Superstable copper nanowire network electrodes by single-crystal graphene covering and their applications in flexible nanogenerator and light-emitting diode

Copper nanowires (CuNWs), with excellent electronic properties and high cost-effectiveness, have tremendous potential in the field of transparent conductive electrodes for flexible electronics, large touch screen display and triboelectric energy harvesters, while their vulnerability to oxidation in air has impeded possible practical applications. Fortunately, it has been recognized that graphene encapsulation of CuNWs is capable of protecting CuNWs. However, neither self-assembled reduced graphene oxide nor chemical vapor deposition-grown polycrystalline graphene coatings can guarantee full protection to CuNWs, due to their ubiquitous voids, grain boundaries and wrinkles that allow water and oxygen molecules to pass through and result in the accelerated electrochemical corrosion at the graphene-copper interface, especially under folding conditions. Herein, we demonstrate a sandwich-structured single-crystal graphene/copper nanowire network/UV-curable resin (SCG/CuNW/UVR) composite film with ultrahigh electronic performance stability. The SCG/CuNW/UVR electrode exhibits a good optical and electrical performance (~19 Ω sq−1 under 84.3% transmittance), excellent mechanical robust and remarkably high oxidation resistance (ΔR/R0 < 0.2 within 180 days), in sharp contrast with the bare CuNWs (ΔR/R0 > 1 after 1 day) and polycrystalline graphene-covered CuNWs counterparts (ΔR/R0 > 1 after 7 days). Furthermore, the SCG/CuNW/UVR electrodes can replace indium tin oxide (ITO) electrodes to construct the triboelectric nanogenerators (TENG) and quantum dot light emitting diodes (QLED), comparable to the flexible commercial ITO counterparts. The fabrication of such high-performance SCG/CuNW/UVR electrode is facile to be scaled-up with low cost, providing the feasibility for industrial applications of flexible ITO-free electronic and optoelectronic devices.