posted on 2018-07-20, 00:00authored byZhi Gen Yu, Boris I. Yakobson, Yong-Wei Zhang
In
the applications of two-dimensional (2D) transition metal dichalcogenides
(TMDs) for solar cell and optoelectronic devices, two challenging
issues remain: (1) the direct-to-indirect band gap transition from
single layer to a few layers and (2) the absence of an effective and
robust doping procedure. In this study, we explore the feasibility
to realize indirect-to-direct band gap transition and control the
Fermi level by intercalating few-layer TMDs with embedded metals.
Specifically, utilizing density functional theory calculations, we
examine the electronic properties of few-layer MX2 (M =
Mo, W; X = S, Se) intercalated with metals (Zn, Sn, Mg and Ga). Our
calculation results reveal that (1) Ga intercalation can realize an
indirect-to-direct band gap transition in few-layer TMDs, and as a
result, the absorption efficiency is increased by two orders compared
with that of pristine MX2; and (2) intercalated Ga acts
as an n-type shallow donor, which markedly increases the charge density
and electrical conductivity. Therefore, Ga intercalation may provide
a potential practical route for manipulating few-layer TMDs for high
performance solar and optoelectronic devices.