Flexible uncooled ultraviolet to middle-wavelength infrared ultrabroadband nanohybrid photodetectors for imaging

Nanohybrids consisting of graphene and colloidal semiconductor quantum dots (QDs/graphene) can combine the benefits of strong quantum confinement in the constituent components, such as high carrier mobility in graphene and large exciton binding energy in QDs, to enable extraordinary photoconductive gain and hence high photoresponse. Furthermore, QDs/graphene nanohybrids are inherently flexible, making them ideal for flexible photodetectors. Despite exciting progress made in rigid and flexible QDs/graphene photodetectors in broadband from UV to short-wave infrared, flexible middle-wave infrared (MWIR) photodetectors remain a challenge. Herein, we report the first success in fabrication of HgTe QDs/graphene nanohybrid ultrabroadband (400–4000 nm wavelength) photodetectors on flexible polyimide substrates via resolving critical issues of device fabrication on flexible substrates, which allowed flexible device performance approaching their counterparts on rigid substrates. Specifically, the flexible HgTe QDs/graphene nanohybrids photodetectors exhibited high responsivity (R*) across the ultrabroadband spectrum at room temperature. At 550 nm, 1.5 μm and 4.0 μm wavelengths, an R* of up to 0.65 AW−1, 5.7 × 10−3 AW−1 and 0.9 × 10−3 AW−1 were achieved respectively. Bending tests confirmed performance stability of the flexible HgTe QDs/graphene nanohybrids photodetectors under repeated bending with up to 5.5 mm radius of curvature. Images taken in the ultrabroadband while the photodetectors in flat and bent states both show promising imaging quality. This result illustrates the potential applications of the uncooled, flexible HgTe QDs/graphene nanohybrids photodetectors in the ultrabroadband range of 400–4000 nm.