BaSnO3 as a Transparent Mixed Ionic-Electronic Conducting Material - Utilizing Novel In Situ Methods to Advance Understanding of Structure-Processing-Property Relations

Massachusetts Institute Of Technology, Cambridge MA

Investigators

Abstract

NON-TECHNICAL DESCRIPTION: Barium tin oxide (BaSnO3) is a remarkable new material and a prime candidate for the much-needed replacement of low-abundance, but presently critical indium-based transparent electrodes for solar cell and display technologies. Additionally, this material, when appropriately chemically modified, is well-suited to serve as a model system for studying the role of defects in influencing the performance of mixed ionic-electronic conducting electrodes in, for example, solid oxide fuel cells, noted for their high chemical-to-electrical energy conversion efficiencies. Novel in situ high temperature measurements are being employed to explore defect formation and transport and the effects of microstructure on the electrical, electrochemical and optical properties of barium tin oxide, as well as exploring and optimizing its thin film growth. Insights gained will aid in developing more robust transparent and mixed conductive electrodes for solar and fuel cell applications and generally provide critical insights into how variations in growth parameters impact the chemistry and morphology of functional thin films and thereby their properties. A science, technology, engineering & mathematics (STEM) project-based course for high school students, drawn from both inner city and suburban schools, with a focus on minority and female students, is developed and implemented, in conjunction with a high school teacher/ teacher-training faculty member, on the topic of clean energy and environmental technologies, to improve their scientific understanding of pressing global issues and stimulate them to consider STEM careers. Research internships, are offered to undergraduate students from the science and engineering disciplines, to provide them with the opportunity to experience research in action. TECHNICAL DETAILS: The electrical, electrochemical and optical behavior of acceptor- and donor-doped barium tin oxide, a prime candidate for the much needed replacement of low-abundance transparent electrodes for solar cells, are being investigated over a wide range of temperature and oxygen partial pressure. Novel in situ characterization methods allow for development of quantitative defect and transport models for donor- and acceptor-doped materials, vital steps towards their practical utilization as a transparent or mixed ionic-electronic conducting materials. A novel method for monitoring film growth in situ will allow for the efficient optimization of film growth, microstructure and properties of these, and ultimately all physical vapor deposited films, with respect to deposition conditions. Additional focus is placed on quantifying and explaining the significant impact of grain boundaries on the effective electron mobility of transparent conductive barium tin oxide. This research approach provides an excellent opportunity for the designated graduate student to learn cutting edge experimental and modeling techniques and gain a broader appreciation of how materials research can address society's major challenges.