title: Exceptional Morphology-Preserving Evolution of Formamidinium Lead Triiodide Perovskite Thin Films via Organic-Cation Displacement.
abstract: Here we demonstrate a radically different chemical route for the creation of HC(NH2)2PbI3 (FAPbI3) perovskite thin films. This approach entails a simple exposure of as-synthesized CH3NH3PbI3 (MAPbI3) perovskite thin films to HC(═NH)NH2 (formamidine or FA) gas at 150 °C, which leads to rapid displacement of the MA(+) cations by FA(+) cations in the perovskite structure. The resultant FAPbI3 perovskite thin films preserve the microstructural morphology of the original MAPbI3 thin films exceptionally well. Importantly, the myriad processing innovations that have led to the creation of high-quality MAPbI3 perovskite thin films are directly adaptable to FAPbI3 through this simple, rapid chemical-conversion route. Accordingly, we show that efficiencies of perovskite solar cells fabricated with FAPbI3 thin films created using this route can reach ∼18%.
authors.affiliation: School of Engineering, Brown University , Providence, Rhode Island 02912, United States.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Chemistry and Nanoscience Center, National Renewable Energy Laboratory , Golden, Colorado 80401, United States.
authors.forename: Mengjin
authors.initials: M
authors.lastname: Yang
authors.affiliation: Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences , Qingdao 266101, P.R. China.
authors.forename: Shuping
authors.initials: S
authors.lastname: Pang
authors.affiliation: Chemistry and Nanoscience Center, National Renewable Energy Laboratory , Golden, Colorado 80401, United States.
authors.forename: Kai
authors.initials: K
authors.lastname: Zhu
authors.affiliation: School of Engineering, Brown University , Providence, Rhode Island 02912, United States.
authors.forename: Nitin P
authors.initials: NP
authors.lastname: Padture