Photovoltaic and Spectral Response of WS2/Silicon Heterojunctions

Transition metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS₂) and tungsten disulfide (WS₂) are attractive because of their ultrathin structure and inimitable electronic band structures with unique functionalities including: indirect-to-direct bandgap transition, semiconductor-to-metal phase engineering, and the large excitonic effect. Further, the TMDs with thickness-dependent tunable optical bandgaps in the near-infrared to visible spectral range can exhibit extremely strong light–matter interactions suitable for energy harvesting devices such as solar cells. Currently, the WS₂-based solar cells are realized via micromechanical exfoliation or transfer of two-dimensional (2D) WS₂ layers onto conventional 3D bulk semiconductors. Here, we report the photovoltaic response of WS₂/Si heterojunction solar cells developed via chemical vapor deposition (CVD). The photoresponse and quantum efficiency of the WS₂/Si-based solar cell devices are also investigated in order to further understand the junction characteristics (trap states and recombination mechanisms). The present study opens avenues for the direct integration of CVD-grown monolayer WS₂ with Si-based heterojunctions for efficient optoelectronic devices.