Organic donor-acceptor cocrystal ferroelectrics: advances and perspectives
Organic/molecular ferroelectrics exhibiting spontaneous polarization have attracted increasing attention due to their flexibility, light weight, low-temperature processability, environmental friendliness, and biocompatibility. Among them, organic donor-acceptor cocrystals, self-assembled from two or more components, offer new insights into ferroelectricity. This review systematically examines recent progress in organic donor-acceptor cocrystal ferroelectrics, focusing on microscopic origins of ferroelectricity, structure modulation strategies, and underlying mechanisms. Ferroelectric origin mechanisms, including intermolecular charge transfer, proton transfer, and order-disorder transitions, are analyzed in detail. Structure-property relationships in crystal engineering are summarized, and recent advances in theoretical simulations, experimental characterization techniques, and practical applications are introduced. Finally, current challenges and future research perspectives are outlined. The review highlights that weak intermolecular interactions often lead to low Curie temperatures (Tc), limiting practical applications. Strategies to enhance Tc involve introducing stronger molecular interactions to increase transition energy barriers. Notably, room-temperature ferroelectricity in organic cocrystals has been achieved, as demonstrated by Wiscons et al. (Angew Chem Int Ed, 2018, 57: 9044–9047). The review underscores the potential of organic cocrystal ferroelectrics for flexible and wearable electronics, while addressing the need for higher Tc and robust switching performance.