Hot-CarrierExtraction Prevailing over Multiple-ExcitonGeneration 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 MoTe₂, with an energy threshold of 2.22 eV (∼2.02<i>E</i>_g) and a MEG conversion efficiency of 90%. We discuss the potential origins of efficient MEG in MoTe₂/WSe₂ 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 MoTe₂ has significant potential for efficient light harvesting and hot-carrier devices.