Infrared Electro-Optical Spectroscopy of Degradation Pathways in Organo-Halide Perovskite Photovoltaics

化学系的化学结构、动力学和机制（CSDM-A）项目支持宾夕法尼亚州立大学的John Asbury教授使用傅里叶变换红外光谱结合电子技术来检查新兴光伏材料中被称为有机卤化物钙钛矿的缺陷的化学起源。这些光伏材料代表了一种极具潜力的廉价高效太阳能电池，是发展不依赖化石燃料的可持续能源经济的优先事项。然而，这些材料的长期稳定性受到缺陷形成的限制。利用电子技术和红外光谱相结合，可以识别导致缺陷的化学物质。这些信息反过来可以指导合成策略的发展，以消除缺陷，从而产生更稳定和更高效率的太阳能电池。PI还计划通过使用太阳能电池模型，让代表性不足的中学生和高中生参与这项研究项目，他们将利用假设、实验和评估的科学过程，探索与太阳能技术直接相关的科学挑战的可能解决方案。该项目的技术目标是利用红外探测导纳光谱，结合电荷陷阱能量分布的电学信息和傅立叶变换红外光谱中产生这些陷阱的分子种类的结构信息，来检查有机卤化物钙钛矿中的电荷陷阱。传统的电表征技术提供了材料中电荷陷阱的密度和能量分布的信息，但不能揭示这些陷阱的化学起源的结构信息。虽然傅里叶变换红外光谱可以通过测量材料的振动频率来提供材料的结构信息，但这种技术通常测量材料的大部分成分，而不能捕获代表少数成分的缺陷的振动光谱。通过结合这些技术，该项目将提供电荷阱能量分布和密度的直接测量，以及引起这些缺陷的化学物质的结构信息。有机卤化物钙钛矿光伏材料的化学结构、组成和制备的系统变化将使人们能够从根本上理解这些有前途的材料的电子结构如何取决于它们潜在的化学和形态特性。这些测量旨在解决关键的科学挑战，这些挑战对于实现更高效、更稳定的钙钛矿太阳能电池至关重要。

With this award, the Chemical Structure, Dynamics, and Mechanisms (CSDM-A) Program of the Division of Chemistry is supporting Professor John Asbury at Penn State University to use Fourier transform infrared spectroscopy combined with electrical techniques to examine the chemical origins of defects in an emerging class of photovoltaic materials known as organo-halide perovskites. These photovoltaic materials represent a promising class of potentially inexpensive and highly efficient solar cells - a high priority for development of a sustainable energy economy that does not rely on fossil fuels. However, the long-term stability of these materials is limited by the formation of defects. The use of electrical techniques combined with infrared spectroscopy enables the identification of chemical species that cause the defects. This information in turn can guide the development of synthetic strategies to eliminate defects, resulting in more stable and higher efficiency solar cells. The PI also plans to engage underrepresented middle school and high school students in this research project through the use of solar cell models by which they will use the scientific process of hypothesis, experiment and evaluation to explore possible solutions to scientific challenges that have direct bearing on solar energy technologies.The technical objective of this project is to examine charge-trapping in organo-halide perovskites using infrared-detected admittance spectroscopy that combines electrical information about charge trap energetic distributions with structural information about the molecular species that give rise to those traps from Fourier transform infrared spectroscopy. Traditional electrical characterization techniques provide information about the density and energetic distribution of charge traps in materials but do not reveal structural information about the chemical origins of such traps. While Fourier transform infrared spectroscopy can provide structural information about materials through measurement of their vibrational frequencies, this technique typically measures the majority component of a material and is not able to capture the vibrational spectra of defects, which represent a minority component. By combining these techniques, this project will provide direct measurements of charge trap energetic distributions and densities along with structural information about the chemical species that give rise to those defects. Systematic variation of the chemical structure, composition, and preparation of organo-halide perovskite photovoltaic materials will enable fundamental understanding of how the electronic structure of these promising materials depends on their underlying chemical and morphological properties. These measurements seek to address key scientific challenges that are important for realizing more efficient and stable perovskite solar cells.