Two-dimensional
inorganic–organic hybrid perovskites are
in the limelight due to their potential applications in photonics
and optoelectronics. They are environmentally stable, and their various
chemical compositions offer a wide range of bandgap energies. Alternatively,
crystal deformation enables in situ control over their optical properties.
Here, we investigate (C6H9C2H4NH3)2PbI4, a hybrid perovskite
whose organic linkers are 2-(1-cyclohexenyl)ethylammonium. Pressure-dependent
optical absorption and emission spectroscopy reveal a hysteretic piezochromism
that was not reported for other lead iodide-based 2D perovskites.
We combine our optical studies with high-pressure X-ray diffraction
experiments and first-principles calculations to demonstrate that
the deformation of the inorganic lead iodide layers is the main reason
for the observed changes in the optical bandgap.