(167f) Enhancing Dye Sensitized Solar Cell J-V Behavior By Integrating Nanoscale Polymer Films
- Conference: AIChE Annual Meeting
- Year: 2016
- Proceeding: 2016 AIChE Annual Meeting
- Group: Nanomaterials for Applications in Energy and Biology
- Time: Monday, November 14, 2016 - 2:20pm-2:40pm
To overcome the limitations of liquid methods for incorporating polymer electrolytes into the mesoporous TiO2, we employ a novel polymerization technique called initiated chemical vapor deposition (iCVD). iCVD is a solvent-free polymerization method that relies on gas-to-surface reactions at low pressures in which the reagents for polymerization, the monomer and initiator, are heated to vapors that can easily penetrate into the mesoscale voids of the TiO2 photoanode. The initiator is activated by a heated filament (250-350 °C) and polymerization as thin films occurs conformally inside the pore surfaces. This makes it especially useful for cases that require penetration of sub-micron and nanometer-sized pores as issues of wettability and surface tension with liquid processing are absent. In addition, the lack of any solvent medium removes the possibility of liquids getting trapped in the photoanode, which may degrade performance, and are difficult to remove .
In this work, iCVD is used for the synthesis and integration of polymer electrolyte thin films within the mesoporous TiO2 photoanode of DSSCs. Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and X-ray photoelectron spectroscopy (XPS) analyses confirm that the polymers formed are stoichiometric in composition expected of linear homopolymers and chemically identical to ones formed with liquid solution methods. The surface reaction kinetics and mass transport have been found to depend on the fractional surface saturation of monomer, , which is an adsorption parameter that provides a measure of the surface availability of the monomer. By carefully controlling , conformal coatings throughout the TiO2 photoanode have been achieved. To gain a better understanding on the effect of the polymer electrolyte on DSSC behavior, current-voltage, UV-VIS absorption, incident photon-to-current efficiency (IPCE) and electrochemical impedance spectroscopy (EIS) measurements have been employed. Experimental results indicate that DSSCs with ultrathin polymer electrolyte thin films integrated on the photoanode pore surface can enhance cell performance. For example, by applying poly(1-vinylimidazole) (PVIZ), power conversion efficiencies are found to be 27% higher than liquid-electrolyte DSSCs due to a simultaneous increase in short circuit current Jsc and open circuit voltage Voc . To our knowledge, this is the first reported demonstration of PVIZ as a polymer electrolyte in DSSCs.
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