**5.1. Characterization of CIGS films obtained by electrodeposition plus mechanical perturbations**

The surface and cross-section morphology of the as-electrodeposited CIGS film are shown in **Figure 10(a, b)**. It is identified that by applying mechanical perturbations, the films are more compact and with less roughness compared to those obtained without applying mechanical

**Figure 9.** A graphic representation of electrodeposition signals versus time obtained during the electrodeposition process plus periodical mechanical perturbations: (a) WE potential and (b) WE current density [13].

perturbations. Films were grown with two different thicknesses, 1200 and 500 nm, that were subjected to the annealing process. The morphology of the annealed films is shown in **Figure 10(c– f)**. In both cases, it is identified that the films are more compact when it is compared to the one obtained by not using mechanical perturbations during the electrodeposition process. As it can be seen on the micrographs, there is coalescence of grains along the film cross section, and the morphology is dense and crack free. Coalescence is achieved due to the fact that the composition is more homogeneous, zones with copper-poor and cooper-rich have been minimized, and the activation energy for grain growth is more uniform throughout the film. This film morphology is completely different from that obtained without applying mechanical perturbations, where there was only coalescence in the first 300 nm of thickness. This is because a more compact

**Figure 9(a, b)** shows the typical signal of the WE potential and current density versus time collected during the electrodeposition process by applying periodical mechanical perturba-

current density were periodically related to the periodicity of the mechanical perturbations. The WE potential had a variation of −1.0 to −0.995 V at each mechanical perturbation. With the periodical mechanical perturbations, it was possible to make CIGS films with 1.2–1.5 μm in 20 min, and the growth was faster with respect to not using mechanical perturbations. The film composition rations were of Ga/(In+Ga) = 0.28 and Cu/(In+Ga) = 0.93. With the mechanical perturbations, no film dissolution was produced as is presented in pulse reverse

**5.1. Characterization of CIGS films obtained by electrodeposition plus mechanical** 

The surface and cross-section morphology of the as-electrodeposited CIGS film are shown in **Figure 10(a, b)**. It is identified that by applying mechanical perturbations, the films are more compact and with less roughness compared to those obtained without applying mechanical

**Figure 9.** A graphic representation of electrodeposition signals versus time obtained during the electrodeposition

process plus periodical mechanical perturbations: (a) WE potential and (b) WE current density [13].

. The WE potential and the

tions to the WE. The average current density value was 2.4 mA/cm<sup>2</sup>

110 Perturbation Methods with Applications in Science and Engineering

electrodeposition.

**perturbations**

**Figure 10.** Micrographs of the surface and cross section of the films that have been grown in a potentiostatic mode with mechanical perturbations. (a,b) without annealing, (c,d) annealed films with a thickness of 1200 nm, and (e,f) annealed films with a thickness of 500 nm [13].

process clearly increased the grain size, as indicated by the reduction of the peak full-width at half-maximum (FWHM). For the CIGS film formed without mechanical perturbation, the crystal size was 26.6 nm, and for the CIGS film formed with mechanical perturbation, the crystal size was 26.0 nm. This can be expected because the peaks of both films have FWHM that are alike. The annealed films, in a similar manner to the as-electrodeposited film, have a greater intensity in the diffraction peaks for the film formed with mechanical perturbation than for the film formed without mechanical perturbation. Probably, one of the reasons is that the films obtained with mechanical perturbation are denser. The results shown by XRD and SEM clearly demonstrate the advantages of applying periodic perturbations during the

Mechanical Perturbations at the Working Electrode to Materials Synthesis by Electrodeposition

http://dx.doi.org/10.5772/intechopen.78544

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Employing periodic mechanical perturbations during the electrodeposition process allows a better distribution of ionic species on the working electrode surface. This methodology represents a novel approach for the fabrication of thin films by electrodeposition. This has been demonstrated successfully in the synthesis of compact CIGS thin films. It has the advantage to obtain a homogeneous morphology CIGS films in the as-electrodeposited films, as well, in the annealed film. In this strategy, there is no dissolution of the film during the electrodeposition process, as taking place in pulse-reverse electrodeposition. It is a route to obtain CIGS films by electrodeposition with compact morphology and large grains. Further studies should be done about the mechanical perturbation frequency and the effect on the solar cell efficiency.

This chapter was supported through the projets C16-FAI-09-58.58, PAPIIT-IN117216, CONACYT-82306 and CONACYT-UNAM (LIFYCS), specially with the use of ICP-AES ULTIMA 2 and SEM S-5500. Also, we would like to thank María Luis Ramón García for the

1 Facultad de Ingeniería, Universidad Autónoma de San Luis Potosí, Zona Universitaria

2 Instituto de Energías Renovables, Universidad Nacional Autónoma de México, Temixco,

3 Centro Universitario de Tonalá, Universidad de Guadalajara, Tonalá, Jalisco, México

, Lizbeth Morales Salas2 and

electrodeposition process, this being a new route to synthesize thin films.

**6. Conclusion(s)**

**Acknowledgements**

**Author details**

Baudel Lara Lara1

Morelos, México

Alejandro Altamirano Gutiérrez<sup>3</sup>

XRD and Rogelio Morán Elvira fo SEM measurements.

\*Address all correspondence to: ing\_lara@uaslp.mx

Poniente, San Luis Potosí, S. L. P., México

\*, Arturo Fernández Madrigal<sup>2</sup>

**Figure 11.** GIXRD diffraction pattern of CIGS films obtained with mechanical perturbation and without mechanical perturbation: (a) as-electrodeposited films and (b) annealed films [13].

morphology was obtained from the electrodeposition process with mechanical perturbations, and it represents a route for obtaining CIGS films by electrodeposition with improved morphology.

**Figure 11** shows the GIXRD diffraction pattern for the film deposited with a potentiostatic mode with and without periodical mechanical perturbations with an incidence angle of 1.5°. The CuIn<sup>x</sup> Ga(1-x)Se2 , Mo, and MoSe<sup>2</sup> structures are identified according to PDF#35–1102, PDF#42–1120, and PDF#29–0914. First of all, the films exhibit a highly (112) preferred orientation. From **Figure 11(a)**, it can be seen that the as-electrodeposited film shows a poor crystallinity, which is a characteristic of CIGS films before annealing. Also, a diffraction peak of the Mo, which is the substrate and back contact, is identified. The main difference in the diffraction patterns is that there is a greater intensity in the film formed with mechanical perturbation than the film formed without mechanical perturbation. This indicates the presence of higher crystallinity in the film obtained with the mechanical perturbation. **Figure 11(b)** presents the diffraction patterns of the annealed films in selenium atmosphere; these show a high crystalline quality, which is revealed by the well-defined chalcopyrite peaks. The annealing process clearly increased the grain size, as indicated by the reduction of the peak full-width at half-maximum (FWHM). For the CIGS film formed without mechanical perturbation, the crystal size was 26.6 nm, and for the CIGS film formed with mechanical perturbation, the crystal size was 26.0 nm. This can be expected because the peaks of both films have FWHM that are alike. The annealed films, in a similar manner to the as-electrodeposited film, have a greater intensity in the diffraction peaks for the film formed with mechanical perturbation than for the film formed without mechanical perturbation. Probably, one of the reasons is that the films obtained with mechanical perturbation are denser. The results shown by XRD and SEM clearly demonstrate the advantages of applying periodic perturbations during the electrodeposition process, this being a new route to synthesize thin films.
