Economical and efficient dye sensitized solar cells using single wall carbon nanotube-titanium dioxide nanocomposites as photoanode and SWCNT as Pt-free counter electrode

Economical and efficient dye sensitized solar cells (DSSC) were fabricated using single wall carbon nanotube and titanium dioxide [SWCNT-TiO₂] nanocomposite as photoanode and SWCNT as Platinum free (Pt-free) counter electrode (CE). By physical mixing, precise amounts (0.006 wt%, 0.018 wt%, 0.03 wt%, and 0.06 wt%) of SWCNT was mixed in TiO₂ nano particles paste to obtain nanocomposite paste [nSWCNT-TiO₂] for the anodes. Attachment and distribution of SWCNT within/among the TiO₂ components has been confirmed using X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and X-ray mapping techniques. The catalytic activity and stability of the SWCNT as catalyst in the CE of fabricated DSSCs have been appraised using cyclic voltammetry (CV), Tafel, and chronoamperometry characterizations. Finally, the fabricated solar cells have been evaluated by current–voltage characteristics (IV) and electrochemical impendence spectroscopy (EIS). The optimized cell containing 0.018 wt% of SWCNTs mixed in TiO₂ paste i.e. [0.018 %SWCNT-TiO₂] for anode preparation and SWCNT as Pt-free CE i.e. [0.018 %SWCNT-TiO₂/N3/SWCNT] showed an overall efficiency of 8.05 %, which is about 44 % higher than the conventional [TiO₂/N3/Pt] based solar cell fabricated under the same conditions. This improvement in the overall power conversion efficiency (PCE) can be ascribed to the improved electron collection at photo-anode i.e. reduced charge recombination, efficient electron transport, good catalytic activity of the SWCNT at CE, and enhanced light harvesting efficiency due to the more dye adsorption.