High-efficiency extraction synthesis for high-purity copper nanowires and their applications in flexible transparent electrodes

Copper nanowires (Cu NWs) are considered an excellent alternative to indium tin oxide (ITO) in flexible transparency electrodes (FTEs). However, the mixed particles and surface oxidation of Cu NWs degrade the transmittance and conductivity of the electrodes. Therefore, highly purified Cu NWs without oxidation are vital for high-performance FTEs. Herein, a facile and effective purification process is introduced to purify Cu NWs in a water and n-hexane system, which takes advantage of the differences in hydrophilicity between Cu NWs and Cu NPs caused by their different adsorption affinities to octadecylamine (ODA). At the same sheet resistance, the transmittance of the purified Cu NW-based FTEs improved approximately 2% compared to that of non-purified Cu NW-based FTEs. Immersion of the electrode in glacial acetic acid removed the surface organics and oxides. After only 40 s of treatment, the sheet resistance dramatically decreased from 10⁵ Ohm/sq to 31 Ohm/sq with a transmittance of 85%. In addition, the Cu NW-based FTE conductors showed excellent flexibility (remaining stable after 1000 bending cycles). The Cu NW-based FTEs were further applied to fabricate a flexible transparent heater. At a voltage of 10 V, the temperature of the heater reached 73 ℃, demonstrating the potential applications of this material in various fields.