Reversible Halide Exchange Reaction of Organometal Trihalide Perovskite Colloidal Nanocrystals for Full-Range Band Gap Tuning

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• 作者：Dong Myung Jang ; Kidong Park ; Duk Hwan Kim ; Jeunghee Park ; Fazel Shojaei ; Hong Seok Kang ; Jae-Pyung Ahn ; Jong Woon Lee ; Jae Kyu Song
• 刊名：Nano Letters
• 出版年：2015
• 出版时间：August 12, 2015
• 年：2015
• 卷：15
• 期：8
• 页码：5191-5199
• 全文大小：670K
• ISSN：1530-6992

文摘

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鈥?i>xCl_x and MAPbBr_3鈥?i>xI_x 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鈥? 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.