Effect of TiO2 thickness on power conversion efficiency in co-sensitized dye-sensitized solar cells

This study investigates the co-sensitization of natural dyes with synthetic dye N719 in dye-sensitized solar cells (DSSCs). Natural dyes from Spinacia oleracea (green spinach) and Plumeria rubra (frangipani) were extracted and analyzed via UV-Visible spectroscopy to assess their light absorption capabilities. Co-sensitization was carried out by blending these extracts with N719, aiming to broaden the absorption spectrum and improve overall efficiency. The impact of titanium dioxide (TiO2) photoanode thickness (55,000 nm and 110,000 nm) and different substrates (indium tin oxide and fluorine-doped tine oxide) on the power conversion efficiency (PCE) was systematically studied under controlled fabrication conditions using 4 different cases (Case A, Case B, Case C, and Case D). Among the four dye combinations tested, the N719-frangipani co-sensitized DSSC fabricated on FTO glass with a 110,000 nm TiO2 layer demonstrated the highest PCE of 0.0324%. In contrast, the lowest performance (0.000014%) was observed in the cell sensitized with a spinach–frangipani blend on ITO. UV-Visible spectral analysis confirmed broader light absorption for co-sensitized dyes, while I–V characterization revealed enhanced charge transport in thicker photoanodes and FTO-based cells. These findings demonstrate the potential of co-sensitization using natural dyes to partially replace synthetic dyes, offering a cost-effective and environmentally friendly approach to DSSC fabrication.