Newly Designed Cu/Cu₁₀Sn₃ Core/Shell Nanoparticles for Liquid Phase-Photonic Sintered Copper Electrodes: Large-Area, Low-Cost Transparent Flexible Electronics

The conductive nanomaterials applicable to unconventional printing techniques have attracted a great deal of attention, and in particular, cost-effective copper-based electrode materials have been recognized as viable candidates for replacement of the expensive silver counterpart. In this study, we synthesize newly designed Cu/Cu₁₀Sn₃ core/shell nanoparticles, as an additive material for overcoming the critical drawbacks in Cu nanoparticle-based electrodes, in combination with a large-area processable, continuous photonic sintering process on a time scale of 10^-3 s. By virtue of the low-melting point nature of the Cu₁₀Sn₃ phase, the facile electrode fabrication process is easily triggered, yielding resistivities of 27.8 and 12.2 μω cm under energy dose conditions of 0.97 and 1.1 J/cm², respectively, at which highly conductive electrodes cannot be obtained from phase-pure Cu nanoparticles. The suspension mixture of Cu and Cu/Cu₁₀Sn₃ nanoparticles permits roll-to-roll processable, highly uniform Cu-based electrodes (with a sheet resistance and a standard deviation of 1.21 and 0.29 ω/square, respectively) even on vulnerable polyethylene naphthalate substrate, while the electrodes derived from Cu₁₀Sn₃ phase-free Cu nanoparticles suffer from nonuniform characteristics and even a partially insulating nature. The practical applicability of Cu/Cu₁₀Sn₃ core/shell nanoparticles is demonstrated with the fabrication of a touch screen panel and an antenna for wireless power transmission.