Enhancement of Ionic Conductivity in PVA/KI/I2-Based Gel Electrolytes Modified by Surfactants for Dye-Sensitized Solar Cells

In this work, polymer gel electrolytes based on poly(vinyl alcohol) (PVA) incorporating the KI/I2 redox couple and different surfactants, sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and cocamidopropyl betaine (CAPB), were formulated and systematically characterized for application in dye-sensitized solar cells (DSSCs). The main objective was to overcome the intrinsic drawbacks of conventional liquid electrolytes, such as leakage, volatility, and poor mechanical stability. The gels were prepared via physical crosslinking of PVA in aqueous media, with surfactants introduced at concentrations below, at, and above their critical micelle concentration (CMC). Structural, electrochemical, and rheological properties were investigated using Fourier-transform infrared (FTIR) spectroscopy, zeta potential and ionic conductivity measurements, oscillatory rheology, and optical microscopy. The results show that surfactant incorporation strongly affects gel organization and ion transport. SDS increased ionic conductivity up to 5.98 mS/cm at the CMC, while CTAB induced ion trapping at sub-CMC levels and reduced conductivity down to 0.0152 mS/cm. CAPB provided a near-neutral electrostatic environment and achieved a peak conductivity of 9.22 mS/cm above the CMC, along with homogeneous microstructure. These findings demonstrate that surfactant-assisted PVA-based gel electrolytes, particularly SDS- and CAPB-containing systems, are promising candidates for stable, flexible, and efficient quasi-solid-state DSSCs.