  Utilizing the excess energy of photoexcitation that is otherwise lost as
thermal effects can improve the efficiency of next-generation light-harvesting
devices. Multiple exciton generation (MEG) in semiconducting materials yields
two or more excitons by absorbing a single high-energy photon, which can break
the Shockley-Queisser limit for the conversion efficiency of photovoltaic
devices. Recently, monolayer transition metal dichalcogenides (TMDs) have
emerged as promising light-harvesting materials because of their high
absorption coefficient. Here, we report efficient MEG with low threshold energy
and high (86%) efficiency in a van der Waals (vdW) layered material, MoS2.
Through different experimental approaches, we demonstrate the signature of
exciton multiplication and discuss the possible origin of decisive MEG in
monolayer MoS2. Our results reveal that vdW-layered materials could be a
potential candidate for developing mechanically flexible and highly efficient
next generation solar cells and photodetectors.
