NW Electrodes Research Articles

Self-Limited Nanosoldering of Silver Nanowires for High-Performance Flexible Transparent Heaters.

Silver nanowires (Ag NWs) are key materials to fabricate next-generation flexible transparent electrodes (FTEs). Currently, the applications of Ag NWs are impeded by the large wire-wire contact resistance. Herein, a self-limited nanosoldering method is proposed to reduce the contact resistance by epitaxially depositing silver nanosolders at the Ag NW junctions, which have a negligible effect on the optical transparency, while decreasing the sheet resistance of the Ag NW film from 18.6 to 7.7 Ω/sq at a transmittance of 90%. In addition, the deposited nanosolders at the junctions remarkably improve the electrical and mechanical stabilities of the Ag NW electrodes. Notably, this simple nanosoldering process can be rapidly conducted under room temperature and ambient conditions and is free of any technical support or specific equipment. This technique is easily applied to the nanosoldering of 210 × 297 mm FTEs. Based on these FTEs, a high-performance flexible transparent heater with a sheet resistance 3.7 Ω/sq at a transmittance of 82.5% is constructed. Because of the high heating rate (4.8 °C/s), the heater can produce uniform heating (145 °C) at a short response time (30 s) and low input voltage (6 V).

Alkaline Water Electrolysis at 20 a cm-2 with a Microfibrous, Flow-through Electrolyzer

Improving both the efficiency and productivity of water electrolysis is necessary for making the electrochemical generation of hydrogen economically competitive. Flow-through electrodes are widely used to improve the efficiency and productivity of electrochemical processes, but studies of their use in alkaline water electrolysis are relatively rare. This work aimed to (1) test the hypothesis that the use of a flow-through electrode could enhance the rate of bubble removal from the electrode surface, thereby improving productivity, and (2) determine what length scale of electrode would maximize the surface area available for electrolysis without hindering bubble removal. To determine how the efficiency and productivity of the flow-through electrode depends on the electrode length scale, the performance of the oxygen evolution reaction was compared with flow-through electrodes consisting of a Ni foam, Ni microfibers (Ni MFs, d = 1.2 mm), and Ni-coated Cu nanowires (NiCu NWs, d = 350 nm). Although the turnover frequency (TOF) for the Ni foam was 2.4 times higher than the Ni MF electrode and 42 times higher than the NiCu NW electrode, its surface area was more than 90 times lower than the other electrodes, resulting in the lowest overall current density. Although the NiCu NW electrode had a higher surface area than the Ni MF electrode, it had a lower overall current density because of its low TOF. We attribute the high performance of the Ni MF electrode to the fact that the mean pore size of the Ni MF electrode (5-10 mm) is on the order of the mean bubble size (20 mm) that was measured by examining the bubbles generated from a mesh electrode. The performance of the Ni MF electrode was further improved by coating it with a Ni-Fe layered double hydroxide (LDH) catalyst, resulting in an OER overpotential of 247 mV at 0.1 A cm-2 and a Tafel slope of 26 mV dec-1. These values are among the lowest reported for Ni-Fe LDH catalysts. A Ni MF anode was paired with a Pt-coated Ni MF cathode to measure the overall productivity for water splitting. The maximum current density for water splitting was 20 A cm-2 at 3.9 V in 30% KOH, which is 20 times greater than the highest current densities previously reported for alkaline water electrolysis. This current density and voltage could be sustained for at least 8 hours with no signs of degradation. This high current density was attributed to the ability of the flowing fluid to promote bubble removal and keep the hot electrode surface from boiling water. This work demonstrates that flow-through microfibrous electrodes can improve the efficiency and productivity of alkaline water electrolysis. Figure 1

Flexible, transparent patterned electrodes based on graphene oxide/silver nanowire nanocomposites fabricated utilizing an accelerated ultraviolet/ozone process to control silver nanowire degradation

