Šimėnas Mantas, Balčiu Nas Sergejus, Mączka Mirosław, Banys Ju Ras, Tornau Evaldas E
Faculty of Physics, Vilnius University , Sauletekio 3, LT-10257 Vilnius, Lithuania.
Institute of Low Temperature and Structure Research, Polish Academy of Sciences , P.O. Box-1410, PL-50-950 Wroclaw 2, Poland.
J Phys Chem Lett. 2017 Oct 5;8(19):4906-4911. doi: 10.1021/acs.jpclett.7b02239. Epub 2017 Sep 26.
The high power conversion efficiency of the hybrid CHNHPbX (where X = I, Br, Cl) solar cells is believed to be tightly related to the dynamics and arrangement of the methylammonium cations. In this Letter, we propose a statistical phase transition model which accurately describes the ordering of the CHNH cations and the whole phase transition sequence of the CHNHPbI perovskite. The model is based on the available structural information and involves the short-range strain-mediated and long-range dipolar interactions between the cations. It is solved using Monte Carlo simulations on a three-dimensional lattice allowing us to study the heat capacity and electric polarization of the CHNH cations. The temperature dependence of the polarization indicates the antiferroelectric nature of these perovskites. We support this result by performing pyrocurrent measurements of CHNHPbX (X = I, Br, Cl) single crystals. We also address the possible occurrence of the multidomain phase and the ordering entropy of our model.
混合CHNHPbX（其中X = I、Br、Cl）太阳能电池的高功率转换效率被认为与甲铵阳离子的动力学和排列紧密相关。在本信函中，我们提出了一个统计相变模型，该模型准确描述了CHNH阳离子的有序化以及CHNHPbI钙钛矿的整个相变序列。该模型基于现有的结构信息，涉及阳离子之间的短程应变介导和长程偶极相互作用。通过在三维晶格上进行蒙特卡罗模拟来求解该模型，这使我们能够研究CHNH阳离子的热容和电极化。极化的温度依赖性表明这些钙钛矿具有反铁电性质。我们通过对CHNHPbX（X = I、Br、Cl）单晶进行热电流测量来支持这一结果。我们还讨论了多畴相的可能出现以及我们模型的有序熵。
