Correlation Study on Biopolymer-Blended Cobalt and Iodine Gel Electrolytes to Enhance the Efficiency of Natural Dye-Based DSSCs

In this study, we prepared a new natural sensitizer from blood berry extract (BB dye) and coupled it with a series of biopolymer gel electrolytes consisting of Co^2+/3+ or I^–/I₃^–, such as GE 1, GE 2, GE 3, GE 4, GE 5, and GE 6. An as-prepared natural dye was characterized via UV–visible spectroscopy to confirm the behavior of the dye, which showed an absorption range at 484 nm. The interaction between the TiO₂ surface and the BB dye was analyzed by density functional theory (DFT) studies. All six biogel electrolytes were characterized using Fourier transform infrared (FTIR), UV, X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and cyclic voltammetry (CV) techniques to validate the integration of redox mediators into polymer hosts. The bioelectrolytes GE 1, GE 2, GE 4, and GE 5 contain a single polymer matrix (xanthan gum or gelatin) and showed a very low photo-conversion efficiency. At the same time, GE 3 and GE 6 contain a blended polymer matrix (xanthan gum and gelatin) and achieved a higher power conversion efficiency (PCE) of 0.86 and 2.06%, respectively, under 1 sun illumination. The redox mediator Co^2+/3+ or I^–/I₃^– incorporated into both single and blended polymer matrixes played a vital role in regenerating the BB dye. In this case, the bioblended polymer gel electrolyte (GE 6) consisting of a Co^2+/3+ redox pair attained a high conductivity of 5.97 × 10^–5 S/cm^–1 and a chemical capacitance of 15.02 ×10^–6 F compared to the I^–/I₃^–-incorporated electrolyte. The PCE reports were sustained by the electrochemical impedance spectrum results such as a larger charge at the Pt/electrolyte interface, a lower charge transfer resistance at the TiO₂/dye/electrolyte interface, and a higher chemical capacitance. The introduction of a biopolymer cobalt redox-based gel electrolyte with the natural BB dye improves the electron lifetime and readily reduces the recombination reaction. The integration of a natural dye with a blended biopolymer gel electrolyte can pave the way to generate new eco-friendly dye-sensitized solar cells (DSSCs) with high stability.