Wei Wei

Renewable energy technologies that simultaneously harvest and store energy are attracting increasing attention as next-generation power solutions for portable, wearable, and self-powered electronic systems. Among these technologies, monolithically integrated solar energy conversion and storage devices that combine solar cells (SCs) with supercapacitors into singular, encapsulated structures offer a promising pathway to address the intermittency of solar power while enabling compact and multifunctional energy platforms. This review systematically summarizes recent progress in monolithically integrated solar energy harvesting and storage systems, with particular emphasis on structural architectures, photovoltaic configurations, electrode/electrolyte engineering, and multifunctional device designs. The advantages and limitations of two-electrode, three-electrode, and shared-substrate configurations are critically compared in terms of internal resistance, power matching, fabrication complexity, mechanical flexibility, and overall energy conversion-storage efficiency. Recent advances in rigid, flexible, and fibrous integrated systems based on silicon, dye-sensitized, perovskite, organic, and quantum-dot solar cells are comprehensively discussed, alongside emerging developments in photorechargeable supercapacitors, electrochromic systems, and multifunctional photovoltaic–triboelectric hybrid devices. Particular attention is given to the roles of advanced materials, including graphene, carbon nanotubes, MXenes, conductive polymers, and other low-dimensional materials, in enhancing electrochemical performance, flexibility, and device stability. Current challenges associated with electrolyte compatibility, device mismatch, mechanical durability, long-term cycling stability, scalability, and performance standardization are further analyzed. Finally, future perspectives toward high-efficiency, mechanically robust, and commercially viable integrated energy systems for wearable electronics, smart textiles, and distributed energy applications are outlined.

A dye-sensitized solar cell (DSSC) employing a Titania (TiO_₂) photoanode sensitized with N3 dye was integrated with a carbon-based supercapacitor to form a three-electrode photo-supercapacitor device. In this architecture, a double-sided carbon-based electrode functions as a dual-purpose intermediate electrode, serving simultaneously as the counter electrode for the DSSC: facilitating efficient redox electrolyte regeneration and as an electrode in an electric double-layer capacitor for energy storage. Four commercially available carbon-based materials, namely, graphite, activated carbon, mesoporous carbon (MC), and graphene, were systematically evaluated as intermediate electrodes to assess their influence on device performance. Prior to integration, the standalone DSSC and supercapacitor components were characterized independently. The DSSC achieved a maximum power conversion efficiency (PCE) of 3.26% when graphite was used as the counter electrode, while the supercapacitor exhibited a maximum specific capacitance of 43.7 F g⁻¹ with MC electrodes. The integrated photo-supercapacitor device was subsequently evaluated under simulated solar illumination (100 mW cm⁻²) using constant-current and constant-voltage charging protocols. The integrated system delivered a maximum PCE of 3.10% and a specific capacitance of 40.0 F g⁻¹ when MC was employed as the intermediate electrode, demonstrating effective photo-charging behavior and energy storage capability. These results highlight the viability of using commercially available carbon materials as multifunctional intermediate electrodes for practical and scalable dye-sensitized photo-supercapacitor systems.

Hydrogenated carbon nanosheets enable tunable PSC interfaces, achieving 18% efficiency and 1000 h stability, offering scalable, durable, and low-cost electrode alternatives.