Photo-assisted rechargeable supercapacitors and applications

Abstract

Photo-assisted rechargeable supercapacitors (PSCs) are a new category of hybrid energy-storage devices that combine solar energy harvesting and electrochemical charge storage within a single device. The review presents the latest developments in PSCs, including their operation principles, material design strategies, architectures, and performance characteristics. Specifically, the emphasis is on asymmetric and integrated architectures that use photoresponsive electrodes, in which light-generated charge carriers enhance redox reactions and ion transport. The advances in photoactive materials, including transition metal oxides and sulfides, TiO₂ nanotubes and hybrid heterostructures, are discussed in connection with the enhancement of specific capacitance, energy density, and photocharging efficiency. Moreover, the electrochemical performance in experimental studies is consistently improved under illumination compared with that under dark conditions, with energy densities in optimized systems reported to be as high as ∼60.9 Wh kg⁻¹ and improved coulombic efficiency. This review focuses on the importance of binder-free nanostructured electrodes, interface engineering, electrolyte optimization, and band-alignment control to enhance cycling performance and long-term stability. Theoretical and in situ studies have also been discussed recently to explain the process of light-initiated charge transfer. Despite the noted improvements, challenges remain with light utilization efficiency, operational stability, and scalable production. Overall, PSCs provide a viable direction to realize self-powered, miniaturized, and sustainable energy storage for future portable, wearable, and smart electronic devices.