Toward Mass Production of Transition Metal Dichalcogenide Solar Cells: Scalable Growth of Photovoltaic-Grade Multilayer WSe<sub>2</sub> by Tungsten Selenization
Kathryn M. Neilson, Sarallah Hamtaei, Koosha Nassiri Nazif, Joshua M. Carr, Sepideh Rahimisheikh, Frederick U. Nitta, Guy Brammertz, Jeffrey L. Blackburn, Joke Hadermann, Krishna C. Saraswat, Obadiah G. Reid, Bart Vermang, Alwin Daus, Eric Pop
Abstract
Semiconducting transition metal dichalcogenides (TMDs) are promising for high-specific-power photovoltaics due to their desirable band gaps, high absorption coefficients, and ideally dangling-bond-free surfaces. Despite their potential, the majority of TMD solar cells to date are fabricated in a nonscalable fashion, with exfoliated materials, due to the lack of high-quality, large-area, multilayer TMDs. Here, we present the scalable, thickness-tunable synthesis of multilayer WSe 2 films by selenizing prepatterned tungsten with either solid-source selenium at 900 °C or H 2 Se precursors at 650 °C. Both methods yield photovoltaic-grade, wafer-scale WSe 2 films with a layered van der Waals structure and superior characteristics, including charge carrier lifetimes up to 144 ns, over 14× higher than those of any other large-area TMD films previously demonstrated. Simulations show that such carrier lifetimes correspond to ∼22% power conversion efficiency and ∼64 W g –1 specific power in a packaged solar cell, or ∼3 W g –1 in a fully packaged solar module. The results of this study could facilitate the mass production of high-efficiency multilayer WSe 2 solar cells at low cost.