Non-Toxic, Low-Temperature Preparations of Earth-Abundant Nanocrystal Inks for High-Efficiency Photovoltaic Modules
Amy L. Prieto, associate professor of chemistry, Colorado State University, hopes to achieve a goal for researchers set by the U.S. Department of Energy. The DOE has called for photovoltaic technology that produces electricity at $1 per watt, including installation costs. In her attempt to reach this goal, while funded by a $100,000 Scialog grant from RCSA, Prieto is focused on making nanocrystals – exceptionally tiny particles—composed of a copper, tin and zinc compound derived from the relatively common mineral kesterite. The nanocrystals Prieto is investigating have exhibited photovoltaic abilities; that is, when struck by the photons in sunlight, atoms in the crystals can generate electricity. By suspending the crystals in a special liquid, Prieto hopes to create an “ink” that can be spread across a thin film surface, which would be, in theory, a less expensive way to make thin film of this material as compared to traditional silicon processing. While kesterite is a common, fairly low-cost material, the processing to convert it into a photovoltaic material currently requires toxic solvents and a high-temperature process called annealing. Prieto aims to design and build a system that will avoid the dangerous – and somewhat expensive – processing. She plans to do this by coating the nanocrystals in a copper-and-selenium compound. When exposed to air, this compound becomes what is called a “superionic conductor,” which basically means that it is good at moving ions, and at the same time becomes reasonably electronically conductive. “If this work is successful, we may be able to reduce the manufacturing costs of thin film solar cells significantly, while still achieving reasonable efficiencies,” Prieto said.