A low-cure-temperature copper nano ink for highly conductive printed electrodes

We have developed a copper metal-organic-based conductive ink which can be applied to printing and roll-to-roll processes. Metal-organics printed on flexible substrates decompose into highly conductive copper metal when annealed at above 250 °C. The new nano ink was prepared by mixing copper carboxylate with copper complex nano particles of a mean size below 100 nm. The viscosity of the copper ink was in the range of 10⁴-10⁵ mPa s (at 50 rpm). The resistivity of the conductive film, after annealing under the condition of 3% H₂ above 250 °C for 20 min, was below 10 μΩ cm and it could be further reduced to 4.4 μΩ cm when annealed at 320 °C for 20 min. We successfully demonstrated a printable copper nano ink that proceeds to form highly conductive metal film when annealed at low temperature on flexible substrates.