Metal halide perovskites, chemical compounds of ABX₃ stoichiometry (A=CH₃NH₃⁺, Cs⁺, …; B=Pb²⁺, Sn²⁺; X=I⁻, Br⁻), have attracted great interest as they emerged as one of the most promising class of materials for low‐cost photovoltaics with over 25 % certified power conversion efficiency. An important open question for further improving their efficiency and stability is the formation and dynamics of point defects, for example, iodide vacancies and interstitials. In particular, recently it has been shown that defects strongly interact with grain boundaries, which, for example, prevents a quick restoration of initial conditions of film when kept in the dark after illumination [Phung et al., Adv. Energy Mater. 2020, 1903735]. It has also been shown that iodide defects may accumulate at grain boundaries, where they induce carriers’ recombination [Park et al., ACS Energy Lett. 2019, 4, 1321–1327]. In this article, we make use of molecular dynamics and ab initio simulations to follow the evolution and compute the energetics of a iodide vacancy, , and an iodide Interstitial, , interacting with Σ5/(102) grain boundaries of different termination, MAI and PbI₂. We show that the polarization charge of Σ5/(102) grain boundary associated to a prescribed termination drives the dynamics of charged defects, and . The long‐range interaction of grain boundaries with charged species might induce the accumulation of point defects present in crystallites or formed under operation conditions. Moreover, the selective attraction of specific defects by a grain boundary may help splitting Frenkel pairs formed in solar cells under illumination, thus preventing the quick annihilation of defects and enhancing the effect of light in inducing degradation processes.

中文翻译：

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MAPbI3多晶膜中的缺陷动力学：晶界的俘获效应

金属卤化物钙钛矿，ABX的化学化合物₃的化学计量（A = CH ₃ NH ₃ ⁺，铯⁺，...; B =铅²⁺，Sn的²⁺ ; X = I ^- ，溴^-）引起了极大的兴趣，因为它们已成为低成本光伏最有前景的材料之一，其认证的电源转换效率超过25％。进一步提高其效率和稳定性的一个重要的开放性问题是点缺陷的形成和动态，例如碘化物空位和间隙。特别地，最近已显示出缺陷与晶界强烈地相互作用，例如，当在光照后保持在黑暗中时，这阻止了膜的初始状态的快速恢复[ Phung等人，Adv.Av.Acad.Sci.USA，89：3587-8877]。能源硕士。2020，1903735]。还显示出碘化物缺陷可能累积在晶界处，它们会引起载流子的重组[ Park等。。，ACS Energy Lett。2019，4，1321-1327]。在本文中，我们利用分子动力学和从头算的方法来跟踪演化并计算碘化物空位 （和碘化物间隙 ）与不同端基，MAI和PbI的Σ5/（102）晶界相互作用的能级₂。我们表明，与规定的终止点相关的Σ5/（102）晶界的极化电荷驱动带电缺陷的动力学，并且 。晶界与带电物质的长程相互作用可能会导致微晶中存在或在工作条件下形成的点缺陷的积累。此外，晶界对特定缺陷的选择性吸引可以帮助在光照下分裂形成在太阳能电池中的Frenkel对，从而防止缺陷的快速消失，并增强光在诱导降解过程中的作用。