  We present prominent photoresponse of bio-inspired graphene-based
phototransistors sensitized with chlorophyll molecules. The hybrid
graphene-chlorophyll phototransistors exhibit a high gain of 10^6 electrons per
photon and a high responsivity of 10^6 A/W, which can be attributed to the
integration of high-mobility graphene and the photosensitive chlorophyll
molecules. The charge transfer at interface and the photogating effect in the
chlorophyll layer can account for the observed photoresponse of the hybrid
devices, which is confirmed by the back-gate-tunable photocurrent as well as
the thickness and time dependent studies of the photoresponse. The
demonstration of the graphene-chlorophyll phototransistors with high gain
envisions a viable method to employ biomaterials for graphene-based
optoelectronics.
