Abstract
Silver nanowires (Ag NWs) possess excellent optoelectronic properties, which have led to many technology-focused applications of transparent and flexible electronics. Many of these applications require patterning of Ag NWs into desired shapes, for which mask-based and printing-based techniques have been developed and widely used. However, there are still several limitations associated to these techniques. These limitations, such as complicated patterning procedures, limited patterning area, and compromised optical transparency, hamper the efficient fabrication of high-performance Ag NW patterns. Here, we propose a coat-and-print approach for effectively patterning Ag NWs. We printed a polymer-based ink on the spin-coated Ag NW films. The ink acts as a protective layer to help remove excess Ag NWs from the substrate and then dissolves itself into an organic solvent. In this way, we can take advantage of both coating-based techniques (lead to Ag NWs with high transparency) and printing-based techniques (efficiently pattern diverse shapes). The resultant Ag NW patterns exhibit comparable conductivity (sheet resistance: 7.1 to 30 Ohm/sq) and transparency (transmittance: 84 to 95% at λ = 550 nm) to those made by conventional coating methods. In addition, the patterned Ag NWs exhibit robust mechanical stability and reliability, surviving extensive bending and peeling tests. Due to higher conductivity, efficient patterning ability and inherent transparency, this material system and application method is highly suitable for transparent and flexible electronics. As a proof of concept, this research demonstrates a wide-band antenna, operating in the mm-wave range that includes the 5G communication band. The proposed antenna exhibits a wide bandwidth of 26 GHz (from 17.9 GHz to 44 GHz), robust return loss under 1000 cyclic bending (bending radius of 3.5 mm), and decent transparency over the entire visible wavelength (86.8% transmittance at λ = 550 nm). This work’s promising results indicate that this method can be adapted for roll-to-roll manufacturing to efficiently produce patterned and optically transparent devices.
Highlights
Transparent, flexible electronics have gained emerging attention in a variety of fields, including optoelectronics, energy storages, sensors, and light emitting displays.[1,2,3,4,5] conventional conductors, such as indium tin oxide (ITO), have long suffered from high processing cost and lack of flexibility
The Ag NWs used for the patterning process had a average diameter of 27 ± 9 nm, and length of 31 ± 7 μm, which was confirmed by the scanning electron microscope (SEM) images presented in Fig. 1a and Fig. S1 in the Supporting Information
The typical X-ray diffraction (XRD) pattern of the Ag NWs exhibited four diffraction peaks indexed to the face-centered cubic Ag without any impurities
Summary
Transparent, flexible electronics have gained emerging attention in a variety of fields, including optoelectronics, energy storages, sensors, and light emitting displays.[1,2,3,4,5] conventional conductors, such as indium tin oxide (ITO), have long suffered from high processing cost and lack of flexibility Motivated by this issue, researchers have developed many ITO alternatives by using conductive materials with decreasing dimensions, including nanoscale metal mesh,[6,7,8,9,10] conductive polymer,[11,12] metal nanowires,[13,14,15] graphene,[16,17,18,19,20,21] and carbon nanotubes.[22,23,24] Among these alternatives, silver nanowires (Ag NWs) are attractive due to their excellent electrical conductivity and mechanical flexibility.[25,26,27,28,29] In the past decade, tremendous efforts have been made to synthesize Ag NWs with high aspect ratio which is critical to the performance enhancement of Ag NWsbased devices. The resultant flexible Ag NW films have simultaneously demonstrated remarkable transparency and low sheet resistance,[33,34,35,36] both of which are comparable and even superior to the ITO films
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