We developed flexible, transparent patterned electrodes, which were fabricated utilizing accelerated ultraviolet/ozone (UV/O3)-treated graphene oxide (GO)/silver nanowire (Ag-NW) nanocomposites via a simple, low-cost pattern process to investigate the feasibility of promising applications in flexible/wearable electronic and optoelectronic devices. The UV/O3 process of the GO/Ag-NW electrode was accelerated by the pre-heat treatment, and the degradation interruption of Ag NWs was removed by the GO treatment. After the deposition of the GO-treated Ag NW electrodes, the sheet resistance of the thermally annealed GO-treated Ag-NW electrodes was significantly increased by using the UV/O3 treatment, resulting in a deterioration of the GO-treated Ag NWs in areas exposed to the UV/O3 treatment. The degradation of the Ag NWs caused by the UV/O3 treatment was confirmed by using the sheet resistances, scanning electron microscopy images, X-ray photoelectron microscopy spectra, and transmittance spectra. While the sheet resistance of the low-density Ag-NW electrode was considerably increased due to the pre-thermal treatment at 90 °C for 10 min, that of the high-density Ag-NW electrode did not vary significantly even after a UV/O3 treatment for a long time. The degradation interference phenomenon caused by the UV/O3 treatment in the high-density Ag NWs could be removed by using a GO treatment, which resulted in the formation of a Ag-NW electrode pattern suitable for promising applications in flexible organic light-emitting devices. The GO treatment decreased the sheet resistance of the Ag-NW electrode and enabled the pattern to be formed by using the UV/O3 treatment. The selective degradation of Ag NWs due to UV/O3 treatment decreased the transparency of the Ag-NW electrode by about 8% and significantly increased its sheet resistance more than 100 times.

Enhanced Silver Nanowire Composite Window Electrode Protected by Large Size Graphene Oxide Sheets for Perovskite Solar Cells.

Despite the outstanding features of high transmittance and low sheet resistance from silver nanowire (Ag NW) based transparent electrodes, their applications in perovskite solar cells (PVSCs) as window electrodes encounter significant obstacles due to the stability issue brought by the corrosion of halogen species from perovskite layer. In this study, we used large size graphene oxide (LGO) sheets as the protective barrier for bottom Ag NW nano-network. Contributed by the LGO with average size of 60 μm, less GO sheet was necessary for forming the fully covered protective barrier with fewer cracks, which consequently improved the optical transparency and anticorrosive ability of the composite electrode compared to the one from relatively small size GO. Our experiments demonstrated the composite electrode of Ag NW/LGO. The glass substrate exhibited transmittance of 83.8% and 81.8% at 550 nm before and after partial reduction, which maintained 98.4% and 95.1% average transmittance (AVT) of the pristine Ag NW electrode. Meanwhile, we utilized the steady hot airflow to assist the fast solvent evaporation and the uniform GO film formation on Ag NW electrode. Before the application of composite electrode in organic-inorganic hybrid perovskite solar cells, the operational stability of composite electrodes from different sizes of GO with perovskite film fabricated on top were characterized under continuing external bias and light irradiation. Experimental results indicate that the Ag NW electrode protected by LGO could maintain original resistance for more than 45 h. Finally, the PVSC fabricated on Ag NW/LGO based composite electrode yielded a power conversion efficiency (PCE) of 9.62%, i.e., nearly 85% of that of the reference device fabricated on the commercial indium-tin oxide (ITO) glass. Our proposed low temperature and solution processed bottom electrode with improved optical transparency and operational stability can serve as the very beginning layer of optoelectronic devices, to promote the development of low cost and large area fabrication perovskite solar cells.

Investigation on the Silver Nanowire/Graphene Transparent Electrode in Electrochromic Device

In this work, we fabricated a flexible silver nanowires (Ag NWs)/graphene transparent conducting film on polyethylene terephthalate (PET) substrate, which was applied in an electrochromic device. The graphene layer was coated on the surface of the Ag NW film utilizing the electrostatic adsorption in order to improve the stability of the metallic nanowire layer and the performance of the electrochromic device. The Ag NWs/graphene composite film exhibited an optical transmittance of 82.5% at 550 nm and a sheet resistance of 57.5 Ω/sq. With the concentration of the adsorbed graphene increased, the transmittance and conductivity of the composite film both decreased. Furthermore, the lifetime of the electrochromic devices based on the tungsten oxide (WO3) thin film and the Ag NW/graphene composite electrodes was greatly extended, compared to that utilizing the pristine Ag NW electrodes. The results indicate that the introduction of the graphene layer could protect the Ag NW film from corrosion of the electrolyte layer, and greatly improve the lifetime and cycle numbers of the electrochromic device. Key words: silver nanowire; graphene; transparent electrode; electrochromic devices

All-Solution-Processed Thermally and Chemically Stable Copper-Nickel Core-Shell Nanowire-Based Composite Window Electrodes for Perovskite Solar Cells.

