Fresh fruits of Siahkooti were collected from the Iran national forest. Following washing with de-ionized water and removing the seeds and flesh of Siahkooti, the fruits were carefully peeled. Subsequently, the peels were kept in a vacuum furnace for about
10 h at 50 C to eliminate the moisture. After being dried, the peels were crushed into powder in a mortar. About 50 g of the powdered sample was put into a beaker, then 150 mL absolute ethanol was added and the mixture was kept in a shaker for 5 h. The obtained solution was protected from direct sunlight exposure and stored at about 5 C. Later, using filter paper, the solid residues were fil- tered out to obtain a pure and clear natural dye solution. Further purification of clear solution was performed using SPE to achieve efficient sensitization. This extract was also stored at 5 C and used for further characterization as sensitizer in fabrication of DSSC.
UV–Vis absorption spectra of the extracted dye solution and dye after adsorption onto TiO2 surface was recorded using a UV-2450 (JENWAY) spectrophotometer. An FTIR spectrum (Vertex 70, Bruker-Germany) of the powder obtained from the dried fruits of Siahkooti was recorded using KBr technique.