Giant and Broadband Multiphoton Absorption Nonlinearities of a 2D Organometallic Perovskite Ferroelectric

Abstract Multiphoton absorption (MPA) has been utilized for important technological applications. High‐order multiphoton harvesting (e.g., five‐photon absorption, 5PA) exhibits unique properties that could benefit biophotonics. Within this field, perovskite oxide ferroelectrics (e.g., BaTiO₃) enable low‐order optical nonlinearities of 2PA/3PA processes. However, it is challenging to obtain efficient, high‐order 5PA effects. Herein, for the first time, giant and broadband MPA properties are presented in the 2D hybrid perovskite ferroelectric (IA)₂(MA)₂Pb₃Br₁₀ (1; IA = isoamylammonium and MA = methylammonium), where multiphoton‐excited optical nonlinearities related to different MPA mechanisms over a broadband range of 550–2400 nm are observed. Strikingly, its 5PA absorption cross‐section (σ₅) reaches up to 1.2 × 10⁻¹³² cm¹⁰ s⁴ photon⁻⁴ (at 2400 nm), almost 10 orders larger than some state‐of‐the‐art organic molecules and a record‐high value among all known ferroelectrics. This unprecedented 5PA effect results from the quantum‐confined motif of inorganic trilayer sheets (wells) and organic cations (barriers) in 1. Moreover, its large ferroelectric polarization of 5 µC cm⁻² could promote modulation of MPA effects under external electric fields. As far as it is known, this is the first report on giant, broadband high‐order MPA properties in ferroelectrics, which provides potential, novel electric‐ordered materials for next‐generation biophotonic applications.