Organic-inorganic hybrid perovskite solar cells (PSCs) have recently attracted tremendous attention because of their excellent efficiency and the advantage of a low-cost fabrication process. As a transparent electrode for PSCs, the application of copper nanowire (CuNW)-network was limited because of its thermal/chemical instability, despite its advantages in terms of high optical/electrical properties and low-cost production. Here, the copper-nickel core-shell nanowire (Cu@Ni NW)-based composite electrode is proposed as a bottom window electrode for PSCs, without the involvement of a high-cost precious metal and vacuum process. The dense and uniform Ni protective shell for CuNWs is attainable by simple electroless plating, and the resulting Cu@Ni NWs exhibit outstanding chemical stability as well as thermal stability compared with bare CuNWs. When the Ni layer with the optimal thickness is introduced, the Cu@Ni NW electrode shows a high transmittance of 80.5% AVT at 400-800 nm, and a sheet resistance of 49.3 ± 5 Ω sq-1. Using the highly stable Cu@Ni NWs, the composite electrode structure is fabricated with sol-gel-derived Al-doped zinc oxide (AZO) over-layer for better charge collection and additional protection against iodine ions from the perovskite. The PSCs fabricated with AZO/Cu@Ni NW-based composite electrode demonstrate a power conversion efficiency (PCE) of 12.2% and excellent long-term stability maintaining 91% of initial PCE after being stored for 500 h at room temperature. Experimental results demonstrate the potential of highly stable Cu@Ni NW-based electrodes as the cost-effective alternative transparent electrode, which can facilitate the commercialization of PSCs.

Iridium oxide on indium-tin oxide nanowires: An all metal oxide heterostructured multi-electrode array for neuronal interfacing

All metal oxide heterostructured multielectrode arrays consisting of indium-tin oxide nanowires (ITO NWs) and an iridium oxide (IrOx) layer were fabricated. The needle-type ITO NWs were grown on an ITO electrode using a radio frequency magnetron sputtering technique followed by electrodeposition of an IrOx layer. The major advantage of this fabrication technique is in its simplicity because it does not require templates and seed layers to grow the ITO NWs. A transmission electron microscope found the IrOx to be uniformly electrodeposited over the surface of the ITO NW. After the electrodeposition process, the charge storage capacitance (CSC) of the ITO NW electrode increased from 0.09 to 4.25 mC cm−2, and the IrOx/ITO NW electrode exhibited a charge injection limit of 1.9 mC cm−2 and CSC utilization efficiency of approximately 45%. The stimulation performance of the IrOx/ITO NW electrode was confirmed using rat hippocampal slices, which exhibited a higher negative peak amplitude in the field excitatory postsynaptic potential when stimulated by a single pulse, and more effectively induced long-term potentiation via a theta burst stimulation compared with an ITO NW electrode. These results indicate that the synergetic combination of ITO NWs and a very thin IrOx layer enhanced the performance of the stimulus.

Cohesively enhanced electrical conductivity and thermal stability of silver nanowire networks by nickel ion bridge joining

A facile method for producing high-performance nickel enhanced silver nanowire (Ag NW) transparent electrodes on a flexible substrate is reported. The modified electroplating method called enhanced nickel ion bridge joining of Ag NWs, which provides a new route for improving the loose junctions in bare Ag NW networks. The sheet resistance of Ag NW electrode drops from over 2000 Ω sq−1 to 9.4 Ω sq−1 with excellent thermal uniformity after the electroplating process within 10 s. Nickel enhanced Ag NW transparent films are applied on flexible heaters with good thermal stability (165 °C for 2 h) and mechanical flexibility (3500 cycles under 2.5 mm bending radius) after mechanical bending process. Moreover, the mechanism of nickel growth is also confirmed that the nickel electroplating of the Ag NWs obeyed Faraday’s Laws.

