NSF/DMR-BSF: Multiscale-Modeling and Raman Spectroscopy to Uncover Correlated Atomic Motions in Hybrid and Halide Perovskites

美国国家科学基金会和美国--以色列双国科学基金会(BSF)共同支持一名美国研究人员和一名以色列研究人员之间的合作。NSF材料研究部门为这一奖项提供资金，该部门支持有关材料如何吸收光、电子在吸收能量后的行为以及离子运动如何影响它们的研究和教育。许多重要的过程涉及光与物质的相互作用，包括太阳能转换、光探测和光学计算。这个项目结合了理论和实验的努力，使用最先进的调查技术来探索这些过程。PI和他的团队计划专注于混合钙钛矿，这是一种最近被证明具有良好的光伏性能的材料。尽管有这样的希望，但对这些材料将光转化为电的能力缺乏物理了解，阻碍了进一步的进展。理论工作包括材料的量子力学建模和模拟，旨在提供对这些材料中的电子态的深刻理解，以及对振动性质的理解。实验工作将围绕用光激发振动运动，揭示离子如何运动，以及离子运动如何受到温度、电场和先前光激发的影响。这些对振动的光谱研究将与理论和模型联系起来，以产生这些材料行为的完整图景。发展易于制造的高效光伏是一种迫切的社会需求。混合钙钛矿似乎正在走向商业认可，只是其良好性能背后的基本物理原理以及它们的进化和退化尚不清楚。该项目为理论凝聚态物理在评估材料性质和为广泛接受这项技术打开大门方面发挥重要作用提供了一个机会。这个项目还提供了独特的机会，通过公开讲座、课堂讨论和定制模块，到本科生、研究生和博士后水平的研究项目，以及两国和国际会议，吸引和培训下一代科学家在他们感兴趣的背景下应用复杂的凝聚态物理。美国的研究生将前往以色列，在以色列PI的小组进行研究。技术摘要美国国家科学基金会和美国-以色列双国科学基金会(BSF)共同支持美国研究人员和以色列研究人员的这一合作。美国国家科学基金会材料研究部资助了这一奖项，该奖项支持发现和了解卤化物(以及有机-无机混合)钙钛矿(HOIP)材料中相关离子运动的研究和教育。这类材料已显示出作为下一代光伏材料的巨大潜力。尽管有这样的希望，但对这些材料将光转化为电的能力缺乏物理了解，阻碍了进一步的进展。离子运动在这些材料的性质演化中起着关键作用，它被认为在异常有利的激发载流子动力学和寿命中起着关键作用。PI提出了理论建模和目标拉曼光谱，以揭示和合理的一系列离子运动，包括谐和非简谐声子，初始极序数，以及不同长度和时间尺度上的其他相关离子运动。第一性原理计算将提供对原子间相互作用和短期动力学特征的洞察。更长的时间尺度将通过分子动力学获得，并将使用一套关联函数工具进行分析。拉曼光谱将探测离子运动，并确认和扩展理论解释。具体活动包括：i)揭示和分析杂化钙钛矿和卤化物钙钛矿中的相关离子运动和极性有序的开始；ii)温度和电场对动态和静态有序的影响；iii)氢键和结构有序；iv)光照诱导的结构有序和无序；v)极性有序和拉什巴效应。混合钙钛矿似乎正在走向商业认可，只是其良好性能背后的基本物理原理以及它们的进化和退化尚不清楚。该项目为理论凝聚态物理在评估材料性质和打开广泛接受这项技术的大门方面发挥重要作用提供了一个机会。这个项目将在不同的科学学科之间建立联系，包括晶体固体、液体和分子材料，并将开发材料的拉曼光谱询问和复杂离子行为的关联函数理论分析的新技术。该项目还提供了独特的机会，通过公开讲座、课堂讨论和定制模块，到本科生、研究生和博士后水平的研究项目，以及两国和国际会议，吸引和培训下一代科学家在他们感兴趣的背景下应用复杂凝聚态物理。这些美国研究生将前往以色列，在以色列派的小组进行研究。

NONTECHNICAL SUMMARYThe National Science Foundation and the United States -- Israel Binational Science Foundation (BSF) jointly support this collaboration between a US-based researcher and an Israel-based researcher. The NSF Division of Materials Research funds this award, which supports research and education on how materials absorb light, how electrons behave after absorbing that energy, and how ionic motions can influence them. Many important processes involve interactions of light with matter, including solar energy conversion, light detection, and optical computing. This project brings together theoretical and experimental efforts to explore these processes using state-of-the-art investigational techniques. The PI and his group plan to focus on hybrid perovskites, materials that have recently been shown to have promising photovoltaic properties. Despite this promise, the lack of physical understanding of the ability of these materials to convert light to electricity impedes further progress. The theoretical work includes quantum mechanical modeling of materials and simulations, aiming to provide a deep understanding of the electronic states in these materials, as well as an understanding of the vibrational properties. The experimental work will center around using light to excite vibrational motions, revealing how the ions move, and how the ionic motions are affected by temperature, electric field, and previous light excitation. These spectroscopic studies of the vibrations will be connected to the theory and modeling to produce a complete picture of the behavior of these materials. The advancement of highly efficient photovoltaics that are easy to fabricate is a compelling societal need. The hybrid perovskites appear to be moving toward commercial acceptance, except that the basic physics behind their favorable properties and their evolution and degradation are not understood. This project represents an opportunity for theoretical condensed matter physics to play a vital role in assessing material properties and in opening the gateway to widespread acceptance of this technology. This could provide a wide range of societal dividends from