Facile Synthesis of Graphene on Cu Nanowires via Low-Temperature Thermal CVD for the Transparent Conductive Electrode

Abstract

We report on the application of graphene (Gr)/copper (Cu) shell/core nanowires (NWs) as a transparent conducting electrode (TCE) for optoelectronic devices. First, we optimize the synthesis conditions of Cu NWs by control of the agent material, which shows excellent TCE properties. Synthesized Cu NWs have high transmittance (T) and low sheet resistance (R-s) which are 88.92% at 450 nm and 17.95 52 Omega/sq, respectively, comparable to those of ITO. However, the Cu NWs' long-term stability problem of oxidation that occurs even at room temperature is an impediment for their application. To suggest a possible solution of the oxidation issue, graphene is deposited on the surface of the Cu NWs by using thermal chemical vapor deposition (CVD) at low temperature. The formation of graphene coated Cu NWs was performed at low temperature (600 degrees C) with systematically optimized conditions to avoid surface damages on Cu NWs. The graphene coated Cu NWs have not only high transmittance and conductivity (88.85% at 450 nm and 36.91 Omega/sq) but also tremendous long-term stability that prevents oxidation of Cu NWs. Finally, we demonstrated the improvement of light extraction in GaN-based light emitting diodes (LEDs) using our suggested Gr/Cu NW film as a TCE. Electroluminescence (EL) of LED IV, with Gr/Cu NW-based TCE at a current injection of 100 mA, was dramatically improved (2.63x) by its current spreading effect, and the efficiency droop phenomenon was slightly slackened due to a reduction in the series resistance of the LEDs. Our experimental results clearly show that the Gr/Cu NWs can be used as a TCE to improve the optoelectronic performance of LEDs, and they can replace the ITO without the degradation of electrical and optical properties.