Wenjie Li1 Hui-Chun Fu2 Yuzhou Zhao1 Jr-Hau He2 Song Jin1

1, University of Wisconsin-Madison, Madison, Wisconsin, United States
2, King Abdullah University of Science and Technology, Saudia Arabia (KAUST), Thuwal, , Saudi Arabia

Challenges posed by the intermittency of solar energy source necessitate its integration with proper energy storage systems. Bridged by carefully chosen reversible redox reactions, the monolithic integration of photoelectrochemical solar energy conversion and electrochemical energy storage offers an efficient and compact approach toward practical solar energy utilization. Here we present an integrated solar flow battery (SFB) device by integrating regenerative solar cells in aqueous electrolytes with RFBs using the same pair of organic redox couples. The SFB can be configured to perform all the requisite functions, including solar energy harvest, conversion, storage and redelivery, without external bias. Exploiting high efficiency photoelectrode, properly chosen redox couples and optimized flow filed design, we demonstrate a record solar-to-output electricity efficiency (SOEE) of 14.1%. In addition, we describe the major advantages of individual components used to assemble the record-breaking device, and discuss the possible pathways for future developments. This work paved the way for a promising new approach to harvesting, storing and utilizing the intermittent solar energy with high energy conversion efficiency and energy storage density. These integrated SFBs will be especially suitable as distributed and standalone solar energy conversion and storage systems in remote locations and enable practical off-gird electrification.