Low-temperature suitability of flexible photo-rechargeable devices integrated with hydrogel-based lithium-ion batteries and perovskite solar cells

Photo-rechargeable devices are viable alternatives for low power consumption and mini-type wearable power systems, but their flexibility, safety, and low-temperature suitability should be considered. Here, we present a flexible photo-rechargeable device for multi-scenario applications in energy harvesting and storage. As an energy-storage unit, the optimized HE-LIB is constructed using a low water content (5.5 wt%) hydrogel film, which exhibits good cycling stability, low-temperature suitability, and normal operation even under different deformation conditions. The flexible perovskite solar cell (f-PSC) as an energy-harvesting unit has a typical high photoelectric conversion efficiency of 21.48%. By the voltage matching strategy, direct connection of the f-PSC unit and HE-LIB unit can eliminate the energy loss in the control circuit, resulting in an overall energy efficiency (OEE) of up to 12.88%, which is one of the highest OEE values obtained for flexible photo-rechargeable devices to date. Furthermore, our study confirms that this type of flexible photo-rechargeable device can protect LIB units from overcharging even after a long-duration photo-charging process, as well as normally harvest and store energy at -20 degrees C. This work provides a practicable strategy to construct flexible photo-rechargeable devices with high OEE, safety, and low-temperature suitability for smart wearable electronics. The flexible photo-rechargeable device with an OEE of 12.88% displays good low-temperature suitability and safety without overcharge-induced thermal runaway.