A high-performance, flexible, and transparent heater based on a hybrid of dry-spun carbon nanotubes (CNT), which is pulled out directly from a super vertically aligned CNT forest, and graphene is fabricated. The electrical, optical, and electromechanical properties of two different kinds of hybrid devices, graphene above or below the CNT film, and simple CNT film heating devices that are made of one or two layers of CNTs, are studied. The results prove that the hybrid structured film heaters are superior to the simple CNT film heaters. The simple single-layer CNT film and double-layer CNT film heaters attain maximum temperatures of 48 and 64 °C with transmittances of 73 and 64% at a wavelength of 550 nm, respectively, whereas the single-layer CNT sheet/ graphene/PET and graphene/single-layer CNT sheet/PET hybrid heaters attain maximum temperatures of 81 and 85 °C with transmittances of 68 and 71%, respectively. The 10 000 bending cycle test suggests that the graphene/single-layer CNT sheet/ PET heater has good mechanical and thermal stability. Further, defrost test and portable heating with a 9 V battery prove the possibility of using the hybrid heater for vehicle defrosting, portable heating, and wearable devices.

In this study, multilayered graphene was easily transferred to the target substrate in one step using thermal release tape. The transmittance of the transferred graphene according to the number of layers was measured using a spectrophotometer. The sheet resistance was measured using a four-point probe system. Graphene formed using this transfer method showed almost the same electrical and optical properties as that formed using the conventional poly (methyl methacrylate) transfer method. This method is suitable for the mass production of graphene because of the short process time and easy large-area transfer. In addition, multilayered graphene can be transferred on various substrates without wetting problem using the one-step dry transfer method. In this work, this easy transfer method was used for dielectric substrates such as glass, paper and polyethylene terephthalate, and a sheet resistance of ~240 ohm/sq was obtained with three-layer graphene. By fabricating organic solar cells, we verified the feasibility of using this method for optoelectronic devices.

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