Phillip Won

Low-haze, annealing-free, very long Ag nanowire synthesis and its application in a flexible transparent touch panel.

Since transparent conducting films based on silver nanowires (AgNWs) have shown higher transmittance and electrical conductivity compared to those of indium tin oxide (ITO) films, the electronics industry has recognized them as promising substitutes. However, due to the higher haze value of AgNW transparent conducting films compared to ITO films, the clarity is decreased when AgNW films are applied to optoelectronic devices. In this study, we develop a highly transparent, low-haze, very long AgNW percolation network. Moreover, we confirm that analyzed chemical roles can easily be applied to different AgNW synthesis methods, and that they have a direct impact on the nanowire shape. Consequently, the lengths of the wires are increased up to 200 μm and the diameters of the wires are decreased up to 45 nm. Using these results, we fabricate highly transparent (96%) conductors (100 Ω/sq) with low-haze (2%) without any annealing process. This electrode shows enhanced clarity compared to previous results due to the decreased diffusive transmittance and scattering. In addition, a flexible touchscreen using a AgNW network is demonstrated to show the performance of modified AgNWs.

Random nanocrack, assisted metal nanowire-bundled network fabrication for a highly flexible and transparent conductor

The most viable flexible and transparent conductor alternative to indium tin oxide (ITO) is metal mesh on plastic including metal micro-lines at regular spacing and metal nanowire percolation networks. Applications in flexible and transparent devices have been hampered by either moire pattern problems caused by regular patterning or low mechanical robustness of the nanowire network. In this study, we demonstrate a novel class of flexible transparent conductor based on metal nanowire micro-bundled networks at random patterns. Original random patterns are prepared from controlled random cracking of high-stress silicon nitride on the silicon substrate, and employed as repetitively usable master molds with independently controllable pattern density and linewidth. Silver nanowires are subsequently placed in the random crack channels through a facile solution process and transferred to the polymer substrate with UV curable epoxy resin. The resultant flexible and transparent conductor, spanning over wafer scale at high reproducibility, not only exhibits enhanced mechanical robustness upon repeated bending or scratching, which often occurs when used as touch-screen panel, but also is free from the moire pattern problem due to the random nature of nanowire bundle patterns. Further application of the resultant flexible transparent conductor as a touch-screen panel confirms easy large-scale fabrication of this robust and flexible transparent conductor.

Simple hydrothermal synthesis of very-long and thin silver nanowires and their application in high quality transparent electrodes

Solution-processed silver nanowire (AgNW) random mesh is a strong contender to commercial indium tin oxide (ITO); however, its performance is limited due to large contact resistance between nanowires and post-processing treatments. As an alternative, long nanowires can decrease the number of contact points and contact resistance. Here, a simple modified hydrothermal method for the synthesis of very-long silver nanowires (AgNWs) and their use in a high quality transparent conducting electrode without post-processing has been developed. Well dispersed very-long and thin silver nanowires are synthesized by using glucose as a reducing agent and silver chloride as a silver source. The lengths of the wires are in the range of 200 to 500 μm with an average diameter of 45–65 nm. To the best of our knowledge, this is the first report on long nanowires having a thin diameter with greater than 200 microns length. As compared to other transparent conductors and nanowire networks, this AgNW network shows a higher percolative figure of merit (FoM, Π) with low haze. A flexible touch screen using the AgNW network is also demonstrated which has shown good performance even on a bendable surface.

High Efficiency, Transparent, Reusable, and Active PM2.5 Filters by Hierarchical Ag Nanowire Percolation Network

Air quality has become a major public health issue in Asia including China, Korea, and India. Particulate matters are the major concern in air quality. We present the first environmental application demonstration of Ag nanowire percolation network for a novel, electrical type transparent, reusable, and active PM2.5 air filter although the Ag nanowire percolation network has been studied as a very promising transparent conductor in optoelectronics. Compared with previous particulate matter air filter study using relatively weaker short-range intermolecular force in polar polymeric nanofiber, Ag nanowire percolation network filters use stronger long-range electrostatic force to capture PM2.5, and they are highly efficient (>99.99%), transparent, working on an active mode, low power consumption, antibacterial, and reusable after simple washing. The proposed new particulate matter filter can be applied for a highly efficient, reusable, active and energy efficient filter for wearable electronics application.

Highly Stretchable and Transparent Electromagnetic Interference Shielding Film Based on Silver Nanowire Percolation Network for Wearable Electronics Applications

Future electronics are expected to develop into wearable forms, and an adequate stretchability is required for the forthcoming wearable electronics considering various motions occurring in human body. Along with stretchability, transparency can increase both the functionality and esthetic features in future wearable electronics. In this study, we demonstrate, for the first time, a highly stretchable and transparent electromagnetic interference shielding layer for wearable electronic applications with silver nanowire percolation network on elastic poly(dimethylsiloxane) substrate. The proposed stretchable and transparent electromagnetic interference shielding layer shows a high electromagnetic wave shielding effectiveness even under a high tensile strain condition. It is expected for the silver nanowire percolation network-based electromagnetic interference shielding layer to be beyond the conventional electromagnetic interference shielding materials and to broaden its application range to various fields that require optical transparency or nonplanar surface environment, such as biological system, human skin, and wearable electronics.

Metal Nanowire-Coated Metal Woven Mesh for High-Performance Stretchable Transparent Electrodes

This work presents a new template-assisted fabrication method to obtain stretchable metal grids for high-performance stretchable transparent conducting electrodes (TCEs). Readily accessible metal woven mesh (MWM) is used as a template to make the fabrication process simple, cost-effective, reproducible, and potentially scalable by combining it with silver nanowire (AgNW) coating and elastomer filling processes. Stretchable TCEs are made with the AgNW-coated MWM and show remarkable optoelectronic performance with a sheet resistance of ∼3.2 Ω/sq and optical transmittance of >80%, large maximum stretchability of 40%, and electrical and mechanical robustness even under repeated stretching and bending deformations (1000 cycles). The device is demonstrated in a highly flexible touch screen panel that can operate well even in a bent state.