 Lund , Sweden
| | - Jesper Wallentin
- Synchrotron Radiation Research and NanoLund , Lund University , 22100 Lund , Sweden
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8
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Zeng X, Mourão RT, Otnes G, Hultin O, Dagytė V, Heurlin M, Borgström MT. Electrical and optical evaluation of n-type doping in In x Ga (1-x)P nanowires. Nanotechnology 2018; 29:255701. [PMID: 29595525 DOI: 10.1088/1361-6528/aabaa5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
To harvest the benefits of III-V nanowires in optoelectronic devices, the development of ternary materials with controlled doping is needed. In this work, we performed a systematic study of n-type dopant incorporation in dense In x Ga(1-x)P nanowire arrays using tetraethyl tin (TESn) and hydrogen sulfide (H2S) as dopant precursors. The morphology, crystal structure and material composition of the nanowires were characterized by use of scanning electron microscopy, transmission electron microscopy and energy dispersive x-ray analysis. To investigate the electrical properties, the nanowires were broken off from the substrate and mechanically transferred to thermally oxidized silicon substrates, after which electron beam lithography and metal evaporation were used to define electrical contacts to selected nanowires. Electrical characterization, including four-probe resistivity and Hall effect, as well as back-gated field effect measurements, is combined with photoluminescence spectroscopy to achieve a comprehensive evaluation of the carrier concentration in the doped nanowires. We measure a carrier concentration of ∼1 × 1016 cm-3 in nominally intrinsic nanowires, and the maximum doping level achieved by use of TESn and H2S as dopant precursors using our parameters is measured to be ∼2 × 1018 cm-3, and ∼1 × 1019 cm-3, respectively (by Hall effect measurements). Hence, both TESn and H2S are suitable precursors for a wide range of n-doping levels in In x Ga(1-x)P nanowires needed for optoelectronic devices, grown via the vapor-liquid-solid mode.
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Affiliation(s)
- Xulu Zeng
- Solid State Physics, NanoLund, Lund University, PO Box 118 Lund, Sweden
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9
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Otnes G, Barrigón E, Sundvall C, Svensson KE, Heurlin M, Siefer G, Samuelson L, Åberg I, Borgström MT. Understanding InP Nanowire Array Solar Cell Performance by Nanoprobe-Enabled Single Nanowire Measurements. Nano Lett 2018; 18:3038-3046. [PMID: 29701974 DOI: 10.1021/acs.nanolett.8b00494] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
III-V solar cells in the nanowire geometry might hold significant synthesis-cost and device-design advantages as compared to thin films and have shown impressive performance improvements in recent years. To continue this development there is a need for characterization techniques giving quick and reliable feedback for growth development. Further, characterization techniques which can improve understanding of the link between nanowire growth conditions, subsequent processing, and solar cell performance are desired. Here, we present the use of a nanoprobe system inside a scanning electron microscope to efficiently contact single nanowires and characterize them in terms of key parameters for solar cell performance. Specifically, we study single as-grown InP nanowires and use electron beam induced current characterization to understand the charge carrier collection properties, and dark current-voltage characteristics to understand the diode recombination characteristics. By correlating the single nanowire measurements to performance of fully processed nanowire array solar cells, we identify how the performance limiting parameters are related to growth and/or processing conditions. We use this understanding to achieve a more than 7-fold improvement in efficiency of our InP nanowire solar cells, grown from a different seed particle pattern than previously reported from our group. The best cell shows a certified efficiency of 15.0%; the highest reported value for a bottom-up synthesized InP nanowire solar cell. We believe the presented approach have significant potential to speed-up the development of nanowire solar cells, as well as other nanowire-based electronic/optoelectronic devices.
