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

Graphical abstract: The POEM-dispersed Ni-NPs were incorporated with PEDOT:PSS as the electro-catalytic composite film for the CE of a DSSC. The η of the DSSC using Ni-NPs/PEDOT:PSS CE (7.81%) is better than that of the cell with a Pt CE (7.63%). The Ni-NPs/PEDOT:PSS CE showed an unfailing stability after long-term potential cycling. - Highlights: • POEM was synthesized for the good dispersion of the Ni-NPs. • PEDOT:PSS was intended to enable a good contact between the Ni-NPs and the substrate. • Ni-NPs was used to improve the conductivity of PEDOT:PSS film. • The η of the DSSC with Ni-NPs/PEDOT:PSS (7.81%) was higher than that of the cell with Pt (7.63%). • The Ni-NPs/PEDOT:PSS CE showed a high stability after long-term potential cycling. - Abstract: 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)