A self-encapsulated broadband phototransistor based on a hybrid of graphene and black phosphorus nanosheets

A phototransistor based on a hybrid of graphene and BP nanosheets with a facile fabrication method and remarkable performance is presented. Unlike previously reported single BP flake-based devices, this phototransistor employs diverse BP nanosheets with different sizes and layer numbers. The wet transfer process of graphene is exploited to integrate the liquid-exfoliated BP nanosheets into the device smoothly. Due to the diversity of BP nanosheets, the device demonstrates a broadband photo-response in the spectrum from 360 nm to 785 nm. The photo-response mechanism is revealed to be the photogating effect caused by the discrete BP nanosheets adsorbed on graphene. The phototransistor has a responsivity of 7.7 × 103 A W−1 in the near-UV region with a wide conductive channel of 200 μm. Moreover, the simplified wet transfer process of graphene leaves a self-encapsulated layer of PMMA on the as-prepared device, inducing a good atmospheric stability in the device. This report provides a valid, implantable, and facile strategy to apply BP nanosheets in a broadband, high-performing and air-stable photodetector.