High Performance GQD/Graphene Heterostructure Field Effect Phototransistor with Efficient Photoinduced Effects

Graphene and highly luminescent graphene quantum dots (GQDs) have been widely used in optoelectronic devices as a photoactive material. Graphene Quantum Dots (GQDs) have been widely used for various optoelectronic devices as a photoactive material due to their high absorption coefficient and tunable bandgap. However, the low mobility of GQD films results in poor charge collection and device performance. By combining GQDs with graphene into hybrid GQDs/Graphene field effect transistors, photocarriers from GQDs are transferred to graphene, improving charge collection and transport, drastically increasing the photoresponsivity. In this study, we report the preparation of a GQDs/Graphene heterostructure in order to investigate the effect of GQDs on photoactive response of graphene. Using UV–vis absorption and photoluminescence (PL) spectra, the optical properties of graphene and the GQDs/Graphene heterostructure were measured and compared. Moreover, to investigate their electronic and charge transfer properties, we fabricated field-effect phototransistors (FEPT) on pristine graphene and GQDs/Graphene heterostructure thin films and investigated their photoactive electrical properties. Under illumination, both pristine and GQDs/Graphene FEPT showed an increase in current and carrier mobility. The increased current and carrier mobility of GQDs/Graphene FEPT is due to the presence of a large number of photoexcited charge carriers. The current and carrier mobility in the GQDs/Graphene heterostructure FEPT were also lower than those in the pristine graphene FEPT. This is explained by GQDs' n-type doping effect on graphene, which reduces the accumulation of holes in the active p-channel near the insulating layer and causes charge to be transferred from the GQDs to the graphene. As a result, we discovered a charge transfer effect in the GQDs/Graphene heterostructure, which could be used in optoelectronic devices.