Negative infrared photocurrent response in layered WS₂/reduced graphene oxide hybrids

We report high performance IR photocurrent response of two-dimensional hybrid materials consisting of layered WS₂ nanosheets and reduced graphene oxide (RGO). Comparative photocurrent response studies of WS₂ nanosheets, RGO, and WS₂/RGO hybrids were carried out by performing current-voltage (I-V) and time-dependent current measurements with a laser excitation source having a wavelength of 808 nm. The experimental investigations indicate that WS₂/RGO hybrids show negative photocurrent response, whereas WS₂ and RGO show positive photocurrent response. The negative photocurrent response of the WS₂/RGO hybrids is explained using a band alignment diagram and attributed to a charge transfer mechanism between WS₂ and RGO. This analysis is further corroborated by first-principles density functional calculations. The fabricated device based on WS₂/RGO hybrids shows a photosensitivity R_λ of about 6 AW⁻¹ and a quantum efficiency η of ∼924%, which demonstrates high sensitivity of the hybrid material towards IR detection. WS₂/RGO hybrids are therefore promising candidates for potential applications in optoelectronic circuits and low cost, high performance, and reliable photodetectors