Tunable Semiconductivity in Nitrogen-Doped Graphene Nanosheets for High Surface-Area Optoelectronics

Semiconducting graphene has been identified for high potential electronic and optical applications since its discovery. Previously, substitutional atomic doping of graphene, particularly nitrogen, has shown to induce semiconducting behavior. However, variability in final dopant defect states, particularly from bottom-up synthesis, results in limited control over band structure and has thus formed a firm ceiling on the application of such structures. Here we report a plasma-enhanced chemical vapor deposition approach for the synthesis of switchable p and n-type nitrogen doped vertically oriented graphene nanosheets and applications towards enhanced carrier extraction in optoelectronics. Tuning between in-situ and ex-situ nitrogen doping has shown fine control over pyridinic/graphitic nitrogen dopant ratio, in turn shifting band structures towards more electron or hole-dominated carrier transport. In conjunction with the vertical orientation and density of nanosheets, these nanostructures allowed for the development of optically active p-i-n and n-i-p heterostructures with charge storage capacity and active surface area many times greater than what is possible with traditional planar architectures. With such structures, we show a route towards developing stable, high-surface area, efficient carrier extractors for optoelectronics. Technologies that are critically limited by active surface area, such as photovoltaic electrochemical cells and optical bioelectronic stimulators, show enhanced potential for co-application with these semiconducting graphene nanostructures and pave a clear road forward toward future hybrid-nanomaterial development.