Ni Hao-Fei, Zhou Qi-Fang, Luo Jia-Qi, Teri Gele, Pan Lei, Ye Lou-Kai, Jia Qiang-Qiang, Huang Pei-Zhi, Liu Pei-Guo, Wang Chang-Feng, Zhang Zhi-Xu, Fu Da-Wei, Zhang Yi
Institute for Science and Applications of Molecular Ferroelectrics, Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, Jinhua, People's Republic of China.
Nat Commun. 2025 Aug 20;16(1):7760. doi: 10.1038/s41467-025-63134-6.
Two-dimensional (2D) hybrid organic-inorganic perovskites (HOIPs) with tunable octahedra are promising for flexible devices due to spontaneous-polarization-driven functionalities like ferroelectric memory, piezoelectric sensing and optical switches. However, achieving large spontaneous polarization and strong second harmonic generation (SHG) remains challenging for 2D HOIP ferroelectrics. Here, we report a 2D HOIP ferroelectric (4,4-difluoropiperidinium)GeBr designed by molecular fluorination. Remarkably, (4,4-difluoropiperidinium)GeBr exhibits large saturation polarization (>15 μC/cm), high Curie temperature (401 K) and the strongest SHG intensity among 2D HOIP ferroelectrics (about 6.2 times of KHPO). These properties arise from the synergy of two mechanisms: the 4s lone pair on Ge and the orientational ordering of 4,4-difluoropiperidinium cations. Moreover, (4,4-difluoropiperidinium)GeBr features eight equivalent polarization directions (the maximum number among reported 2D HOIP ferroelectrics), enabling its composite (4,4-difluoropiperidinium)GeBr@thermoplastic polyurethane device to exhibit prominent piezoelectric sensing. Our work offers a reliable route to high-performance 2D hybrid ferroelectrics and highlights their potential in flexible devices.
具有可调节八面体的二维（2D）有机-无机杂化钙钛矿（HOIPs）因其具有铁电记忆、压电感测和光开关等自发极化驱动的功能，在柔性器件方面具有广阔前景。然而，对于二维HOIP铁电体来说，实现大的自发极化和强二次谐波产生（SHG）仍然具有挑战性。在此，我们报道了一种通过分子氟化设计的二维HOIP铁电体（4,4-二氟哌啶鎓）GeBr。值得注意的是，（4,4-二氟哌啶鎓）GeBr表现出大的饱和极化（>15 μC/cm²）、高居里温度（401 K）以及在二维HOIP铁电体中最强的SHG强度（约为KH₂PO₄的6.2倍）。这些特性源于两种机制的协同作用：Ge上的4s孤对电子和4,4-二氟哌啶鎓阳离子的取向有序化。此外，（4,4-二氟哌啶鎓）GeBr具有八个等效极化方向（在已报道的二维HOIP铁电体中数量最多），使其复合材料（4,4-二氟哌啶鎓）GeBr@热塑性聚氨酯器件表现出显著的压电感测性能。我们的工作为高性能二维混合铁电体提供了一条可靠途径，并突出了它们在柔性器件中的潜力。
