Enhanced photoresponse in curled graphene ribbons.

Graphene has become one of the most promising materials for future optoelectronics due to its ultrahigh charge-carrier mobility, high light transmission, and universal absorbance in the near-infrared and visible spectral ranges. However, a zero band gap and ultrafast recombination of the photoexcited electron-hole pairs limit graphene's potential in photovoltaic generation. Recent studies have shown that hot carriers can enhance photovoltaic generation in graphene p-n junctions through the photothermoelectric effect (PTE). It is, therefore, desirable to synthesize graphene nanostructures with an intrinsic PTE-induced photocurrent response. Here we report a simple method to synthesize quasi-one dimensional (quasi-1D) curled graphene ribbons (CGRs) that generate a photocurrent response with two orders of magnitude enhancement. Scanning photocurrent and photoluminescence measurements reveal that the photocurrent response is primarily attributed to the PTE and that the infrared emission may arise from thermal radiation. These results offer a new way to fabricate graphene-based optoelectronics with an enhanced photoresponse.