Recent advances in molecular ferroelectrics

Due to their structural flexibility, tunability and easy processing, molecular ferroelectric materials have emerged to complement the well-known ferroelectric perovskite oxides. A number of compounds have been investigated but, with the exception of polymeric polyvinylidene fluoride, most have not succeeded in achieving their potential, mainly because of their poor ambient stability. It is only recently, with the surge of electronic type ferroelectricity, that molecular ferroelectrics with superior properties have been synthesized, making them competitive with respect to oxides. Nevertheless, the uniaxial nature of most of the compounds still represents the main bottleneck because it limits the transposition of the bulk properties into films. A possible solution is represented by the use of multiaxial molecular compounds or of low-dimensional systems. In this review, we highlight the main achievements in this field and summarize the open questions to be addressed if molecular ferroelectrics are to be exploited in devices.