Air-Sinterable Copper Precursor Inks via Mixed Bidentate/Tridentate Ligands: Synergistic Oxidation Resistance and High Conductivity

Copper-based conductive inks offer a cost-effective alternative to silver-based inks in printed electronics but face critical oxidation challenges that degrade electrical performance. While single bidentate ligands have been explored to enhance oxidation resistance, their limited coordination stability hinders practical application. This study addresses this gap by investigating mixed-ligand strategies to improve atmospheric stability of copper precursor inks. Five ligand systems were designed, including a base system with 2-amino-2-methyl-1-propanol (AMP) and four hybrid systems combining AMP with secondary ligands (1,3-diaminopropane, 3-amino-1-propanol, isopropanolamine, or serinol). Comprehensive analysis revealed that mixed-ligand coordination, particularly the AMP-serinol system with tridentate binding, achieved enhanced oxidative stability, maintaining low resistivity (69.8 ± 5.5 μΩ·cm) at 250 °C for 10 s with <5% variation after 60 days in ambient air. A multiscale protection mechanismcombining molecular-level coordination control, nanoscale organic encapsulation, and microstructure optimizationexplains the improved long-term stability of tridentate ink systems. Finally, the ink’s processability and operational reliability was validated through direct-write fabrication of circuit patterns. This work establishes a ligand-engineering approach for developing oxidation-resistant copper-based conductive inks through rational ligand selection, providing both fundamental insights into coordination chemistry and practical guidelines for ink formulation design.