Vertical Graphene/Pentacene Single Crystal/Graphene Transistors for Self-Powered Weak Light Detection and High-Speed Imaging

Organic semiconductors are promising candidates for next-generation photodetectors owing to their unique properties including large absorption coefficient and intrinsic mechanical flexibility. However, limited by high defect density, large exciton binding energy, and short exciton diffusion length, many challenges remain for fabricating high-performance organic photodetectors, especially for scenarios where weak light sensing and high-speed imaging are required. Herein, by coupling single-crystal pentacene with monolayer graphene, a vertical organic phototransistor with excellent zero-bias photon detecting capacity is demonstrated. Under self-powered weak light condition, the responsivity and specific detectivity are 2.86 AW-1 and 3.3 x 1011 Jones (based on experiment spectral noise density), respectively. It is demonstrated that weak light down to 25 nWcm-2 can be detected. When operating with an external bias, the responsivity of the device increases dramatically (up to 105 AW-1), and a better 3 dB bandwidth (approximate to 74 kHz) is obtained. Finally, imaging functionality is demonstrated by employing this vertical transistor as a single-sensing pixel. This work suggests organic single crystals exhibit enormous potential in advanced optoelectronic systems, and may provide a viable route for weak light detecting and high-speed imaging. Vertical organic phototransistor with excellent zero-bias photon detecting capacity is demonstrated, and this self-powered characteristic can be modulated by the gate voltage.image