Sensitive organic/inorganic polarized photodetectors enhanced by charge transfer with image sensing capacity

Abstract

Organic photodetectors (OPDs) have attracted increasing attention in the future wearable sensing and real-time health monitoring, due to their intrinsic features including the mechanical flexibility, low-cost processing and cooling-free operations; while their performances are lagging as the results of inferior carrier mobility and small exciton diffusion coefficient of organic molecules. Graphene exhibits the great photoresponse with wide spectral bandwidth and high response speed. However, weak light absorption and the absence of a gain mechanism have limited its photoresponsivity. Here, we report a sensitive organic/inorganic phototransistor with fast response speed by coupling PTCDA organic single crystal with the monolayer graphene. The long range exciton diffusion in highly ordered π-conjugated molecules, efficient exciton dissociation and charge transfer at the PTCDA/graphene heterointerfaces, and the high mobility of graphene enable a high responsivity (8 × 104A/W), short response time (220 µs) and excellent specific detectivity (>1011 Jones), which is higher than the level of commercial on-chip device. This interfacial photogating effect is verified by the high-resolution spatial photocurrent mapping experiment. In addition, the high sensitivity to polarization is clear and the ultrahigh photoconductive gain enables a near-infrared (NIR) response for 980 and 1550 nm. Finally, high-speed visible and NIR imaging applications are successfully demonstrated. This work suggests that high quality organic single crystal/graphene is a promising platform for future high performance optoelectronic systems and imaging applications.