posted on 2016-06-21, 00:00authored byDaichi Kozawa, Alexandra Carvalho, Ivan Verzhbitskiy, Francesco Giustiniano, Yuhei Miyauchi, Shinichiro Mouri, A. H. Castro Neto, Kazunari Matsuda, Goki Eda
Strongly
bound excitons confined in two-dimensional (2D) semiconductors are
dipoles with a perfect in-plane orientation. In a vertical stack of
semiconducting 2D crystals, such in-plane excitonic dipoles are expected
to efficiently couple across van der Waals gap due to strong interlayer
Coulomb interaction and exchange their energy. However, previous studies
on heterobilayers of group 6 transition metal dichalcogenides (TMDs)
found that the exciton decay dynamics is dominated by interlayer charge
transfer (CT) processes. Here, we report an experimental observation
of fast interlayer energy transfer (ET) in MoSe2/WS2 heterostructures using photoluminescence excitation (PLE)
spectroscopy. The temperature dependence of the transfer rates suggests
that the ET is Förster-type involving excitons in the WS2 layer resonantly exciting higher-order excitons in the MoSe2 layer. The estimated ET time of the order of 1 ps is among
the fastest compared to those reported for other nanostructure hybrid
systems such as carbon nanotube bundles. Efficient ET in these systems
offers prospects for optical amplification and energy harvesting through
intelligent layer engineering.