The electrical, optical, thermal, chemical, mechanical and tribological characteristics of a highly flexible transparent conductive electrode (HFTCE) coating based on reduced graphene oxide (rGO), carbon nanotubes (CNTs) and silver nanowires (AgNWs) were investigated under various conditions. The motivation was to develop a highly durable and flexible film for transparent conductive electrode applications. The overall characteristics of multilayers based on rGO, CNTs and AgNWs were found to be much better than those of the single-layer AgNW coating. The rGO and CNT layers served to protect the AgNW layer from damage due to bending and contact sliding motions. The contact pressure and bending stress were effectively distributed by the CNT layer deposited on top of the AgNW layer due to its spring-like behavior. In addition, the shear force from the friction force was reduced by the rGO top layer, which acted as a solid lubricant. Furthermore, the excellent performance of an HFTCE heater based on the rGO/CNT/AgNW coating was demonstrated by the results of a defrosting test. NPG Asia Materials (2017) 9, e438; doi:10.1038/am.2017.177; published online 13 October 2017
INTRODUCTIONIn recent decades, various transparent conductive films electrodes have been widely used in electronic devices such as solar cells, displays, memories and batteries. 1 In particular, indium tin oxide (ITO) has attracted considerable attention as a transparent conductive electrode because of its excellent optical and electrical properties. 2 However, indium, which is the main raw material used in ITO, has some disadvantages in terms of production and cost. Moreover, ITO application in flexible devices is limited by its brittleness. 3 To replace ITO in flexible devices, several types of conductive polymers, such as poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C61-butyric acid methyl ester have been suggested. 4,5 However, the electrical efficiency of these conductive polymers is much lower than that of ITO. Moreover, the mechanical properties of these conductive polymers are very weak despite their flexibility. Therefore, it is necessary to combine these conductive polymers with other electrodes to improve efficiency.Many studies using other types of conductive materials, such as graphene and carbon nanotubes (CNTs), have been conducted. [6][7][8][9][10][11][12] While carbon-based nanosheets and nanowires are known as materials with excellent mechanical and electrical properties, the sheet resistance of the coatings based on carbon is higher. Li et al. 6 demonstrated that the number of graphene layers deposited on the surface had a significant effect on their conductivity and transmittance. They found