We demonstrate plasma-treated Ag nanowires (NWs) as flexible transparent electrode materials with enhanced long-term stability against oxidation even in a high humidity environment (80% humidity, 20 °C). Through a simple fluorocarbon (C4F8 or C4F6) plasma treatment method, a CxFy protective polymer was sufficiently cross-linked and attached on the surface of the AgNWs strongly and uniformly. Even though C4F8 and C4F6 activate differently on the AgNW surface due to the different dissociated radicals formed in the plasma, it was found that the CxFy protective polymers obtained by both chemicals work similarly as a protective layer for transparent conductive electrodes; a nearly constant sheet resistance ratio (Rs/Ro) of 1.6 was found for AgNWs treated with C4F8 and C4F6 plasmas, while the AgNWs without the plasma treatment exhibited a ratio of 176.2 after 36 days in a harsh environment. It is believed that the fluorocarbon plasma treatment can be used as a key method for ensuring long-term oxidation stability in numerous electronic applications including flexible solar cells utilizing various types of metallic nanowires.

In this study, the SiO2 etch characteristics of perfluorocarbon such as C4F8, C5F8, and C7F8 were investigated using inductively coupled plasmas (ICPs) to study the effect of a high C/F ratio on the etch characteristics of SiO2 for the ICP. The SiO2 rates and etch selectivities over Si3N4 and amorphous carbon layer (ACL) were measured by using the mixtures of Cx(x = 4, 5, 7)F8/Ar/O2. The higher C/F ratio of perfluorocarbon showed lower SiO2 etch rate but exhibited higher etch selectivities over Si3N4 and ACL due to the higher C2 while keeping the similar F in the plasma as observed by optical emission spectroscopy and due to the thicker fluorocarbon layer with more carbon-rich fluorocarbon on the materials surface as observed by X-ray photoelectron spectroscopy. Especially, C7F8 is environmentally benign material because it not only has a relatively low global warming potential but also can be captured easily using a capture system (a liquid state at the room temperature). Therefore, C7F8 could be applicable as one of the next generation perfluorocarbon etching materials.

Graphene nanoplatelets (GNP) have attracted considerable attention due to their high yield and fabrication route that is scalable to enable graphene production. However, the absence of a means of fabricating a transparent and conductive GNP film has been the biggest obstacle to the replacement of pristine graphene. Here, we report on a novel means of fabricating uniform and thin GNP-based high-performance transparent electrodes for flexible and stretchable optoelectronic devices involving the use of an adhesive polymer layer (PMMA) as a GNP layer controller and by forming a hybrid GNP/AgNW electrode embedded on PET or PDMS. Relative to the commercially available indium tin oxide (ITO) film on a PET substrate, a GNP-based electrode composed of hybrid GNP/AgNW on PET exhibits superb optical, physical, and electrical properties: a sheet resistance of 12 Ω sq with 87.4% transmittance, a variable work function from 4.16 to 5.26 eV, an ultra-smooth surface, a rate of resistance increase of only 4.0% after 100 000 bending cycles, stretchability to 50% of tensile strain, and robust stability against oxidation. Moreover, the GNP-based electrode composed of hybrid Cl-doped GNP/AgNW shows outstanding performance in actual organic light-emitting diodes (OLEDs) by exhibiting an increased current efficiency of 29.5% and an increased luminous efficiency of 36.2%, relative to the commercial ITO electrode on PET.

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