Type-III organic/two-dimensional multi-layered phototransistors with promoted operation speed at the communication band

Abstract

The 2D materials Bi₂O₂Se and graphene have emerged with ultrahigh mobility, showing great potential in near-infrared optical communication and photo-detection with high speed. Nevertheless, for acquiring high photo-responsivity, the prolonged carrier lifetime leads to the photoconductor having an inferior operation speed. In this work, a type-III junction dipyrazino[2,3-f:2′,3′-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HAT-CN)/Bi₂O₂Se is constructed on a graphene field-effect transistor, which facilitates photo-generated electron recombination. We observe a broadband response covering the communication band with a highly optimized recovery time down to 101 μs. Consequently, a 3 dB bandwidth of nearly 2 kHz (5-fold improved) is achieved with a 3-fold promotion of detectivity compared to graphene/Bi₂O₂Se, which is superior in photoconductors. More importantly, with the existence of middle-layer HAT-CN, the external quantum efficiency was improved up to 11.82% with a responsivity to 2420 A W⁻¹. Furthermore, the demonstration of the 3 × 3 array gives potential opportunity in large scale focal imaging. This work not only provides an appropriate path for manufacturing large scale high-performance phototransistors but also exhibits significant potential for high speed optoelectronic applications in the communication band and ultrafast sensing.