The IL C₈mimPF₆ was synthesized in one step without the use of solvents, according to the procedure described by Fang et al. [22] , which comprises reacting equimolar amounts of 1-methylimidazole (99%), 1-bromooctane (99%) and potassium hexafluorophosphate salt, KPF₆ (98%); all reactive were purchased from Aldrich.

The monomer was synthesized as described by Martinez et al. [23] . First, was synthesized the Grignard reagent, octyl magnesium bromide (Figure 1(a)), a new C-C bond was then generated by Kumada coupling between the octyl group and the thiophene ring through the catalyst NiCl₂ (dppp) (Figure 1(b)). Next, formylation, also known as Vilsmeier reaction, was formed in situ from DMF and POCl₃ (Figure 1(c)). Finally, (E)-1,2-di-(3-octyl-2-thienyl) vinylene (OTV) was performed by the McMurry reaction using the Mukaiyama reagent (TiCl₄/ Zn in THF) [24] [25] [26] (Figure 1).

The polymer (POTV) was obtained by galvanostatic electrodeposition technique on three types of anode: Pt, ITO glass and PET with a work surface of 2 cm²; before using the electrodes, they were washed with H₂O and then with acetone in ultrasonic bath. As counter electrode a graphite bar or Pt sheet was used. The electrochemical cell has two compartments separated by a glass frit, allowing both electrodes in a parallel arranging in each compartment. The polymerization was conducted at a current density of 2 mA/cm² and at temperature of 30˚C, under nitrogen inert atmosphere. The IL is dried under vacuum at 75˚C prior to use. POTV was obtained from 0.4 mmol mixture IL/CH₂Cl₂ = 5/2 mL. The polymer was thoroughly washed with methanol, and then dried in vacuum oven at 70˚C for 6h.

The cell is based on superposed multilayer structured on ITO-glass according to the following layer order: ITO/MoO₃/POTV/C₆₀/BCP/Al/Se (BCP: bathocuproine). Two types of cells were made, depending on the deposition techniques: spin coating and vacuum evaporation. By the technique of spin coating a polymer solution of 10 mg/mL was used. 50 uL of solution is deposited on the substrate (glass ITO/MoO₃) at a speed of 1500 rpm for 30 seconds. The other components were deposited under vacuum at 10⁻⁴ Pa, the thin film deposition rate and thickness were estimated in situ on a quartz monitor: MoO₃ (2 nm), POTV (Deposited by stin coating), C₆₀ (40 nm), BCP (5 nm), Al (3.4 nm) and Se (10 nm). By the technique of vacuum deposition, in a vacuum chamber at 10^-4 Pa was placed the ITO-glass substrate and then was deposited the following components, layer by layer: MoO₃ (2 nm), POTV (10/20 nm), C₆₀ (40 nm), BCP (5 nm), Al (3.4 nm) and Se (10 nm). The use of buffer layer (MoO₃, BCP) is very important in these devices, because this layer produces good work function adjustment, surface defects passivation, and ITO surface smoothing [27] . The devices were measured under conditions of darkness and light (AM 1.5 solar simulator of 100 mW/cm²) through the ITO glass. I-V graphs were obtained which were performed at room temperature without an inert atmosphere.

NMR, IR and UV-Vis. confirmed precursor and monomer purities and structures. The ILs were characterized by NMR, IR, cyclic voltammetry and refractive index. The POTV was analyzed using mass spectroscopy, UV-vis, IR, XPS, Raman, morphological analysis SEM-EDX and differential pulse voltammetry (DPV).

Obtaining polymers using as solvent ILs was feasible without the need to add support electrolyte to the process. However, even having a structural similarity between the monomer unit and the cation of IL, i.e. both have a planar aromatic structure and side alkyl chain it was not possible to solubilize the monomer in pure IL. This situation may be associated with a faint solvation by the IL, due to the strong interactions between cation-anion of IL, being at a disadvantage the interactions cation-solute and anion-solute. Therefore CH₂Cl₂ was used only in the necessary amount to solubilize the monomer unit in the required volume of IL. In turn, this process reduces slightly the viscosity of IL.

While the electropolymerization was a quick process that after the first few seconds of was started the current path, the coating was observed at the anode, the polymers obtained on anode of ITO glass and ITO-PET had poor adhesion on the electrodes. Rather important part diffused into the solution and avoided the formation of homogeneous polymeric films on the anode surface, appearing as islands. The Table 1 summarizes the experimental conditions of the electropolymerization.

