Efficient self-charging monolithic photocapacitors comprised of perovskite solar cell and quasi-solid-state supercapacitor through a shared Janus carbon electrode

• A monolithic perovskite photocapacitor integrates a C-PSC and a quasi-solid-state SC via a shared Janus carbon electrode. • Record overall efficiencies of 7.29% and 4.71% are achieved for small-area and large-area devices. • 77.14% and 98.90% of the initial η overall and capacitance remain after 50 continuous photo-charging/discharging cycles. • A power pack consisting of three monolithic photocapacitors successfully powers small electronic devices. As demand for sustainable energy surges, overcoming the challenges of the fluctuating and intermittent nature of solar electricity requires the development of integrated devices that can effectively harvest, convert, and store solar electricity in one device for continuous power utilization. Carbon materials, known for their cost-effectiveness, chemical stability, and hydrophobicity, are promising as a common electrode for a perovskite solar cell (PSC) and a supercapacitor (SC) in monolithic perovskite-based photocapacitors (MPPCs). However, current MPPCs using shared carbon electrodes suffer from low overall efficiencies ( η overall , <6%), and large-area devices (>1 cm 2 ) for rapid photo-charging remain unexplored. Herein, we present high-performance self-charging MPPCs integrating a carbon electrode-based PSC with a quasi-solid-state symmetrical SC using biomass-derived activated carbon. Systematic evaluation of MPPCs with active areas of 0.115 cm 2 and 1.0 cm 2 produce record η overall of 7.29 % and 4.71 %, respectively, making them among the highest-performing carbon electrode-based MPPCs. The devices exhibit great operational stability with 77.14 % η overall and 98.90 % capacitance retention over 50 continuous photo-charging/discharging cycles. Moreover, we demonstrate a power pack comprising three MPPCs connected in series that can power small electronic devices, including a digital hygrometer, buzzer, and LEDs, underscoring their potential as efficient, sustainable power sources for low-power electronics in real-world applications.