Preparation and improvement in photovoltaic performance of dye-sensitized solar cells using carbon dioxide

Abstract

We report preparation and improvement in photovoltaic performance of N719-based dye-sensitized solar cells (DSSCs) using pressurized carbon dioxide (CO2) as a co-solvent for the absorption process on the TiO2 photoelectrode surface. Effective absorption of the N719 molecules on the TiO2 surface was achieved using CO2 processing, and the absorption time was shortened drastically from 24 h (in the dip process) to less than 3 h. The cells prepared under pressurized CO2 for the absorption showed greater photovoltaic performance, especially higher short-circuit current density and conversion efficiency, compared with that from typical dip method. It was revealed that the suitable CO2 pressure for the absorption was 5 MPa and the efficiency was achieved to be more than 7.5 %. Prevention of back electron transfer reactions from TiO2 to oxidized dyes or iodides was caused currently, because the homogeneous coverage of N719 molecules on the TiO2 surface was obtained by the use of pressurized CO2.