The optical control of polarization switching is attracting tremendous interest because photoirradiation stands out as a nondestructive, noncontact, and remote-control means beyond an electric or strain field. The current research mainly uses various photoexcited electronic effects to achieve the photocontrol polarization, such as a light-driven flexoelectric effect and a photovoltaic effect. However, since photochromism was discovered in 1867, the structural phase transition caused by photoisomerization has never been associated with ferroelectricity. Here, we successfully synthesized an organic photochromic ferroelectric with polar space group Pna21, 3,4,5-trifluoro-N-(3,5-di-tert-butylsalicylidene)­aniline, whose color can change between yellow and orange via laser illumination. Its dielectric permittivity and spontaneous polarization can be switched reversibly with a photoinduced phase transition triggered by structural photoisomerization between the enol form and the trans-keto form. To our knowledge, this is the first photoswitchable ferroelectric crystal to achieve polarization switching through a structural phase transition triggered by photoisomerization. This finding paves the way toward photocontrol of smart materials and biomechanical applications in the future.

A ferroelectric/ferroelastic is a material whose spontaneous polarization/ strain can be switched by applying an external electric field/mechanical stress. However, the optical control of spontaneous polarization/strain remains relatively unexplored in crystalline materials, although photoirradiation stands out as a nondestructive, noncontact, and remote-controlled stimulus beyond stress or electric field. Here, we present two new organic single-component homochiral photochromic multiferroics, (R)-and (S)-N-3,5-di-tert-butylsalicylidene-1−4-bromophenylethylamine (SA-Ph-Br(R) and SA-Ph-Br(S)), which show a full ferroelectric/ferroelastic phase transition of 222F2 type at 336 K. Under photoirradiation, their spontaneous polarization/strain can be switched quickly within seconds and reversibly between two ferroelectric/ ferroelastic phases with the respective enol and trans-keto forms triggered by structural photoisomerizations. In addition, they possess a superior acoustic impedance characteristic with a value of ∼2.42 × 10 6 kg•s −1 •m −2 , lower than that of polyvinylidene fluoride (PVDF, (3.69−4.25) × 10 6 kg•s −1 •m −2 ), which can better match human tissues. This work realizes for the first time that multiple ferroic orders in single-component organic crystals with ultralow acoustic impedance can be simultaneously controlled and coupled by three physical channels (electric, stress, light fields), suggesting their great potential in multichannel data storage, optoelectronics, and related applications compatible with all-organic electronics and human tissues.

Along with the rapid development of ferroelectrochemistry, piezoresponse force microscopy (PFM) with high detection speed and accuracy has become a powerful tool for screening the potential candidates for molecular ferroelectrics.

Organic radical ferroics such as TEMPO have attracted widespread interest. However,the relatively low Curie temperature of 287 Ka nd melting point of 311 Ks everely hinder its application potential. Despite extensive interest, high-temperature radical ferroics have not yet been found. Here,taking advantage of chemical design and supramolecular radical chemistry,w ed esigned two high-temperature organic supramolecular radical ferroics [(NH 3 -TEMPO)([18]crown-6)](ReO 4 )( 1)and [(NH 3 -TEMPO)([18]crown-6)](ClO 4 )(2), which can retain ferroelectricity up to 413 Ka nd 450 K, respectively.T oo ur knowledge,t hey are both the first supramolecular radical ferroics and unprecedented hightemperature radical ferroics,w here the supramolecular component is vital for the stabilization of the radical and extending the working temperature window. Both also have paramagnetism, non-interacting spin moments,a nd excellent piezoelectric and electrostrictive behaviors comparable to that of LiNbO 3 .

Two new homochiral 1D ABX3-type lead-halide perovskites exhibit dual dielectric and quadratic nonlinear optical switchings at high temperatures.