Bilayered Hybrid Perovskite Ferroelectric with Giant Two-Photon Absorption

Perovskite
ferroelectrics with prominent nonlinear optical absorption
have attracted great attention in the field of photonics. However,
they are traditionally dominated by inorganic oxides and exhibit relatively
small nonlinear optical absorption coefficients, which hinder their
further applications. Herein, we report a new organic–inorganic
hybrid bilayered perovskite ferroelectric, (C4H9NH3)2(NH2CHNH2)­Pb2Br7 (1), showing an above-room-temperature
Curie temperature (∼322 K) and notable spontaneous polarization
(∼3.8 μC cm–2). Significantly, the
unique quantum-well structure of 1 results in intriguing
two-photon absorption properties with a giant nonlinear optical absorption
coefficient as high as 5.76 × 103 cm GW–1, which is almost two-orders of magnitude larger than those of mostly
traditional all-inorganic perovskite ferroelectrics. To our best knowledge, 1 is the first example of hybrid ferroelectrics with giant
two-photon absorption coefficient. The mechanisms for ferroelectric
and two-photon absorption are revealed. This work will shed light
on the design of new ferroelectrics with two-photon absorption and
promote their potentials in the photonic application.