Askar Abdelrahman M, Karmakar Abhoy, Bernard Guy M, Ha Michelle, Terskikh Victor V, Wiltshire Benjamin D, Patel Sahil, Fleet Jonathan, Shankar Karthik, Michaelis Vladimir K
Department of Electrical and Computer Engineering , University of Alberta , Edmonton , Alberta , Canada T6G 1H9.
Department of Chemistry , University of Alberta , Edmonton , Alberta , Canada T6G 2G2.
J Phys Chem Lett. 2018 May 17;9(10):2671-2677. doi: 10.1021/acs.jpclett.8b01084. Epub 2018 May 7.
Mixed-halide lead perovskites are becoming of paramount interest in the optoelectronic and photovoltaic research fields, offering band gap tunability, improved efficiency, and enhanced stability compared to their single halide counterparts. Formamidinium-based mixed halide perovskites (FA-MHPs) are critical to obtaining optimum solar cell performance. Here, we report a solvent-free mechanochemical synthesis (MCS) method to prepare FA-MHPs, starting with their parent compounds (FAPbX; X = Cl, Br, I), achieving compositions not previously accessible through the solvent synthesis (SS) technique. By probing local Pb environments in MCS FA-MHPs using solid-state nuclear magnetic resonance spectroscopy, along with powder X-ray diffraction for long-range crystallinity and reflectance measurements to determine the optical band gap, we show that MCS FA-MHPs form atomic-level solid solutions between Cl/Br and Br/I MHPs. Our results pave the way for advanced methods in atomic-level structural understanding while offering a one-pot synthetic approach to prepare MHPs with superior control of stoichiometry.
混合卤化物铅基钙钛矿在光电子和光伏研究领域正变得至关重要，与单一卤化物钙钛矿相比，它们具有带隙可调性、更高的效率和更强的稳定性。基于甲脒的混合卤化物钙钛矿（FA-MHPs）对于获得最佳太阳能电池性能至关重要。在此，我们报告了一种无溶剂机械化学合成（MCS）方法来制备FA-MHPs，从其母体化合物（FAPbX；X = Cl、Br、I）开始，实现了通过溶剂合成（SS）技术以前无法获得的组成。通过使用固态核磁共振光谱探测MCS FA-MHPs中的局部Pb环境，以及利用粉末X射线衍射测量长程结晶度和反射率测量来确定光学带隙，我们表明MCS FA-MHPs在Cl/Br和Br/I MHPs之间形成了原子级固溶体。我们的结果为原子级结构理解的先进方法铺平了道路，同时提供了一种一锅法合成方法，以在化学计量比的卓越控制下制备MHPs。
