High performance graphene/C60/Sb composite film phototransistor with broadband and tunable bidirectional photoresponse

The high-performance phototransistor based on two-dimensional materials is very attractive in integrated logic function chips and large-scale real-time optical imaging. Recently, graphene-semiconductor composite film phototransistors have already achieved ultrahigh photoconductive gain due to the strong absorption capacity of the semiconductor layer and the strong mobility of graphene. However, low absorption and high dark current limit the photoresponsivity and detective band of the graphene phototransistors. Here, we fabricate a graphene/C₆₀/Sb composite film photo transistor with a broadband response (450 nm - 1500 nm), fast response speed (20 ms) and ultrahigh peak photoresponsivity (3.927 × 10⁵ A/W). The charge transfer mechanism between layers of the device has been analyzed by adjusting Sb layer thicknesses (5 nm, 10 nm, 20 nm). In addition, we observe the positive and negative photocurrent response in the experiment and study the bidirectional response of the device by applying different gate voltages. The ultrathin phototransistor (10 - 20 nm) is compatible with the traditional CMOS and nanoimprinting process to achieve large area and high-precision array integrated devices.