Compact Photostorage Systems: New Materials and Designs for Integrated Energy Harvesting and Storage

The growing demand for flexible and autonomous electronics hasaccelerated the development of compact energy systems capable of both harvesting and storing solar energy. Photobatteries and photocapacitorsrepresent a new generation of self-charging devices that merge photovoltaic and electrochemical functions within a single structure. These systems overcome the conversion losses and bulkiness of conventional solar-battery combinations, enabling miniaturized, efficient, and sustainable power sources. This review summarizes recent progress in materials, architectures, and design strategies for compact photostorage systems. This work will focus, in particular, on two-terminal (2T) monolithic configurations that provide the highest integration level. Advances in inorganic semiconductors such as transition-metal oxides, sulfides, and lead-free perovskites, as well as organic materials including conductive polymers, dyes, and carbon nanostructures, have greatly enhanced photo-charge generation, mobility, and retention. Furthermore, innovations in gel and solid-state electrolytes have improved flexibility, safety, and long-term stability. Despite significant progress, major challenges remain in mitigating charge recombination, optimizing energy density and standardizing performance evaluation. By integrating recent results and emerging trends, this review outlines key directions for the rational design of next-generation self-powered photostorage systems that could underpin the future of portable, wearable, and sustainable energy technologies.