Tailoring Interlayered Spacers of Two‐Dimensional Cesium‐Based Perovskite Ferroelectrics toward Exceptional Ferro‐Pyro‐Phototronic Effects

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.