Raman scattering characterisation of electrochemical growth of CuInSe ₂ nanocrystalline thin films for photovoltaic applications: Surface and in-depth analysis

A detailed Raman scattering analysis of the electrodeposition process of nanocrystalline CuInSe₂ layers for solar cell devices is reported. The correlation of the Raman spectra measured after the growth of the layers with different times has allowed investigating the chemical phases involved in the film formation process and their resulting nanocrystalline structure. The experimental data indicate the presence of elemental Se and Cu-Se binary compounds as the main secondary phases in the layers, which are directly related to the Se and Cu excess conditions used in the electrodeposition growth. These data show the existence of a high content of elemental Se at the region close to the interface of the layer with the Mo-coated glass substrate, this being likely related to a lack of incorporation of In at the initial growth stages. Nanoscopic Cu-deficient domains are also revealed by the presence of a band at the low frequency side of the main CuInSe₂ peak.