Graphene mesh as hybrid electrode for foldable devices
Journal
Nanoscale
Date
2017.11.24
Abstract
A graphene mesh with arrays of micro-holes was fabricated on a polymer substrate using a photolithography process for use as an electrode of a flexible device. First, the optimal mesh structure with high optical transmittance and electrical conductivity was designed using finite element method, in which the conductivity of mesh was simulated as a function of the structure, size, and period of hole array. After making a highly transparent graphene mesh, the sheet resistance of the graphene mesh was lowered to the level of the graphene monolayer by chemical doping and measured to be 330 ohm/sq at 98.5％ of the transparency. The figure of merit of the doped graphene mesh was calculated to be 106 at 98％ transmittance, which has not been reported in any conventional transparent electrode material. Notably, the hybrid electrode of silver nanowire(AgNW)/graphene mesh coated with over coating layer exhibited a very stable electrical characteristic over mechanical fatigue deformation compared to the hybrid film of AgNW/graphene sheet owing to the strong bonding with the polymer substrate through hole. The AgNW/graphene sheet underwent breakdown at less than 20,000 cycles in cyclic bending with 6.5％ strain, but the AgNW/graphene mesh showed 38％ of the resistance increase at 20,000 cycles and no breakdown even at 100,000 cycles. Therefore, in this paper, we propose a hybrid structure of AgNW/graphene mesh, optically and mechanically superior to AgNW/graphene sheet, as a transparent electrode for the foldable device with a long-term stability.