Amorphous transparent conductive oxide films in the In–Zn–O system were deposited on polycarbonate (PC) substrates by simultaneous DC sputtering of an In 2O 3 target and a ZnO target with either 4 wt% Al 2O 3 or 7.5 wt% Ga 2O 3 impurities. Although the resistivity of the amorphous, non-doped In–Zn–O film on PC was about one order of magnitude higher than that on the glass substrate, the resistivity of the In–Zn–O films with Ga 2O 3 impurities on PC substrates was reduced to the level of the non-doped In–Zn–O films on glass substrates. The addition of Al 2O 3 or Ga 2O 3 to the In–Zn–O films also induced the widening of the optical band gap, which would improve transparency at blue wavelengths.