| 1. |
- Alcer, David, et al.
(författare)
-
Comparison of Triethylgallium and Trimethylgallium Precursors for GaInP Nanowire Growth
- 2021
-
Ingår i: Physica Status Solidi (B) Basic Research. - : Wiley. - 0370-1972. ; 258:2
-
Tidskriftsartikel (refereegranskat)abstract
- Nanowire (NW) arrays containing a top segment of GaxIn1–xP are investigated, comparing NWs grown using two different Ga precursors, trimethylgallium (TMGa) and triethylgallium (TEGa). TMGa is the precursor commonly used for the particle-assisted vapor–liquid–solid (VLS) growth of GaxIn1–xP NWs. However, it shows inefficient pyrolysis at typical NW growth conditions. The use of the alternative precursor TEGa is investigated by making a direct comparison between NWs grown using TEGa and TMGa at otherwise identical growth conditions. Growth rates, resulting NW materials composition, and time-resolved photoluminescence (TRPL) lifetimes are investigated. With increasing Ga content of the NWs, the TRPL lifetimes decrease, indicating trap states that are associated with GaP. Somewhat longer TRPL lifetimes for the samples grown using TEGa indicate a lower concentration of deep trap states. For doped NWs, it is found that the strong effect of the p-type dopant diethylzinc (DEZn) on the NW composition, observed for GaxIn1–xP NWs grown using TMGa, is absent when using TEGa.
|
|
| 2. |
- Alcer, David, et al.
(författare)
-
Processing and characterization of large area InP nanowire photovoltaic devices
- 2023
-
Ingår i: Nanotechnology. - 0957-4484. ; 34:29
-
Tidskriftsartikel (refereegranskat)abstract
- III−V nanowire (NW) photovoltaic devices promise high efficiencies at reduced materials usage. However, research has so far focused on small devices, mostly ≤1 mm2. In this study, the upscaling potential of axial junction InP NW photovoltaic devices is investigated. Device processing was carried out on a full 2″ wafer, with device sizes up to 1 cm2, which is a significant increase from the mm-scale III−V NW photovoltaic devices published previously. The short-circuit current density of the largest 1 cm2 devices, in which 460 million NWs are contacted in parallel, is on par with smaller devices. This enables a record power generation of 6.0 mW under AM1.5 G illumination, more than one order of magnitude higher than previous III−V NW photovoltaic devices. On the other hand, the fill factor of the larger devices is lower in comparison with smaller devices, which affects the device efficiency. By use of electroluminescence mapping, resistive losses in the indium tin oxide (ITO) front contact are found to limit the fill factor of the large devices. We use combined light-beam induced current (LBIC) and photoluminescence (PL) mapping as a powerful characterization tool for NW photovoltaic devices. From the LBIC and PL maps, local defects can be identified on the fully processed devices.
|
|
| 3. |
- Alcer, David, et al.
(författare)
-
Vertically Processed GaInP/InP Tandem-Junction Nanowire Solar Cells
- 2024
-
Ingår i: ACS Applied Nano Materials. - 2574-0970. ; 7:2, s. 2352-2358
-
Tidskriftsartikel (refereegranskat)abstract
- We present vertically processed photovoltaic devices based on GaInP/InP tandem-junction III-V nanowires (NWs), contacting approximately 3 million NWs in parallel for each device. The GaInP and InP subcells as well as the connecting Esaki tunnel diode are all realized within the same NW. By processing GaInP/InP tandem-junction NW solar cells with varying compositions of the top junction GaInP material, we investigate the impact of the GaInP composition on the device performance. External quantum efficiency (EQE) measurements on devices with varying GaInP composition provide insights into the performance of the respective subcells, revealing that the GaInP subcell is current-limiting for all devices. I-V measurements under AM1.5G illumination confirm voltage addition of the subcells, resulting in an open-circuit voltage of up to 1.91 V. However, the short-circuit current density is low, ranging between 0.24 and 3.44 mA/cm2, which leads to a resulting solar conversion efficiency of up to 3.60%. Our work shows a path forward toward high-efficiency NW photovoltaics and identifies critical issues that need improvement.
|
|
| 4. |
- Barrigón, Enrique, et al.
(författare)
-
Light current-voltage measurements of single, as-grown, nanowire solar cells standing vertically on a substrate
- 2020
-
Ingår i: Nano Energy. - : Elsevier BV. - 2211-2855. ; 78
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 5. |
- Barrigón, Enrique, et al.
(författare)
-
Unravelling processing issues of nanowire-based solar cell arrays by use of electron beam induced current measurements
- 2020
-
Ingår i: Nano Energy. - : Elsevier BV. - 2211-2855. ; 71
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 6. |
- Chayanun, Lert, et al.
