Characterization of TiO2 photoanodes and natural dyes (Allamanda Blanchetti and Allamanda Cathartica) extract as sensitizers for dye-sensitized solar cell applications

In the present work, Dye-Sensitized Solar Cells (DSSC) were fabricated using fabricated TiO2 photoanodes and natural dyes (Allamanda Blanchetti (AB) and Allamanda Cathartica (AC)) as the sensitizers. Initially, TiO2 nanoparticles were synthesized by sol–gel technique and a thin film of TiO2 was formed on the FTO substrate by Doctor Blade technique. Then, they were annealed at 400, 500, and 600 °C to act as the photoanode. X-ray diffraction analysis shows the prepared samples have tetragonal crystal structure with anatase and rutile phase. The average crystallite size was found to be 10–17 nm when the annealing temperature (TA) was increased from 400 to 600 °C. From UV–DRS analysis, the percentage of reflectance was found to starts at 315 nm. The bandgap analysis shows the transitions were indirect allowed and the bandgap value decreases from 3.6 to 2.8 eV when the TA increases from 400 to 600 °C. From the optical absorption spectra, the absorption of dye and dye-sensitized TiO2 was found to be in the visible region. From PL analysis, the emission peak intensity of Ti4+ was increasing with decrease in oxygen (O2−) vacancies with TA increases from 400 to 600 °C was noted. FESEM analysis shows the synthesized particles were spherical and from EDS the presence of Ti and O was confirmed. From FTIR analysis, the functional groups presented in the prepared extracts were confirmed. The Efficiency of DSSC was found to be 1.16 and 0.30% for AB sensitized TiO2 (400 °C) and AC sensitized TiO2 (400 °C) as photoanodes. From Electrochemical Impedance Spectroscopic (EIS) analysis, DSSC with AB + TiO2 shows low charge transfer resistance compared with AC + TiO2.