The In–Sn alloy nanoparticle ink was purchased from ULVAC,Inc. (ITO nanometal ink, ITO1Cden, solvent: tetradecane, In–Sn alloy nanoparticle content in the ink: 20.4 wt%, Sn content in theIn–Sn alloy: ∼10 wt%, ULVAC Inc., 2014). The In–Sn alloy nanoparticle ink was produced using a gas evaporation method (gas phase condensation) with an average particle size of approximately 4 nm,and the nanoparticles were individually dispersed in tetradecane.