High
light absorption (∼15%) and strong photoluminescence
(PL) emission in monolayer (1L) transition metal dichalcogenides (TMDs)
make them ideal candidates for optoelectronic device applications.
Competing interlayer charge transfer (CT) and energy transfer (ET)
processes control the photocarrier relaxation pathways in TMD heterostructures
(HSs). In TMDs, long-distance ET can survive up to several tens of
nm, unlike the CT process. Our experiment shows that an efficient
ET occurs from the 1Ls WSe2-to-MoS2with an
interlayer hexagonal boron nitride (hBN), due to the resonant overlapping
of the high-lying excitonic states between the two TMDs, resulting
in enhanced HS MoS2PL emission. This type of unconventional
ET from thelower-to-higheroptical bandgap material
is not typical in the TMD HSs. With increasing temperature, the ET
process becomes weaker due to the increased electron–phonon
scattering, destroying the enhanced MoS2emission. Our
work provides new insight into the long-distance ET process and its
effect on the photocarrier relaxation pathways.