(författare)
-
Direct Three-Dimensional Imaging of an X-ray Nanofocus Using a Single 60 nm Diameter Nanowire Device
- 2020
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 20:11, s. 8326-8331
-
Tidskriftsartikel (refereegranskat)abstract
- Nanoscale X-ray detectors could allow higher resolution in imaging and diffraction experiments than established systems but are difficult to design due to the long absorption length of X-rays. Here, we demonstrate X-ray detection in a single nanowire in which the nanowire axis is parallel to the optical axis. In this geometry, X-ray absorption can occur along the nanowire length, while the spatial resolution is limited by the diameter. We use the device to make a high-resolution 3D image of the 88 nm diameter X-ray nanofocus at the Nanomax beamline, MAX IV synchrotron, by scanning the single pixel device in different planes along the optical axis. The images reveal fine details of the beam that are unattainable with established detectors and show good agreement with ptychography.
|
|
| 7. |
- Chen, Yang, et al.
(författare)
-
Semiconductor nanowire array for transparent photovoltaic applications
- 2021
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 118:19
-
Tidskriftsartikel (refereegranskat)abstract
- The surface area of a building that could potentially be used for Building Integrated Photovoltaics would increase dramatically with the availability of transparent solar cells that could replace windows. The challenge is to capture energy from outside the visible region (UV or IR) while simultaneously allowing a high-quality observation of the outside world and transmitting sufficient light in the visible region to satisfactorily illuminate the interior of the building. In this paper, we show both computationally and experimentally that InP nanowire arrays can have good transparency in the visible region and high absorption in the near-infrared region. We show experimentally that we can achieve mean transparencies in the visible region of 65% and the radiative limit of more than 10% based on measured absorption and calculated emission. Our results demonstrate that nanowire arrays hold promise as a method to achieve transparent solar cells, which would fulfill the requirements to function as windows. In addition, we show that by optical design and by designing the geometry of nanowire arrays, solar cells can be achieved that absorb/transmit at wavelengths that are not decided by the bandgap of the material and that can be tailored to specific requirements such as colorful windows.
|
|
| 8. |
- Eriksson, Axl, et al.
(författare)
-
Synthesis of Well-Ordered Functionalized Silicon Microwires Using Displacement Talbot Lithography for Photocatalysis
- 2024
-
Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 9:18, s. 20623-20628
-
Tidskriftsartikel (refereegranskat)abstract
- Metal-assisted chemical etching (MACE) is a cheap and scalable method that is commonly used to obtain silicon nano- or microwires but lacks spatial control. Herein, we present a synthesis method for producing vertical and highly periodic silicon microwires, using displacement Talbot lithography before wet etching with MACE. The functionalized periodic silicon microwires show 65% higher PEC performance and 2.3 mA/cm2 higher net photocurrent at 0 V compared to functionalized, randomly distributed microwires obtained by conventional MACE at the same potentials.
|
|
| 9. |
- Hrachowina, Lukas, et al.
(författare)
-
Development and characterization of photovoltaic tandem-junction nanowires using electron-beam-induced current measurements
- 2022
-
Ingår i: Nano Research. - : Springer Science and Business Media LLC. - 1998-0124 .- 1998-0000. ; 15:9, s. 8510-8515
-
Tidskriftsartikel (refereegranskat)abstract
- Nanowires have many interesting properties that are of advantage for solar cells, such as the epitaxial combination of lattice-mismatched materials without plastic deformation. This could be utilized for the synthesis of axial tandem-junction nanowire solar cells with high efficiency at low material cost. Electron-beam-induced current measurements have been used to optimize the performance of single-junction nanowire solar cells. Here, we use electron-beam-induced current measurements to break the barrier to photovoltaic tandem-junction nanowires. In particular, we identify and subsequently prevent the occurrence of a parasitic junction when combining an InP n—i—p junction with a tunnel diode. Furthermore, we demonstrate how to use optical and electrical biases to individually measure the electron-beam-induced current of both sub-cells of photovoltaic tandem-junction nanowires. We show that with an applied voltage in forward direction, all junctions can be analyzed simultaneously. The development of this characterization technique enables further optimization of tandem-junction nanowire solar cells.
|
|
| 10. |
- Hrachowina, Lukas, et al.
(författare)
-
Imaging the influence of oxides on the electrostatic potential of photovoltaic InP nanowires
- 2021
-
Ingår i: Nano Research. - : Springer Science and Business Media LLC. - 1998-0124 .- 1998-0000. ; 14:11, s. 4087-4092
-
Tidskriftsartikel (refereegranskat)abstract
- Nanowires require surface passivation due to their inherent large surface to volume ratio. We investigate the effect of embedding InP nanowires in different oxides with respect to surface passivation by use of electron beam induced current measurements enabled by a nanoprobe based system inside a scanning electron microscope. The measurements reveal remote doping due to fixed charge carriers in the passivating POx/Al2O3 shell in contrast to results using SiOx. We used time-resolved photoluminescence to characterize the lifetime of charge carriers to evaluate the success of surface passivation. In addition, spatially resolved internal quantum efficiency simulations support and correlate the two applied techniques. We find that atomic-layer deposited POx/Al2O3 has the potential to passivate the surface of InP nanowires, but at the cost of inducing a field-effect on the nanowires, altering their electrostatic potential profile. The results show the importance of using complementary techniques to correctly evaluate and interpret processing related effects for optimization of nanowire-based optoelectronic devices. [Figure not available: see fulltext.].
|
|