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Affiliation(s)
- Gaute Otnes
- Solid State Physics and NanoLund , Lund University , P.O. Box 118, SE-221 00 Lund , Sweden
| | - Enrique Barrigón
- Solid State Physics and NanoLund , Lund University , P.O. Box 118, SE-221 00 Lund , Sweden
| | | | | | - Magnus Heurlin
- Solid State Physics and NanoLund , Lund University , P.O. Box 118, SE-221 00 Lund , Sweden
- SolVoltaics AB , Scheelevägen 22 , SE-223 63 Lund , Sweden
| | - Gerald Siefer
- Fraunhofer ISE , Heidenhofstrasse 2 , D-79110 Freiburg , Germany
| | - Lars Samuelson
- Solid State Physics and NanoLund , Lund University , P.O. Box 118, SE-221 00 Lund , Sweden
| | - Ingvar Åberg
- SolVoltaics AB , Scheelevägen 22 , SE-223 63 Lund , Sweden
| | - Magnus T Borgström
- Solid State Physics and NanoLund , Lund University , P.O. Box 118, SE-221 00 Lund , Sweden
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10
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Harberts JI, Koitmäe A, Zierold R, Fendler C, Fernandez-Cuesta I, Loers G, Thereza Perez M, Prinz C, Otnes G, Borgström M, Linke H, Blick RH. Solar Cell Nanowires as Approach for Single Cell Direct Activation. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.3610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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11
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Dagytė V, Barrigón E, Zhang W, Zeng X, Heurlin M, Otnes G, Anttu N, Borgström MT. Time-resolved photoluminescence characterization of GaAs nanowire arrays on native substrate. Nanotechnology 2017; 28:505706. [PMID: 29087959 DOI: 10.1088/1361-6528/aa974b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Time-resolved photoluminescence (TRPL) measurements of nanowires (NWs) are often carried out on broken-off NWs in order to avoid the ensemble effects as well as substrate contribution. However, the development of NW-array solar cells could benefit from non-destructive optical characterization to allow faster feedback and further device processing. With this work, we show that different NW array and substrate spectral behaviors with delay time and excitation power can be used to determine which part of the sample dominates the detected spectrum. Here, we evaluate TRPL characterization of dense periodic as-grown GaAs NW arrays on a p-type GaAs substrate, including a sample with uncapped GaAs NWs and several samples passivated with AlGaAs radial shell of varied composition and thickness. We observe a strong spectral overlap of substrate and NW signals and find that the NWs can absorb part of the substrate luminescence signal, thus resulting in a modified substrate signal. The level of absorption depends on the NW-array geometry, making a deconvolution of the NW signal very difficult. By studying TRPL of substrate-only and as-grown NWs at 770 and 400 nm excitation wavelengths, we find a difference in spectral behavior with delay time and excitation power that can be used to assess whether the signal is dominated by the NWs. We find that the NW signal dominates with 400 nm excitation wavelength, where we observe two different types of excitation power dependence for the NWs capped with high and low Al composition shells. Finally, from the excitation power dependence of the peak TRPL signal, we extract an estimate of background carrier concentration in the NWs.
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Affiliation(s)
- Vilgailė Dagytė
- Solid State Physics, Department of Physics and NanoLund, Lund University, Box 118, SE-221 00 Lund, Sweden
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12
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Anttu N, Dagytė V, Zeng X, Otnes G, Borgström M. Absorption and transmission of light in III-V nanowire arrays for tandem solar cell applications. Nanotechnology 2017; 28:205203. [PMID: 28436381 DOI: 10.1088/1361-6528/aa6aee] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
III-V semiconductor nanowires are a platform for next-generation photovoltaics. An interesting research direction is to embed a nanowire array in a transparent polymer, either to act as a stand-alone flexible solar cell, or to be stacked on top of a conventional Si bottom cell to create a tandem structure. To optimize the tandem cell performance, high energy photons should be absorbed in the nanowires whereas low energy photons should be transmitted to and absorbed in the Si cell. Here, through optical measurements on 1.95 eV bandgap GaInP nanowire arrays embedded in a polymer membrane, we identify two mechanisms that could be detrimental for the performance of the tandem cell. First, the Au particles used in the nanowire synthesis can absorb >50% of the low-energy photons, leading to a <40% transmittance, even though the Au particles cover <15% of the surface area. The removal of the Au particles can recover the transmission of low energy photons to >80%. Second, after the removal of the Au particles, a 40% reflectance peak shows up due to resonant back-scattering of light from in-plane waveguide modes. To avoid the excitation of these optical modes in the nanowire array, we propose to limit the pitch of the nanowire array.
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Affiliation(s)
- Nicklas Anttu
- Division of Solid State Physics and NanoLund, Lund University, Box 118, SE-22100 Lund, Sweden
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13
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Abstract
Electrical characterization of nanowires is a time-consuming and challenging task due to the complexity of single nanowire device fabrication and the difficulty in interpreting the measurements. We present a method to measure Hall effect in nanowires using a three-probe device that is simpler to fabricate than previous four-probe nanowire Hall devices and allows characterization of nanowires with smaller diameter. Extraction of charge carrier concentration from the three-probe measurements using an analytical model is discussed and compared to simulations. The validity of the method is experimentally verified by a comparison between results obtained with the three-probe method and results obtained using four-probe nanowire Hall measurements. In addition, a nanowire with a diameter of only 65 nm is characterized to demonstrate the capabilities of the method. The three-probe Hall effect method offers a relatively fast and simple, yet accurate way to quantify the charge carrier concentration in nanowires and has the potential to become a standard characterization technique for nanowires.
