Lone pair expression in fluorinated two-dimensional hybrid perovskite enables multiaxial ferroelectricity and nonlinear optical response.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 40835845.
- Also identified by DOI 10.1038/s41467-025-63134-6 and PMC identifier 12368121.
- No licence information is recorded for this record.
- Because redistribution is not established, this page shows the abstract only. Follow the links below for the full text.
Abstract
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 (>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.