Spanopoulos Ioannis, Hadar Ido, Ke Weijun, Tu Qing, Chen Michelle, Tsai Hsinhan, He Yihui, Shekhawat Gajendra, Dravid Vinayak P, Wasielewski Michael R, Mohite Aditya D, Stoumpos Constantinos C, Kanatzidis Mercouri G
Department of Chemistry , Northwestern University , Evanston , Illinois 60208 , United States.
Department of Materials Science & Engineering , Northwestern University , Evanston , Illinois 60208 , United States.
J Am Chem Soc. 2019 Apr 3;141(13):5518-5534. doi: 10.1021/jacs.9b01327. Epub 2019 Mar 18.
The unique hybrid nature of 2D Ruddlesden-Popper (R-P) perovskites has bestowed upon them not only tunability of their electronic properties but also high-performance electronic devices with improved environmental stability as compared to their 3D analogs. However, there is limited information about their inherent heat, light, and air stability and how different parameters such as the inorganic layer number and length of organic spacer molecule affect stability. To gain deeper understanding on the matter we have expanded the family of 2D R-P perovskites, by utilizing pentylamine (PA)(MA) Pb I ( n = 1-5, PA = CH(CH)NH, C5) and hexylamine (HA)(MA) Pb I ( n = 1-4, HA = CH(CH)NH, C6) as the organic spacer molecules between the inorganic slabs, creating two new series of layered materials, for up to n = 5 and 4 layers, respectively. The resulting compounds were extensively characterized through a combination of physical and spectroscopic methods, including single crystal X-ray analysis. High resolution powder X-ray diffraction studies using synchrotron radiation shed light for the first time to the phase transitions of the higher layer 2D R-P perovskites. The increase in the length of the organic spacer molecules did not affect their optical properties; however, it has a pronounced effect on the air, heat, and light stability of the fabricated thin films. An extensive study of heat, light, and air stability with and without encapsulation revealed that specific compounds can be air stable (relative humidity (RH) = 20-80% ± 5%) for more than 450 days, while heat and light stability in air can be exponentially increased by encapsulating the corresponding films. Evaluation of the out-of-plane mechanical properties of the corresponding materials showed that their soft and flexible nature can be compared to current commercially available polymer substrates (e.g., PMMA), rendering them suitable for fabricating flexible and wearable electronic devices.
二维Ruddlesden-Popper（R-P）钙钛矿独特的杂化性质不仅赋予了它们电子性质的可调性，还带来了与三维类似物相比具有更高环境稳定性的高性能电子器件。然而，关于它们固有的热、光和空气稳定性以及无机层数和有机间隔分子长度等不同参数如何影响稳定性的信息有限。为了更深入地了解这一问题，我们通过使用戊胺（PA）（MA）PbI（n = 1-5，PA = CH(CH)NH，C5）和己胺（HA）（MA）PbI（n = 1-4，HA = CH(CH)NH，C6）作为无机板之间的有机间隔分子，扩展了二维R-P钙钛矿家族，分别创建了两个新的层状材料系列，无机层数最多分别为5层和4层。通过物理和光谱方法相结合，包括单晶X射线分析，对所得化合物进行了广泛表征。使用同步辐射的高分辨率粉末X射线衍射研究首次揭示了高层二维R-P钙钛矿的相变。有机间隔分子长度的增加并不影响它们的光学性质；然而，它对制备的薄膜的空气、热和光稳定性有显著影响。对有封装和无封装情况下的热、光和空气稳定性进行的广泛研究表明，特定化合物在空气（相对湿度（RH）= 20-80% ± 5%）中可稳定超过450天，而通过封装相应薄膜，空气中的热稳定性和光稳定性可呈指数增加。对相应材料的面外机械性能评估表明，它们柔软且灵活的性质可与目前市售的聚合物基板（如聚甲基丙烯酸甲酯）相媲美，使其适合制造柔性和可穿戴电子设备。
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