Two-Dimensional Organic–Inorganic Perovskite Ferroelectric Semiconductors with Fluorinated Aromatic Spacers

Abstract

Two-dimensional (2D) organic–inorganic perovskites (OIPs), with improved material stability over their 3D counterparts, are highly desirable for device applications. It is their considerable structural diversity that offers an unprecedented opportunity to engineer materials with fine-tuning functionalities. The isosteric substitution of hydrogen by an electronegative fluorine atom has been proposed as a useful route to improve the photovoltaic performance of 2D OIPs, whereas its valuable role in developing ferroelectricity is still waiting for further exploration. Herein, for the first time we applied fluorinated aromatic cations in extending the family of 2D OIP ferroelectrics, and successfully obtained [2-fluorobenzylammonium]2PbCl4 as a high-performance ferroelectric semiconductor. The failures in the nonferroelectric [4-fluorobenzylammonium]2PbCl4 and [3-fluorobenzylammonium]2PbCl4 demonstrate that the selective introduction of fluorine in correct structural positions is particularly essential. This work represents an unprecedented proof-of-concept in the use of fluorinated aromatic cations for the targeted design of excellent 2D OIP ferroelectrics, and is believed to inspire the future development of low-cost, high-efficiency, and stable device applications.

Piezoelectric Energy Harvesting from a Ferroelectric Hybrid Salt [Ph3MeP]4[Ni(NCS)6] Embedded in a Polymer Matrix

“…The observed E g value is comparable with well-known ferroelectric metal oxides and organic-inorganic hybrid systems. [15] Furthermore, the increase in the conductivity of 1 with an increase in temperature in the range of 294 to 373 K supports the semiconducting nature of 1 (Supporting Information, Figure S16b). The presence of direct piezoelectric polarization in 1 was probed by using the Berlincourt method.…”

“…The polarization (P) versus electric field (E) hysteresis loop measurements on single-crystals of this compound show a high remnant polarization (P r ) of 18.71 mC cm À2 , at room temperature. Polymeric composite films with various weight percentages (5,10,15, and 20 wt %) of 1 embedded in thermoplastic polyurethane (TPU) polymer were prepared and utilized for mechanical energy harvesting applications. The maximum output voltage and power density of 19.29 V and 2.51 mW cm À3 , respectively, were recorded for the composite with 15 wt % of 1-TPU.…”

Two Rare‐Earth Molecular Ferroelectrics with High Curie Temperatures, Large Spontaneous Polarization, Switchable Second Harmonic Generation Effects, and Strong Photoluminescence

“…To our knowledge, these large P s values are the first to be found in the field of rare‐earth ferroelectrics, and their high P s values can be tentatively attributed to the large charges of the cations and anions as well as the position deviation between them (Figure S6, Supporting Information). Further, we used piezoresponse force microscopy (PFM) imaging measurements on the thin crystal films to verify the polarization switching and local ferroelectric behavior . Figure c and d show the lateral amplitude and phase mapping, respectively, of compound 1 , and the corresponding vertical amplitude and phase mapping of compound 1 at the same position are presented in Figure c1 and d1.…”

Ferroelectricity‐Driven Self‐Powered Ultraviolet Photodetection with Strong Polarization Sensitivity in a Two‐Dimensional Halide Hybrid Perovskite

“…Particularly, halogen substitution in inorganic lead‐halogen layers offers great flexibility for band gap engineering, thus allowing an exciting opportunity in exploring wide band‐gap semiconductor materials for UV light detection . Additionally, their structure diversity and tunability endows the tantalizing prospects for the rational design of ferroelectrics, such as (C 4 H 9 NH 3 ) 2 (CH 3 NH 3 ) 2 Pb 3 Br 10 , [CH 3 (CH 2 ) 3 NH 3 ] 2 (CH 3 NH 3 )Pb 2 Br 7 , [2‐fluorobenzylammonium] 2 PbCl 4 . It is noteworthy that the BPVE has been observed in these 2D hybrid perovskite ferroelectrics .…”