Nanowire Mesh Research Articles

Solution processed zinc oxide nanopyramid/silver nanowire transparent network films with highly tunable light scattering properties

Metal nanowire transparent networks are promising replacements to indium tin oxide (ITO) transparent electrodes for optoelectronic devices. While the transparency and sheet resistance are key metrics for transparent electrode performance, independent control of the film light scattering properties is important to developing multifunctional electrodes for improved photovoltaic absorption. Here we show that controlled incorporation of ZnO nanopyramids into a metal nanowire network film affords independent, highly tunable control of the scattering properties (haze) with minimal effects on the transparency and sheet resistance. Varying the zinc oxide/silver nanostructure ratios prior to spray deposition results in sheet resistances, transmission (600 nm), and haze (600 nm) of 6-30 Ω □(-1), 68-86%, and 34-66%, respectively. Incorporation of zinc oxide nanopyramid scattering agents into the conducting nanowire mesh has a negligible effect on mesh connectivity, providing a straightforward method of controlling electrode scattering properties. The decoupling of the film scattering power and electrical characteristics makes these films promising candidates for highly scattering transparent electrodes in optoelectronic devices and can be generalized to other metal nanowire films as well as carbon nanotube transparent electrodes.

216 銀ナノワイヤメッシュ作製と特性評価(材料力学IV)

216 銀ナノワイヤメッシュ作製と特性評価(材料力学IV)

Flexible Silver Nanowire Meshes for High-Efficiency Microtextured Organic-Silicon Hybrid Photovoltaics

Hybrid organic-silicon heterojunction solar cells promise a significant reduction on fabrication costs by avoiding energy-intensive processes. However, their scalability remains challenging without a low-cost transparent electrode. In this work, we present solution-processed silver-nanowire meshes that uniformly cover the microtextured surface of hybrid heterojunction solar cells to enable efficient carrier collection for large device area. We systematically compare the characteristics and device performance with long and short nanowires with an average length/diameter of 30 μm/115 nm and 15 μm/45 nm, respectively, to those with silver metal grids. A remarkable power conversion efficiency of 10.1% is achieved with a device area of 1 × 1 cm(2) under 100 mW/cm(2) of AM1.5G illumination for the hybrid solar cells employing long wires, which represents an enhancement factor of up to 36.5% compared to the metal grid counterpart. The high-quality nanowire network displays an excellent spatial uniformity of photocurrent generation via distributed nanowire meshes and low dependence on efficient charge transport under a high light-injection condition with increased device area. The capability of silver nanowires as flexible transparent electrodes presents a great opportunity to accelerate the mass deployment of high-efficiency hybrid silicon photovoltaics via simple and rapid soluble processes.

Solution-processed polymer–silver nanowire top electrodes for inverted semi-transparent solar cells

We present a transparent, fully solution-processed top anode system comprising a thin, conductive polymer interlayer below a silver nanowire mesh for efficient organic electronic devices. We fabricate inverted semi-transparent polymer solar cells exhibiting power conversion efficiencies that are comparable to devices incorporating an opaque electrode. By means of scanning electron microscopy and light beam induced photocurrent measurements we show that the thin polymer interlayer facilitates charge extraction from the active layer and efficient transport to the metallic nanowire mesh.

Solution-processed flexible transparent conductors composed of silver nanowire networks embedded in indium tin oxide nanoparticle matrices