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Affiliation(s)
- Olof Hultin
- Division of Solid State Physics, Lund University , P.O. Box 118, SE-221 00 Lund, Sweden
| | - Gaute Otnes
- Division of Solid State Physics, Lund University , P.O. Box 118, SE-221 00 Lund, Sweden
| | - Lars Samuelson
- Division of Solid State Physics, Lund University , P.O. Box 118, SE-221 00 Lund, Sweden
| | - Kristian Storm
- Acreo Swedish ICT AB , Beta 2, Scheelev. 17, SE-223 70 Lund, Sweden
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14
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Otnes G, Heurlin M, Zeng X, Borgström MT. In xGa 1-xP Nanowire Growth Dynamics Strongly Affected by Doping Using Diethylzinc. Nano Lett 2017; 17:702-707. [PMID: 28054783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Semiconductor nanowires are versatile building blocks for optoelectronic devices, in part because nanowires offer an increased freedom in material design due to relaxed constraints on lattice matching during the epitaxial growth. This enables the growth of ternary alloy nanowires in which the bandgap is tunable over a large energy range, desirable for optoelectronic devices. However, little is known about the effects of doping in the ternary nanowire materials, a prerequisite for applications. Here we present a study of p-doping of InxGa1-xP nanowires and show that the growth dynamics are strongly affected when diethylzinc is used as a dopant precursor. Specifically, using in situ optical reflectometry and high-resolution transmission electron microscopy we show that the doping results in a smaller nanowire diameter, a more predominant zincblende crystal structure, a more Ga-rich composition, and an increased axial growth rate. We attribute these effects to changes in seed particle wetting angle and increased TMGa pyrolysis efficiency upon introducing diethylzinc. Lastly, we demonstrate degenerate p-doping levels in InxGa1-xP nanowires by the realization of an Esaki tunnel diode. Our findings provide insights into the growth dynamics of ternary alloy nanowires during doping, thus potentially enabling the realization of such nanowires with high compositional homogeneity and controlled doping for high-performance optoelectronics devices.
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Affiliation(s)
- Gaute Otnes
- Division of Solid State Physics and NanoLund, Lund University , P.O. Box 118, SE-221 00 Lund, Sweden
| | - Magnus Heurlin
- Division of Solid State Physics and NanoLund, Lund University , P.O. Box 118, SE-221 00 Lund, Sweden
| | - Xulu Zeng
- Division of Solid State Physics and NanoLund, Lund University , P.O. Box 118, SE-221 00 Lund, Sweden
| | - Magnus T Borgström
- Division of Solid State Physics and NanoLund, Lund University , P.O. Box 118, SE-221 00 Lund, Sweden
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15
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Lindelöw F, Heurlin M, Otnes G, Dagytė V, Lindgren D, Hultin O, Storm K, Samuelson L, Borgström M. Doping evaluation of InP nanowires for tandem junction solar cells. Nanotechnology 2016; 27:065706. [PMID: 26762762 DOI: 10.1088/0957-4484/27/6/065706] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
In order to push the development of nanowire-based solar cells further using optimized nanowire diameter and pitch, a doping evaluation of the nanowire geometry is necessary. We report on a doping evaluation of n-type InP nanowires with diameters optimized for light absorption, grown by the use of metal-organic vapor phase epitaxy in particle-assisted growth mode using tetraethyltin (TESn) as the dopant precursor. The charge carrier concentration was evaluated using four-probe resistivity measurements and spatially resolved Hall measurements. In order to reach the highest possible nanowire doping level, we set the TESn molar fraction at a high constant value throughout growth and varied the trimethylindium (TMIn) molar fraction for different runs. Analysis shows that the charge carrier concentration in nanowires grown with the highest TMIn molar fraction (not leading to kinking nanowires) results in a low carrier concentration of approximately 10(16) cm(-3). By decreasing the molar fraction of TMIn, effectively increasing the IV/III ratio, the carrier concentration increases up to a level of about 10(19) cm(-3), where it seems to saturate. Axial carrier concentration gradients along the nanowires are found, which can be correlated to a combination of changes in the nanowire growth rate, measured in situ by optical reflectometry, and polytypism of the nanowires observed in transmission electron microscopy.
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Hultin O, Otnes G, Borgström MT, Björk M, Samuelson L, Storm K. Comparing Hall Effect and Field Effect Measurements on the Same Single Nanowire. Nano Lett 2016; 16:205-211. [PMID: 26599297 DOI: 10.1021/acs.nanolett.5b03496] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We compare and discuss the two most commonly used electrical characterization techniques for nanowires (NWs). In a novel single-NW device, we combine Hall effect and back-gated and top-gated field effect measurements and quantify the carrier concentrations in a series of sulfur-doped InP NWs. The carrier concentrations from Hall effect and field effect measurements are found to correlate well when using the analysis methods described in this work. This shows that NWs can be accurately characterized with available electrical methods, an important result toward better understanding of semiconductor NW doping.
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Affiliation(s)
- Olof Hultin
- Division of Solid State Physics, Lund University , P.O. Box 118, SE-22100 Lund, Sweden
| | - Gaute Otnes
- Division of Solid State Physics, Lund University , P.O. Box 118, SE-22100 Lund, Sweden
| | - Magnus T Borgström
- Division of Solid State Physics, Lund University , P.O. Box 118, SE-22100 Lund, Sweden
| | - Mikael Björk
- Sol Voltaics AB , Scheelevägen 22, SE-22363 Lund, Sweden
| | - Lars Samuelson
- Division of Solid State Physics, Lund University , P.O. Box 118, SE-22100 Lund, Sweden
| | - Kristian Storm
- Division of Solid State Physics, Lund University , P.O. Box 118, SE-22100 Lund, Sweden
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