Two-dimensional
(2D) hybrid organic–inorganic metal halide
perovskites (HOIPs) with considerably hydrophobic phenyl ethylammonium
(PEA) organic cations have been used in highly efficient solar cells
and LEDs, which are stable and enjoy a long lifetime, even when exposed
to moisture. Different from other 2D HOIPs with alkyl amine cations,
a benzene ring is present in the PEA cation. Until recently, an understanding
of the effects of PEA on the structural, electronic, and optical properties
of 2D HOIPs under pressure has remained limited. We find that there
is a direct–indirect band gap transition at around 5.8 GPa
and that the direct band gap recovers when the pressure is released.
The stacking order of the benzene rings in the PEA cation plays a
critical role in the mechanical and electronic properties. Our present
work demonstrates that 2D HOIPs with organic cations containing benzene
rings prove highly attractive for use in flexible optoelectronics.
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