Semi-transparent polymer solar cells with all-copper nanowire electrodes

Transparent electrodes based on copper nanowires (Cu NWs) have attracted significant attention owing to their advantages including high optical transmittance, good conductivity, and excellent mechanical flexibility. However, low-cost, high-performance, and environmental friendly solar cells with all-Cu NW electrodes have not been realized until now. Herein, top and bottom transparent electrodes based on Cu NWs with low surface roughness and homogeneous conductivity are fabricated. Then, semi-transparent polymer solar cells (PSCs) with the inverted structure of polyacrylate/Cu NWs/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) (PH1000)/Y-TiO2/poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid 3,4,5-tris(octyloxy)benzyl/PEDOT:PSS (4083)/Cu NWs/polyimide/polydimethylsiloxane are constructed; these could absorb light from both sides with a power conversion efficiency reaching 1.97% and 1.85%. Furthermore, the PSCs show an average transmittance of 42% in the visible region, which renders them suitable for some specialized applications such as power-generating windows and building-integrated photovoltaics. The indium tin oxide (ITO)- and noble metal-free PSCs could pave new pathways for fabricating cost-effective semi-transparent PSCs.

Copper nanowire-TiO2-polyacrylate composite electrodes with high conductivity and smoothness for flexible polymer solar cells

Copper nanowire (Cu NW) transparent electrodes have attracted considerable attention due to their outstanding electrical properties, flexibility and low cost. However, complicated post-treatment techniques are needed to obtain good electrical conductivity, because of the organic residues and oxide layers on the surface of the Cu NWs. In addition, commonly used methods such as thermal annealing and acid treatment often lead to nanowire damage. Herein, a TiO2 sol treatment was introduced to obtain Cu NW transparent electrodes with superb performance (13 Ω/sq @ 82% T) at room temperature within one minute. Polymer solar cells with excellent flexibility were then fabricated on the copper nanowire-TiO2-polyacrylate composite electrode. The power conversion efficiency (PCE) of the cells based on a blend of poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PC61BM) reached 3.11%, which was better than the control devices that used indium tin oxide (ITO)-PET electrodes, and outperforms other Cu NW based organic solar cells previously reported. The PCE of the solar cells based on Cu NW electrodes remained at 90% after 500 cycles of bending, while the PET/ITO solar cells failed after 20 and 200 cycles, with sheet resistance of 35 and 15 Ω/sq, respectively.

Fabrication of Multi-Electrode Array with Iridium Oxide-Electrodeposited on Indium-Tin Oxides Nanowires

Event Abstract Back to Event Fabrication of Multi-Electrode Array with Iridium Oxide-Electrodeposited on Indium-Tin Oxides Nanowires Yonghee KIM1, SNAG-DON JUNG1*, Ho Koo2 and Min Sun Kim2 1 Electronics and Telecommunications Research Institute, Republic of Korea 2 Wonkwang University, Department of Physiology, Republic of Korea Multi-electrode arrays (MEAs) were fabricated with electrodes consisting of iridium oxide (IrOx) electrodeposited on indium-tin oxide nanowires (ITO NWs) grown on ITO electrode using RF magnetron sputtering technique. The elemental mapping analysis of the cross-sectional structure of the IrOx/ITO NW hybrid electrodes revealed that the IrOx had been uniformly deposited on the surface of the surface of ITO nanowire. The charge injection limit of the IrOx/ITO NW MEA was estimated to be 1.9 mC cm-2 by measuring the voltage transient, and this value is sufficiently greater than the neural damage threshold (ca. 1 mC cm-2). The efficacy of the improvement in the charge injection limit of the IrOx/ITO NW MEA was evaluated with rat hippocampal slices. The IrOx/ITO NW electrodes exhibited a steeper increase in the negative peak amplitude of the field excitatory postsynaptic potentials, even with an electrical stimulation of a lower amplitude, prolonged negative fEPSPs wave after peak response, all of which strongly indicate an improved charge injection for the IrOx/ITO NW MEA. Acknowledgements This work was supported by ETRI (18ZH1500). Keywords: Indium-tin oxide nanowire, electrodeposited iridium oxide, multielectrode array, Electrical Stimulation, Charge injection limit, Field excitatory postsynaptic potential, Long-Term Potentiation Conference: MEA Meeting 2018 | 11th International Meeting on Substrate Integrated Microelectrode Arrays, Reutlingen, Germany, 4 Jul - 6 Jul, 2018. Presentation Type: Poster Presentation Topic: Microelectrode Array Technology Citation: KIM Y, JUNG S, Koo H and Kim M (2019). Fabrication of Multi-Electrode Array with Iridium Oxide-Electrodeposited on Indium-Tin Oxides Nanowires. Conference Abstract: MEA Meeting 2018 | 11th International Meeting on Substrate Integrated Microelectrode Arrays. doi: 10.3389/conf.fncel.2018.38.00107 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 19 Mar 2018; Published Online: 17 Jan 2019. * Correspondence: Dr. SNAG-DON JUNG, Electronics and Telecommunications Research Institute, Daejeon, 34129, Republic of Korea, jungpol@etri.re.kr Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Yonghee KIM SNAG-DON JUNG Ho Koo Min Sun Kim Google Yonghee KIM SNAG-DON JUNG Ho Koo Min Sun Kim Google Scholar Yonghee KIM SNAG-DON JUNG Ho Koo Min Sun Kim PubMed Yonghee KIM SNAG-DON JUNG Ho Koo Min Sun Kim Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Hierarchical cobalt oxide-functionalized silicon carbide nanowire array for efficient and robust oxygen evolution electro-catalysis

