As a booming functional material, ferroelectrics have become one of the hot research topics in the field of condensed matter physics and solid electronics. They have important applications in storage, detection, sensing and other device fields.
The two-dimensional (2D) metal halide double perovskites have attracted people's attention because of its tunable structure, environmentally friendly and long carrier life, which brings bright prospects for the design of new ferroelectric materials.
In a study published in Angew. Chem. Int. Ed., a group led by Prof. LUO Junhua and Prof. SUN Zhihua from Fujian Institute of Research on the Structure of Matter (FJIRSM) of the Chinese Academy of Sciences reported a room-temperature ferroelectric of 2D metal-halide double perovskite (CPA)4AgBiBr8 (CPA = Chloropropylamine) providing Curie temperature of 305 K and large spontaneous polarization of 3.2 μC/cm2, which achieved a strong responses to X-ray irradiation.
The researchers found that the halogen bonding effect of chloropropylamine molecules leads to a highly distorted molecular configuration. The introduction of the asymmetric chain ligand is conducive to inducing polar crystals to produce larger dipole moments while providing a driving force for structural phase transitions.
(CPA)4AgBiBr8 was found to be a room-temperature ferroelectric exhibiting a phase transition at 305 K. Synergic cooperativity between ordering of organic cation and tilting motion of inorganic octahedra skeleton results in spontaneous polarization of ~3.2μC/cm2. The polarization reversal process under external electric field confirms its ferroelectric properties.
It is worth noting that (CPA)4AgBiBr8 has a strong response to X-rays, and the organic-inorganic components similar to the two-dimensional quantum well are arranged alternately, giving the material a larger carrier migration life μτ = 1.0 × 10-3 cm2 V-1. It is related to the built-in electrostatic field caused by the inherent separation of the positive and negative charge centers of the ferroelectric, which is beneficial to optoelectronic applications.
This study designed a 2D double-perovskite room temperature ferroelectric, indicating the potential application prospect of (CPA)4AgBiBr8 in X-ray detection.
Schematic illustration of the design (Image by Prof. LUO’s group)
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