Zhang Han-Yue, Zhang Zhi-Xu, Song Xian-Jiang, Chen Xiao-Gang, Xiong Ren-Gen
Jiangsu Key Laboratory for Science and Applications of Molecular Ferroelectrics, Southeast University, Nanjing 211189, People's Republic of China.
J Am Chem Soc. 2020 Nov 25;142(47):20208-20215. doi: 10.1021/jacs.0c10686. Epub 2020 Nov 12.
Two-dimensional (2D) hybrid organic-inorganic perovskites (HOIPs), which possess the merits of good material stability, structural diversity, and ease of fabrication, are highly desirable for widespread applications of ferroelectrics, solar cells, and electroluminescent devices. Although some molecular design strategies toward ferroelectrics have been proposed, however, it is still a great challenge to precisely induce and optimize the ferroelectricity in 2D HOIPs. Here, for the first time through perfluorinated substitution strategy, we successfully design a high-performance 2D HOIP ferroelectric, (perfluorobenzylammonium)PbBr, exhibiting more obvious second harmonic generation intensity, larger piezoelectric response, more polar axes, larger spontaneous polarization of 4.2 μC cm, and higher Curie temperature of 440 K than those of parent (benzylammonium)PbBr. Compared to the selective effect of monofluorinated substitution on different positions of the benzene ring, where (3-fluorobenzylammonium)PbBr and (4-fluorobenzylammonium)PbBr are not ferroelectrics, the pioneering perfluorinated substitution is more universal and effective for targeted design of aromatic ferroelectrics. This work offers an efficient strategy for precisely designing high-performance 2D HOIP ferroelectrics.
二维（2D）有机-无机杂化钙钛矿（HOIPs）具有材料稳定性好、结构多样且易于制备等优点，在铁电体、太阳能电池和电致发光器件的广泛应用中极具吸引力。尽管已经提出了一些针对铁电体的分子设计策略，然而，在二维HOIPs中精确诱导和优化铁电性仍然是一个巨大的挑战。在此，我们首次通过全氟取代策略成功设计出一种高性能的二维HOIP铁电体，（全氟苄基铵）PbBr，与母体（苄基铵）PbBr相比，其表现出更明显的二次谐波产生强度、更大的压电响应、更多的极性轴、4.2 μC cm的更大自发极化以及440 K的更高居里温度。与单氟取代在苯环不同位置的选择性效应相比，其中（3-氟苄基铵）PbBr和（4-氟苄基铵）PbBr不是铁电体，开创性的全氟取代对于芳香族铁电体的靶向设计更具通用性和有效性。这项工作为精确设计高性能二维HOIP铁电体提供了一种有效策略。