A hierarchical cobalt oxide (Co3O4)-functionalized silicon carbide nanowire (SiC NW) array electrode is synthesized on 4H–SiC(0001) substrates and investigated for use in the oxygen evolution reaction (OER) of water splitting. Ni-catalyzed chemical vapor deposition is employed to obtain vertically-aligned SiC NWs, and electrodeposition is used to functionalize the nanowires with hierarchical Co3O4 nano-clusters and a thin Co3O4 layer on the top side and the side-walls of the NWs, respectively. By using the Co3O4-functionalized SiC NW electrode for OER, the overpotential required to drive an anodic current density (Janodic) of 10 mA cm−2 is 0.22 V, a value much lower than those of Co3O4 nano-clusters (0.42 V), of bare SiC NWs (1.27 V) electrodes and of Pt foil (0.56 V). The overpotential value of 0.22 V is among the most active for the noble metal-free electro-catalytic electrode to produce Janodic of 10 mA cm−2. The deposition of Co3O4 on the SiC NW substrate produces an extremely hydrophilic surface, which improves the charge transfer characteristics at the interface between the electrode and the aqueous electrolyte. Moreover, the vertically-aligned SiC NWs provide a directional charge transport route along the nanowire length, as seen from a lower charge transfer resistance (Rct) in the Co3O4-functionalized SiC NW electrode compared to the Co3O4-functionalized SiC electrode under the same OER operating conditions. Finally, the Co3O4-functionalized SiC NW electrode maintains stable performance in an alkaline electrolyte (i.e., 1 M KOH aqueous solution) during continuous electrolysis testing over 16 h. The outstanding electro-catalytic performance and stability make the Co3O4-functionalized SiC NW electrode a promising noble metal-free electro-catalytic electrode for the OER and other renewable energy applications.

The use of conducting polymer to stabilize the nanostructured photocatalyst for water remediation

The graphene (G) doping in both titanium oxide (TiO2) and zinc oxide (ZnO) in our earlier studies, has brought about a reduction in photocorrosion, and an increase in the photocatalytic efficiency for remediation of organics under visible light (λ>400nm). The graphene doped photocatalysts have proven to be hard to coat on a surface, due to the strong hydrophobic nature of graphene. So, attempts have been made to use polyaniline (PANI), a conducting polymer, as a binder material by insitu polymerization of aniline over G-TiO2 nanoparticles (G-TiO2 NP) and G-ZnO nanowires (G-ZnO NW). The undoped PANI:G-TiO2 NP and PANI:G-ZnO NW, synthesized are dissolved in a solution of N-methyl-2-pyrrolidone (NMP) was coated over various surfaces and dried at 100°C & characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), UV–vis spectroscopy (UV-vis) and Fourier transform infrared spectroscopy (FTIR) techniques. Pristine PANI was also synthesized for comparative studies. The photocatalytic, as well as photoelectrochemical catalytic performance of PANI:G-TiO2 NP and PANI:G-ZnO NW, were investigated. The standard methyl orange (pollutant) in water was used for both PANI:G-TiO2 NP and PANI:G-ZnO NW electrodes on conducting substrates. The ease in coating of PANI:G-TiO2 NP and PANI:G-ZnO NW on various substrates, on top of the visible light remediation allows for the use of these materials and process to be used for applications of remediation of organics from water.

