SusChEM: Atomic Structure and Dynamic Behaviors of Extended Defects in Earth-Abundant Solar-Cell Materials

非技术描述：太阳能电池材料CZTS由低成本、地球上丰富的元素Cu、Zn、Sn、S和Se制成。开发高效CZTS太阳能电池的挑战包括控制杂质和缺陷。该项目的目的是获得原子结构的基本理解和CZTS缺陷的局部性质在电和光激发下，使用国家的最先进的透射电子显微镜（TEM）结合新的原位TEM方法在主要研究者的实验室开发。这些新技术将使我们能够直接探测单个缺陷的原子结构以及这些缺陷对所施加的电场和/或光照射的响应，从而确定单个缺陷的原子尺度结构-性质关系。其结果将是优化材料的微观结构和成分所需的知识，推动太阳能技术性能改善的低成本和可持续材料的开发。 此外，该项目还为当今工业和学术研究所需的本科生和研究生的跨学科教育和培训提供了广泛的机会。技术说明：该项目将使用先进的像差校正透射电子显微镜（TEM）和新型原位TEM技术相结合，研究地球上丰富的太阳能电池材料的结构和动态行为。本论文主要研究了铜锌锡合金Cu2ZnSn（S，Se）4（CZTS）薄膜，它是一种替代Cu（In，Ga）Se2（CIGS）的候选材料。由于CZTS薄膜的多晶性质和多种杂质相的共存，理解缺陷和界面在控制电性能和太阳能转换效率中的作用是至关重要的，但也是非常具有挑战性的。在这个项目中，PI结合了最先进的像差校正TEM成像，光谱学和他的实验室最近开发的新的原位技术，以研究CZTS材料中单个缺陷，晶界和界面的原子结构和动态行为。空间分辨阴极发光和扫描隧道显微镜支架与光激发相结合，结合全息术和电子能量损失谱（EELS），用于识别缺陷的活性和非活性区域（晶界、界面、二次相界等），而相同区域的原子结构、化学组成和局部电子性质通过TEM成像和具有原子分辨率的光谱确定。结合从相同材料测量的光电特性，可以理解缺陷在控制材料特性中的作用。

Nontechnical Description: The solar-cell material CZTS is made of the low-cost, Earth-abundant elements Cu, Zn, Sn, S, and Se. Challenges to the development of high-efficiency CZTS solar cells include control of impurities and defects. This project is designed to gain a fundamental understanding of the atomic structure and local properties of defects in CZTS under electrical and optical excitations, using state-of-the-art transmission electron microscopy (TEM) in combination with novel in-situ TEM methods developed in the Principle Investigator's lab. These new techniques will allow us to directly probe the atomic structure of individual defects and the responses of those defects to an applied electric field and/or light illumination providing for the determination of the atomic scale structure-property relationships of individual defects. The result will be knowledge needed for the optimization of the material's microstructure and composition, advancing the development of low-cost and sustainable materials with improved properties for solar energy technology. In addition, this project provides a wide range of opportunities for the interdisciplinary education and training of undergraduate and graduate students needed in both industry and academic research today.Technical Description: This SusChEM project is to study the structure and dynamic behaviors of Earth-abundant solar-cell materials using a combination of advanced aberration-corrected transmission electron microscopy (TEM) and novel in-situ TEM techniques. The research primarily focuses on thin films of kesterite Cu2ZnSn(S,Se)4 (CZTS), a candidate material to replace Cu(In,Ga)Se2 (CIGS). Because of the polycrystalline nature and the co-existence of multiple impurity phases in CZTS thin films, it is critical, but very challenging to understand the role of defects and interfaces in controlling the electrical properties and solar conversion efficiency. In this project, the PI combines the state-of-the-art aberration-corrected TEM imaging, spectroscopy, and the novel in-situ techniques recently developed in his lab to study the atomic structure and dynamic behaviors of individual defects, grain boundaries, and interfaces in CZTS materials. Spatially resolved cathode-luminescence and scanning tunneling microscopy holders with optical excitation, combined with holography and electron energy-loss spectroscopy (EELS), are used to identify the active and inactive regions of defects (grain boundaries, interfaces, secondary phase boundaries, etc.), while the atomic structure, chemical composition and local electronic properties of the same regions are determined by TEM imaging and spectroscopy with atomic resolution. In combination with the optoelectronic properties measured from the same material, the role of defects in controlling the materials properties can be understood.