Ab Initio Molecular Dynamics Simulations of Methylammonium Lead Iodide Perovskite Degradation by Water,Chemistry of Materials

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Ab Initio Molecular Dynamics Simulations of Methylammonium Lead Iodide Perovskite Degradation by Water
Chemistry of Materials ( IF 7.2 ) Pub Date : 2015-07-01 00:00:00 , DOI: 10.1021/acs.chemmater.5b01991
Edoardo Mosconi ₁ , Jon M. Azpiroz _{1,

2} , Filippo De Angelis ₁

Affiliation

Protecting organohalide perovskite thin films from water and ambient humidity represents a paramount challenge for the commercial uptake of perovskite solar cells and, in general, of related optoelectronic devices. Therefore, understanding the perovskite/water interface is of crucial importance. As a step in this direction, here we present ab initio molecular dynamics simulations aimed at unraveling the atomistic details of the interaction between the methylammonium lead iodide (MAPbI₃) perovskite surfaces and a liquid water environment. According to our calculations, MAI-terminated surfaces undergo a rapid solvation process, driven by the interaction of water molecules with Pb atoms, which prompts the release of I atoms. PbI₂-terminated surfaces, instead, seem to be more robust to degradation, by virtue of the stronger (shorter) Pb–I bonds formed on these facets. We also observe the incorporation of a water molecule into the PbI₂-terminated slab, which could represent the first step in the formation of an intermediate hydrated phase. Interestingly, PbI₂ defects on the PbI₂-terminated surface promote the rapid dissolution of the exposed facet. Surface hydration, which is spontaneous for both MAI- and PbI₂-terminated slabs, does not modify the electronic landscape of the former, while the local band gap of the PbI₂-exposing model widens by ∼0.3 eV in the interfacial region. Finally, we show that water incorporation into bulk MAPbI₃ produces almost no changes in the tetragonal structure of the perovskite crystal (∼1% volume expansion) but slightly opens the band gap. We believe that this work, unraveling some of the atomistic details of the perovskite/water interface, may inspire new interfacial modifications and device architectures with increased stabilities, which could in turn assist the commercial uptake of perovskite solar cells and optoelectronic devices.

中文翻译：

甲基铵碘化铅钙钛矿被水降解的从头算分子动力学模拟

保护有机卤化物钙钛矿薄膜不受水和环境湿度的影响，对于钙钛矿太阳能电池以及通常的相关光电设备的商业应用而言，是一项极为重要的挑战。因此，了解钙钛矿/水界面至关重要。作为朝这个方向迈出的一步，我们在这里提供了从头开始的分子动力学模拟，旨在揭示甲基铵碘化铅（MAPbI ₃）钙钛矿表面与液态水环境之间相互作用的原子细节。根据我们的计算，在水分子与Pb原子的相互作用的驱动下，MAI封端的表面经历了快速的溶剂化过程，促使I原子释放。铅₂相反，由于在这些小面上形成的Pb-I键更强（更短），所以端接的表面似乎对降解更有抵抗力。我们还观察到将水分子掺入到PbI ₂封端的平板中，这可能代表了形成中间水合相的第一步。有趣的是，PBI ₂的碘化铅上的缺陷₂封端的表面推动露出小面的快速溶解。对于MAI和PbI ₂终止的平板来说，表面水合是自发的，不会改变前者的电子景观，而PbI ₂暴露模型的局部带隙在界面区域扩大了〜0.3 eV。最后，我们表明水掺入到大块MAPbI中₃在钙钛矿晶体的四方结构中几乎没有变化（〜1％的体积膨胀），但是稍微打开了带隙。我们认为，这项工作揭示了钙钛矿/水界面的一些原子学细节，可能会激发新的界面修饰和具有更高稳定性的器件架构，从而有助于钙钛矿太阳能电池和光电器件的商业应用。

更新日期：2015-07-01

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