Improved Flexible Transparent Conductive Electrodes based on Silver Nanowire Networks by a Simple Sunlight Illumination Approach

Pengfei Kou,Liu Yang,Cheng Chang,Sailing He

doi:10.1038/srep42052

Pengfei Kou, Liu Yang + Show 2 more

Open Access

https://doi.org/10.1038/srep42052

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Abstract

Silver nanowire (Ag NW) networks have attracted wide attention as transparent electrodes for emerging flexible optoelectronics. However, the sheet resistance is greatly limited by large wire-to-wire contact resistances. Here, we propose a simple sunlight illumination approach to remarkably improve their electrical conductivity without any significant degradation of the light transmittance. Because the power density is extremely low (0.1 W/cm2, 1-Sun), only slight welding between Ag NWs has been observed. Despite this, a sheet resistance of <20 Ω/sq and transmittance of ~87% at wavelength of 550 nm as well as excellent mechanical flexibility have still been achieved for Ag NW networks after sunlight illumination for 1 hour or longer, which are significant upgrades over those of ITO. Slight plasmonic welding together with the associated self-limiting effect has been investigated by numerical simulations and further verified experimentally through varied solar concentrations. Due to the reduced resistance, high-performance transparent film heaters as well as efficient defrosters have been demonstrated, which are superior to the previously-reported Ag NW based film heaters. Since the sunlight is environmentally friendly and easily available, sophisticated or expensive facilities are not necessary. Our findings are particularly meaningful and show enormous potential for outdoor applications.

Highlights

Become increasingly important for flexible device applications
We show in this paper that the Ag NWs fabricated by our previously-reported full-solution polymethylmethacrylate (PMMA)-assisted spin-coating method[50] can be partially welded under the exposure of natural sunlight with power density of only 0.1 W/cm[2] (i.e., 1 Sun, 300 times weaker than that reported in ref. (44))
We have demonstrated a promising method based on sunlight irradiation to remarkably improve the electrical conductivity of Ag NW networks without any significant degradation of the light transmittance

Summary

Introduction

Become increasingly important for flexible device applications. Besides, polyvinylpyrrolidone (PVP) insulating coatings on the surface of Ag NWs, which originate from the PVP stabilizer typically used to control the nanowire shape and help finely disperse the synthesized nanowires in solution, form barriers for electron transport between wires and give rise to high wire-to-wire contact resistances, which, as a result, further limit the conductivity of the whole network[12,20]. Since Gannet et al reported a light-induced plasmonic nanowelding technique based on the localized and self-limited welding effects[44], this method has been developed quickly and widely applied as an effective post-treatment of Ag NW networks[45,46,47] In those reports, light source with excessively high intensity were used, e.g., a broadband tungsten-halogen lamp with a power density of approximately 30 W/cm[2 44], and pulsed xenon lamps[45] or UV lasers[46,47]. It is very economical and convenient, and promising for large-scale applications, especially outdoor applications, e.g., automobile-window defrosters, flexible outdoor panel displays, and solar cells, where the Ag NW networks can be incorporated directly without any post-treatment and will be self-improved over the course of natural exposure to natural sunlight

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