The peaks absorption of UV-vis (Figure 2) was associated with the transitions of the aromatic rings π − π*. It was observed that there are no significant variations in the displacement of the bands by the use either platinum electrodes or ITO glass; the maximum peaks only differ in 7 nm.

Figure 3 shows the FTIR spectrum for POTV, which were measured through the attenuated total reflection (ATR). The blue spectrum corresponds to the polymer obtained on the electrode ITO-PET, while green spectrum corresponds to POTV obtained on Pt. The absorption bands in the range of 2900 - 2800 cm⁻¹ are assigned to C-H stretching of alkyl chain (octyl group). To The 1557 cm⁻¹ stretching vibration is assigned to C = C. The vibrations of the ring corresponding to C-C and C-H appear to 1268 and 1129 cm⁻¹, respectively. P-F vibration binding of the counterion appears in 828 cm⁻¹. Finally, C-H deformation (out of plane) corresponds to the thiophene ring in the 2,5-disubstituted α-α’ [17] link to 709 cm⁻¹.

In the resonance Raman spectrum (Figure 4) 1601 cm⁻¹ signal was assigned to the vinyl bond stretch between C = C. The signals at 1542 and 1421 cm⁻¹ corresponds to the asymmetrical and symmetrical stretching of the C = C of the thiophene ring, respectively. Finally, vinyl bond C-H deformation was observed at 1298 cm⁻¹ and C-C stretching at 1196 cm⁻¹.

a. 4 electrodes of ITO-PET were submerged c/1h.

In the XPS spectrum, Figure 5, the elements present in the sample were: C1s, S2p, F1s, O1s y P2p [28] . The prominent mark was assigned to F1s located at 686.3 eV. This signal together with signal P2p clearly confirm the incorporation of the dopant anion and the polymer matrix [29] .

The morphology of the different polymers was determined by SEM (Figure 6). The image for POTV on ITO-PET (picture on the left of Figure 6) shows a no- dular morphology, whose nuclei have the appearance of a cauliflower, coincident with those reported in literature [30] [31] . A similar situation was observed for POTV on Pt (picture on the right of Figure 6), in whose morphology it is possible to appreciate granular and coral-like growths. These small differences may be associated with the nucleation and growth type of the polymer in the electropolymerization process on the different substrates. Also can be attributed to the influence of possible links in positions α, β in the POTV. Observing morphology can be deduced that the process was determined by the type of nucleation in 3D [32] [33] .

From the EDX (Figure 6) the incorporation of the anion PF⁶⁻ (part of IL) was confirmed in the polymer.

Differential pulse voltammetry (DPV) (Figure 7) was performed in benzonitrile using TBAPF₆ (0.1 M) as supporting electrolyte. A platinum wire as the counter electrode, the pseudo reference electrode Ag/AgCl and platinum as working electrode. Ferrocene was used as internal reference. From the graph were obtained the oxidation and reduction potential of the polymer. The band gap for

the polymer was calculated from the HOMO-LUMO voltammetric measurements, giving values of 5.33eV and 3.43 for HOMO and LUMO respectively, thus the calculated band gap energy was.

The cell was based on the following structure: ITO-glass/MoO₃/POTV/C₆₀/BCP/ Al/Se. Two techniques were employed to place the polymer on the substrate: spin coating and vacuum evaporation. For each cell a total of six I-V graphs were obtained, the average of its parameters allowed us to elucidate the capacity of the OSC. The Table 2 summarizes the values obtained from the I-V charts. Energy conversion efficiencies for cell whose polymeric material was deposited by spin-coating was 2.1 × 10⁻³% and by evaporation was 2.9 × 10⁻⁴%. The Figure 8 shows one of the most representative I-V graphs of each cell.

It can be observed that the best PCE values are achieved by spin-coating deposition, recording a value of 2.1 × 10⁻³%. A strong decrease of Rsh and Rs is observed in comparison to evaporation deposits, in the same way the values of Voc, Jsc and FF are better. On the other hand, evaporation leads to the breakdown of polymer chains, resulting in structures with less conjugation, a situation that is reflected in a slightly lower value of PCE of 2.9 × 10⁻⁴%. This contributes to an increase of the value Rs in the device which leads to a decrease in the performance of the device, and finally to a low value of the FF.