Ionic liquid diffusion properties in tetrapod-like ZnO photoanode for dye-sensitized solar cells

Dye-sensitized solar cells (DSCs) are a promising PV device to solve global energy-related problems because it is clean, inexhaustible and readily available. In order to improve the stability and reliability of the DSCs, ionic liquid (IL) electrolyte is a good choice for replacement of volatile solvent electrolyte systems (e.g. acetonitrile). However, the high viscosity of ionic liquids leads to mass-transport limitations on the photocurrents in the DSCs. In this report, a new porous photoanode made by tetrapod-like ZnO (T-ZnO) nanopowders provides not only a fast electron transport path in ZnO but also an efficient ionic diffusion pathway in the photoanode pore, comparing to the spherical commercial ZnO (C-ZnO) nanopowders. In addition, the ionic diffusion dynamics of T-ZnO and C-ZnO devices are characterized by electrochemical impedance analysis (EIS), photocurrent transient dynamics. We observed the presence of a tetrapod-like framework, which allowed the photoanode to provide a more efficient ionic diffusion pathway than conventional one made of commercial spherical nanopowders provided.