Bending Effects in Graphene: Implication for Flexible Transparent Electronics

Employing the density functional theory, a graphene device model for flexible transparent electronics is studied in terms of mechanical, electronic, and optical properties. A small bending modulus of approximate to 0.25 nNnm indicates the high flexibility of graphene. Bending can open a small band gap within 0.05eV due to the decreased pi orbital electrons, but hardly destroy the electronic conductance of graphene near the Fermi energy, as indicated by the electronic conductance transmission. However, large bending angles above 70 degrees will lead to a drop in the conductance in high energy regions above approximate to 2eV. On the other hand, despite the decreased optical transmittance of graphene under bending due to new absorption peaks at 0.9 and 4.1eV from the pi ->pi* interband transitions, the optical transmittance is still above 94% even at the high bending angle of 90 degrees. Also, there is a clear drop in optical transmittance above the bending angle of 70 degrees. Therefore, a critical bending angle of 70 degrees is predicted where the graphene can maintain the performance under bending in flexible transparent electronics.