This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Graphene is a single layer of carbon atoms in which electrons can move with high mobility, making it promising for high-speed electronic components. Yet it is not very efficient at converting light into electricity.
While light absorbed by graphene does excite electrons, leaving behind positively charged carriers called 'holes,' the absorbed light energy cannot be harnessed effectively unless electrons and holes are separated and directed to different contacts. Conventional solar cells use semiconductors such as silicon, whose bandgap plays a key role in converting light into electrical energy. Graphene does not have such a gap.
"That's why we have to come up with a different mechanism," says Ralf Schützhold, director of the HZDR Institute of Theoretical Physics. One option is to cut or fold the graphene to create tiny edges. When light is absorbed by the material, creating charge carriers, a magnetic field applied to the graphene forces these carriers into circular paths.
The edges act like guardrails, guiding the charge carriers in opposite directions—electrons and holes drift apart and are separated. Creating such edges is challenging, however, and the approach is difficult to scale up to larger surfaces—a prerequisite for practical applications. That is why the HZDR team is proposing a new concept: "Instead of an edge, we propose using electrical voltages, generating potential barriers, as guardrails," explains Schützhold.
Specifically, the plan is to place narrow metal electrodes onto an insulating layer above or below the graphene. Applying voltages to the electrodes creates potential barriers in the graphene. The research is published in the journal Physical Review Applied.
Crucially, a magnetic field applied perpendicular to the graphene plane causes electrons and holes to follow circular paths in opposite directions. Together with the potential barriers, this produces directed motion: An electron traces an arc, is reflected at the barrier, and continues along another arc. A negative potential barrier reflects electrons and lets holes pass, while a positive barrier has the opposite effect.
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