Ferroelectrochemistry

Xin Mu,Hang Peng,Ren-Gen Xiong,Yuan-Yuan Tang,Lei Xu,Yi-Yi Xu,Han-Yue Zhang

doi:10.1063/5.0051129

Abstract

100 years have passed since the initiate of ferroelectrics, molecular ferroelectrics with homochirality. Although inorganic ceramics have gained widespread utilization, especially in electronic, optical, and energy harvesting devices, the development of a molecular ferroelectric is still in its infancy because of the difficulty in finding a new one, let alone controllably optimizing its performance. It is noteworthy that some recently developed chemical design approaches, including the ideas of quasi-spherical theory, introducing homochirality, and H/F substitution, significantly contribute to the chemical design as well as performance optimization of a wide range of molecular ferroelectrics. This, in fact, changes the way of discovering a new molecular ferroelectric from blind search into targeted design. In this Perspective, we lay out three key strategies for chemical design and performance optimization of molecular ferroelectrics, which are the vital components for ferroelectrochemistry and provide fresh insights into how to design a new molecular ferroelectric relying on the established methodology. This, undoubtedly, opens the floodgate in the development of molecular ferroelectrics, especially for their academic and commercial desire. We wish to briefly exhibit our systematical studies on the targeted design and performance optimization of molecular ferroelectrics and set off the trend of targeted design in the next 100 years for ferroelectrics.

Highlights

Ferroelectric Random-Access Memory (FeRAM), a nonvolatile memory with low power usage, fast write performance, and high read/write endurance, has shown its superiority beyond the conventional Dynamic Random Access Memory (DRAM).[1,2,3] This should be mainly attributed to the ferroelectric layer that achieves nonvolatility.[4,5] In ferroelectrics, inherent spontaneous polarization emerges below a critical temperature, termed Curie temperature (Tc), and the ferroelectric polarization can be reoriented under an external electric field.[6]
The introduction of difluorinated atoms supports several successful targeted designs for 2D layered lead iodide organic–inorganic halide perovskite (OIHP) ferroelectrics, namely, [4,4-difluoropiperidinium]2PbI4,45 [4,4difluorohexahydroazepine]2PbI4,79 and [4,4-difluorocyclohexylammonium]2PbI4.47 Owing to the confinement effect, where the organic cations can be constrained in the environment of the 2D lead-halide framework through the C–F⋅ ⋅ ⋅H–C molecular interaction, the difluorinated ordered cations present an aligned arrangement along a specific direction, which significantly results in the ferroelectric polarization
Relying on the Landau phenomenological theory, we proposed a series of targeted design strategies for molecular ferroelectrics, which can directly predict which compound is ferroelectric and how to construct ferroelectricity in one compound

Summary

Introduction

Ferroelectric Random-Access Memory (FeRAM), a nonvolatile memory with low power usage, fast write performance, and high read/write endurance, has shown its superiority beyond the conventional Dynamic Random Access Memory (DRAM).[1,2,3] This should be mainly attributed to the ferroelectric layer that achieves nonvolatility.[4,5] In ferroelectrics, inherent spontaneous polarization emerges below a critical temperature, termed Curie temperature (Tc), and the ferroelectric polarization can be reoriented under an external electric field (greater than the coercive field).[6]. Some cations with spherical structures, such as [Me4N]+, 1,4-diazabicyclo[2.2.2]octane (dabco), and quinuclidine, usually accompany the structural phase transition, which is desirable for ferroelectrics.[17,18] Owing to the high symmetry of such spherical molecules, they scitation.org/journal/apm usually crystallize in a centrosymmetric point group, being incompatible with ferroelectricity.

Results

Conclusion