Dual-gated WTe2/MoSe2 van der Waals tandem solar cells

We propose and numerically investigate, through a multiscale approach, a tandem solar cell based on a van der Waals heterostructure comprising of two monolayers of transition-metal dichalcogenides. The electronic connection between the two subcells is obtained via tunneling through the van der Waals heterojunction, which is electrostatically controlled by means of a dual gate. Furthermore, by adjusting the dual-gate voltages, the photocurrents in the two subcells can be matched and the tandem cell performances can be optimized. Assuming an optimal absorptance, as expected in light-trapping systems, we predict that a power conversion efficiency of 30.7%, largely exceeding that of the single subcells, can be achieved. The proposed design being suitable for other van der Waals heterojunctions shows that it represents a viable option for future high-efficiency photovoltaic systems