Photocapacitor integrating voltage-adjustable hybrid supercapacitor and silicon solar cell generating a Joule efficiency of 86%

Photocapacitor integrating both energy harvest and storage functions into a single device is a frontier research orientation, which facilitates the efficient and sustainable utilization of green energy. However, the multi-functions in one device and structural complexity of the integrated device, particularly the mismatch between energy harvest and storage units, lead to a relatively large energy loss in the energy storage and output processes. Here, we design a voltage adjustable hybrid supercapacitor (VAHSC) as an energy storage unit of a three-terminal photocapacitor. The VAHSC effectively harmonizes the energy harvest and storage units, resulting in the current, voltage, power, and energy match between both units. The optimal photocapacitor achieves a storage efficiency as high as 98.28% and Joule efficiency of 86.01%, along with excellent charge/discharge cycle stability. The great leap in this efficiency marks a substantial step towards the practical application of solar-charging energy storage integrated devices.