Direct synthesis of natural dye mixed titanium dioxide nano particles by sol–gel method for dye sensitized solar cell applications

Abstract

Titanium dioxide (TiO2) is an important photo anode material for solar energy conversion in dye sensitized solar cells (DSSC). Among the three polymorphs of TiO2 namely, anatase, rutile and brookite, the anatase phase is having better photo catalytic activity. The anatase phase TiO2 nano particles were synthesized by sol–gel method. A natural dye was mixed during the synthesis of TiO2 nano particles itself to obtain dyed titanium dioxide nano particles which can be used as photo anode for DSSC. The juice extracted from beetroot which is rich in betanin was used as a natural dye sensitizer. The direct mixing of natural dye sensitizer during synthesis has yielded TiO2 nano particles with uniform adsorption of dye and the photo anode material (TiO2+dye sensitizer) for the fabrication of DSSC was ready in a single step. The dye mixing during the synthesis of TiO2 nano particles results very low dye aggregation. The pure and natural dye mixed TiO2 nano particles were subjected structural, optical, morphological and compositional studies. DSSC was fabricated using this dye mixed TiO2 nano particles into a thin film on fluorine-doped tin oxide (FTO) glass plate by ‘doctor-blade’ technique. The betanin sensitized DSSC showed a solar light energy to electron conversion efficiency of 0.69%.