Stability and Reliability of Dye-Sensitized Solar-Cell Mini-Module for Photocharging Li-Ion-Battery-Connected Internet of Things

Dye-sensitized solar cells (DSSCs)-integrated Li-ion batteries (LIBs) are considered a promising solution as a wireless power source for the increasing number of miniaturized portable devices and the internet of things (IoTs). However, DSSCs suffer from stability issues because of the using volatile electrolyte solvents that leak through the seal. To solve this problem, in this study, a polymer gel electrolyte based on the high-boiling solvent 3-methoxypropionitrile (bp = 164–165 °C) is used, and the backside of the cells are sealed by hot press using surlyn and Al foil. A highly stable and efficient counter electrode, Pt/porous carbon (Pt/PC), is also used to fabricate the devices, which show a high PCE of 25.7%–29.4% under the illumination of 500–2000 lux. The fabricated DSSC shows outstanding stability in the room condition and under the operating condition at 50 °C. A mini-module of 13.3 cm², PCE of 22.9–23.3%, and P_max of 166.4–643.0 μW can recharge a LIB while powering an IoT device by producing an output greater than the IoT device consumes. The store charge can be used when the light source is cut off, indicating the reliability of the DSSC for photocharging the LIB as a wireless power source for IoT devices.