  Excitons in optoelectronic devices have been generated through optical
excitation, external carrier injection, or employing pre-existing charges.
Here, we reveal a new way to electrically generate excitons in transition metal
dichalcogenides (TMDs). The TMD is placed on top of a gold-hBN-graphene tunnel
junction, outside of the tunneling pathway. This electrically driven device
features a photoemission spectrum with a distinct peak at the exciton energy of
the TMD. We interpret this observation as exciton generation by energy transfer
from tunneling electrons, which is further supported by a theoretical model
based on inelastic electron tunneling. Our findings introduce a new paradigm
for exciton creation in van der Waals heterostructures and provide inspiration
for a new class of optoelectronic devices in which the optically active
material is separated from the electrical pathway.
