A multiaxial molecular ferroelectric with record high TC designed by intermolecular interaction modulation

Exceptional structural phase transition near room temperature in an organic-inorganic hybrid ferroelectric

An organic-inorganic hybrid ferroelectric, (C6H5CH2CH2NH3)2[HgI4], undergoes an exceptional structural phase transition near room temperature, triggered by a flip of half the organic cations and an order-disorder transition of the inorganic anions, and may be regarded as a displacive-type ferroelectric. This finding provides a new structural phase transition mechanism in molecule-based ferroelectrics.

Synthesis and Characterization of a Displacement-Type Ferroelectric-Ferroelectric Phase Transition Compound [(NH3)(CH2)3(NH3)]2[InBr6]Br·H2O

Ferroelectric materials have aroused the researchers' great interest due to their wide applications. Here, a displacement-type ferroelectric-ferroelectric phase transition material [(NH₃)(CH₂)₃(NH₃)]₂[InBr₆]Br·H₂O (1) with T_c = 143 K was successfully prepared. The ferroelectric phase transition is verified by the characterization techniques such as differential scanning calorimetry, single-crystal structure elucidation, dielectric and ferroelectric measurements. The single-crystal structure elucidation reveals that the displacement and distortion of [(NH₃)(CH₂)₃(NH₃)]²⁺ cations lead to the phase transition from Cmc2₁ to Pca2₁. The spontaneous polarizations at 293 and 133 K are 0.15 and 0.12 μC·cm^-2, respectively. We expect that this work will help in further exploration of some new ferroelectric materials.

Two-Step Dielectric Responsive Organic-Inorganic Hybrid Material with Mid-Band Light Emission

Hybrid organic-inorganic perovskite (HOIP) have received tremendous scientific attention because of the phase transition and photovoltaic properties. However, achieving the special perovskite structure with both two-step dielectric response and luminescence characteristics is rarely reported. Herein, we report an organic-inorganic hybrid perovskite, [(BA)₂  ⋅ PbI₄ ] (Compound 1, BA=n-butylamine) by introducing flexible organic cations (HBA⁺ ), with direct mid-band gap as 2.28 eV. Interestingly, this material exhibits two-step reversible dielectric response at 350 K and 460 K (in heating process), respectively. Besides, the photoluminescence was found: it emits charming green light under 365 nm lamp (Photoluminescence quantum yield is 9.52 %). The outstanding two-step dielectric response and luminescence characteristics of this compound might pave the way for the application of dielectric and ferroelectric functional materials in temperature sensors and mechanical switches.

Solvent Selective Effect Occurs in Iodinated Adamantanone Ferroelectrics

Organic ferroelectrics, as a type of crystalline compound, are generally solution processing. However, for most crystalline compounds, the changing of solvent would not influence the crystalline phase, let alone their physical performance. Here, the solvent selective effect occurs in the iodinated adamantanone ferroelectrics. By changing the solvent with different polarities, the ferroelectric crystals can be induced in two different phases, which is unprecedented to the knowledge. More strikingly, this solvent-induced transformation could realize the physical performance optimization in the orthorhombic phase (orth-I-OA, obtained from ethanol) with a stronger second harmonic generation (SHG) response, greater piezoelectric coefficient d₃₃ of 5 pC N^-1 , and larger spontaneous polarization (P_s ) of 3.43 µC cm^-2 than those of monoclinic one (mono-I-OA, obtained from ethyl acetate). Such an intriguing phenomenon might be closely related to solvent polarity. Based on the quantitative and qualitative analyses, the similar interaction energies of these two phases suggest that their transformation could be easily realized via changing the solvent. This work provides new insights into the chemical design and performance optimization of organic ferroelectrics.

Band gap modulation of organic–inorganic Sb(iii) halide by molecular design

Four organic–inorganic hybrid materials were designed, and a successful adjustment of the band gap was obtained, from 2.933 eV to as low as 2.788 eV, via replacing the third hydrogen atom of the benzene ring in the organic cation with a halogen.

Two quasi-spherical molecules [1,4-diazabicyclo(3.2.2)nonane]X (X = ClO4, ReO4) exhibit switchable phase transition, dielectric and second-harmonic-generation properties

Two quasi-spherical molecules [3.2.2-Hdabc]X (1,4-diazabicyclo[3.2.2]nonane = 3.2.2-dabcn, X = ClO4, ReO4) with a high phase transition temperature exhibited switchable phase transition as well as dielectric and SHG properties.

High temperature molecular-based phase transition compounds with tunable and switchable dielectric properties

Molecular-based dielectric switching compounds [ClEt-Dabco][ReO4]2 and [BrEt-Dabco][ReO4]2 with high-temperature phase transition.

A novel organic–inorganic hybrid phase transition compound based on 4-ethylmorpholine with switchable dielectric and luminescent properties

[4-Ethylmorpholine]2MnCl4 shows a significant thermal hysteresis in the phase transition with switchable dielectric and luminescent properties.

A Photoluminescent Lead Bromide Hybrid Perovskite Molecular Ferroelastic Semiconductor with Sequential High-Tc Phase Transitions

Organic-inorganic hybrid lead halide perovskites have attracted great interest for their use in promising optoelectronic applications. However, reports of photoluminescent perovskite molecular ferroelastic semiconductors with sequential high-T_c phase transitions have been scarce. In this work, a one-dimensional lead bromide hybrid perovskite [N,N-dimethylethanolammonium]PbBr₃ has been synthesized, undergoing high-T_c sequential phase transitions at around 351 and 444 K, higher than those of most previously discovered hybrid perovskite phase transition materials. The specific intermolecular hydrogen bond between cationic molecules provides the greatest contribution to its high T_c by increasing the barrier of molecular motion under the temperature stimuli. The prominent ferroelastic domain evolution is visually observed under orthogonally polarized light. In addition, [N,N-dimethylethanolammonium]PbBr₃ exhibits semiconducting and orange light emission characteristics. This finding opens up an avenue for designing high-performance ferroelastic materials and provides great motivation for discovering new multifunctional materials for the next generation of smart devices.

Homochiral anionic modification toward the chemical design of organic enantiomeric ferroelectrics

The well-developed design strategy of molecular modification for assembling molecular ferroelectrics mainly focuses on the cations. Herein, by homochiral anionic modification of the non-ferroelectric (quinuclidinium)(HSO₄), we designed high-temperature multiaxial organic enantiomeric ferroelectrics, (quinuclidinium)(l- and d-camphorsulfonate). This work paves a new road for precisely constructing excellent molecular ferroelectrics.

(C2H5NH3)3[InBr6]: an indium(iii) organic–inorganic hybrid phase transition compound exhibiting a switchable dielectric response

The organic–inorganic hybrid compound (C2H5NH3)3[InBr6] undergoes a phase transition at 248/253 K, and exhibits a switchable dielectric response. The phase transition is associated with the order–disorder changes of ethylammonium cations.