Photoresponse of Physically Oxidized Graphene Sensitized by an Organic Dye

We investigated the charge transport and photoresponse characteristics of a hybrid structure comprising physically oxidized graphene and Rhodamine-based organic dye molecules. The oxidation of the graphene surface was deterministically controlled by varying the UV/ozone exposure time. The oxidized graphene surface was then modified with the organic dye molecules using a simple dip-coating method. The electrical conductance and photoresponse of the resulting hybrid films were investigated systematically using Raman spectroscopy and environment-dependent charge transport measurements. The oxygen-containing groups generated by the UV/ozone exposure dramatically enhanced the photoresponses of the hybrid films while maintaining a high device performance. Importantly, we found that the photoresponses of the hybrid films were strongly related to chemical reactions between the photoexcited electrons and adsorbates (water or oxygen) in the dye layer as well as to the migration of the photoexcited electrons toward the top surface of the dye layer due to the negatively charged oxygen-containing groups at the graphene-dye interface. Our simple and effective method involving oxidizing graphene and hybridizing the resultant layer with organic dyes will inspire new approaches to the development of electronics and optoelectronics based on graphene.