Determination of Thermal Expansion Coefficients and Locating the Temperature-Induced Phase Transition in Methylammonium Lead Perovskites Using X-ray Diffraction
Determination of Thermal Expansion Coefficients and Locating the Temperature-Induced Phase Transition in Methylammonium Lead Perovskites Using X-ray Diffraction
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DOI：
10.1021/acs.inorgchem.5b01481
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发表时间：
2015-11-16
影响因子：
4.6
通讯作者：
Edvinsson, Tomas
中科院分区：
文献类型：
--
作者：
Jacobsson, T. Jesper;Schwan, L. Josef;Edvinsson, Tomas
铅卤钙钛矿，特别是甲基铵铅碘，CH3NH3PbI3，最近作为替代太阳能电池材料引起了人们的极大兴趣，并且创纪录的太阳能电池效率现已超过 20%。然而，人们对甲基铵碘铅的热稳定性提出了担忧，并且据报道在高温下会发生从四方相到立方相的相变。在这里，我们使用温度相关的 X 射线衍射测量详细研究了这种相变。相变温度精确到 54 摄氏度，完全在典型太阳能电池的正常工作范围内。提取电池参数作为温度的函数，从中计算热膨胀系数。对于四方相和立方相，后者被发现相当高（alpha(v) = 1.57 X 10(-4) K-1）。这比钠钙玻璃和 CIGS 的热膨胀系数高 6 倍，比 CdTe 的热膨胀系数高 11 倍。这对于钙钛矿太阳能电池在正常昼夜操作下经历的温度循环中的机械稳定性可能具有重要意义。在对这些系统进行密度泛函理论模拟以提供更准确的能带结构计算时，热膨胀系数的实验知识和电池参数的精确确定也可能很有价值。
Lead halogen perovskites, and particularly methylammonium lead iodine, CH3NH3PbI3, have recently attracted considerable interest as alternative solar cell materials, and record solar cell efficiencies have now surpassed 20%. Concerns have, however, been raised about the thermal stability of methylammonium lead iodine, and a phase transformation from a tetragonal to a cubic phase has been reported at elevated temperature. Here, this phase transition has been investigated in detail using temperature-dependent X-ray diffraction measurements. The phase transformation is pinpointed to 54 degrees C, which is well within the normal operating range of a typical solar cell. The cell parameters were extracted as a function of the temperature, from which the thermal expansion coefficient was calculated. The latter was found to be rather high (alpha(v) = 1.57 X 10(-4) K-1) for both the tetragonal and cubic phases. This is 6 times higher than the thermal expansion coefficient for soda lime glass and CIGS and 11 times larger than that of CdTe. This could potentially be of importance for the mechanical stability of perovskite solar cells in the temperature cycling experienced under normal day night operation. The experimental knowledge of the thermal expansion coefficients and precise determination of the cell parameters can potentially also be valuable while conducting density functional theory simulations on these systems in order to deliver more accurate band structure calculations.