Photochargeable Materials for Persistent Solar Energy Storage and "Dark" Catalysis

Photochargeable materials (PCMs) enable the simultaneous harvesting and storage of solar energy by accumulating charge carriers in trap states upon light absorption. These materials have garnered significant attention for applications in "dark" photocatalysis, where stored electrons facilitate catalytic reactions in the absence of light, as well as in photochromism and consecutive photoinduced electron transfer (conPET) processes. Despite substantial progress, challenges remain in understanding the fundamental charge storage mechanisms, optimizing material properties, and expanding practical applications. This review provides a comprehensive analysis of the mechanisms governing charge accumulation, storage, and release in PCMs, highlighting key factors influencing their performance. We discuss advanced characterization techniques, which offer critical insights into electron storage capacity, charge lifetime, and reaction kinetics. Furthermore, we summarize recent advancements in "dark" photocatalysis for hydrogen evolution and organic transformations, photochromic materials for smart display and sensing, and conPET strategies that extend the thermodynamic limits of conventional photocatalysis. Finally, we identify major challenges and future directions, emphasizing the need for materials with higher electron storage capacity, tunable charge release kinetics, and improved stability. By bridging fundamental insights with emerging applications, this review aims to provide a roadmap for the continued development of PCMs toward sustainable energy conversion and storage.