Search

Since the discovery of TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl) in 1973, organic radical ferroics attracted widespread interest among the scientific community. However, the relatively low Curie temperature of 287 K and melting point of 311 K severely hinder its application potential. Despite extensive interest, high-temperature radical ferroics have not been found to date. Here, taking advantage of chemical design theory and supramolecular radical chemistry, we successfully designed two high-temperature organic supramolecular radical ferroics [(NH3-TEMPO)([18]crown-6)](ReO4) (1) and [(NH3-TEMPO)([18]crown-6)](ClO4) (2), which can retain the ferroelectricity up to 413 K and 450 K, respectively. To our knowledge, they are both the first supramolecular radical ferroics and unprecedented high-temperature radical ferroics, where the supramolecular component plays a vital role in the stabilization of radical and extending working temperature window. Additionally, both of them can also present the paramagnetism and non-interacting spin moments, as well as excellent piezoelectric and electrostrictive behaviors comparable to that of LiNbO3. This work provides an efficient design strategy for enriching the family of high-temperature radical ferroics, and should inspire further exploration of multi-functional organic ferroics.

Multiferroic materials have attracted great interest because of their underlying new science and promising applications in data storage and mutual control devices. However, they are still very rare and highly imperative to be developed. Here, we report an organic–inorganic hybrid perovskite trimethylchloromethylammonium chromium chloride (TMCM–CrCl3), showing the coexistence of magnetic and electric orderings. It displays a paraelectric–ferroelectric phase transition at 397 K with an Aizu notation of 6/mFm, and spin-canted antiferromagnetic ordering with a Néel temperature of 4.8 K. The ferroelectricity originates from the orientational ordering of TMCM cations, and the magnetism is from the [CrCl3]− framework. Remarkably, TMCM–CrCl3 is the first experimentally confirmed divalent Cr2+-based multiferroic material as far as we know. A new category of hybrid multiferroic materials is pointed out in this work, and more Cr2+-based multiferroic materials will be expectedly developed in the future., An organic–inorganic hybrid perovskite Trimethylchloromethylammonium chromium(ii) chloride (TMCM–CrCl3) can simultaneously show excellent ferroelectricity and antiferromagnetism, which is the first experimentally confirmed Cr2+-based multiferroic material.

Chiral perovskites have emerged as a significant class of materials showing promising optoelectronic and spintronic applications. Reports of chiral perovskite ferroelectrics, however, have been scarce. In this work, we have successfully synthesized homochiral lead-iodide perovskite ferroelectrics [(R)-N-(1-phenylethyl)ethane-1,2-diaminium]PbI4 and [(S)-N-(1-phenylethyl)ethane-1,2-diaminium]PbI4 by the chemical design of introducing a methyl group into the organic cation of the parent (N-benzylethane-1,2-diaminium)PbI4. Vibrational circular dichroism spectra identify the chiral mirroring relationship. They both undergo 222F2 type paraelectric-ferroelectric behavior at around 378 K coupled with clear ferroelastic domains "ON/OFF" switching. Besides, they exhibit an evident thermochromism with color change from orange-yellow to orange-red. To our knowledge, the discovery of integrated ferroelectricity, ferroelasticity and reversible thermochromism in chiral perovskites is unprecedented. This finding offers a resultful path to design chiral perovskite ferroelectrics and is of great inspiration to the discovery of multifunctional perovskite materials.

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.

An organic molecular-ionic crystal of (TPPO–H)2SO4 exhibits moderate NLO response which is twice that of KDP and competing hydrogen-bonding interactions triggered high-Tc phase transition.

A high transition temperature (Tc ) is essential for the practical application of ferroelectrics as electronic devices under extreme thermal conditions in the aerospace, automotive, and energy industries. In recent decades, the isotope effect and strain engineering are found to effectively modulate Tc ; however, these strategies are limited to certain systems. Developing simple, universal, and practical methods to improve Tc has become an imminent challenge for expanding the applications of ferroelectrics. Here, by adopting a molecular design strategy involving H/F substitution on an organic-inorganic hybrid perovskite (1-azabicyclo[2.2.1]heptane)CdCl3 at a Tc of 190 K, the successful synthesis of a multiaxial, ferroelectric hybrid perovskite (4-fluoro-1-azabicyclo[2.2.1]heptane)CdCl3 is reported, which demonstrates a large spontaneous polarization of 11.2 µC cm-2 (greater than that of polyvinylidene difluoride) and a Tc of 419 K (greater than that of BaTiO3 ). This temperature enhancement (229 K) is the largest reported for molecular ferroelectrics, far exceeding the reported enhancements induced by the isotope effect and other techniques. This pioneering technique provides an effective and universal method for improving Tc in ferroelectrics and represents an important step toward the development of high-performance ferroelectric technology.

Porphyrin, despite chosen by Nature as light har- vesting units, hasn't revealed its full potentials as a structural unit in porphyrin-incorporated polymers (PPors). A novel PPor was synthesized to investigate the origins of the low perform- ances of PPor-based polymer solar cells (PSCs). The polymer features broad absorption in the blue-light region, because the diindenothieno(2,3-b)thiophene (DITT) unit extended the conju- gation in the polymer backbone. PPor-DITT/PC71BM based PSCs have a high Voc (0.79 V). Their low Jsc and fill factor (FF) were attributed to the un-optimized morphology, as indicated by the photoluminescence quenching and atomic force micros- copy (AFM) experiments. Using PPor-DITT as a blue-light har- vesting dopant in an amorphous host leverage the strong 400- 550 nm absorption of PPor-DITT and circumvent the difficulties in reaching optimized morphology in the PPor/PCBM thin films. An addition of 2 wt % of PPor-DITT in ternary-blend PSCs resulted in a 10 % increase of external quantum effi- ciency (EQE) in the blue-light region. However, in a crystalline host, the dopant decreased the crystallinity of the host and led to large drops in FF and power conversion efficiencies (PCEs). The study provides an alternative route and expands the appli- cation of PPors in PSCs as a blue-light harvester in ternary- blend PSCs using amorphous polymers as host. V C 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 5032- 5040, 2012