Ferroelectric polarization in 2D halide hybrid perovskites: influence on bulk crystals, thin films, and applications

Ferroelectric materials undergo spontaneous polarization that can be reversed by applying an external electric field. This property plays the most important role in applications such as logic gates, microwave communications, piezo energy harvesting, memory storage such as ferroelectric random-access memory (FeRAM), and ferroelectric sensors and actuators. Recently, hybrid halide perovskites (HHPs) have started demonstrating impressive ferroelectric properties in addition to their excellent photovoltaic performance. Compared to traditional oxide perovskites and organic ferroelectric materials, HHPs have the advantage that they can be simple solution-processed yet with immaculate crystal quality which is suitable for realizing next-generation thin film flexible electronics and FeRAM in neuromorphic computing. This review focuses on the current status of ferroelectric properties of two-dimensional (2D) halide perovskite single crystals and covers the limited reports available on thin film HHPs. Furthermore, we explain the challenges in the ferroelectric characterization of thin film HHPs and compare them with those of single crystals.