Joint Institute for Advanced Materials, Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN, 37996, USA.
Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
Adv Mater. 2018 Mar;30(11). doi: 10.1002/adma.201705298. Epub 2018 Jan 22.
Organometallic halide perovskites (OMHPs) have attracted broad attention as prospective materials for optoelectronic applications. Among the many anomalous properties of these materials, of special interest are the ferroelectric properties including both classical and relaxor-like components, as a potential origin of slow dynamics, field enhancement, and anomalous mobilities. Here, ferroelectric properties of the three representative OMHPs are explored, including FAPb Sn I (x = 0, x = 0.85) and FA MA PbI using band excitation piezoresponse force microscopy and contact mode Kelvin probe force microscopy, providing insight into long- and short-range dipole and charge dynamics in these materials and probing ferroelectric density of states. Furthermore, second-harmonic generation in thin films of OMHPs is observed, providing a direct information on the noncentrosymmetric polarization in such materials. Overall, the data provide strong evidence for the presence of ferroelectric domains in these systems; however, the domain dynamics is suppressed by fast ion dynamics. These materials hence present the limit of ferroelectric materials with spontaneous polarization dynamically screened by ionic and electronic carriers.
金属卤化物钙钛矿（OMHPs）作为光电应用的有前途的材料引起了广泛关注。在这些材料的许多异常性质中，特别有趣的是铁电性质，包括经典和弛豫体成分，这可能是慢动力学、场增强和异常迁移率的起源。在这里，使用带激发压电力显微镜和接触模式 Kelvin 探针力显微镜研究了三种代表性 OMHPs 的铁电性质，包括 FAPbSnI（x=0，x=0.85）和 FA MA PbI，深入了解了这些材料中长程和短程偶极子和电荷动力学，并探测了铁电态密度。此外，还观察到 OMHPs 薄膜中的二次谐波产生，为这些材料中的非中心对称极化提供了直接信息。总的来说，这些数据为这些体系中存在铁电畴提供了强有力的证据；然而，畴动力学受到快速离子动力学的抑制。因此，这些材料表现出具有自发极化的铁电材料的极限，其自发极化被离子和电子载流子动态屏蔽。
