Charge Transport at the Interface between Graphene Oxide and Silk in Highly Flexible Commercial Silk-Based e-Textile Treated at High Temperatures

Graphene oxide (GO)-coated silk-based electronic textiles (e-textiles) are of great interest and have high potential because of their advantages, including high electrical conductivity and flexibility. Although heat treatment of the GO-coated textiles at high temperatures results in e-textiles with high electrical conductivity, flexibility and structural stability are not guaranteed. Here, we demonstrate heat-treated GO-coated silk (HGS) at high temperatures (HTTs; 500, 600, 700, and 800 °C) with superior flexibility. For HGS800, the resistance change during bending remained under 1% even after 5000 cycles. We also investigated the charge transport mechanism of the HGSs and the interface between GO and the silk. The temperature-dependent resistivity of the HGSs from 8 to 300 K was clearly explained by the fluctuation-induced tunneling model for all HTTs. The temperature-dependent resistance of the interface follows multidimensional variable-range hopping. The conducting behavior of the HGSs was interpreted to be due to structural changes induced by HTT, based on scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray diffraction.