CAREER: Structural dynamics and optoelectronics of anharmonic soft semiconductors

非技术描述金属卤化物钙钛矿是一类有前途的材料，具有太阳能电池和发光二极管等器件应用。它们卓越的电子性能与廉价的低温溶液处理相结合。这种组合是令人惊讶的，因为缺陷可以在膜形成期间或通过杂质引入。这个CAREER项目的动机是需要更好地了解这些材料，并推进软半导体的科学和技术。理解卤化物钙钛矿特殊性质的关键在于它们的结构动力学，即组成材料的原子如何通过振动相互作用。与传统半导体不同，卤化物钙钛矿中的结构动力学是非谐的，由软晶格中的长程和阻尼非线性相互作用引起。本研究项目旨在建立关于软半导体如何在极端晶格非谐性下发挥作用的基本概念。PI将研究这些材料与先进的光学和振动光谱的组合，再加上计算建模。在这项研究中开发的见解将有助于理解这些新兴材料中的集体运动，并实现其定制。该项目的教育重点包括并利用计算的兴起来进行物理化学的教学和学习。计算作为一种媒介和方法将被纳入教学，课程和课外项目，以及学生的研究。PI还将探索科学数据的可视化和声音化，以弥合科学和艺术，将其带给学生和公众。技术说明这项研究计划的重点是金属卤化物钙钛矿，一个相对较新的一类软半导体与传统的准谐波半导体形成鲜明对比强烈的非谐结构动力学。在这个未知的领域，我们需要重新思考电子和结构自由度如何相互耦合。在我们的理解存在的差距，要求基本的知识和新的概念，以充分认识的起源，程度和后果的软非谐晶格在光电材料。为了弥合这些差距，PI试图量化普遍的晶格非谐性及其对卤化物钙钛矿软半导体中电荷载流子弛豫的影响;表征卤化物钙钛矿软半导体中的铁弹畴壁光电子学;并识别新的二维和分子软半导体。该项目的特点是在多个时间和长度尺度上进行相关的光谱研究。太赫兹频率晶格动力学将被探测和相关的光学范围内的电子跃迁以及在静态极限的弹性性能。重点将放在从金属卤化物钙钛矿中提取通用设计原则并将这些见解推广到其他新兴材料上。该项目由电子和光子材料计划和刺激竞争研究的既定计划（EPSCoR）共同资助该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查进行评估，被认为值得支持的搜索.

Nontechnical DescriptionMetal halide perovskites are a promising class of materials with device applications such as solar cells and light-emitting diodes. Their exceptional electronic properties are coupled with inexpensive, low-temperature solution processing. This combination is surprising, given that defects can be introduced during film formation or through impurities. This CAREER project is motivated by the need to better understand these materials and to advance the science and technology of soft semiconductors. The key to understanding the exceptional properties of halide perovskites lies with their structural dynamics, that is, how atoms composing a material interact with one another through vibrations. Unlike conventional semiconductors, structural dynamics in halide perovskites are anharmonic, arising from long-ranged and damped nonlinear interactions in a soft lattice. This research project aims to establish fundamental concepts as to how soft semiconductors function with extreme lattice anharmonicity. The PI will investigate these materials with a combination of advanced optical and vibrational spectroscopy, coupled with computational modeling. Insights developed in this research will help to comprehend collective motions in these emerging materials and enable their customization. The educational focus of this project embraces and leverages the rise of computation for the teaching and learning of physical chemistry. Computation as a medium and approach will be incorporated into instruction, curricular and extracurricular projects, and student research. The PI will also explore the visualization and sonification of scientific data to bridge science and art, bringing this to students and the general public.Technical DescriptionThis research proposal focuses on metal halide perovskites, a relatively new class of soft semiconductors with strongly anharmonic structural dynamics in sharp contrast to conventional quasi-harmonic semiconductors. In this yet uncharted territory, we need to rethink how electronic and structural degrees of freedom couple with each other. Gaps in our understanding exist that call for basic knowledge and new concepts to fully appreciate the origin, extent, and consequence of a soft anharmonic lattice in optoelectronic materials. To bridge these gaps, the PI seeks to quantify universal lattice anharmonicity and its impact on charge carrier relaxation in halide perovskite soft semiconductors; characterize ferroelastic domain wall optoelectronics in halide perovskite soft semiconductors; and identify new two-dimensional and molecular soft semiconductors. The project features correlated spectroscopic investigations across multiple time and length scales. Terahertz frequency lattice dynamics will be probed and correlated to optical range electronic transitions as well as elastic properties in the static limit. Emphasis will be placed on distilling universal design principles from metal halide perovskites and generalizing these insights to other emerging materials.This project is jointly funded by the Electronic and Photonic Materials program and the Established Program toStimulate Competitive Research (EPSCoR).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.