Layered co-sensitization for enhancement of conversion efficiency of natural dye sensitized solar cells

This paper describes a double layered co-sensitization in dye sensitized solar cells (DSSCs) by using natural pigments from Ixora flower (Ixora sp. (Rubiaceae)) and the outer dark purple skin of ‘Kembayau’ (Canarium odontophyllum) fruit. UV–vis absorption data revealed that both dyes were anthocyanins. Co-sensitization was done by first adsorbing the dye from C. odontophyllum into TiO2 electrode by dipping, and then by removing adsorbed dye of the top layer of TiO2 using a de-sorption solution before the Ixora sp. dye was allowed to adsorb. Power conversion efficiency of the co-sensitized solar cell was 1.55%. The conversion efficiencies of DSSCs sensitized with Ixora sp. , C. odontophyllum and the mixture of both dyes (1:1) were 0.96%, 0.59% and 1.13% respectively. The superior conversion efficiency achieved by layered co-sensitization is attributed to the high adsorption capacities of Ixora sp. and C. odontophyllum, and the homogeneous monolayer adsorption of Ixora sp. as revealed by Freundlich and Langmuir adsorption isotherms.