High-Curie Temperature Multilayered Hybrid Double Perovskite Photoferroelectrics Induced by Aromatic Cation Alloying.

Due to the breakthrough development of layered hybrid perovskites, the multilayered hybrid double perovskites have emerged as outstanding semiconducting materials owing to their environmental friendliness and superior stability. Despite recent booming advances, the realization of above-room temperature ferroelectricity in this fascinating family remains a huge challenge. Herein, when the molecular design strategy of aromatic cation alloying is applied, an above-room temperature "green" bilayered hybrid double perovskite photoferroelectric, (C6H5CH2NH3)2CsAgBiBr7 (BCAB), is successfully developed with a notable saturation polarization of 10.5 μC·cm-2 and high-Curie temperature (Tc ∼ 483 K). Strikingly, such a Tc achieves a new record in multilayered hybrid perovskite ferroelectrics, which extends the ferroelectric working temperature to a high level. Further computational investigation reveals that the high-Tc originated from the high phase-transition energy barrier switched by the rotation of the aromatic cation in the confined environment of the inorganic layers. In addition, benefiting from the attractive polarization and remarkable photoelectric properties, a bulk photovoltaic effect (BPVE) with a prominent zero-bias photocurrent (2.5 μA·cm-2) is achieved. As far as we know, such a high-Tc multilayered hybrid double perovskite ferroelectric is unprecedented, which sheds light on the rational design of an environmental photoferroelectric for high performance photoelectric devices.