Graphdiyne Nanowalls as Anode for Lithium—Ion Batteries and Capacitors Exhibit Superior Cyclic Stability

In this study, we reported the design and application of hierarchical porous Graphdiyne Nanowall (GDY−NW) for energy storage device as lithium−ion batteries (LIBs) and capacitors (LICs). The unique hierarchical porous with the presence of butadiyne linkages comprising sp− and sp2− hybridized carbon atoms reinforces not only providing rich active sites for lithium storage, but also the efficient pathways for fast ion diffusion. Future more, the stable SEI layer formed on the GDY−NW surface after the initial cycle which can effectively reduce the resistance of interface and thus stable the circulating batteries, confirmed directly through the in−situ Raman measurement. The GDY−NW electrodes exhibit a reversible capacity of approximately 908mAhg−1 at 0.05A g−1, excellent cyclic stability with retention of 526mAhg−1 at large rate of 1Ag−1 after 1000 cycles applied as anode for LIBs. Thus GDY−NW films could deliver a capacitance more than 189Fg−1 over 10000 cycles at 1Ag−1 for LICs with active carbon cathode and exhibit an initial specific energy as high as 217 Wh kg−1 at a power density of 100W kg−1, presenting the benefit of the unique hierarchical porous structure comprising amount of macro, meso− and micro−pores, for thus high performance capability and cyclicity for renewable energy lithium storage.

Hybrid Ag nanowire transparent conductive electrodes with randomly oriented and grid-patterned Ag nanowire networks

To improve the electrical properties of silver nanowire (Ag NW) transparent conductive electrodes (TCEs), the density of Ag NW networks should be increased, to increase the number of percolation paths. However, because of the inverse relationship between optical transmittance and electrical resistivity, the optical properties of Ag NW TCEs deteriorate with increasing density of the Ag NW network. In this study, a hybrid Ag NW electrode composed of randomly oriented and grid-patterned Ag NW networks is demonstrated. The hybrid Ag NW electrodes exhibit significantly improved sheet resistances and slightly decreased transmittances compared to randomly oriented Ag NW networks. Hybrid Ag NW TCEs show excellent mechanical flexibilities and durabilities in bending tests with a 5 mm radius of curvature. Moreover, flexible transparent film heaters (TFHs) based on the hybrid Ag NW electrodes show elevated maximum temperatures relative to TFHs based on randomly oriented Ag NW electrodes, when operated at the same input voltages.

Novel Silicon Nanowire Electrodes Grown by Chemical Vapor Deposition Method for High‐Performance Electrochemical Capacitors

We report on novel electrochemical capacitors with silicon nanowire (Si NW) electrodes prepared by a chemical vapor deposition (CVD) method. Si NWs were deposited on conductive stainless steel through the CVD method to form electrodes of the electrochemical capacitors. Electrochemical characteristics of Si NW electrodes were investigated and compared with those of bulk silicon wafer electrodes. Si NWs resulted in larger area‐specific capacitance (>10 times) than bulk silicon, which is attributed to the enhanced surface area of NW morphology. NWs also exhibited high maximum and average mass‐specific capacitances of 510 and 117 F g−1, respectively. Our study demonstrates that semiconductor Si NWs can be useful as electrodes of high‐performance supercapacitors and next generation NWs‐based architecture for electrochemical energy storages.

Electrochromic modulation of near-infrared light by WO3 films deposited on silver nanowire substrates

Silver nanowire (Ag NW) transparent conductive electrodes with high conductivity and optical transmittance are fabricated. Then, WO3 films are deposited on Ag NW electrodes by an electrochemical deposition method. The WO3/Ag NW films act as obvious optical modulators in the visible region. More importantly, the WO3/Ag NW films have distinct advantage on NIR modulation over conventional WO3/ITO electrode. Meanwhile, the WO3/Ag NW films own high electrochromic efficiency of 86.9 cm2 C−1 at NIR region of 1100 nm. Furthermore, electrochromic devices (ECDs) based on Ag NW substrates are fabricated in this study, which exhibit excellent cycling stability and distinct modulation of near-infrared light compared with ITO-based ECDs. This work is the first study that reports the application of Ag NW-based electrochromic films and electrochromic devices in modulation of NIR light. It exhibits bright prospects that the electrochromic materials deposited on Ag NW electrodes may find potential application in thermal control and emission detectors for spacecraft.

