Strong Photon Absorption in 2-D Material-Based Spiral Photovoltaic Cells

Atomically thin transition-metal dichalcogenides (TMD) hold promise for making ultrathin-film photovoltaic devices with a combination of excellent photovoltaic performance and mechanical flexibility. However, reported absorption for photovoltaic cells based on two dimensional materials (2D) materials is still just a few percent of the incident light due to their sub-wavelength thickness leading to low cell efficiencies. Here we discuss that taking advantage of the mechanical flexibility of 2D materials by rolling their Van der Waal heterostructures such as molybdenum disulfide (MoS2)/graphene (Gr)/hexagonal boron nitride (hBN) to a spiral solar cell, leads to strong light matter interaction allowing for solar absorptions up to 90%. The optical absorption of a 1 m-long hetero-material spiral cell consisting of the aforementioned hetero stacks is about 50% stronger compared to a planar MoS2 cell of the same thickness; although the volumetric absorbing material ratio is only 6%. We anticipate these results to provide guidance for photonic structures that take advantage of the unique properties of 2D materials in solar energy conversion applications.