Chapter 5: Optoelectronics and Photovoltaics

Joseph Shinar, Senior Physicist at the Ames Laboratory, Professor and Chair of the Department of Physics and Astronomy, and Professor of Electrical and Computer Engineering at Iowa State University, discussed five critical materials or families of materials in optoelectronic technologies: erbium-doped fiber amplifiers, which are critical components of the repeaters in optical fiber networks; solid-state lasers based on lanthanide dopants in yttrium aluminum garnet, which are used extensively in spectroscopy and laser lithotripsy; indium in various ubiquitous III-V devices; transparent conducting indium tin oxide films, which are currently behind virtually 100 percent of all displays and figure similarly in the emerging organic light-emitting diode (OLED)-based solid-state lighting paradigm; and heavy rare earth elements which are currently critical for efficient OLED-based displays. He described examples highlighting the importance, availability, and estimated amounts of these metals that will be needed as these technologies mature and pervade the world economy in the coming decades.

Ken Zweibel, Director of the George Washington University Solar Institute, discussed the rapidly dropping cost and increasing use of photovoltaic (PV) solar cells and prospects for further expansion of these materials. The most important materials that are needed to produce solar power today include silicon, silver, tellurium, and cadmium. Emerging technologies could require significant quantities of indium, selenium, molybdenum, gallium, germanium, arsenic, and ruthenium. Some of these materials have supply or cost issues, which has spurred interest in developing strategies to reduce the amounts of materials needed to effectively produce electricity. New sources and additional refining capacity will be essential if demand for these materials greatly increases.

Chapter 6: Critical Materials in Large-Scale Battery Applications

David Bradwell, Chief Technology Officer at Liquid Metal Battery Corporation and Visiting Scientist at the Massachusetts Institute of Technology, explained that batteries designed for grid-scale energy storage applications face a unique set of material selection challenges. Whereas many other power technologies can improve performance via enhanced material microstructure or device design optimization, the energy capacity of a battery is directly related to the amount of active material. For broad-scale energy-intensive applications, this means the active materials must be inherently low cost and sufficiently abundant. Interestingly, the cost of the raw active materials is not always the primary cost driver; thus, to more fully evaluate the opportunity for emerging storage technologies, the entire system must be considered. A host of new battery technologies—including a set of liquid metal battery projects—are being pursued at universities, startup companies, and large well-established corporations across the country.

Jay Whitacre, Chief Technology Officer of Aquion and Professor of Engineering and Public Policy at Carnegie Mellon University, looked at battery technologies for energy applications, including lithium-ion and aqueous electrolyte batteries. The adoption of lithium-ion battery technology is, as of this workshop, not constrained by materials. Rather, it is constrained by the way the materials function and the complexity of the device itself. In contrast, low-cost, low-energy-density, and long-lifetime batteries could serve as a feasible and economic means of energy storage.

Chapter 7: General Observations

The final chapter compiles some general observations made by the individual workshop speakers that apply broadly to critical materials and the role of the chemical sciences in addressing these issues.

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