Tailoring Interlayered Spacers of Two‐Dimensional Cesium‐Based Perovskite Ferroelectrics toward Exceptional Ferro‐Pyro‐Phototronic Effects
Yi Liu, Xiong Pan, Xitao Liu, Shiguo Han, Jiaqi Wang, Lei Lu, Haojie Xu, Zhihua Sun, Junhua Luo
Abstract
Abstract Ferro‐pyro‐phototronic (FPP) effect is a triple coupling of ferroelectricity, light‐induced pyroelectricity, and photo‐excitation, which holds a bright promise for next‐generation modern optoelectronic devices. However, except for few oxides (e.g., BaTiO 3 ), new FPP‐active candidates remain extremely scarce due to the knowledge lacking on the underlying role of three coupling components. By tailoring the interlayered spacers, the authors present a series of 2D cesium‐based perovskite ferroelectrics, (A′) 2 CsPb 2 Br 7 (where A′‐site cation is organic spacer), showing remarkable FPP‐active properties. As expected, the dynamic ordering and reorientation of spacers along with atomic displacement of Cs + in the perovskite cavity lead to their ferroelectric polarizations. Particularly, exceptional FPP properties are created through this cooperation; the most FPP‐active candidate ( n ‐hexylammonium) 2 CsPb 2 Br 7 endows a giant contrast up to 1500% for photopyroelectric current to photovoltaic signal. This figure‐of‐merit is far beyond most inorganic oxide counterparts, such as ≈110% for BaTiO 3 . Further, the electric switching and controlling of FPP directions confirm a crucial role of ferroelectric polarization to this coupling effect. To the authors’ best knowledge, this is the first study on an FPP‐active candidate of 2D hybrid perovskites, which affords a new avenue to design ferroelectrics with targeted physical properties and forward their potentials to smart optoelectronic device application.