Impedance characterization of dye-sensitized solar cells in a tandem arrangement for hydrogen production by water splitting

The present work reports the photoelectrochemical characterization of a dye-sensitized solar cell (DSC) to assist water split in a photoelectrochemical (PEC) cell. Performance parameters were extracted from standard current-voltage characteristic (I-V) and the charge transfer phenomena occurring at different interfaces of the DSC were evaluated by electrochemical impedance spectroscopy (EIS). The DSC comprised the N719 dye and a robust electrolyte (1-propyl-3-methylimidazolium iodide in guanidinium thiocyanate additive). At 1 sun illumination the DSC yielded a short-circuit photocurrent density of 14.9 mA cm(-2), an open-circuit voltage of 0.797 V, a fill factor of 0.712 and an overall efficiency of 8.5%. Different PEC systems based on silicon-doped and undoped hematite photoelectrodes were considered. The required additional anodic bias necessary for actual water cleavage was supplied by two DSCs in series operating just under open-circuit voltage (1.56 V), allowing a conversion efficiency of about 1.12% for the silicon-doped hematite deposited by APCVD, 0.51% for the silicon-doped prepared by USP and 0.12% for the undoped hematite sample. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.