Dynamic Modeling of Supercapacitor Self‐Discharge Through a Solar Cell in Photosupercapacitor Systems

Integrating perovskite solar cells (PSCs) with supercapacitors (SCs) offers a promising solution for energy conversion and storage in low‐power systems, such as internet of things (IoT) devices. However, these integrated systems can experience SC self‐discharge through the PSC under dark conditions and in absence of external load, thereby reducing the storage capacity. To investigate this self‐discharge mechanism, we use impedance spectroscopy (IS) at different DC bias voltages to evaluate the passive elements of the equivalent electric circuit of (FAPbI ₃ ) _0.7 (MAPbBr ₃ ) _0.3 PSCs, and carbon‐based SCs, which show a power conversion efficiency of 10.5%, and a capacitance of 0.31 F, respectively. Based on the IS characterization, we propose a model that accounts for the voltage‐dependance of the passive elements in the PSC as the SC discharges. Finally, we conduct a Simulink–Simscape simulation using the experimentally determined parameters to demonstrate the charge loss of the SC during the initial hundred seconds, when its voltage exceeds the PSC’s threshold where the transition from shunt resistance to diode dominated behavior occurs (approximately 0.5 V). Once the SC reaches this voltage, its stored charge is maintained for several hours. These findings provide a predictive framework for optimizing the energy autonomy of next‐generation self‐powered IoT devices.