Integrated Energy Conversion and Storage Device for Stable Fast Charging Power Systems

Herein, an integrated device that comprises inorganic kesterite solar cells and Li-ion batteries (LIBs) has been proposed for application in fast photo-charging power systems. LiFePO4 and Li4Ti5O12 were selected as the battery electrode materials and six kesterite solar cells connected in series were fabricated to satisfy the charging voltage required for LIBs. Photo-charging was conducted at the rate of 1C (1.790 mAh g(-1)) at 2.1 V. An energy conversion and storage efficiency of 3.87% was acquired in the integrated device, and a storage efficiency of over 70% was observed in LIBs. Furthermore, by synchronizing the charging voltage of the solar cell and LIB, over 70% of the capacity was obtained at the rate of 1C, while preventing overvoltage during long-term charging.