Highly Conductive, Flexible, and Oxidation-Resistant Cu-Ni Electrodes Produced from Hybrid Inks at Low Temperatures

Abstract

Recently, Ni and Ni-Cu nanoparticle-based inks have gained considerable research interest because of their high corrosion resistance as conductors in electronic devices. However, reported inks based on Cu-Ni nanoparticles need to be sintered at high temperatures above 300 °C to obtain electrodes with high conductivity on the order of 10–5 Ω·cm. This study proposes a new conductive Cu-Ni-based hybrid ink that could be sintered at only 150–180 °C for producing Cu-Ni electrodes with low electrical resistance, high oxidation resistance, and flexibility. The hybrid ink contains Cu flakes and a complex of nickel formate and 1-amino-2-propanol (NiF-AmIP complex). At 150–180 °C, the Cu flakes catalyze the self-reduction of the NiF-AmIP complex, and Cu-Ni electrodes with high conductivity (on the order of 10–5 Ω·cm) are formed on flexible polymer substrates at temperatures exceeding 150 °C. Analysis indicates that metallic Ni was decorated on the Cu flakes (especially on the edge) to improve the electrode’s conductivity, oxidation resistance, and flexibility by forming bridging interconnections between the Cu flakes. The Cu-Ni electrodes demonstrated high stability against oxidation up to approximately 400 °C in air, as well as at 80 °C and 80% RH after 7 days. In addition to the excellent oxidation stability, the Cu-Ni electrode showed high durability under mechanical bending stress. Such sintered Cu-Ni electrodes obtained from hybrid inks have great potentials in printed/flexible devices due to their oxidation resistance and cost-effectiveness.

Self-Organizing, Environmentally Stable, and Low-Cost Copper–Nickel Complex Inks for Printed Flexible Electronics

“…The second part is attributed to the decomposition of the Ni complex contained in the Cu–Ni complex ink, which is accompanied by a large endothermic peak and the release of CO 2 , H 2 , and amine fragments again. Importantly, the starting decomposition temperature of the Ni complex decreased to ∼170 °C (i.e., ∼15 °C lower than before) because of the catalytic function of fresh Cu nanoparticles formed by decomposition of the Cu complex. , Figure g shows high-resolution TEM (HR-TEM) images of the obtained Cu–Ni patterns and the corresponding schematic of the microstructure, which clarify the characteristics of the self-organized Cu@Ni core–shell nanostructures. Two points are clear: (1) the Cu nanoparticles are covered by a Ni layer of uniform ∼3 nm thickness, and (2) numerous Ni particles fill the gaps between Cu particles.…”

“…Moreover, the sintering temperature of ∼350 °C is not compatible with most flexible polymeric substrates. Although a hybrid ink consisting of Cu flakes and a nickel complex was developed to reduce the sintering temperature, the microstructure of the printed patterns was poor due to the large voids among the flakes . Cu–Ni complex inks were also proposed, but the properties of the obtained Cu–Ni patterns needed to be further improved .…”

“…Although a hybrid ink consisting of Cu flakes and a nickel complex was developed to reduce the sintering temperature, the microstructure of the printed patterns was poor due to the large voids among the flakes. 34 Cu−Ni complex inks were also proposed, but the properties of the obtained Cu−Ni patterns needed to be further improved. 28 Therefore, the development of highperformance Cu−Ni inks and low-temperature sintering processes are still challenging and hinder the application of low-cost Cu-based inks in PE products.…”

Hansen Solubility Parameter Analysis on Dispersion of Oleylamine-Capped Silver Nanoinks and their Sintered Film Morphology

“…Nanoparticles (NPs) with sizes of <100 nm have been explored for their novel physical, chemical, electronic, magnetic, optoelectronic, and catalytic properties, and have been widely applied in various fields [1][2][3]. Printed electronics can be used to form conductive wires in electronic components, owing to the printing technology [4,5]. Compared to conventional methods (e.g., photolithography and vacuum processes), the printing technology is more straightforward and has a lower environmental impact.…”

Fabrication of the Silver Grids by Interfacial Interaction

“…[1] As a result, many materials such as conductive polymers, graphene, carbon nanotubes, metal oxides, and metals have been investigated as substitutes to ITO. [2][3][4][5][6][7][8][9][10][11][12][13] Unfortunately, most of them cannot manage the good balance between transmittance and conductivity. As an exception, Ag grids have been one of the most competitive alternatives to ITO with virtues as high transmittance, low haze, excellent conductivity, good mechanical properties, and low cost.…”