Ultrafast Charge Transfer and Enhanced Absorption in MoS₂-Organic van der Waals Heterojunctions Using Plasmonic Metasurfaces

Hybrid organic-inorganic heterostructures are attracting tremendous attention for optoelectronic applications due to their low-cost processing and high performance in devices. In particular, van der Waals p-n heterojunctions formed between inorganic two-dimensional (2D) materials and organic semiconductors are of interest due to the quantum confinement effects of 2D materials and the synthetic control of the physical properties of organic semiconductors, enabling a high degree of tunable optoelectronic properties for the heterostructure. However, for photovoltaic applications, hybrid 2D-organic heterojunctions have demonstrated low power conversion efficiencies due to the limited absorption from constraints on the physical thickness of each layer. Here, we investigate the ultrafast charge transfer dynamics between an organic polymer:fullerene blend and 2D n-type MoS₂ using transient pump-probe reflectometry. We employ plasmonic metasurfaces to enhance the absorption and charge photogeneration within the physically thin hybrid MoS₂-organic heterojunction. For the hybrid MoS₂-organic heterojunction in the presence of the plasmonic metasurface, the charge generation within the polymer is enhanced 6-fold, and the total active layer absorption bandwidth is increased by 90 nm relative to the polymer:fullerene blend alone. We demonstrate that MoS₂-organic heterojunctions can serve as hybrid solar cells, and their efficiencies can be improved using plasmonic metasurfaces.