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.