Although silver nanowire meshes have already demonstrated sheet resistance and optical transmittance comparable to those of sputter-deposited indium tin oxide thin films, other critical issues including surface morphology, mechanical adhesion and flexibility have to be addressed before widely employing silver nanowire networks as transparent conductors in optoelectronic devices. Here, we demonstrate the efficacy of low temperature solution-processed flexible metal nanowire networks embedded in a conductive metal oxide nanoparticle matrix as transparent conductors, and investigate their microstructural, optoelectronic, and mechanical properties in attempting to resolve nearly all of the technological issues imposed on silver nanowire networks. Surrounding silver nanowires by conductive indium tin oxide nanoparticles offers low wire to wire junction resistance, smooth surface morphology, and excellent mechanical adhesion and flexibility while maintaining the high transmittance and the low sheet resistance. In addition, we discuss the relationship between sheet resistance and transmittance in the silver nanowire composite transparent conductors and their maximum achievable transmittance. Although we have selected silver nanowires and indium tin oxide nanoparticle matrix as demonstration materials, we anticipate that various metal nanowire meshes embedded in various conductive metal oxide nanoparticle matrices can effectively serve as transparent conductors for a wide variety of optoelectronic devices owing to their superior performance, simple, cost-effective, and gentle processing.

Fabrication of a nickel nanowire mesh electrode suspended on polymer substrate

We report on an efficient strategy for the fabrication of an ultra-long suspended nanowire mesh suitable for nanodevice architectures on a polymer surface. First, nickel nanowires are synthesized directly on a template substrate by magnetron sputtering. Laser interference lithography followed by deep reactive ion etching is used to create the nanograted template substrate constituted of one-dimensional line pattern arrays of 240 nm in periodicity. Ordered alignment of ultra-long nanowires (∼180 nm in diameter) with high fidelity to the template pattern is observed by scanning electron microscopy. The transfer of the pre-defined parallel nanowire array from the template surface to a target polymer substrate for electrical characterization of the system is demonstrated. The electrical behaviour of the nanowire mesh, suspended between two electrodes, was found to be linear, stable, and reproducible. This result suggests that this nanofabrication process will open an efficient way to the design and construction of novel nanodevices.

UV induced formation of transparent Au–Ag nanowire mesh film for repairable OLED devices

The next generation of optoelectronic devices requires transparent conductive electrodes to be flexible, cheap, and compatible with large scale manufacturing processes. Indium Tin Oxide (ITO) electrodes are often used due to their superior transparency and conductance, however they are brittle, expensive and their fabrication requires vacuum conditions which restrict scale-up. One possible alternative to the traditional ITO electrode is the metal nanowire mesh (MNWM) electrode, which is transparent, conductive, flexible and easy to produce. In this work we present the preparation and characterization of a simple organic light emitting diode (OLED) device based on a transparent electrode made of ultrathin MNWM and a comparison to an ITO based device. We have found that MNWM electrodes offer a suitable alternative to ITO electrodes in OLED devices. We have also found that the failure rate for devices due to short circuits between the top and bottom electrodes was smaller in MNWM based devices compared to ITO based devices since the MNWM devices could be repaired to present normal OLED behavior by selectively burning the nanowires forming the short. The ability to “heal” organic devices presents an important advantage and also allows for future uses in applications such as roll to roll printing.

Strongly adhesive and flexible transparent silver nanowire conductive films fabricated with a high-intensity pulsed light technique

Large-scale silver nanowire (AgNW) mesh films have received increasing attention as new transparent conductive films used in various printed devices. However, there are two crucial issues in implementing AgNWs that need to be addressed: (1) strong adhesion between AgNW film and substrate and (2) high conductivity with short treatment time for low-cost printed technology. Here, a high-intensity pulsed light (HIPL) sintering technique, which provides extreme heating locally in the AgNW film and at the interface between the film and polymer substrate, sinters the AgNW film to produce high conductivity with strong adhesion on the substrate. Importantly, light intensity, exposure time, and AgNW amount can be adjusted simply to form films that meet specific device needs. A flexible AgNW film with sheet resistance of 19 Ω sq−1 and transmittance of 83% at 550 nm is obtained with only one-step on a polyethylene terephthalate substrate with a light intensity of 1.14 J cm−2 under an exposure time of only 50 μs. The film can endure multiple peeling tests, which will play an important role in printed electronics.

