Scalable production of photovoltaic-grade WSe2 via tungsten selenization

Abstract

Transition metal dichalcogenides (TMDs) hold significant promise for photovoltaic applications with high specific power thanks to their high absorption coefficients enabling ultrathin form factor, desirable band gaps for solar energy harvesting, and dangling-bond-free surfaces. Nevertheless, their small-scale synthesis methods have limited their practicality for commercial use. Here, we address this shortcoming and report an industrial, wafer-scale, and rapid selenization method to synthesize thickness-tunable TMD films (i.e., WSe2) from (pre-patterned) sputtered tungsten layers, using solid source selenium or H2Se precursors. These absorbers are shown to have a smooth surface, with a layered van der Waals structure, and charge carrier lifetimes up to 144 ns, over 14× higher than large-area TMD films previously demonstrated. Such high carrier lifetimes correspond to a power conversion efficiency of nearly 22% and a specific power of nearly 64 W/g in a packaged solar cell or almost 3 W/g in a fully packaged module.