title: Compositional engineering of perovskite materials for high-performance solar cells.
abstract: Of the many materials and methodologies aimed at producing low-cost, efficient photovoltaic cells, inorganic-organic lead halide perovskite materials appear particularly promising for next-generation solar devices owing to their high power conversion efficiency. The highest efficiencies reported for perovskite solar cells so far have been obtained mainly with methylammonium lead halide materials. Here we combine the promising-owing to its comparatively narrow bandgap-but relatively unstable formamidinium lead iodide (FAPbI3) with methylammonium lead bromide (MAPbBr3) as the light-harvesting unit in a bilayer solar-cell architecture. We investigated phase stability, morphology of the perovskite layer, hysteresis in current-voltage characteristics, and overall performance as a function of chemical composition. Our results show that incorporation of MAPbBr3 into FAPbI3 stabilizes the perovskite phase of FAPbI3 and improves the power conversion efficiency of the solar cell to more than 18 per cent under a standard illumination of 100 milliwatts per square centimetre. These findings further emphasize the versatility and performance potential of inorganic-organic lead halide perovskite materials for photovoltaic applications.
authors.affiliation: Division of Advanced Materials, Korea Research Institute of Chemical Technology, 141 Gajeong-Ro, Yuseong-Gu, Daejeon 305-600, South Korea.
authors.forename: Nam Joong
authors.initials: NJ
authors.lastname: Jeon
authors.affiliation: Division of Advanced Materials, Korea Research Institute of Chemical Technology, 141 Gajeong-Ro, Yuseong-Gu, Daejeon 305-600, South Korea.
authors.forename: Jun Hong
authors.initials: JH
authors.lastname: Noh
authors.affiliation: Division of Advanced Materials, Korea Research Institute of Chemical Technology, 141 Gajeong-Ro, Yuseong-Gu, Daejeon 305-600, South Korea.
authors.forename: Woon Seok
authors.initials: WS
authors.lastname: Yang
authors.affiliation: Division of Advanced Materials, Korea Research Institute of Chemical Technology, 141 Gajeong-Ro, Yuseong-Gu, Daejeon 305-600, South Korea.
authors.forename: Young Chan
authors.initials: YC
authors.lastname: Kim
authors.affiliation: Division of Advanced Materials, Korea Research Institute of Chemical Technology, 141 Gajeong-Ro, Yuseong-Gu, Daejeon 305-600, South Korea.
authors.forename: Seungchan
authors.initials: S
authors.lastname: Ryu
authors.affiliation: Division of Advanced Materials, Korea Research Institute of Chemical Technology, 141 Gajeong-Ro, Yuseong-Gu, Daejeon 305-600, South Korea.
authors.forename: Jangwon
authors.initials: J
authors.lastname: Seo
authors.affiliation: 1] Division of Advanced Materials, Korea Research Institute of Chemical Technology, 141 Gajeong-Ro, Yuseong-Gu, Daejeon 305-600, South Korea [2] Department of Energy Science, 2066 Seoburo, Jangan-gu, Sungkyunkwan University, Suwon 440-746, South Korea.
authors.forename: Sang Il
authors.initials: SI
authors.lastname: Seok