All-two-dimensional semitransparent and flexible photodetectors employing graphene/MoS₂/graphene vertical heterostructures

As human society develops, electronic/optoelectronic devices are further required to be foldable, wearable, and even visually comfortable, but simultaneous achievement of both performance and comfort is a tough task. Here, we first report all-two-dimensional (2D) bis (trifluoromethanesulfonyl)-amide (TFSA)-doped graphene (GR) (TFSA-GR)/MoS₂/ triethylene tetramine (TETA)-doped GR (TETA-GR) vertical-heterostructure semitransparent photodetectors (PDs) on rigid/flexible substrates. The PD exhibits 0.128 A/W responsivity (R) and 1.69 × 10⁹ cm Hz^1/2/W detectivity at 532 nm wavelength with average visible transmittance being 58%. By adding an Al reflective mirror to the semitransparent PD, the R is improved to 0.137 A/W. The unencapsulated PD maintains ~75% of its initial R under 25 °C/30% relative humidity for 1000 h. The flexible PD shows excellent bending stability by maintaining 32% of its initial R even after 2000 bending cycles at a radius of curvature of 2 mm. These results suggest that the all-2D TFSA-GR/MoS₂/TETA-GR vertical heterostructures are very promising for their applications in flexible, foldable, and/or semitransparent electronic/optoelectronic appliances.