Optically Controlled Polarization Switching in an Organic Ferroelectric with Light- and Temperature-Triggered Phase Transitions

Polarization in ferroelectrics is generally switched by an applied external electric field. Light is highly attractive as a noncontact and noninvasive means, but optically controlled ferroelectric polarization has been mainly realized in some inorganic ferroelectrics, and rarely found in molecular ferroelectrics, which have superiorities of easy processing, light weight, mechanical flexibility, and good biocompatibility. In this work, we reported an organic ferroelectric salicylideneaniline derivative N-3,5-di-tert-butylsalicylidene-2-aminoaniline (1), which shows optically controlled polarization switching. 1 not only exhibits a light-induced phase transition of photoisomerization between enol and trans-keto molecular configurations but also presents a temperature-triggered phase transition at around 364 K related to the order–disorder transition of a tert-butyl group in the structure. P–E (polarization–electric field) hysteresis loops and box-in-box ferroelectric domain reversal confirm its ferroelectricity. Upon photoirradiation, the ferroelectric domains show obvious variations and demonstrate reversible polarization switching under UV and visible light, originating from the photoinduced structural isomerization. This finding sheds light on the development of molecular ferroelectrics with noncontact and remote control of polarization switching by light for potential application in next-generation optically controlled ferroelectric devices.