Effects of polymer chemistry on polymer-electrolyte dye sensitized solar cell performance: A theoretical and experimental investigation

The effects of polymer chemistry on interfacial properties and overall performance in polymer-electrolyte dye sensitized solar cells (DSSCs) are investigated theoretically and experimentally. Specifically, polymer electrolytes based on poly(2-hydroxyethyl methacrylate) (PHEMA), poly(glycidyl methacrylate) (PGMA), and poly(4-vinylpyridine) (P4VP) are considered. These polymers are grown directly within the mesoporous TiO₂ photoanode via a single step polymerization and coating using initiated chemical vapor deposition (iCVD) to maximize pore filling. The experimental study coupled with a 1-D first-principles macroscopic DSSC mathematical model provides insight into the cell interfacial processes and overall performance. Parameter estimation using the macroscopic model indicates that the pendant groups on the polymers strongly affect the conduction band position of TiO₂, the back electron transfer at the photoanode-electrolyte interface, and the exchange current density at the platinum cathode. The estimated difference between the TiO₂ conduction band edge and the redox potential of the electrolyte are 0.87, 0.99 and 1.06 eV for P4VP, PGMA, and PHEMA, respectively. Estimated recombination rate constants for P4VP and PGMA are respectively 54% and 19% lower than that of PHEMA. This study indicates that by varying polymer electrolyte chemistry, DSSC characteristics including open-circuit voltage, short-circuit current density, and fill factor can be tuned.