Karuppiah Nagaraj
In this era of decarbonization, decentralization, and resilience, combining solar energy harvesting and storage into unified platforms is critical for next-generation sustainable energy solutions. Solar batteries, which combine solar energy conversion and electrochemical storage, provide a means to cut carbon emissions, reduce transmission losses, and enable self-sufficient off-grid electricity. This paper discusses current advances in solar battery systems, focusing on classifications (integrated vs. modular), operating principles, and key performance indicators such as energy efficiency, cycle life, power density, and long-term reliability. Photoactive electrodes (perovskites, organic semiconductors, carbon-based materials), various battery chemistries (Li-ion, Na-ion, Zn-ion, redox flow, organic), and novel electrolytes (solid-state, gel, ionic liquids) are all critically examined, with a focus on interface engineering and synergistic design. This review examines system-level developments in fully integrated photo-rechargeable architectures, multifunctional 2-in-1/3-in-1 devices, and commercially viable scalable fabrication. Real-world applications include off-grid electrification, critical infrastructure backup, and smart city/IoT integration. Finally, the article examines significant concerns such as efficiency, sustainability, environmental impact, and scalability, as well as new trends including AI/ML-driven optimization, circular design methods, developing standards, and investment frameworks. The assessment focuses on the transformative significance of solar batteries in driving a sustainable and equitable energy transition.