Electronic Properties of 2D Vander Waals Heterostructures of Janus Transition Metal Dichalcogenides with WS2 Monolayer for Photovoltaic Devices: A First Principle Study
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Date
2020-06
Authors
Journal Title
Journal ISSN
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Publisher
Addis Ababa University
Abstract
Building two-dimensional (2D) heterostructure emerges novel properties, with promising
applications in photovoltaic (PV) cells. By performing density functional theory (DFT) based firstprinciples
calculations,
electronic
properties
of
WS2
and
Janus
transition-metal
dichalcogenides
(JTMDs)
monolayers were calculated and depending on the lattice mismatch, layered 2D
JTMDs/WS2 heterostructures were formed. The formation of the JTMDs/WS2 van der Waals
(vdW) heterostructures have shown great potential for the design of novel electronic devices. In
this study, Janus MoSSe/WS2, WSSe/WS2, and MoSTe/WS2 heterostructures were developed and
their structural and electronic properties were evaluated using first principles calculations based
on DFT calculations using Quantum ESPRESSO and VASP codes. It was found that the
heterostructures bandgap is smaller than the Janus TMDs and WS2 monolayer. Structural
relaxations were performed using generalized-gradient approximation (GGA) approaches for both
the monolayers and heterostructures. Structural stability and electronic properties of JTMDs/WS2
vdW heterostructures with AC and AD stacking were investigated which are the most stable
configuration compared with other configurations based on the binding energy and the interlayer
distance. Results show that the Janus MoSTe/WS2, MoSSe/WS2, and AD-configuration of
WSSe/WS2 vdW heterostructures are indirect bandgap semiconductor, but WSSe/WS2 with ACconfiguration
is
a
direct
bandgap.
The
JTMDs/WS2
vdW
heterostructures
exhibited
a
bandgap
in
the
range
of
1.54
to
0.54eV.
In
addition,
MoSSe/WS2
and
MoSTe/WS2
heterostructures
displayed
a
type-II
band
alignment
which
is
important
to
improve
the
photoelectric
conversion
efficiency.
However,
the band alignment of WSSe/WS2 heterostructure is difficult to identify and need
additional calculations. First principles study shows that the investigated 2D heterostructures have
a suitable bandgap for photovoltaic applications. Among the JTMDs/WS2 vdW heterostructures,
MoSSe/WS2 and MoSTe/WS2 manifest type-II band alignment, making them promising
candidates for photovoltaic (PV) applications.
Description
Keywords
JTMDs/WS2 heterostructures, Type-II band alignment, bandgap, photovoltaic