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

Abstract

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.