improved and less expensive photovoltaics to sensors and optical computing elements.This project also offers unique opportunities for engaging and training the next generation of scientists to apply complex condensed-matter physics in a context of compelling interest to them, through venues ranging from public lectures, in-class discussions and tailored modules, to research projects at the undergraduate, graduate, and postdoctoral levels, and binational and international conferences. The US-based graduate students will travel to Israel to carry out research at the Israeli PI's group.TECHNICAL SUMMARY The National Science Foundation and the United States -- Israel Binational Science Foundation (BSF) jointly support this collaboration between a US-based researcher and an Israel-based researcher. The NSF Division of Materials Research funds this award, which supports research and education on uncovering and understanding the correlated ionic motions in halide (and hybrid organic-inorganic) perovskite (HOIP) materials. This class of materials has shown enormous potential as next-generation photovoltaic materials. Despite this promise, the lack of physical understanding of the ability of these materials to convert light to electricity impedes further progress. Ionic motion plays a key role in the property evolution of these materials, and it has been proposed to play a signature role in the anomalously favorable excited-carrier dynamics and lifetime.The PIs propose theoretical modeling and targeted Raman spectroscopy to reveal and rationalize a range of ionic motions, including harmonic and anharmonic phonons, incipient polar order, and other correlated ionic motions on various length- and time-scales. First-principles calculations will provide insight into interatomic interactions and short-time dynamical features. Longer time scales will be accessed via molecular dynamics and will be analyzed with a suite of correlation function tools. Raman spectroscopy will probe ionic motions and confirm and extend theoretical interpretations. Specific activities include: i) revealing and analyzing correlated ionic motions and the onset of polar order in the hybrid and halide perovskites; ii) the effect of temperature and electric field on dynamic and static ordering; iii) hydrogen bonding and structural ordering; iv) illumination-induced structural ordering and disordering; v) polar ordering and the Rashba effect.The advancement of highly efficient photovoltaics that are easy to fabricate is a compelling societal need. The hybrid perovskites appear to be moving toward commercial acceptance, except that the basic physics behind their favorable properties and their evolution and degradation are not understood. This project represents an opportunity for theoretical condensed matter physics to play a vital role in assessing material properties and opening the gateway to widespread acceptance of this technology. This project will make connections between disparate scientific disciplines including crystalline solids, liquids, and molecular materials, and will develop new techniques for Raman spectroscopic interrogation of materials and correlation function theoretical analysis of complex ionic behaviors.This project also offers unique opportunities for engaging and training the next generation of scientists to apply complex condensed-matter physics in a context of compelling interest to them, through venues ranging from public lectures, in-class discussions and tailored modules, to research projects at the undergraduate, graduate, and postdoctoral levels, and binational and international conferences. The US-based graduate students will travel to Israel to carry out research at the Israeli PI's group.