Laminating solution-processed silver nanowire mesh electrodes onto solid-state dye-sensitized solar cells

Solution processed silver nanowire meshes (Ag NWs) were laminated on top of solid-state dye-sensitized solar cells (ss-DSCs) as a reflective counter electrode. Ag NWs were deposited in <1 min and were less reflective compared to evaporated Ag controls; however, AgNW ss-DSC devices consistently had higher fill factors (0.6 versus 0.69), resulting in comparable power conversion efficiencies (2.7%) compared to thermally evaporated Ag control (2.8%). Laminated Ag NW electrodes enable higher throughput manufacturing and near unity material usage, resulting in a cheaper alternative to thermally evaporated electrodes.

Semitransparent Organic Photovoltaic Cells with Laminated Top Electrode

We demonstrate semitransparent small molecular weight organic photovoltaic cells using a laminated silver nanowire mesh as a transparent, conductive cathode layer. The lamination process does not damage the underlying solar cell and results in a transparent electrode with low sheet resistance and high optical transmittance without impacting photocurrent collection. The resulting semitransparent phthalocyanine/fullerene organic solar cell has a power conversion efficiency that is 57% of that of a device with a conventional metal cathode due to differences in optical absorption.

Transparent Cu nanowire mesh electrode on flexible substrates fabricated by transfer printing and its application in organic solar cells

We report the flexible transparent Cu nanowire mesh electrode fabricated by simple transfer printing from flexible PDMS stamp as a potential replacement for the conventional ITO electrode in organic solar cell applications. Fabricated Cu mesh electrode shows a greater flexibility than conventional ITO electrode deposited on plastic substrates, and exhibits high optical transmittance and electrical conductance. It can be bent to 3 mm radius of curvature with no degradation of the conductance. Large area nanoscale metal electrodes on flexible substrates are demonstrated using a roll-to-roll process. The organic solar cell made with the transparent Cu electrode performs as good as the one with ITO electrode, which indicates that such electrode has the potential to replace conventional ITO electrode for low-cost, large-area flexible organic solar cell applications.

Self‐Organization of a Highly Integrated Silicon Nanowire Network on a Si(110)–16 × 2 Surface by Controlling Domain Growth

AbstractHere, bottom‐up nanofabrication for the two‐dimensional self‐organization of a highly integrated, well‐defined silicon nanowire (SiNW) mesh on a naturally‐patterned Si(110)–16 × 2 surface by controlling the lateral growths of two non‐orthogonal 16 × 2 domains is reported. This self‐ordered nanomesh consists of two crossed arrays of parallel‐aligned SiNWs with nearly identical widths of 1.8–2.5 nm and pitches of 5.0–5.9 nm, and is formed over a mesoscopic area of 300 × 270 nm2 so as to show a high integration density in excess of 104 µm−2. These crossed SiNWs exhibit semiconducting character with an equal band gap of ∼0.95 eV as well as unique quantum confinement effect. Such an ultrahigh‐density SiNW network can serve as a versatile nanotemplate for nanofabrication and nanointegration of the highly‐integrated metal‐silicide or molecular crossbar nanomesh on Si(110) surface for a broad range of device applications. Also, the multi‐layer, vertically‐stacked SiNW networks can be self‐assembled through hierarchical growth, which opens the possibility for creating three‐dimensionally interconnected crossbar circuits. The ability to self‐organize an ultrahigh‐density, functional SiNW network on a Si(110) surface represents a simple step toward the fabrication of highly‐integrated crossbar nanocircuits in a very straightforward, fast, cost‐effective, and high throughput process.

Transparent Metal Nanowire Thin Films Prepared in Mesostructured Templates

The preparation of conductive and transparent gold/silver nanowire mesh films is reported. The nanowires formed after the reduction of the metal ions was triggered and a thin growth solution film was spread on a substrate. Metal reduction progressed within a template of a highly concentrated surfactant liquid crystalline mesostructure formed on the substrate during film drying to form ordered bundles of ultrathin nanowires. The films exhibited metallic conductivity over large areas, high transparency, and flexibility.