Asymmetric Interfacial Potential Barrier Driven Photovoltaic Effect Enhancement in 2H-Stacked Bilayer MoS2

Two-dimensional photovoltaic-type devices operate by artificially stacked heterostructures with atomically thin p-n junctions or non-centrosymmetric layers, in which photogenerated carriers are separated under built-in or internal electric fields. However, their photocurrent conversion efficiency is restricted by small electric field strength and large carrier recombination, which poses a major limitation with the requirement of specific 2D materials. Herein, large-area centrosymmetric 2H-stacked bilayer MoS 2 with low defect density was synthesized by slow-kinetic chemical vapor deposition and showed a remarkable photovoltaic response (0.13 mA/W at 520 nm) with a small vertical barrier of 23.2 mV. The local energy levels and doping effects derived from Raman spectroscopy and Kelvin probe force microscopy revealed the resulting sharp slope of interfacial band bending, which explains the efficient separation of photogenerated carriers by precise work function differences. A higher asymmetric barrier of 139.6 mV resulted in enhanced photocurrents in the 405–1064 nm and achieved a maximum responsivity of 0.51 mA/W at 520 nm as well as a consistent six-fold enhancement at 638 nm (0.04 to 0.24 mA/W). Our research reveals an enhanced physical mechanism with low-defect-density centrosymmetric 2D materials as photovoltaic-type layers by tuning interfacial barriers for optoelectronic devices.