Converting and storing solar energy and releasing it on demand by using solar flow batteries (SFBs) is a promising way to address the challenge of solar intermittency. Although high solar-to-output electricity efficiencies (SOEE) have been recently demonstrated in SFBs, the complex multi-junction photoelectrodes used are not desirable for practical applications. Here, we report an efficient and stable integrated SFB built with back-illuminated single-junction GaAs photoelectrode with an n-p-n sandwiched design. Rational potential matching simulation and operating condition optimization of this GaAs SFB lead to a record SOEE of 15.4% among single-junction SFB devices. Furthermore, the TiO2 protection layer and robust redox couples in neutral pH electrolyte enable the SFB to achieve stable cycling over 408 h (150 cycles). These results advance the utilization of more practical solar cells with higher photocurrent densities but lower photovoltages for high performance SFBs and pave the way for developing practical and efficient SFBs.
Bibliographical noteKAUST Repository Item: Exported on 2021-01-12
Acknowledged KAUST grant number(s): OSR-2017-CRG6-3453.02
Acknowledgements: This research is supported by the King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research under award No. OSR-2017-CRG6-3453.02. C.H.L. and J.H.H. are supported by the KAUST baseline fund for the design and fabrication of the single-junction GaAs cells. The authors thank Mr. Hongyuan Sheng for performing the XPS analysis on the GaAs photoelectrodes.