High-specific-power Schottky-junction photovoltaics from CVD-grown MoS2

High-specific-power ultralight photovoltaics (PV) can provide space missions with solar power generation at minimal weight and volume. Two-dimensional (2D) transition metal dichalcogenides exhibit high absorption at sub-nanometer thickness, enabling one to three orders of magnitude higher power density than top existing ultrathin PV cells. However, quality and scalability hinder the production of ultrathin and ultralightweight 2D PV. To obtain high quality monolayer films, we optimized the chemical vapor deposition process with resulting films of >cm2 showing 85% uniformity when analyzed via Raman spatial mapping. To show promise towards the fabrication of >cm2 scale PV devices, we present 25 mm2 scale Schottky PV, fabricated by transferring monolayer MoS2 films onto asymmetric Ti and Pt interlocking finger contacts. Under 1 sun AM1.5D illumination, 2.2 kW/kg specific power was achieved with 0.65 nm thick MoS2. Modeling of the MoS2 Schottky junction solar cell showed that 69.9 kW/kg specific power is attainable with a single monolayer device. Furthermore, we studied the absorption of single and stacked MoS2 monolayers computationally, using the transfer matrix method, and experimentally, by incrementally stacking and characterizing the monolayers. This stacking maintains an enhanced absorption per layer, not observed in directly synthesized multilayer films, pointing to an expected proportional increase in the efficiency of the MoS2 Schottky PV. Lastly, we propose a full-scale, 2D material-based 60 W solar array for a 6U CubeSat and investigate feasibility with preliminary sub-scale prototypes.