▎ 摘　　要

Graphene-organic heterojunction phototransistors have great potential to achieve sensitive photoresponse owing to the excellent absorption of organic layers and fast charge transport in graphene. However, the photoresponse of most graphene-based phototransistors is limited within visible light region with narrow bandwidth and poor sensitivity in the near-infrared (NIR) region. Herein, a graphene-organic NIR phototransistor is fabricated by integrating an organic heterojunction layer composing of phthalocyanine molecules and fullerene C-60 onto the graphene channel. The phototransistor exhibits a high photoresponsivity of 2.2 x 10(3) A W-1 under 850 nm irradiation with the power density of 35.4 mW cm(-2) (V-ds = 1 V). Meanwhile, a bidirectional photoresponse (both positive and negative) is obtained at different wavelength regions. Further studies indicate that the gate voltage enables to effectively tune the photoresponse in the wavelength range where PbPc has a significant optical absorption. Such a tunability of photoresponse is especially beneficial for the exploration of new functionalities in logic function devices. This work presents a feasible strategy to prepare graphene-organic heterojunction phototransistor with broadband photoresponse as well as sensitive and tunable bidirectional signals at NIR region.