Chemical Distribution of Multiple Cation (Rb+, Cs+, MA+, and FA+) Perovskite Materials by Photoelectron Spectroscopy
Chemical Distribution of Multiple Cation (Rb+, Cs+, MA+, and FA+) Perovskite Materials by Photoelectron Spectroscopy
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DOI：
10.1021/acs.chemmater.7b00126
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发表时间：
2017-04-25
影响因子：
8.6
通讯作者：
Rensmo, Hakan
中科院分区：
文献类型：
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作者：
Philippe, Bertrand;Saliba, Michael;Rensmo, Hakan
铅基混合钙钛矿材料在过去几年中作为有前途的光伏材料出现。最近，已经表明，通过引入少量的无机阳离子（Cs+和Rb+），部分地替代更常见的有机阳离子（例如，甲基铵，MA和甲脒鎓，FA）。特别地，最近显示出含有Rb+、Cs+、MA（+）和FA（+）的混合阳离子组合物具有有益的光电性质并且在高温下稳定。这项工作的重点是使用同步加速器为基础的光电子能谱这种材料的组成。通过改变X射线源的光子能量来考虑不同的探测深度，从而提供对样品表面附近的化学组成和化学分布的了解。分析和比较了含有两种、三种或四种一价阳离子的过氧化物材料。Cs和Rb的存在下，观察到在样品表面和朝向散装，我们发现，在三个或四个阳离子的存在下，较少的未反应的PbI2留在样品中。有趣的是，Rb和Cs似乎共同作用，导致与三重对应物相比，不同的阳离子深度分布。我们的研究结果提供了重要的理解复杂的深度依赖性的化学成分在钙钛矿材料使用阳离子混合的常见做法。
Lead-based mixed perovskite materials have emerged in the last couple of years as promising photovoltaic materials. Recently, it was shown that improved material stability can be achieved by incorporating small amounts of inorganic cations (Cs+ and Rb+), partially replacing the more common organic cations (e.g., methylammonium, MA, and formamidinium, FA). Especially, a mixed cation composition containing Rb+, Cs+, MA(+), and FA(+) was recently shown to have beneficial optoelectronic properties and was stable at elevated temperature. This work focuses on the composition of this material using synchrotron-based photoelectron spectroscopy. Different probing depths were considered by changing the photon energy of the X-ray source providing insights on the chemical composition and the chemical distribution near the surface of the samples. Perovskite materials containing two, three, or four monovalent cations were analyzed and compared. The presence of Cs and Rb was observed both at the sample surface and toward the bulk, and we found that in the presence of three or four cations, less unreacted PbI2 remains in the sample. Interestingly, Rb and Cs appear to act jointly resulting in a different cation depth profile compared to that of the triple counterparts. Our findings provide significant understanding of the intricate depth-dependent chemical composition in perovskite materials using the common practice of cation mixing.