title: Reversible Halide Exchange Reaction of Organometal Trihalide Perovskite Colloidal Nanocrystals for Full-Range Band Gap Tuning.
abstract: In recent years, methylammonium lead halide (MAPbX3, where X = Cl, Br, and I) perovskites have attracted tremendous interest caused by their outstanding photovoltaic performance. Mixed halides have been frequently used as the active layer of solar cells, as a result of their superior physical properties as compared to those of traditionally used pure iodide. Herein, we report a remarkable finding of reversible halide-exchange reactions of MAPbX3, which facilitates the synthesis of a series of mixed halide perovskites. We synthesized MAPbBr3 plate-type nanocrystals (NCs) as a starting material by a novel solution reaction using octylamine as the capping ligand. The synthesis of MAPbBr(3-x)Clx and MAPbBr(3-x)Ix NCs was achieved by the halide exchange reaction of MAPbBr3 with MACl and MAI, respectively, in an isopropyl alcohol solution, demonstrating full-range band gap tuning over a wide range (1.6-3 eV). Moreover, photodetectors were fabricated using these composition-tuned NCs; a strong correlation was observed between the photocurrent and photoluminescence decay time. Among the two mixed halide perovskite series, those with I-rich composition (x = 2), where a sole tetragonal phase exists without the incorporation of a cubic phase, exhibited the highest photoconversion efficiency. To understand the composition-dependent photoconversion efficiency, first-principles density-functional theory calculations were carried out, which predicted many plausible configurations for cubic and tetragonal phase mixed halides.
authors.affiliation: †Department of Chemistry, Korea University, Jochiwon 339-700, Korea.
authors.forename: Dong Myung
authors.initials: DM
authors.lastname: Jang
authors.affiliation: †Department of Chemistry, Korea University, Jochiwon 339-700, Korea.
authors.forename: Kidong
authors.initials: K
authors.lastname: Park
authors.affiliation: †Department of Chemistry, Korea University, Jochiwon 339-700, Korea.
authors.forename: Duk Hwan
authors.initials: DH
authors.lastname: Kim
authors.affiliation: †Department of Chemistry, Korea University, Jochiwon 339-700, Korea.
authors.forename: Jeunghee
authors.initials: J
authors.lastname: Park
authors.affiliation: ‡Department of Chemistry and Bioactive Material Sciences and Research Institute of Physics and Chemistry, Jeonbuk National University, Jeonju 560-756, Korea.
authors.forename: Fazel
authors.initials: F
authors.lastname: Shojaei
authors.affiliation: §Department of Nano and Advanced Materials, College of Engineering, Jeonju University, Jeonju 560-759, Korea.
authors.forename: Hong Seok
authors.initials: HS
authors.lastname: Kang
authors.affiliation: ∥ Nano Materials Analysis Center, Korea Institute of Science and Technology, Seoul 136-791, Korea.
authors.forename: Jae-Pyung
authors.initials: JP
authors.lastname: Ahn
authors.affiliation: ⊥Department of Chemistry, Kyung Hee University, Seoul 130-701, Korea.
authors.forename: Jong Woon
authors.initials: JW
authors.lastname: Lee
authors.affiliation: ⊥Department of Chemistry, Kyung Hee University, Seoul 130-701, Korea.
authors.forename: Jae Kyu
authors.initials: JK
authors.lastname: Song
keywords: Perovskite; anion exchange reaction; composition tuning; nanocrystals; photodetectors