Electric field induced enhancement of photovoltaic effects in graphene nanoribbons

The terahertz (THz) to visible irradiation induced current in zigzag and armchair graphene nanoribbons were investigated by focusing on the modulation of the photovoltaic effects by tuning the electric field ($E$) strength. The numerical results show that spin photovoltaic effects in zigzag-edged graphene nanoribbons can be significantly improved by enhancing the $E$ strength. In detail, an acceptable broadband photoresponsivity with a full optical spin polarization in a broad range of photon energies, including the THz region, can be obtained that can be preserved in the presence of the edge roughness. Furthermore, armchair-edged graphene nanoribbons could reveal a tunable photoresponsivity induced by THz to ultraviolet wavelengths. These results could lead to the enhancement of photovoltaic effects and especially the generation of a spin-polarized photocurrent in all-carbon junctions.