A composite catalytic film of Ni-NPs/PEDOT: PSS for the counter electrodes in dye-sensitized solar cells

As the catalytic material for the counter electrode (CE) of a dye-sensitized solar cell (DSSC), a composite film of nickel nanoparticles (Ni-NPs) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) was deposited on an FTO glass substrate, by using a home-made polymeric dispersant, poly(oxyethylene)-segmented imide (POEM). Scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy dispersive X-ray spectroscopy (EDX) were used to characterize the films. A solar-to-electricity conversion efficiency (η) of 7.81% was achieved for the DSSC using Ni-NPs/PEDOT: PSS, while the DSSC with the Pt CE showed a ηof 7.63%. The best composite film showed a high stability, when it was subjected to potential cycling for 100 cycles in an electrolyte containing the redox couple, iodide/triiodide (I^-/I₃^-), while the Pt film showed a considerable decrease in its stability. In replacing the conventional sputtered Pt film as the CE in a DSSC, the Ni-NPs/PEDOT: PSS film exhibited multiple advantages of higher power conversion efficiency, higher stability of the catalytic film, and less expensive material cost. The photovoltaic parameters of the cells were substantiated by incident photon-to-current conversion efficiency (IPCE) spectra, electrochemical impedance spectroscopy (EIS), Tafel polarization plots, and cyclic voltammetry (CV).