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<p>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)<sub>2</sub>GeBr<sub>4</sub> designed by molecular fluorination. Remarkably, (4,4-difluoropiperidinium)<sub>2</sub>GeBr<sub>4</sub> exhibits large saturation polarization (&gt;15 μC/cm<sup>2</sup>), high Curie temperature (401 K) and the strongest SHG intensity among 2D HOIP ferroelectrics (about 6.2 times of KH<sub>2</sub>PO<sub>4</sub>). These properties arise from the synergy of two mechanisms: the 4s<sup>2</sup> lone pair on Ge<sup>2+</sup> and the orientational ordering of 4,4-difluoropiperidinium cations. Moreover, (4,4-difluoropiperidinium)<sub>2</sub>GeBr<sub>4</sub> features eight equivalent polarization directions (the maximum number among reported 2D HOIP ferroelectrics), enabling its composite (4,4-difluoropiperidinium)<sub>2</sub>GeBr<sub>4</sub>@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.</p>

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Lone pair expression in fluorinated two-dimensional hybrid perovskite enables multiaxial ferroelectricity and nonlinear optical response

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年8月20日

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  • Hao-Fei Ni,
  • Qi-Fang Zhou,
  • Jia-Qi Luo,
  • Gele Teri,
  • Lei Pan,
  • Lou-Kai Ye,
  • Qiang-Qiang Jia,
  • Pei-Zhi Huang,
  • Pei-Guo Liu,
  • Chang-Feng Wang,
  • Zhi-Xu Zhang,
  • Da-Wei Fu,
  • Yi Zhang

摘要

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)2GeBr4 designed by molecular fluorination. Remarkably, (4,4-difluoropiperidinium)2GeBr4 exhibits large saturation polarization (>15 μC/cm2), high Curie temperature (401 K) and the strongest SHG intensity among 2D HOIP ferroelectrics (about 6.2 times of KH2PO4). These properties arise from the synergy of two mechanisms: the 4s2 lone pair on Ge2+ and the orientational ordering of 4,4-difluoropiperidinium cations. Moreover, (4,4-difluoropiperidinium)2GeBr4 features eight equivalent polarization directions (the maximum number among reported 2D HOIP ferroelectrics), enabling its composite (4,4-difluoropiperidinium)2GeBr4@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.