Graphene–Ferroelectric Hybrid Structure for Flexible Transparent Electrodes

Abstract

Graphene has exceptional optical, mechanical and electrical properties, making it an emerging material for novel optoelectronics, photonics and for flexible transparent electrode applications. However, the relatively high sheet resistance of graphene is a major constrain for many of these applications. Here we propose a new approach to achieve low sheet resistance in large-scale CVD monolayer graphene using non-volatile ferroelectric polymer gating. In this hybrid structure, large-scale graphene is heavily doped up to 3×10 13 cm -2 by non-volatile ferroelectric dipoles, yielding a low sheet resistance of 120 Ω/□ at ambient conditions. The graphene-ferroelectric transparent conductors (GFeTCs) exhibit more than 95 % transmittance from the visible to the near infrared range owing to the highly transparent nature of the ferroelectric polymer. Together with its excellent mechanical flexibility, chemical inertness and the simple fabrication process of ferroelectric polymers, the proposed GFeTCs represent a new route towards large-scale graphene based transparent electrodes and optoelectronics.KEYWORDS CVD graphene, ferroelectric polymer gating, sheet resistance, high transparency, mechanical flexibility, charged impurity scattering 2 Graphene keeps attracting much attention with enormous amount of experimental and theoretical activity, since its first micromechanical exfoliation in 2004. [1][2][3][4] As one atomic layer membrane, graphene is highly transparent (97.3 %) over a wide range of wavelengths from the visible to the near infrared (IR). 5Owing to its covalent carbon-carbon bonding, graphene is also one of the strongest materials with a remarkably high Young's modulus of ~ 1 TPa. 6 The combination of its high transparency, wideband tunability and excellent mechanical properties make graphene a very promising candidate for flexible electronics, optoelectronics and phonotics. 7-9The technical breakthrough of large-scale graphene synthesis has further accelerated the use of graphene films as transparent electrodes. 10,11To utilize graphene as transparent electrodes for applications such as solar cells 12 , organic light emitting diodes, 13 touch panels and displays 14, the key challenge is to reduce the sheet resistance to values comparable with indium tin oxide (ITO), which provides the best known combination of transparency (> 90 %) and sheet resistance (< 100 Ω/□). 8,15 Conventional methods to reduce the sheet resistance like electrostatic doping of graphene requires complex fabrication steps of dielectric deposition and gate electrode preparations, which are not practical for doping large-scale graphene and consume power to maintain the doping levels. 12,14 Chemical doping has been shown to effectively reduce the sheet resistance of graphene. [16][17][18][19] However, the doping mechanism of chemical dopants is not yet fully understood and the relationship between charge density and carrier mobility is still under debate. [20][21][22] Furthermore, the adsorption of moisture and other chemical molecul...

Ferroelectrically driven spatial carrier density modulation in graphene

“…Devices based on this concept have demonstrated non-volatile resistance hysteresis [13][14][15] and transparent conductivity in flexible electronics 16,17 . Initial experimental studies, however, achieved charge density changes in graphene much smaller than anticipated from full compensation of the polarization 18 , since the electrostatic coupling can be limited by extrinsic effects caused by adsorbed molecules 15,19,20 .…”

Mechanical Analyses and Structural Design Requirements for Flexible Energy Storage Devices

“…The in-situ measurement of electrochemical properties of flexible devices is much preferred during the mechanical bending process, including the CV curves of SCs, [41,46] open-circuit voltage of LIBs, [42][43][44] and electrical resistance of conductive electrodes. [74,75] The specific capacities of LIBs and capacitance of SCs should also be measured after the mechanical deformation given the long time required in the charge-discharge process. The failure point should therefore be reported using the electrical performance variation to avoid systematical errors produced by the equipment and personnel operation.…”

Handwriting enabled harvested piezoelectric power using ZnO nanowires/polymer composite on paper substrate

“…In addition to the development of systems depending only on ZnO NW arrays, ZnO composite structures have been suggested. As a polymer piezoelectric material and owing to the good optical transparency and mechanical flexibility, poly (vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)), has been exploited [37,38].…”