Organic Cation-Dependent Degradation Mechanism of Organotin Halide Perovskites
Organic Cation-Dependent Degradation Mechanism of Organotin Halide Perovskites
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有机锡卤化物钙钛矿的有机阳离子依赖性降解机制
DOI：
10.1002/adfm.201505127
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发表时间：
2016-05-24
影响因子：
19
通讯作者：
Zhao, Ni
中科院分区：
文献类型：
--
作者：
Wang, Feng;Ma, Jiale;Zhao, Ni
有机锡卤化物钙钛矿在常温下存在化学不稳定性，限制了其应用。当暴露在空气中时，Sn2+可以迅速被氧化成Sn4+，导致电子性质的很大变化。在这里，通过比较甲基碘化锡铵(MASNI(3))和甲胺基碘化锡(FASnI(3))来研究有机阳离子在降解过程中的作用。通过化学分析和理论计算，发现有机阳离子对Sn2+的氧化和H2O分子与钙钛矿晶格的结合有很强的影响。一方面，Sn2+在MasNi(3)中容易被氧化为Sn4+，用FA取代MA降低了Sn4+的氧化程度；另一方面，FA与H2O形成了比MA更强的氢键，导致钙钛矿网络的部分扩张。这两个过程在确定材料的导电性方面相互竞争。值得注意的是，氧化是一个很难防止的过程，而水的影响可以通过降低水分水平来很大程度上抑制。因此，与基于MASNi(3)的器件相比，基于FASnI(3)的导体和光伏电池显示出更好的重复性。该研究为开发稳定的无铅钙钛矿型光电子器件提供了新的材料设计思路。
The applications of organotin halide perovskites are limited because of their chemical instability under ambient conditions. Upon air exposure, Sn2+ can be rapidly oxidized to Sn4+, causing a large variation in the electronic properties. Here, the role of organic cations in degradation is investigated by comparing methylammonium tin iodide (MASnI(3)) and formamidinium tin iodide (FASnI(3)). Through chemical analyses and theoretical calculations, it is found that the organic cation strongly influences the oxidation of Sn2+ and the binding of H2O molecules to the perovskite lattice. On the one hand, Sn2+ can be easily oxidized to Sn4+ in MASnI(3), and replacing MA with FA reduces the extent of Sn oxidation; on the other hand, FA forms a stronger hydrogen bond with H2O than does MA, leading to partial expansion of the perovskite network. The two processes compete in determining the material's conductivity. It is noted that the oxidation is a difficult process to prevent, while the water effect can be largely suppressed by reducing the moisture level. As a result, FASnI(3)-based conductors and photovoltaic cells exhibit much better reproducibility as compared to MASnI(3)-based devices. This study sheds light on the development of stable Pb-free perovskite optoelectronic devices through new material design.