A Photochromic Organic–Inorganic Hybrid Schiff Base Metal Halide Ferroelectric

Integration of photochromism and ferroelectricity in one material is significant for not only an in-depth understanding of the physiochemical process but also advances in multipurpose optoelectronic devices. Research on the combination of them has been mainly constrained in ferroelectric liquid crystals doped with photochromic components, ferroelectric ceramics doped with rare-earth ions, and single-component organic photochromic crystals, leading to scant material diversity and limited application range. Recently booming organic–inorganic hybrid materials may serve as potential candidates for neoteric photochromic ferroelectrics due to their species diversity, easy chemical fabrication, and versatile physical properties. In this work, two new organic–inorganic hybrid metal halide Schiff base derivatives of [SAPD]2CdX4 (SAPD = 1-((2-hydroxybenzylidene)amino)pyridin-1-ium, X = Br and I) have been successfully synthesized. Both of them present reversible photochromism, originating from the photoinduced proton transfer and structural isomerization. More interestingly, [SAPD]2CdI4 exhibits room-temperature ferroelectricity, which has extended the photochromic ferroelectric family. Besides, optically controlled polarization switching has been achieved in [SAPD]2CdI4, demonstrating the ability of modulation of ferroelectricity via a photoinduced structural change. This work provides inspiration for the combination of functionalities in hybrid materials, which holds great potential for intriguing optoelectronic integrated applications.