14.1% Efficient Monolithically Integrated Solar Flow Battery

Challenges posed by the intermittency of solar energy source necessitate the integration of solar energy conversion with scalable energy storage systems. 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 the design principles for and the demonstration of a highly efficient integrated solar flow battery (SFB) device with a record solar-to-output electricity efficiency of 14.1%. Such SFB devices can be configured to perform all the requisite functions from solar energy harvest to electricity redelivery without external bias. Capitalizing on high-efficiency and high-photovoltage tandem III-V photoelectrodes that are properly matched with high-cell-voltage redox flow batteries and carefully designed flow field architecture, we reveal the general design principles for efficient SFBs. These results will enable a highly efficient approach for practical off-grid solar utilization and electrification. Because of the intermittent nature of sunlight, the design of practical round-trip solar energy utilization systems requires both efficient solar energy conversion and storage. Compared with separated solar energy conversion and storage devices, combining the functions of separated devices into a single device allows us to bypass the intermediate step of electricity generation, which represents a more efficient, compact, and cost-effective approach to utilizing solar energy. Here, we present a monolithically integrated solar flow battery device that builds on III-V solar cells and organic redox species. The excellent performance of this device and the general design principles proposed here promise a general approach for storing the intermittent solar energy electrochemically with high storage capacity and efficiency, which will accelerate the large-scale deployment of solar energy technologies, especially in remote locations, to enable practical off-grid electrification. The monolithic integration of photoelectrochemical solar energy conversion and electrochemical energy storage offers an efficient and compact approach toward practical solar energy utilization. This work presents the design principles for and the demonstration of a highly efficient integrated solar flow battery device with a record solar-to-output electricity efficiency. These results will enable a highly efficient approach for practical off-grid solar utilization and electrification.