Controlling the TiO₂–Dye Nanomolecular Interactions for Improving the Photoconversion in Transparent Dye‐Sensitized Solar Cells

Herein, transparent dye‐sensitized solar cells (DSSCs) are fabricated using two sensitizing dyes aiming toward panchromatic photon harvesting following two different approaches of dye adsorption such as using dye cocktail and sequential dye adsorption. A combination of complementary yellow‐colored dye (D‐131) and green‐colored far‐red‐sensitive squaraine dye (SQ‐140) is judiciously selected not only for panchromatic light absorption but also for bypassing the absorption in the high eye‐sensitivity wavelength region (500–600 nm) region to improve the transparency. The DSSC fabricated using a dye cocktail of D‐131 and SQ‐140 in a 9:1 molar ratio exhibits a photoconversion efficiency (PCE) and average visible transparency (AVT) of 3.89% and 36.9%, respectively. In contrast, stepwise and controlled dye adsorption of SQ‐140 followed by D‐131 on mesoporous TiO₂ leads to further improvement in the PCE from 3.89% to 4.50%, while AVT is reduced from 36.9% to 15.6%. This marked improvement in the PCE for the stepwise co‐sensitized transparent DSSCs is attributed to the suppression of unfavorable inter‐dye interaction leading to synergistic photon harvesting by both of the constituent sensitizing dyes.