Dye-sensitized MoS₂ photodetector with enhanced spectral photoresponse

We fabricated dye-sensitized MoS₂ photodetectors that utilized a single-layer MoS₂ treated with rhodamine 6G (R6G) organic dye molecules (with an optical band gap of 2.38 eV or 521 nm). The proposed photodetector showed an enhanced performance with a broad spectral photoresponse and a high photoresponsivity compared with the properties of the pristine MoS₂ photodetectors. The R6G dye molecules deposited onto the MoS₂ layer increased the photocurrent by an order of magnitude due to charge transfer of the photoexcited electrons from the R6G molecules to the MoS₂ layer. Importantly, the photodetection response extended to the infrared (λ < 980 nm, which corresponded to about half the energy band gap of MoS₂), thereby distinguishing the device performance from that of a pristine MoS₂ device, in which detection was only possible at wavelengths shorter than the band gap of MoS₂, i.e., λ < 681 nm. The resulting device exhibited a maximum photoresponsivity of 1.17 AW^-1, a photodetectivity of 1.5 × 10⁷ Jones, and a total effective quantum efficiency (EQE) of 280% at 520 nm. The device design described here presents a significant step toward high-performance 2D nanomaterial-based photodetector.