Photorechargeable Supercapacitors (PRSCs): Recent Advances from Materials to Devices

Solar energy emerges as one of the most promising sources for green electricity to tackle the issues caused by the continuous emission of greenhouse gases from the excessive use of fossil fuels. The intermittency of renewable, especially solar, energy-related challenges can be mitigated by integrating efficient energy storage technologies to complement the demand for off-sun hours. Supercapacitors (SCs) are promising energy storage devices due to their high power density and longer life spans, yet they rely on conventional electrical charging. Integrating photoactive materials in SCs may provide an additional degree of freedom to utilize solar energy simultaneously for charging; such devices are known as photorechargeable SCs (PRSCs). PRSCs enable both energy conversion and storage in a single device. PRSCs can provide consistent power to various applications ranging from smart, small portable devices to aerospace equipment. Hybrid-PRSCs can combine dual-functional electrodes (i.e., energy conversion and storage) and battery-type and carbon material-based electrodes. These hybrid-PRSCs are attracting much attention due to their higher specific capacitance and energy density. This review provides a detailed view of the recent advancement in PRSCs with different configurations, including four-electrode, three-electrode, and two-electrode systems based on the properties of materials for energy conversion and storage. The review also discusses the working mechanism of simultaneous energy conversion and storage processes for different PRSCs and characterization techniques with parameters to evaluate their performance. Two-electrode integrated PRSCs are preferred over other PRSCs and are discussed in detail, including the dual-functional materials and respective device parameters. This review emphasizes the current limitations and highlights the future perspectives of these PRSC devices as energy storage systems.