Three awards from US Department of Energy to fuel UW solar cell research

Three teams led by University of Washington researchers have received competitive awards totaling more than $2.3 million from the U.S. Department of Energy Solar Energy Technologies Office for projects that will advance research and development in photovoltaic materials, which are an essential component of solar cells and impact the amount of sunlight that is converted into electricity.

The UW teams are led by Scott Dunham, a professor of electrical and computer engineering; Hugh Hillhouse, a professor of chemical engineering; and Devin MacKenzie, an associate professor of both mechanical engineering and materials science and engineering. All are also researchers with the UW-based Clean Energy Institute, and MacKenzie serves as director of the institute's Washington Clean Energy Testbeds. Dunham and Hillhouse are also members of the UW Molecular Engineering & Sciences Institute.

Hillhouse and MacKenzie are leading projects to explore the properties and manufacturing potential of thin-film perovskites. These are printable crystalline compounds that are able to harvest photons at power conversion efficiencies almost equal to silicon-based semiconductors used in today's solar cells, but at lower costs. But before perovskites can have a global impact on solar energy, researchers need to improve their stability and develop improved, scalable manufacturing methods.

Hillhouse's project, awarded $1.5 million, will focus on understanding how the composition, structure, and environmental exposure of pervoskites can affect their stability and performance. This project will apply new photoluminescence imaging and video methods to combinatorial material libraries, which were fabricated at a facility built by Hillhouse with funding from the M.J. Murdock Charitable Trust. His team will use machine learning methods to extract new information from these extremely large datasets, which could reveal the fundamental connections between nanoscopic and microscopic material features and macroscopic solar cell performance and stability. UW partners in this work are Marina Meila, professor of statistics, and David Beck, director of research at the UW's eScience Institute and research associate professor of chemical engineering.

MacKenzie's project, awarded nearly $200,000, focuses on perovskite manufacturing using roll-to-roll processing techniques. In the solar energy field, roll-to-roll processing involves additively printing and coating ultra-thin solar-cell components "” including thin-film perovskites "” directly onto rolls of flexible material, much like applying paint to a wall or printing out a document. MacKenzie's team will analyze the effectiveness of different techniques for depositing perovskite onto the rolls by rapidly analyzing the films as they are being printed. They will use optical probes and photoluminescence techniques to gather data on how well various roll-to-roll-produced perovskites interact with light. They can use this data to change the ways perovskites are deposited in roll-to-roll processing to manufacture higher-quality, flexible solar cells more efficiently, as well as at the production scales needed to make an economic and environmental impact. His team's work will make use of the Washington Clean Energy Testbeds near the UW campus, which include world-class roll-to-roll manufacturing facilities supported by the state of Washington and the Washington Research Foundation.

Dunham's project, awarded $681,000, will investigate another promising material in photovoltaics research, known by its acronym CIGS "” or copper indium gallium selenide. Like perovskites, CIGS is another strong and efficient absorber of photons from sunlight "” a necessity for any material used in photovoltaic applications. CIGS can also be deposited onto flexible materials for incorporation into thin-film solar cells. Dunham's research centers on understanding how variations in CIGS crystalline structure and composition affects how carriers move within the crystal and impact its sunlight-to-energy conversion rate. They plan to use this information to create models for CIGS manufacturing processes and their impact on performance efficiency, which they'll test and refine in partnership with Siva Power, a California-based solar energy company.

The awards to UW teams are part of $53 million federal funding effort from the Solar Energy Technologies Office to develop new technologies and solutions that both reduce solar electricity costs and support growing employment in the solar field. These include projects to boost the performance and reliability of photovoltaic cells, modules and systems "” as well as to reduce materials and processing costs.