Copper Nanowires and Their Applications for Flexible, Transparent Conducting Films: A Review

Abstract

Cu nanowires (NWs) are attracting considerable attention as alternatives to Ag NWs for next-generation transparent conductors, replacing indium tin oxide (ITO) and micro metal grids. Cu NWs hold great promise for low-cost fabrication via a solution-processed route and show preponderant optical, electrical, and mechanical properties. In this study, we report a summary of recent advances in research on Cu NWs, covering the optoelectronic properties, synthesis routes, deposition methods to fabricate flexible transparent conducting films, and their potential applications. This review also examines the approaches on protecting Cu NWs from oxidation in air environments.

Assembly and Electronic Applications of Colloidal Nanomaterials

“…Striking the optimal balance between contradicting material properties calls for creative materials engineering through the selection of suitable nanomaterials and their assembly methods. [396,399,438] To quantify these two parameters concurrently, a generally accepted Figure of merit uses the ratio of the DC to optical conductivity (σ DC /σ OP ) to evaluate different nanomaterial networks. [396,432,433] High-aspect-ratio nanostructures, such as 1D silver or copper nanowires or carbon nanotubes, and 2D graphene sheets, form percolating networks with minimal thicknesses, allowing low electrical resistance and high optical transparency.…”

“…[399] This analysis leads to the conclusion that smaller-diameter nanowires afford a better combination of high optical transmittance and electrical conductance. [438] State-of-the-art sheet resistances and optical transmittances at a wavelength of 550 nm for nanomaterial networks are 10 Ω sq −1 @ 85% for Ag nanowires, [440] 15 Ω sq −1 @ 86% for Cu nanowires, [441] 328 Ω sq −1 @ 79% for SWCNTs, [26] and 260 Ω sq −1 @ 86% for graphene flakes. [438] State-of-the-art sheet resistances and optical transmittances at a wavelength of 550 nm for nanomaterial networks are 10 Ω sq −1 @ 85% for Ag nanowires, [440] 15 Ω sq −1 @ 86% for Cu nanowires, [441] 328 Ω sq −1 @ 79% for SWCNTs, [26] and 260 Ω sq −1 @ 86% for graphene flakes.…”

Controllable Synthesis and Study on Morphology of Copper Nanowires

“…Copper is only 6% less conductive than silver but is 1000 times more abundant in the Earth's crust. Moreover, copper is also about 100 times cheaper than silver and 6000 times cheaper than gold …”

Nanomaterial-based stretchable and transparent electrodes

“…Among the most critical concerns about CuNWs are their thermal stability and oxidization characteristics [47]. Although there have been efforts to prevent the oxidization of CuNWs through chemical treatments, the use of only CuNWs always accompanies the likelihood of oxidation [45,46].…”

“…These chemical and thermal instabilities of CuNWs are the main challenges to their use as stretchable and transparent electrodes. Thus, to solve these problems, a variety of reports have introduced stretchable and transparent electrodes with hybrid structures of CuNWs and other materials, such as carbon nanomaterials, conductive polymers, and metal-based materials [44,[47][48][49][50][51][52]. Graphene, a representative carbon nanomaterial, has high mechanical strength and thermal resistance and low water vapor and oxygen permeability [48][49][50].…”