Non-newtonian PEO–TiO2 nanocomposite gel polymer electrolytes for DSSCs: rheology guided crystallinity, ionic transport, and long-term device performance

Artikel i vetenskaplig tidskrift, 2026

This study explores the role of non-Newtonian gel-polymer electrolytes, infused with TiO2 nano-fillers, in improving the performance of dye-sensitized solar cells (DSSCs). The key focus was understanding how these nano-fillers alter the ionic conductivity of the electrolytes and influence DSSC efficiency, particularly probing the transient nature of the conductivity in non-Newtonian electrolytes. TiO2 nano-fillers induce structural rearrangements in polymer chains, transitioning the electrolyte into a more amorphous state. This shift enhances ionic mobility within the electrolyte, a characteristic behavior of non-Newtonian fluids in which viscosity and flow properties change under stress or temperature. This behavior is confirmed by analyzing the transient behavior of the conductivity of the electrolyte. The FTIR and UV–Visible spectroscopy confirmed chemical stability and light-harvesting capability, respectively, without introducing undesired reactions. This study reveals a distinct performance optimum at 15.0 wt% TiO2 content, beyond which the performance decreases due to nanoparticle aggregation and polymer chain immobilization. Key electrochemical analyses, including Nyquist plots and temperature-dependent conductivity measurements, reveal that ionic conductivity exhibits non-Arrhenius behavior, indicating complex thermally activated transport within the gel matrix. The conductivity peaked at 9.73 mS cm⁻¹ at 80 °C for the 15% TiO2 sample, confirming the non-Newtonian dynamics of the electrolyte. AC conductivity, variations in dielectric constant, and polarization microscopy provided further evidence of enhanced amorphous character and improved charge transport. This study pioneers the exploitation of non-Newtonian dynamics in gel-polymer electrolytes for DSSCs, revealing transient conductivity as a novel mechanism for tunable ionic transport. In terms of DSSC performance, the electrolyte sample containing 15.0 wt% TiO2 yielded a power conversion efficiency (PCE) of 7.18%, representing a 26.0% increase over the TiO2-free baseline. This improvement is linked to increased iodide ion mobility, reduced charge recombination, longer electron diffusion lengths, and enhanced photoelectron lifetimes, as demonstrated by EIS analysis. Conclusively, TiO2 nano-filler–infused non-Newtonian gel-polymer electrolytes significantly enhance DSSC stability, conductivity, and efficiency. This work presents a viable pathway toward the development of high performance, stable, and sustainable solar cells using solid-state electrolyte technologies.