We
systematically study the giant anisotropic optoelectronics in
layered PbSnX2 (X = S/Se). The highly anisotropic optoelectronics
mainly originates from the asymmetric sublattices SnX, resulting in
the anisotropy of photoelectronic properties with fascinating visible
light absorption range in single-layer and bilayer PbSnX2. We employ uniaxial strain in both the x and y directions and find an indirect-to-direct band gap transition,
while the quasiparticle indirect band gap presents excellent linear
scaling with biaxial strain in monolayer PbSnX2. We also
demonstrate ultrahigh anisotropic mobilities of electrons (μ
y
> μ
x
)
and holes (μ
x
> μ
y
) in both single-layer and bilayer PbSnX2 (X = S/Se), and spin–orbit coupling effects and the increase
of layer number significantly reduce exciton binding energies and
band gaps. Finally, the strong layer dependence of the band structure
is clearly seen when the film thickness is less than 4 layers. Our
results provide a fundamental understanding of highly anisotropic
PbSnX2 (X = S/Se) and show two potential candidates in
photoelectric applications.
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