2D Doping Layer for Flexible Transparent Conducting Graphene Electrodes with Low Sheet Resistance and High Stability

Graphene, an ultrathin flexible material with high carrier mobility and transparency, is a promising candidate for flexible transparent conducting electrodes (TCEs). However, its resistance is too high for use as a TCE material by itself. Therefore, fabricating graphene with low sheet resistance and high stability is a significant challenge for practical applications of graphene TCEs. In this study, a 2D doping layer (DL) is proposed, which can stably dope graphene to develop a highly transparent graphene TCE with low sheet resistance. For this purpose, the 2D DL is prepared by immobilizing dopant molecules on transparent graphene oxide and simply stacking it with graphene enables efficient and stable charge transfer doping of the graphene. A TCE fabricated by alternately stacking the DL and graphene has a high optical transmittance of over 90% at a wavelength of 550 nm and a low sheet resistance of 50 Ω sq⁻¹. Furthermore, the sheet resistance shows an excellent thermal and mechanical stability with a change of only about 2% in a bending test of 20 000 cycles or at a high temperature of 220 °C. This result shows that stacking graphene with stable 2D DL is a promising approach for graphene-based next generation TCE.