ABSTRACT

The main aim of the present thesis is the synthesis of hybrid materials based in zinc oxide (ZnO), through the electrodeposition technique. The hybrid materials compounds of ZnO/organic dye have shown new physical, chemical and electrical properties that can be modified for photovoltaic application, mainly in dye sensitized solar cell (DSSC). 
The combination of ZnO and dye based in Ruthenium (Ru) as N3 and N719, Copper (Cu) as Copper phthalocyanine (Ts-CuPc), Bromine (Br) as Eosin-Y can be used to meet the right combination for creating nanostructures able to increase the absorption of light. 
The electrodeposition process has been performed in a three electrode electrochemical cell. The solution consisted the ZnCl2, Zn(NO3)2 as precursors in aqueous solvent and KCl  to form the electrolyte. The grown conditions such as temperature, potential and concentration of dye, for the deposition of hybrid films were obtained by cyclic voltammetry. For the study and optimization of these hybrid films were used different techniques of physical characterization: Scan Electronic Microscopy (SEM), Dispersive Energy Espectroscopy (EDS), Atomic Force Microscopy (AFM), The X-Ray Diffraction (XRD), transmittance, photocurrent. And finally, these films were integrated into DSSC devices.  
The results obtained were as follows:
- Optimization and characterization of the growth of the thin film of ZnO
 It was observed that the hexagonal structure of ZnO is modifiable and highly dependent on the concentration of both the precursors and the solvent in the solution. Films with better crystalline properties were obtained at a deposition temperature of 80 °C and a potential of -0.9 V.
- Growth optimization and characterization of thin films of ZnO/hybrid using different dyes: Eosin-Y, T-CuPc and N719
Electrical and physical properties can be modified by varying the concentrations of dyes. In the case of Eosin-Y porous structures were observed in films for dye concentrations lower than 1x10-4 M. In the case of TS-CuPc were never homogeneous structures obtained for concentrations greater than 1x10-4 M, reducing the capacity of their electrical properties. Finally, for the N719 use the immersion technique due to poor incorporation of the molecules in the crystal structure of ZnO. With this technique were obtained porous structures with high absorption of light regardless of the concentration of dye.
- Integration of hybrid films in DSSC type cells. 
The integration of the hybrid films in DSSC devices made with ZnO/ZnO/Eosin-Y generated an approximate efficiency of energy conversion of 0.8 %. The kinetic studies showed that electron transport is possible to generate the injection of electrons in the semiconductor and generating a flow of electrons in spite of similar energy levels between the ZnO (conduction band) and Eosin-Y (Molecular Orbital lowest unoccupied, LUMO).
Hybrid film of ZnO/Ts-CuPc generated a conversion efficiency of less than 1 % found only for DSSC having a low dye concentration. By DFT theoretical studies showed that it is possible a direct charge transfer between the energy levels of the dye only when a certain level LUMO +1.
Finally, for the DSSC of ZnO/N719 had an efficiency of approximately 1.7 % and a rapid injection of electrons in the semiconductor. This last acceptable value and comparable efficiencies obtained until 2.4% by Baxter et al. for this type of DSSC.
This research shows that the cathodic electrodeposition technique is a technique suitable for obtaining ZnO hybrid films with different dyes. Furthermore, it is a low-cost technique that permits the electrodeposition of compounds at low temperatures and controlling the growth conditions of the structures due to that is the key to the maximum absorption of photons and generation of intensity in a DSSC.