(92b) Integration of iCVD Polymer Electrolytes in Quasi Solid State Dye Sensitized Solar Cells

Quasi solid state dye sensitized solar cells have been fabricated with iCVD poly(2-hydroxyethyl methacrylate) (PHEMA) as the polymer electrolyte. The polymer was directly synthesized and deposited using a unique initiated chemical vapor deposition (iCVD) process on the dye sensitized porous TiO2 film, and an iodide-triiodide redox couple solution in propylene carbonate and ã-butyrolactone was then incorporated into the polymer electrolyte. The ionic conductivity of the polymer electrolyte with propylene carbonate and ã-butyrolactone as solvents was measured to be 0.05 mS/cm and is a function of the iCVD polymer molecular weight Under AM 1.5 solar illumination (100 mW/cm2 ), the fabricated photovoltaic devices yielded a short circuit photocurrent density of 5.2 mA/cm2, an open circuit voltage of 0.64 V and a fill factor of 0.69. This corresponds to an overall power conversion efficiency of 2.3%. The open circuit voltage of the cell incorporating the iCVD polymer was found to be higher than that using a liquid electrolyte alone. This is attributed to the suppression of electron back transfer between the conduction band of the titanium oxide and the triiodide ion in the polymer electrolyte matrix due to improved filling of the semiconductor mesopores using the liquid-free iCVD polymer processing technique. Scanning electron microscopy and energy dispersive x-ray spectrometry analyses confirmed improved filling of the TiO2 mesopores with the iCVD polymer.

Keyword: initiated chemical vapor deposition (iCVD), polymer electrolyte, poly(2-hydroxyethyl methacrylate (PHEMA), dye sensitized solar cell, pore filling