Fluorinated 2D Lead Iodide Perovskite Ferroelectrics

• Published in: Advanced materials (Weinheim) Vol. 31; no. 30; pp. e1901843 - n/a
• Main Authors: Sha, Tai‐Ting, Xiong, Yu‐An, Pan, Qiang, Chen, Xiao‐Gang, Song, Xian‐Jiang, Yao, Jie, Miao, Shu‐Rong, Jing, Zheng‐Yin, Feng, Zi‐Jie, You, Yu‐Meng, Xiong, Ren‐Gen
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.07.2019
• Subjects: Blindness; Charge transport; Design modifications; Ferroelectric materials; ferroelectric photovoltaic effect; Ferroelectricity; Ferroelectrics; Fluorination; Fluorine; Lead compounds; lead halide perovskites; Materials science; Metal halides; molecular ferroelectrics; Optical properties; Optoelectronics; perovskite ferroelectrics; Perovskites; Photoluminescence; Photovoltaic cells; Photovoltaic effect; Polarization; Solar cells; Transport properties; lead halide perovskites; molecular ferroelectrics; perovskite ferroelectrics; ferroelectric photovoltaic effect
• ISSN: 0935-9648; 1521-4095; 1521-4095
• DOI: 10.1002/adma.201901843

Hybrid perovskite materials are famous for their great application potential in photovoltaics and optoelectronics. Among them, lead‐iodide‐based perovskites receive great attention because of their good optical absorption ability and excellent electrical transport properties. Although many believe the ferroelectric photovoltaic effect (FEPV) plays a crucial role for the high conversion efficiency, the ferroelectricity in CH3NH3PbI3 is still under debate, and obtaining ferroelectric lead iodide perovskites is still challenging. In order to avoid the randomness and blindness in the conventional method of searching for perovskite ferroelectrics, a design strategy of fluorine modification is developed. As a demonstration, a nonpolar lead iodide perovskite is modified and a new 2D fluorinated layered hybrid perovskite material of (4,4‐difluorocyclohexylammonium)2PbI4, 1, is obtained, which possesses clear ferroelectricity with controllable spontaneous polarization. The direct bandgap of 2.38 eV with strong photoluminescence also guarantees the direct observation of polarization‐induced FEPV. More importantly, the 2D structure and fluorination are also expected to achieve both good stability and charge transport properties. 1 is not only a 2D fluorinated lead iodide perovskite with confirmed ferroelectricity, but also a great platform for studying the effect of ferroelectricity and FEPV in the context of lead halide perovskite solar cells and other optoelectronic applications. Through a design strategy of fluorine modification, a nonpolar lead iodide perovskite is modified and a new 2D fluorinated layered hybrid perovskite material of (4,4‐difluorocyclohexylammonium)2PbI4 is obtained, which possesses clear ferroelectricity with controllable spontaneous polarization and ferroelectric photovoltaic effect. The discovery of such a material provides a great platform for the fundamental study of lead halide perovskite solar cells and other optoelectronic applications.