Electron transport analysis in zinc oxide-based dye-sensitized solar cells: A review

This research review highlights the use of zinc oxide (ZnO) nanostructure as a photoanode in the fabrication of dye-sensitised solar cells (DSSC). ZnO nanostructure thin films offer large surface area, direct electron pathways and effective light scattering centre. The fabrication work can produce a variety of ZnO nanostructures, from nanotubes, nanoporous, nanosheets, nanoflowers, nanoflakes, nanobranches and nanolipsticks. The internal mechanism inside the cell gives useful information on the electron transport properties and efficiency of ZnO-based DSSC. The review ends with an outlook highlighting the electron transport parameters analysed by electrochemical impedance spectroscopy (EIS) unit. Such parameters including charge transport resistance (Rct), transport resistance (Rt), chemical capacitance (Cμ), effective electron lifetime (τeff), effective electron chemical diffusion coefficient (Deff), effective rate constant for recombination (keff), effective electron diffusion length of the photoanode (Ln) and finite Warburg impedance in the electrolyte (ZD). Monitoring the electron transport properties may improve the photovoltaic performances of the ZnO-based DSSC such as open circuit voltage (Voc), short circuit current density (Jsc), fill factor (FF) and power conversion efficiency (η).