Preparation Of Graphene-Silver Nanowires Hybrid Transparent Electrodes And Their Applications For Liquid Crystal Devices

Indium tin oxide (ITO) is the most commonly used transparent electrode materials in electro-optical devices. However, the use of ITO as a transparent electrode has certain limitations because of increased costs, scarcity of indium, brittleness and so on. Recently, single-layer graphene (SLG), silver nanowires (AgNWs) and other conducting materials are regarded as ideal alternative materials to replace ITO. However, both SLG and AgNWs have several drawbacks. For example, SLG obtained by chemical vapor deposition method has surface defects which reduce its electrical property. Meanwhile, AgNWs are easily oxidized and hard to keep long-term stability. In order to address these problems, here we develop two novel series of hybrid transparent conductive materials by combining SLG and AgNWs.First of all, polyvinyl alcohol (PVA) encapsulated AgNWs (top)/SLG (bottom) hybrid transparent conducting films are fabricated by introducing PVA layer onto the corresponding AgNWs/graphene structure. This novel composites exhibit improved electrical and considerable optical performances, the sheet resistance is 14.1Ω/sq and the corresponding transmittance is 84% at 550 nm for the most optimized sample. Additionally, due to the existence of PVA-protective layer, this novel hybrid film has low surface roughness, high resistance to oxidation and mechanical flexibility. Finally, a photo-addressed/electric-erased flexible cholesteric liquid crystal (Ch-LCs) device was built by employing this novel conducting film, in which the PVA layer also could be used as an alignment film to induce the planar orientation of LC molecules. This Ch-LCs device shows impressive electro-optical performance.Secondly, to solve the low adhesion between SLG and AgNWs in the SLG (top)/AgNWs (bottom) hybrid structure, we further develop another novel SLG/PLA/AgNWs hybrid transparent conducting film by introducing biodegradable polylactic acid (PLA) layer between the two main components. Meanwhile, PLA is also used as the alternative material of polymethyl methacrylate (PMMA) to fabricate a SLG/AgNWs hybrid film as a reference sample. Compared with the reference sample, the novel hybrid film has a similar electro-optical performance. Here the sheet resistance of the optimized sample is 13.6Ω2/sq and the transmittance is 83.2% at 550nm. In addition, the introduction of PLA layer reduces the surface roughness, enhances the mechanical flexibility and the chemical stability of the hybrid film. Finally, a pressure-sensitive/electric-erased flexible Ch-LCs device has been prepared by using this novel hybrid films as transparent electrodes. The mentioned Ch-LCs device shows a comfortable pressure-addressing /electric-erasing performance.To sum up, the comprehensive performances of these two type of SLG-AgNWs hybrid transparent conducting films have significantly been improved because of the introduction of multi-functional polymer layer. This work provides a valuable reference for the practical application of SLG and AgNWs, demonstrating the great potential of these novel transparent conductive materials for flexible optoelectronic devices.