Hot-Carrier Extraction Prevailing over Multiple-Exciton Generation in Two-Dimensional Semiconductor Heterostructures.

Multiple-exciton generation (MEG) represents an effective strategy to break the Shockley-Queisser (SQ) limit, thereby enhancing the efficiency of photon-to-electron conversion. Here, we investigate MEG in monolayer MoTe, with an energy threshold of 2.22 eV (∼2.02) and a MEG conversion efficiency of 90%. We discuss the potential origins of efficient MEG in MoTe/WSe type I heterostructures, with a particular focus on the competition between MEG and hot-carrier extraction. We conclude that impact ionization is likely responsible for exciton multiplication. Our results suggest that monolayer MoTe has significant potential for efficient light harvesting and hot-carrier devices.