Experimental and theoretical investigation of dye sensitized solar cells integrated with crosslinked poly(vinylpyrrolidone) polymer electrolyte using initiated chemical vapor deposition

Initiated chemical vapor deposition is used to integrate crosslinked poly(vinylpyrrolidone) (PVP) as a polymer electrolyte into the mesoporous TiO₂ photoanode of dye sensitized solar cells (DSSCs). By adjusting the fractional saturation ratio of ethylene glycol diacrylate (EGDA) crosslinker to vinylpyrrolidone (VP) monomer, the amount of crosslinker within the crosslinked polymer is controlled directly, and a minimum ratio of 0.2:1 (EGDA to VP) is found to form a robust insoluble crosslinked film. Fineman-Ross copolymer analysis indicates that both VP and EGDA prefer to polymerize with VP rather than with EGDA, likely due to reduced steric hindrance. DSSCs incorporating crosslinked PVP polymer electrolyte are found to have 51% higher power conversion efficiency (37% higher in open circuit voltage and 25% higher in fill factor) compared to DSSCs with liquid electrolytes. First-principles macroscopic mathematical modeling reveals that the polymer electrolyte shifts the conduction band of TiO₂ (vs. normal hydrogen electrode) negatively, increases shunt resistance, and affects interfacial processes like back-electron surface recombination in the cell. - Highlights: • Initiated chemical vapor deposition forms crosslinked poly(vinylpyrrolidone) (PVP). • Minimum 0.2:1 ratio of crosslinker-to-monomer produces insoluble crosslinked film. • Fineman-Ross copolymer analysis indicates copolymerization favors addition to VP. • PVP polymer electrolyte improves solar cell efficiency by 51%. • First-principles modeling predicts PVP shifts the TiO₂ conduction band by 0.18 eV.