chemistry-world-2017-keynote

4 / 9

alliedacademies
Page 12
Journal of Biotechnology and Phytochemistry
Volume 1 Issue 3
Notes:
Chemistry World 2017
November 13-15, 2017 Athens, Greece
7th World Congress on
Chemistry
Junrong Zheng, J Biotech and Phyto 2017
Electron/hole transformation between two
atomic layers
Electron/hole transformations on interfaces
determine fundamental properties of opto-electro-
chemical devices, but remain a grand challenge to
experimentally investigate and theoretically describe.
Herein combining ultrafast VIS/NIR/MIR frequency-
mixed micro-spectroscopy and state-of-the-art two-
dimensional atomic device fabrications, we are able
to directly monitor the phase transitions of charged
quasiparticles in real time on the ultimate interfaces –
between two atomic layers. On type II semiconductor/
semiconductor interfaces between two transition
metal dichalcogenide (TMDC) monolayers, interfacial
charge transfers occur within 50fs and interlayer
hot excitons (unbound interlayer e/h pairs) are the
necessary intermediate of the process for both energy
and momentum conservations. On semiconductor/
conductor (graphene) interfaces, interlayer charge
transfers result in an unexpected transformation of
conducting free carriers into insulating interlayer
excitons between the conducting graphene and the
semiconducting TMDC. The formation of interlayer
excitons significantly improves the charge separation
efficiency between the two atomic layers for more than
twenty times.
Biography
Junrong Zheng completed his PhD and postdoctoral studies from Stanford
University. He is professor of chemistry at Peking University, and a co-founder of
Uptek Solutions, a Long-Island-based laser company. He is a recipient of numerous
prestigious awards including the Sloan Fellowship, and the Packard Fellowship.
Junrong Zheng
Peking University, China
Figure 1. Interlayer charge transfers between MoSe2/WS2 atomic layers.
The interlayer charge transfers (<50fs) result in the formation of interlayer hot
excitons, much faster than the formation of intralayer excitons (~600fs).