Titanium dioxide coated on titanium/stainless steel foil as photoanode for high efficiency flexible dye-sensitized solar cells

Employment of titanium dioxide (TiO₂) coated titanium (Ti)/stainless steel (StSt) photoanode on the reduction of the interfacial resistance of dye sensitized solar cell (DSSC) has been reported. The thickness of Ti layer on the StSt is increased by varying sputtering time. Surface morphological characteristics of the thin TiO₂ film, generated by calcination of Ti/StSt film at 500 °C, are investigated by Raman spectra and atomic force microscopy. Moreover, cyclic voltammetric studies reveal that the presence of dense TiO₂ film retards the redox reaction of I ^-/I₃^- on the Ti/StSt substrate. The thickness of the Ti layer and R_TiO2/Ti/St values critically depend on the time of sputtering and calcination respectively. The rear-illuminated flexible DSSC containing screen printed TiO₂/Ti/StSt (Ti sputtered for 90 min) shows maximum conversion efficiency of 5.64%, as a result of reduction of charge transport resistance from 159.2 ω to 0.4 ω at TiO ₂/Ti/StSt interface. The conversion efficiency further improves to 6.96% when containing 0.01 M I₂ in electrolyte. The durability test of the flexible DSSC under 100 mW cm^-2 light soaking for more than 1000 h reveals that the conversion efficiency maintains up to >95% of initial value.