Degradation mechanisms of silver nanowire electrodes under ultraviolet irradiation and heat treatment

Dong Chul Choo,Tae Whan Kim

doi:10.1038/s41598-017-01843-9

Abstract

We report the degradation mechanisms of the silver nanowire (Ag NW) electrodes that play a significantly important role in the stability of wearable and flexible devices. The degradation mechanisms behind the increase in the sheet resistances of Ag NW electrodes were clarified by investigating the variations in the structure and the chemical composition of the Ag NW electrodes caused by ultraviolet irradiation and thermal treatment. While the shapes of the Ag NWs were affected by melting during the thermal degradation process, the chemical composition of the polyvinylpyrrolidone protective layer on the surfaces of the Ag NWs was not changed. Ultraviolet irradiation deformed the shapes of the Ag NWs because nitrogen or oxygen atoms were introduced to the silver atoms on the surfaces of the Ag NWs. A graphene-oxide flake was coated on the Ag NW electrodes by using a simple dipping method to prevent ultraviolet irradiation and ozone contact with the surfaces of the Ag NWs, and the increase in the sheet resistance in the graphene-oxide-treated Ag NWs was suppressed. These observations will be of assistance to researchers trying to find novel ways to improve the stability of the Ag NW electrodes in next-generation wearable devices.

Highlights

Research on the formation of transparent electrodes and nanocomposite active layers for next-generation flexible optoelectronic applications by using graphene and graphene-related materials[1,2,3,4], carbon nanotubes[5,6,7], polymers[8,9,10] and silver nanowires (Ag NWs) has been actively conducted[11,12,13,14,15]
The Ag NW electrodes were thermally treated for 10 min under an atmospheric environment after a certain temperature had been set on the hot plate because the sheet resistance of the Ag NW electrodes was stabilized after a 10-min thermal treatment
The degradation mechanisms generated by the UV and the thermal treatments needed to be clarified separately because the temperature of the Ag NW electrodes was increased up to 36 °C in the UV/O3 cleaner, a temperature at which thermal deterioration was barely observed

Summary

Introduction

Research on the formation of transparent electrodes and nanocomposite active layers for next-generation flexible optoelectronic applications by using graphene and graphene-related materials[1,2,3,4], carbon nanotubes[5,6,7], polymers[8,9,10] and silver nanowires (Ag NWs) has been actively conducted[11,12,13,14,15]. Transparent, conductive electrode candidates, Ag NW electrodes have already been applied to some commercial products and have exhibited great advantages in cost due to the rapid development of synthesis and production technologies[22,23,24,25,26]. Even though several studies have reported on deterioration phenomena in electronic and optoelectronic devices caused by moisture or heat, systematic investigations concerning the underlying origins of the degradations of Ag NWs and the degradation mechanisms are necessary to enhance the lifetimes and the stabilities of Ag NWs27–32. The mechanisms underlying the degradation of Ag NWs due to ultraviolet irradiation and thermal treatment were investigated based on the electrical, the optical, the chemical, and the structural properties of the Ag NWs. The electrical and the optical properties of the Ag NW electrodes were investigated by measuring their sheet resistances and absorption spectra. The variations in the chemical composition on the surfaces of the Ag NWs due to ultraviolet irradiation and thermal treatment were analyzed using X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDS) measurements

Methods

Results

Conclusion