An ultrathin MoSe₂ photodetector with near-perfect absorption

An ultrathin near-perfect MoSe₂ absorber working in the visible regime is demonstrated theoretically and experimentally, and it consists of a MoSe₂/Au bi-layer film. The polymer-assisted deposition method is used to synthesize MoSe₂ films, which can reduce the roughness and thus improve the film absorption. Simulation results show that the absorption of the absorber with 22 nm MoSe₂ reaches to larger than 90% between 628.5 nm and 718 nm with a peak value up to 99.5% at 686 nm. Moreover, the measured absorption also shows near-perfect absorption of this simple absorber. Finally, an ultrathin photodetector is fabricated based on this perfect absorber and shows on/off reproducibility and remarkable photocurrent, which is three orders of magnitude higher than the dark current.