Marin-Villa Pelayo, Gaboardi Mattia, Joseph Boby, Alabarse Frederico, Armstrong Jeff, Drużbicki Kacper, Fernandez-Alonso Felix
Materials Physics Center, CSIC-UPV/EHU, Paseo de Manuel Lardizabal, 5, 20018 Donostia - San Sebastian, Spain.
C.S.G.I. and Chemistry Department, University of Pavia, Viale Taramelli 16, 27100 Pavia, Italy.
J Phys Chem Lett. 2025 Jan 9;16(1):184-190. doi: 10.1021/acs.jpclett.4c03336. Epub 2024 Dec 23.
Hybrid perovskites exhibit complex structures and phase behavior under different thermodynamic conditions and chemical environments, the understanding of which continues to be pivotally important for tailoring their properties toward improved operational stability. To this end, we present for the first time a comprehensive neutron and synchrotron diffraction investigation over the pressure-temperature phase diagram of the paradigmatic hybrid organic-inorganic perovskite methylammonium lead iodide (MAPbI). This ambitious experimental campaign down to cryogenic temperatures and tens of kilobars was supported by extensive molecular dynamics simulations validated by the experimental data, to track the structural evolution of MAPbI under external physical stimuli at the atomic and molecular levels. These combined efforts enable us to identify the mechanisms underpinning structural phase transitions, including those exhibiting negative thermal expansion across the boundary between the cation-ordered low-temperature phase and the dynamically disordered high-pressure cubic phase. Our results bring to the fore how pronounced octahedral distortions at high pressures ultimately drive the structural collapse and amorphization of this material.
杂化钙钛矿在不同的热力学条件和化学环境下呈现出复杂的结构和相行为，对其的理解对于调整其性能以提高操作稳定性仍然至关重要。为此，我们首次对典型的有机-无机杂化钙钛矿甲基碘化铅（MAPbI）的压力-温度相图进行了全面的中子和同步加速器衍射研究。这项雄心勃勃的实验研究涵盖了低温至数十千巴的范围，并得到了由实验数据验证的广泛分子动力学模拟的支持，以在原子和分子水平上跟踪MAPbI在外部物理刺激下的结构演变。这些共同努力使我们能够确定结构相变的基础机制，包括那些在阳离子有序低温相和动态无序高压立方相之间的边界上表现出负热膨胀的机制。我们的结果凸显了高压下明显的八面体畸变最终如何导致这种材料的结构坍塌和非晶化。
