Layered semiconductor molybdenum disulfide nanomembrane based Schottky-barrier solar cells

Abstract

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, E¹_2g (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 ∼110 nm MoS₂ and 1.8% for ∼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.