Effect on Cell Efficiency following Thermal Degradation of Dye-Sensitized Mesoporous Electrodes Using N719 and D5 Sensitizers

This work examines the comparative durability of two common dyes at temperatures that may be experienced during fabrication of dye-sensitized solar cells (DSCs) such as through the application of thermoplastics for encapsulation or the use of a molten solid-state hole conductor. Dye-sensitized electrodes were heated in an atmosphere of air or nitrogen and thereafter used as working electrodes in DSCs. Electrodes sensitized with N719 appeared more sensitive to thermal degradation than electrodes sensitized with D5, although absorbance measurements suggest similar first-order degradation rates for the two dyes. Intensity modulated photovoltage spectroscopy and intensity modulated photocurrent spectroscopy were used to measure the effect of heating on electron lifetime and transport. It was found that the electron diffusion length may be as low as 10% for heated samples, compared to that of the unheated counterpart, and therefore, we assess recombination as an additional efficiency limiting process in our experiments.