Roll-to-roll production of 30-inch graphene films for transparent electrodes

Abstract

The outstanding electrical, mechanical and chemical properties of graphene make it attractive for applications in flexible electronics. However, efforts to make transparent conducting films from graphene have been hampered by the lack of efficient methods for the synthesis, transfer and doping of graphene at the scale and quality required for applications. Here, we report the roll-to-roll production and wet-chemical doping of predominantly monolayer 30-inch graphene films grown by chemical vapour deposition onto flexible copper substrates. The films have sheet resistances as low as approximately 125 ohms square(-1) with 97.4% optical transmittance, and exhibit the half-integer quantum Hall effect, indicating their high quality. We further use layer-by-layer stacking to fabricate a doped four-layer film and measure its sheet resistance at values as low as approximately 30 ohms square(-1) at approximately 90% transparency, which is superior to commercial transparent electrodes such as indium tin oxides. Graphene electrodes were incorporated into a fully functional touch-screen panel device capable of withstanding high strain.

Booming Development of Group IV–VI Semiconductors: Fresh Blood of 2D Family

“…CVD‐grown graphene has made great breakthrough in the growth of large‐area graphene 17, 155, 156, 157, 158, 159, 160. Recently, the synthesis of 2DLMs via CVD methods has been illustrated in many reports especially for MoS 2 ,30, 31, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185 which also shows promising applications in electronics and optoelectronics.…”

Human‐Like Sensing and Reflexes of Graphene‐Based Films

“…As the above mentioned, the theoretical value of the sheet resistance of monolayer graphene is very satisfactory. The resistance of graphene synthesized by chemical vapor deposition (CVD), the acknowledged well‐suited method for growing large‐area and high quality graphene, can low to several hundreds of Ω sq –1 on nickel (Ni) and copper (Cu) 7. For the graphene prepared by another common used methods, chemical and thermal methods, the sheet resistance of reduced graphene oxide (rGO) can reduce to ≈640 Ω sq –1 after thermal annealing at 1000 °C 8.…”

“…Kong et al reported 1 to ≈12 graphene layers simultaneously obtained on polycrystalline Ni film via ambient pressure chemical vapor deposition (APCVD) 18. Cu foil with low carbon solubility was also most commonly used to obtain predominantly single‐layer graphene 7, 19. In addition, Ni–molybdenum (Mo) alloy,20 platinum (Pt),21 cobalt (Co)22 also have been designed for large area monolayer graphene.…”

“…Iijima et al successfully obtained 30‐inch graphene films with 97.4% optical transmittance and 125 Ω sq –1 sheet resistances, as the result of the half‐integer quantum Hall effect 7. After that, Hobara et al synthesized graphene on a suspended Cu foil at a low pressure thermal CVD.…”

“…In the past years, various transfer routes have been reported,7, 26, 47, 48 which have achieved big breakthrough in many aspects, such as the decrease of cracks and wrinkles and the area expanding of graphene. The ordinary widely used transfer approach is to etch the metal substrate with the graphene supported by polymer, such as poly(methyl methacrylate) (PMMA) 49.…”