Natural alkannin and anthocyanin as photosensitizers for dye-sensitized solar cells

DSSCs were assembled by using natural dyes extracted from alkanet root (Arnebia nobilis), ornamental millet (Pennisetum glaucum), coleus (Solenostemon scutellarioides `Saturn´) and amaranth (Celosia Cristata) as sensitizers. Ornamental millet, amaranth and coleus are anthocyanin containing pigment where as alkannin (isohexenylnaphthazarin) is the coloring pigment in alkanet root. DSSCs sensitized with alkannin dyes extracted from alkanet root, open-circuit voltage (V_OC) of 0.420 V, short-circuit current density (J_sc) of 1.08 mAcm^-2, fill factor (FF) of 0.60 and IPCE of 13 %. The DSSCs sensitized with coleus petal extract, ornamental millet leaf extract and amaranth flower extract were also discussed.