Preparation of narrow copper nanowires with less oxidized surface for flexible and transparent electrodes under octadecylamine

Copper nanowires without post-treatment were manufactured by a hydrothermal method, which was suitable for flexible and transparent conductive films. The synthesized copper nanowires had much less oxide layer and stable surface layer for more than 100 days when stored in IPA solution. Cu nanowires with a diameter of 20–40 nm and length up to hundreds of micrometers, sometimes even around several millimeters, were manufactured through standard reaction condition. The roles of capping agents including Octadecylamine (ODA) were investigated. ODA as a capping agent provided mostly a uniform diameter to nanowires. In addition, a fairly suitable transparent electrode was prepared by the Cu nanowires having a high level of flexibility without breaking. Even after 500 cycles of bending, sheet resistance was from 36 Ωsq−1 to 48 Ωsq−1 with 90% transmittance. When applied to a flexible PEDOT:PSS/PTB7:PC70BM organic solar cell, it shows a high external quantum efficiency of 7.31%, which is a greatly enhanced result. •Synthesis methods are shown for very thin copper nanowires suitable for transparent conductive films.•Basic principle of this synthesis is Red-Ox nano-reaction supplemented with capping agents.•Processing parameters play a significant role in copper nanowires without surface layer oxidation.•Copper nanowires can be used for solar cell electrodes as an alternative transparent electrode.