## 2 Materials and Methods  
### Cell's Fabrication Procedure  
For the WE preparation, a conductive FTO (SnO\({}_{2}\): F; 2.2 mm TCO22-15) glass was firstly shaped as a square of 2.5 \(\times\) 2.5 cm and cleaned with water, soap, acetone, and ethanol in an ultrasonic bath, 10 min each wash. Initially, electrodes were immersed for 30 min at 70 \({}^{\circ}\)C in a solution of TiCl\({}_{4}\) (844 \(\upmu\)L in 100 mL of distilled H\({}_{2}\)O; since the reaction is exothermic, the solution is obtained in an immersed beaker in an ice bath). This treatment mainly has two effects: increasing the resistance of the interaction between the FTO substrate and the TiO\({}_{2}\) film and blocking the charge recombination process between the electrons present on the semiconductor conduction band and the I\({}_{2}\) in the electrolyte. The suspension of TiO\({}_{2}\) plays a central role in the construction of the solar cell. Factors such as the size of the TiO\({}_{2}\) nanoparticles, the crystalline purity of the same, and the subsequent sintering steps are extremely important for the efficiency of the cell. In order to reduce the number of variables in the cell, we used a commercial TiO\({}_{2}\) suspension  
Figure 1: Molecular structure of (**a**) C106 dye and of (**b**) Y123 dye. for all devices: the DYESOL DSL 18 NR-T (particle size of about 10-15 nm). The screen-printing technique was used in this study to deposit the TiO\({}_{2}\) paste [37]. This method allows obtaining TiO\({}_{2}\) films with precisely defined areas and constant thickness: the screen printing frame is made with a variable porosity polyester fabric, stretched on a frame of aluminum or iron. After blocking the conductive glass plate (15 cm \(\times\) 4 cm) below the area of interest, several drops of TiO\({}_{2}\) paste are deposited on the frame and distributed through a doctor blade, maintaining, during this operation, a steady pressure. Finally, we proceed with a slow ramp sintering until 500 \({}^{\circ}\)C. The active area of the obtained photo anodes is approximately 0.181 cm\({}^{2}\). C106 (purity \(\geq\) 85%) and Y123 (purity 99%) dyes were purchased from Dyesol and Dyenamo, respectively. WE were soaked in the dye solution (5 mM in terbutanol/acetonitrile in a 1:1 ratio) and the dye sensitization was carried out at room temperature for one night. Colored electrodes were washed with distilled water, then ethanol, and then dried. The homemade electrolytic solution J8* was prepared in acetonitrile (AN), a low-viscosity solvent (0.47 cp), and valenoritrile (whose viscosity is 0.78 cp) in a volumetric ratio of 85:15 v/v. In this way, a less volatile solution was obtained, resulting in a mixture with the following composition: LiI 0.1 M, I\({}_{2}\) 0.05 M, tertbutyl pyridine (TBP) 0.5 M, and methyl-propyl imidazolium iodide (MPII) 0.6 M (J8*) [25]. High-stability electrolyte (EI-HSE) was purchased from Great Solar; its composition is not quantitatively indicated, and it consists of a dissolved redox couple of triiodide/iodide in 3-methoxypropionitrile (3 MPN) solvent with inorganic iodide salt, organic iodide salt, and imidazole compound as additives as reported from the seller. Similar to WE, a conductive glass of FTO was cut, 2.5 \(\times\) 2.5 cm, and cleaned to prepare the CE. The conductive surface was covered with a thin layer of catalyst. The latter performs the task of lowering the activation energy for the reduction of the I\({}^{-}\)/I\({}^{3-}\) torque. A few drops of hexachloroplatinic acid (H\({}_{2}\)PtCl\({}_{6}\)) solution were deposited on the substrates, arranged on a heating plate at 50 \({}^{\circ}\)C with the conductive surface facing upwards. The heat allows the evaporation of the solvent. Subsequently, the glasses were heated at 400 \({}^{\circ}\)C for 15 min, to eliminate hydrogen and chlorine, leaving only the metallic platinum.