Song Jin1

1, University of Wisconsin–Madison, Madison, Wisconsin, United States

Due to the intermittent nature of sunlight, practical solar energy utilization systems demand both efficient solar energy conversion and inexpensive large scale energy storage. We have developed novel hybrid solar-charged storage devices that integrate organic redox flow batteries (RFBs) and regenerative semiconductor solar cells that share the same pair of redox couples. In these integrated solar flow batteries (SFBs), solar energy is absorbed by semiconductor electrodes and photoexcited caries are collected at the semiconductor-liquid electrolyte interface and used to convert the redox couples in the RFB to fully charge up the battery. When electricity is needed, the charged up redox couples are discharged to generate the electricity. We have demonstrated that solar energy harvest, conversion, storage, and redelivery can be completed by such a single integrated SFB without any external electrical energy input. After developing high performance III-V solar cells that are carefully matched with various high voltage organic couples and optimizing several generations of SFB device designs, we have achieved integrated SFB device with an overall direct solar-to-output electricity efficiency (SOEE) of 14%. We have further improved the cycling performance of the SFBs by integrating robust organic redox couples. To enable SFBs in practical distributed and standalone solar energy conversion and storage systems in remote locations, we aim to keep a low overall cost for SFB devices while maintaining its high performance, thus lowering the chemical cost of redox active materials could be one of the effective ways to achieve such goal. Therefore, we are particularly interested in new, inexpensive, and robust redox couples with diverse redox potentials.