Guest-Host Interactions in Symmetrical Carboxy Heptamethine Cyanine Dyes-Titanium Dioxide Systems: Synthesis, Theoretical Calculations, Aggregation Properties, and Application in Dye-Sensitized Solar Cells

Figure 4

Normalized solid-state absorption spectra of dye 13 obtained from the different adsorption methodologies (#1-#5), where #1: dye concentration—5.0 mM, DCA concentrations—20 or 40 mM, TiO₂ temperature—80°C, and adsorption time—24 h; #2: dye concentration—5.0 mM, DCA concentration—40 mM, TiO₂ temperature—22°C, and adsorption time—24 h; #3: dye concentration—5.0 mM, DCA concentration—40 mM, TiO₂ temperature—22°C, and adsorption time—1 h; #4: dye concentration—0.1 mM, DCA concentration—20 mM, TiO₂ temperature—22°C, and adsorption time—1 h; #5: first step: DCA concentration—20 mM and second step: dye concentration—0.1 mM, TiO₂ temperature—22°C, and adsorption time—1 h.