Despite their outstanding optoelectronic properties, metal halide perovskites have not yet seen widespread use in commercial applications. This is mostly due to their lack of stability with respect to several external factors, e.g., humidity, heat, light, and oxygen. Even though extensive studies have been carried out over the last decade, a lot of questions regarding their thermal stability still remain, and various publications have put forth different approaches for measuring and quantifying the conditions of their decomposition. However, differences in the experimental setups and in the reported values make comparisons of the reported results challenging. We show an approach, where ${\mathrm{MAPbI}}_3$ thin films are thermally decomposed in high vacuum within a temperature range from $220{}^{\circ }\mathrm{C}$ to $250{}^{\circ }\mathrm{C}$, while monitoring changes in the crystal structure using an in situ x-ray diffraction setup. This process reveals the complete phase evolution of the thin films from ${\mathrm{MAPbI}}_3$ into ${\mathrm{PbI}}_2$. The time resolved data was then evaluated in view of the reaction kinetics using three different approaches. First, an Arrhenius fit was applied to $lnk$ over $1/T$, where the rate constant $k$ was determined by fitting a first order exponential decay onto the decreasing peak area of the most prominent diffraction peaks. Secondly, a model fitting approach was used, where the data was tested against a set of different reaction models. Lastly, a model free isoconversional approach was applied. By doing this, we succeed in characterizing the decomposition and determine the kinetic triplet, consisting of the activation energy $E$, the frequency factor $A$, and the reaction model $f\left(\alpha \right)$. With the help of the kinetic triplet the decomposition reaction can be expressed in a physically meaningful way and allows us to predict the decomposition dynamics of ${\mathrm{MAPbI}}_3$ thin films for varying temperatures.

中文翻译：

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MAPbI3薄膜热分解反应动力学

尽管具有出色的光电性能，但金属卤化物钙钛矿尚未在商业应用中得到广泛应用。这主要是由于它们对若干外部因素（例如湿度、热、光和氧气）缺乏稳定性。尽管在过去十年中进行了广泛的研究，但关于它们的热稳定性的许多问题仍然存在，各种出版物提出了不同的方法来测量和量化它们的分解条件。然而，实验设置和报告值的差异使得报告结果的比较具有挑战性。我们展示了一种方法，其中${\mathrm{MAPbI}}_3$ 薄膜在高真空中在以下温度范围内发生热分解 $220{}^{\circ }\mathrm{C}$ 至 $250{}^{\circ }\mathrm{C}$，同时使用原位X 射线衍射装置监测晶体结构的变化。这个过程揭示了薄膜从${\mathrm{MAPbI}}_3$ 进入 ${铅}_2$. 然后使用三种不同的方法根据反应动力学评估时间分辨数据。首先，将 Arrhenius 拟合应用于$输入克$ 超过 $1/吨$，其中速率常数 $克$通过将一阶指数衰减拟合到最突出的衍射峰的减小峰面积上来确定。其次，使用模型拟合方法，其中数据针对一组不同的反应模型进行测试。最后，应用了无模型等转化方法。通过这样做，我们成功地表征了分解并确定了由活化能组成的动力学三重态$乙$, 频率因子 $\mathrm{一种}$, 和反应模型 $F\left(\alpha \right)$. 在动力学三元组的帮助下，分解反应可以用物理上有意义的方式表达，并允许我们预测分解动力学${\mathrm{MAPbI}}_3$ 适用于不同温度的薄膜。