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.

An organic plastic ferroelectric, (−)-Camphanic acid, shows multiaxial ferroelectric feature and large entropy gain during the phase transition.

(R)- and (S)-(N,N-dimethyl-3-fluoropyrrolidinium) iodide show the highest phase transition temperature (Tc) of 470 K among enantiomeric ferroelectrics.

Chiral organic–inorganic perovskites (COIPs) have recently attracted increasing interest due to their unique inherent chirality and potential applications in next-generation optoelectronic and spintronic devices. However, COIP ferroelectrics are very sparse. In this work, for the first time, we present the nickel-nitrite ABX3 COIP ferroelectrics, [(R and S)-N-fluoromethyl-3-quinuclidinol]­Ni­(NO2)3 ([(R and S)-FMQ]­Ni­(NO2)3), where the X-site is the rarely seen NO2 – bridging ligand. [(R and S)-FMQ]­Ni­(NO2)3 display mirror-relationship in the crystal structure and vibrational circular dichroism signal. It is emphasized that [(R and S)-FMQ]­Ni­(NO2)3 show splendid ferroelectricity with both an extremely high phase-transition point of 405 K and a spontaneous polarization of 12 μC/cm2. To our knowledge, [(R and S)-FMQ]­Ni­(NO2)3 are the first examples of nickel-nitrite based COIP ferroelectrics. This finding expands the COIP family and throws light on exploration of high-performance COIP ferroelectrics.