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.

具有显著非线性光学吸收（nonlinear optical absorption）的钙钛矿（Perovskite）铁电体，在光子学领域受到广泛关注。然而，传统这类材料多以无机氧化物为主体，且非线性光学吸收系数相对偏小，这限制了其进一步的应用拓展。在此，我们报道一种新型有机-无机杂化双层钙钛矿铁电体：(C4H9NH3)2(NH2CHNH2)­Pb2Br7（编号1），其展现出高于室温的居里温度（Curie temperature，约322 K）与显著的自发极化（spontaneous polarization，约3.8 μC cm–2）。尤为关键的是，该材料独特的量子阱结构（quantum-well structure）赋予其优异的双光子吸收（two-photon absorption）性能，其超大非线性光学吸收系数高达5.76×10³ cm·GW⁻¹，几乎比绝大多数传统全无机钙钛矿铁电体高出两个数量级。据我们所知，编号1是首例兼具超大双光子吸收系数的杂化铁电体。本研究揭示了该材料铁电性与双光子吸收的内在机制，此项工作可为新型兼具双光子吸收性能的铁电体的设计提供思路，并推动其在光子学领域的应用潜能释放。