Enhanced conductivity and stability of Cu-embedded zinc tin oxide flexible transparent conductive thin films

Great challenges remain concerning the cost-effective manufacture of high performance flexible transparent conductive thin films (TCFs). Here, we report flexible TCFs using Cu-embedded zinc tin oxide (ZTO) multilayer structures that are prepared on polyethylene terephthalate (PET) substrates at room temperature. The effects of Cu embedded layer thickness on conductivity and transparency are studied, and a new conduction mechanism is proposed to describe the conduction before and after the critical thickness. At the optimal condition, the films exhibit excellent performance in terms of optical and electrical characteristics, a largest figure of merit value is obtained as 173.2, while the sheet resistance is 9.92 Ω/sq. at an adequate transmittance of 81.2%. The resistance does not show great change after 1000 bending cycles, indicating good flexibility. Meanwhile, the resistance remains nearly constant after 100 tape tests, suggesting a good adhesion to the PET substrate. Moreover, the multilayer thin film exhibits good stability to resist humid and/or hot environments. The improvement of adhesion and stability of multilayer films can be attributed to the effective covering of ZTO on the Cu and disordered molecule arrangement of ZTO layers. In addition, the successful implementation of the multilayer films into a flexible transparent film heater is demonstrated, verifying the applicability.