Layered semiconductor molybdenum disulfide nanomembrane based Schottky-barrier solar cells

We demonstrate Schottky-barrier solar cells employing a stack of layer-structured semiconductor molybdenum disulfide (MoS2) nanomembranes, synthesized by the chemical-vapor-deposition method, as the critical photoactive layer. An MoS2 nanomembrane forms a Schottky-barrier with a metal contact by the layer-transfer process onto an indium tin oxide (ITO) coated glass substrate. Two vibrational modes in MoS2 nanomembranes, E-2g(1) (in-plane) and A(1g) (perpendicular-to-plane), were verified by Raman spectroscopy. With a simple stacked structure of ITO-MoS2-Au, the fabricated solar cell demonstrates a photo-conversion efficiency of 0.7% for similar to 110 nm MoS2 and 1.8% for similar to 220 nm MoS2. The improvement is attributed to a substantial increase in photonic absorption. The MoS2 nanomembrane exhibits efficient photo-absorption in the spectral region of 350-950 nm, as confirmed by the external quantum efficiency. A sizable increase in MoS2 thickness results in only minor change in Mott-Schottky behavior, indicating that defect density is insensitive to nanomembrane thickness attributed to the dangling-bond-free layered structure.