CAREER: Integrated X-ray Ptychography and Optical Luminescence to Understand the Interplay between Local Structural Dynamics and Optoelectronic States

非技术性描述：太阳能电池和低成本发光二极管（LED）的大规模部署为减少当今能源技术对环境的影响提供了巨大的机会。卤化物钙钛矿提供了一个潜在的破坏性的低成本替代现有的传统半导体用于太阳能电池和LED现在。该项目开发了新的纳米级表征方法，以更好地了解这些新兴的卤化物钙钛矿材料如何生长，并帮助消除所得晶体中的缺陷。了解结晶和降解途径以合成高质量，坚固的卤化物钙钛矿薄膜可以促进其部署，以实现对能源足迹的全社会影响。作为这一努力的一部分，该项目纳入了一种系统的方法，以扩大代表性不足的少数民族在STEM中的参与，重点是光化学和纳米科学教育。教育活动吸引了高中、本科和研究生层次的学生，包括建立太阳能夏令营，当地高中学生在夏令营中制作和测试太阳能电池，培养对现代太阳能电池材料背后科学的理解，并使学生能够在科学前沿实践经验。技术描述：该项目研究了复杂卤化物钙钛矿中化学和结构的纳米级变化如何决定其稳定性。为此，该项目为纳米级的X射线表征增加了一个新的维度，通过测量光电材料在X射线照射下发出的光，即X射线激发的光学发光，提供对光电材料特性的深入了解。该项目团队开发了X射线激发光致发光和重叠关联技术在基于同步加速器的纳米探针X射线光束线上对卤化物钙钛矿的应用。使用这套纳米级表征技术，研究小组以最先进的空间分辨率量化了局部组成，结构和电子状态之间的关系。在一个迭代反馈的循环中，以提高钙钛矿晶体的质量和稳定性，该项目使用原位实验研究了卤化物钙钛矿材料的结晶和降解反应机制。该项目开发的工具具有灵活性和广泛的适用性，为同步洞察决定光电材料功能性能的电子、化学和结构性质之间的关系创造了一个强大的实验平台。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标准进行评估，被认为值得支持。

Nontechnical description: Large scale deployment of solar cells and low-cost light emitting diodes (LEDs) present an enormous opportunity to reduce the environmental impact of today's energy technologies. The halide perovskites offer a potentially disruptive lower-cost alternative to existing traditional semiconductors used in solar cells and LEDs now. This project develops new nanoscale characterization approaches to better understand how these emerging halide perovskite materials grow and help eliminate defects in the resulting crystals. Understanding crystallization and degradation pathways to synthesize high-quality, robust halide perovskite thin films can facilitate their deployment to achieve society-wide impacts on the energy footprint. As part of this effort, a systematic approach to broadening participation of underrepresented minorities in STEM with a focus on photovoltaics and nanoscience education is incorporated in this project. Educational activities engage students at the high school, undergraduate, and graduate levels, including establishing a Solar Summer Bootcamp, where local high school students fabricate and test solar cells, building an appreciation for the science behind modern solar cell materials and enabling students hands-on experience at the frontiers of science.Technical description: This project investigates how the nanoscale variations in chemistry and structure in complex halide perovskites determines their stability. To do so, this project adds a new dimension to X-ray characterization at the nanoscale, providing insight into optoelectronic material properties by measuring light given off by optoelectronic materials under X-ray irradiation, i.e. X-ray excited optical luminescence. The project team develops the application of X-ray excited optical luminescence and ptychography techniques to the halide perovskites at synchrotron-based nanoprobe X-ray beamlines. Using this suite of nanoscale characterization techniques, the research team quantifies the relationship between local composition, structure, and electronic states with state-of-the-art spatial resolution. In a cycle of iterative feedback to improve perovskite crystal quality and stability, the project examines the crystallization and degradation reaction mechanisms in the halide perovskite materials using in situ experiments. The flexibility and wide applicability of the tools developed in this project creates a powerful experimental platform for achieving synchronous insight into the relationship between the electronic, chemical, and structural properties that determine functional performance in optoelectronic materials.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.