We have used aqueous dispersions of silver nanowires to prepare thin, flexible, transparent, conducting films. The nanowires are of length and diameter close to 6.5 μm and 85 nm, respectively. At low thickness, the films consist of networks but appear to become bulk-like for mean film thicknesses above ∼160 nm. These films can be very transparent with optical transmittance reaching as high as 92% for low thickness. The transmittance (550 nm) decreases with increasing thickness, consistent with an optical conductivity of 6472 S/m. The films are also very uniform; the transmittance varies spatially by typically <2%. The sheet resistance decreases with increasing thickness, falling below 1 Ω/◻ for thicknesses above 300 nm. The DC conductivity increases from 2 × 105 S/m for very thin films before saturating at 5 × 106 S/m for thicker films. Similarly, the ratio of DC to optical conductivity increases with increasing thickness from 25 for the thinnest films, saturating at ∼500 for thicknesses above ∼160 nm. We...

http://www.tara.tcd.ie/bitstream/handle/2262/64106/De%20ACS%20Nano%2009%202.pdf;sequence=1

Silver Nanowire Networks as Flexible, Transparent, Conducting Films: Extremely High DC to Optical Conductivity Ratios

Transparent conductors as solar energy materials: A panoramic review

Ultrathin films of single-walled carbon nanotubes (SWNTs) represent an attractive, emerging class of material, with properties that can approach the exceptional electrical, mechanical, and optical characteristics of individual SWNTs, in a format that, unlike isolated tubes, is readily suitable for scalable integration into devices. These features suggest the potential for realistic applications as conducting or semiconducting layers in diverse types of electronic, optoelectronic and sensor systems. This article reviews recent advances in assembly techniques for forming such films, modeling and experimental work that reveals their collective properties, and engineering aspects of implementation in sensors and in electronic devices and circuits with various levels of complexity. A concluding discussion provides some perspectives on possibilities for future work in fundamental and applied aspects.

http://www.ifc.dicp.ac.cn/library/cailiao/pdf1/11.pdf

Ultrathin Films of Single-Walled Carbon Nanotubes for Electronics and Sensors: A Review of Fundamental and Applied Aspects

Transparent electrodes, indespensible in displays and solar cells, are currently dominated by indium tin oxide (ITO) films although the high price of indium, brittleness of films, and high vacuum deposition are limiting their applications. Recently, solution-processed networks of nanostructures such as carbon nanotubes (CNTs), graphene, and silver nanowires have attracted great attention as replacements. A low junction resistance between nanostructures is important for decreasing the sheet resistance. However, the junction resistances between CNTs and boundry resistances between graphene nanostructures are too high. The aspect ratios of silver nanowires are limited to ∼100, and silver is relatively expensive. Here, we show high-performance transparent electrodes with copper nanofiber networks by a low-cost and scalable electrospinning process. Copper nanofibers have ultrahigh aspect ratios of up to 100000 and fused crossing points with ultralow junction resistances, which result in high transmitance at low sheet resistance, e.g., 90% at 50 Ω/sq. The copper nanofiber networks also show great flexibility and stretchabilty. Organic solar cells using copper nanowire networks as transparent electrodes have a power efficiency of 3.0%, comparable to devices made with ITO electrodes.

/pdf/electrospun-metal-nanofiber-webs-as-high-performance-1mskof2e0b.pdf

Electrospun metal nanofiber webs as high-performance transparent electrode.

The fabrication of transparent, conductive, and uniform silver nanowire films using the scalable rod-coating technique is described in this study. Properties of the transparent conductive thin films are investigated, as well as the approaches to improve the performance of transparent silver nanowire electrodes. It is found that silver nanowires are oxidized during the coating process. Incubation in hydrogen chloride (HCl) vapor can eliminate oxidized surface, and consequently, reduce largely the resistivity of silver nanowire thin films. After HCl treatment, 175 Ω/sq and approximately 75% transmittance are achieved. The sheet resistivity drops remarkably with the rise of the film thickness or with the decrease of transparency. The thin film electrodes also demonstrated excellent flexible stability, showing < 2% resistance change after over 100 bending cycles.

/pdf/silver-nanowire-based-transparent-flexible-and-conductive-1jnmb7cr54.pdf

Silver nanowire-based transparent, flexible, and conductive thin film

Mechanical integrity of transparent conductive oxide films for flexible polymer-based displays

Calculation of adhesive and cohesive fracture toughness of a thin brittle coating on a polymer substrate

The present work investigates the mechanical integrity of multilayer films developed for flexible displays. The layers comprise tin-doped indium oxide (ITO) conductive coatings and alumina barrier coatings sputtered onto high temperature aromatic polyesters. The onset strain for tensile failure and related cohesive strength of the coatings, and their adhesion to the polymer substrate, are analyzed by means of bending tests and fragmentation tests. The former test enables accurate electrical resistivity measurements during bending of film specimens, and correlates the failure of the ITO coating to the abrupt increase of resistivity. In the fragmentation test, the progressive failure of the thin coating is examined in situ in an optical microscope as a function of tensile strain, with simultaneous measurement of the electrical resistance, for the ITO coatings. The results and their analysis enable to determine the influence of internal stresses and layer thickness on the failure mechanisms of the multilayer composite films, despite the occurrence of coupled failure processes between adjacent layers.

/pdf/mechanical-properties-of-transparent-funcional-thin-films-jozlg4oo93.pdf

L. Médico

Papers

Mechanical integrity of transparent conductive oxide films for flexible polymer-based displays

Calculation of adhesive and cohesive fracture toughness of a thin brittle coating on a polymer substrate

Mechanical properties of transparent funcional thin films for flexible displays

Failure of brittle functional layers on flexible devices

The Influence of the Polyester Substrate on the Structure and Performance of Vacuum-deposited Coatings