Solar-Powered Supercapacitors: A Review and Outlook on Next-Generation Sustainable Energy Storage Solutions

The shift from nonrenewable fossil fuels to sustainable energy sources has highlighted the critical need for efficient energy storage solutions. Solar energy, recognized for its affordability and environmental benefits, has emerged as a leading sustainable alternative. However, their intermittent nature necessitates the integration of energy storage devices with photovoltaic (PV) cells. Supercapacitors (SCs) have gained prominence among energy storage systems for their efficient energy storage capabilities, making them essential in photocharging systems. Solar-powered supercapacitors (SPSCs), which combine PV cells and SCs, present a promising approach for the simultaneous energy harvesting and storage. In the era of smart electronics, flexible SPSCs have emerged as viable options for wearable applications, offering high power-to-weight ratios and adaptability. This review comprehensively examines the fundamental components of SPSCs, including the various types and operating mechanisms of PV cells and SCs. It further discusses recent progress in SPSCs, with an emphasis on SCs integrated with dye-sensitized, quantum dot-sensitized, perovskite, and organic solar cells, and highlights innovative strategies for performance enhancement. Additionally, the review presents key characterization techniques, identifies critical parameters influencing device performance, and illustrates applications across diverse fields. Finally, it summarizes fabrication methodologies, performance evaluation metrics, and structural design aspects while outlining current challenges and prospective research directions for the advancement of SPSC technology.