Plasmonic‐Tuned Flash Cu Nanowelding with Ultrafast Photochemical‐Reducing and Interlocking on Flexible Plastics

Herein, a high‐performance copper nanowire (Cu NW) network (sheet resistance ≈ 17 Ω sq−1, transmittance 88%) fabricated by plasmonic‐tuned flash welding (PFW) with ultrafast interlocking and photochemical reducing is reported, which greatly enhance the mechanical and chemical stability of Cu NWs. Xenon flash spectrum is tuned in an optimized distribution (maximized light intensity at 600 nm wavelength) through modulation of electron kinetic energy in the lamp by generating drift potential for preferential photothermal interactions. High‐intensity visible light is emitted by the plasmonic‐tuned flash, which strongly improves Cu nanowelding without oxidation. Near‐infrared spectrum of the flash induced an interlocking structure of NW/polyethylene terephthalate interface by exciting Cu NW surface plasmon polaritons (SPPs), increasing adhesion of the Cu nanonetwork by 208%. In addition, ultrafast photochemical reduction of Cu NWs is accomplished in air by flash‐induced electron excitations and relevant chemical reactions. The PFW effects of localized surface plasmons and SPPs on junction welding and adhesion strengthening of Cu network are theoretically studied as physical behaviors by finite‐difference time‐domain simulations. Finally, a transparent resistive memory and a touch screen panel are demonstrated by using the flash‐induced Cu NWs, showing versatile and practical uses of PFW‐treated Cu NW electrodes for transparent flexible electronics.

Degradation mechanisms of silver nanowire electrodes under ultraviolet irradiation and heat treatment

We report the degradation mechanisms of the silver nanowire (Ag NW) electrodes that play a significantly important role in the stability of wearable and flexible devices. The degradation mechanisms behind the increase in the sheet resistances of Ag NW electrodes were clarified by investigating the variations in the structure and the chemical composition of the Ag NW electrodes caused by ultraviolet irradiation and thermal treatment. While the shapes of the Ag NWs were affected by melting during the thermal degradation process, the chemical composition of the polyvinylpyrrolidone protective layer on the surfaces of the Ag NWs was not changed. Ultraviolet irradiation deformed the shapes of the Ag NWs because nitrogen or oxygen atoms were introduced to the silver atoms on the surfaces of the Ag NWs. A graphene-oxide flake was coated on the Ag NW electrodes by using a simple dipping method to prevent ultraviolet irradiation and ozone contact with the surfaces of the Ag NWs, and the increase in the sheet resistance in the graphene-oxide-treated Ag NWs was suppressed. These observations will be of assistance to researchers trying to find novel ways to improve the stability of the Ag NW electrodes in next-generation wearable devices.

Failure criterion of silver nanowire electrodes on a polymer substrate for highly flexible devices

Nanomechanical characteristics of standalone silver nanowires (Ag NWs) are a key issue for providing a failure criterion of advanced flexible electrodes that are trending towards smaller radius of curvatures (ROCs). Through in-situ tensile and buckling tests of pentagonal Ag NWs, we demonstrated that the intrinsic fracture strain provides a significant criterion to predict the mechanical and electrical failure of Ag NW electrodes under various strain modes, because the decrease in fracture strain limits figure of merit of flexible devices. The Ag NW electrodes on a polymer substrate exhibited a strain-dependent electrical failure owing to the unique deformation characteristics with a size-dependent brittle-to-ductile transition of the five-fold twinned Ag NWs. All the Ag NWs greater than approximately 40 nm in diameter exhibited brittle fracture with a size-independent stress-strain response under tensile and buckling modes, which leads to the electrical failure of flexible electrodes at the almost same threshold ROC. Meanwhile, the higher ductility of Ag NWs less than 40 nm in diameter resulted in much smaller threshold ROCs of the electrodes due to the highly extended fracture strains, which can afford a high degree of freedom for highly flexible devices.