Meeting Program — November 2012
Jason B. Baxter
Department of Chemical and Biological Engineering
Abstract — The sunlight incident on the earth provides 10,000 times more power than is needed to meet global demand. However, converting this energy into electricity or fuels efficiently and cost effectively remains a great challenge. Nanostructured solar cells present opportunities to inexpensively convert sunlight to electricity through the use of architectures tailored on the nanometer to micrometer length scale. Planar solar cells are subject to opposing constraints where thick films are required for light absorption while thinner films are desirable for efficient charge separation. Extremely thin absorber (ETA) solar cells can decouple these constraints by using a thin absorber at the interface between highly structured p- and n-type layers. In this talk, I will describe our work on ETA solar cells that use a thin CdSe coating on a ZnO nanowire array to absorb light and inject electrons into the oxide. Rational design of these architectures requires control over morphology and microstructure of the materials, as well as knowledge of material properties such as photoexcited carrier lifetimes and mobilities. Our approach utilizes a combination of solar cell measurements and ultrafast transient absorption spectroscopy to understand the effects of CdSe thickness, annealing conditions, and interfacial treatments on the dynamics and efficiency of charge carrier separation, and ultimately on the solar-to-electric energy conversion efficiency. These studies provide guidelines for architecture design and materials selection for ETA solar cells.
Dr. Baxter’s current research interests are in designing, fabricating, and probing semiconductor nanomaterials and thin films for solar energy conversion. Most current efforts focus on solar-to-electric energy conversion, but the group has growing interest in photocatalytic water splitting for clean and renewable hydrogen production. Various projects in the group include extremely thin absorber solar cells, organic solar cells, microreactor deposition of graded thin films for high-throughput characterization, and ultrafast pump-probe spectroscopy to measure charge carrier dynamics. The general focus of the group is on striving to understand how materials and interfaces affect device performance, and how these materials and interfaces can be controlled during the fabrication process. Low-temperature solution processing methods are used whenever possible to provide a pathway to low-cost, scalable manufacturing.
Dr. Baxter advises a group of 4 PhD students, 2 MS students, and 8 BS students. He has published nearly 25 papers, which have collectively garnered well over 1000 citations. He has been awarded over $1 million in funding as lead investigator and another $3 million as co-investigator. He received the NSF CAREER Award in 2009.