Real-time raman scattering analysis of the electrochemical growth of CuInSe₂ precursors for CuIn(S,Se)₂ solar cells

This work reports the in-situ analysis of the electrochemical growth of CuInSe₂ precursors for the production of low cost CuIn(S,Se) ₂ based solar cells by Raman scattering measurements performed at real time conditions. The measured data point out the existence of three stages in the growth of the layers: (a) initial stage characterised by the preferential growth of elemental Se and Cu rich phases, (b) intermediate stage where the preferential growth of the main CuInSe₂ phase takes place, and (c) final stage with a gradual increase in the spectral contributions from Se and CuSe secondary phases. This correlates with the spectral evolution of Cu poor ordered vacancy compound phases present in the layers, in spite of the overall Cu excess conditions typically used in these processes. These in-situ measurements allow elucidating the main growth mechanisms involved in the electrochemical synthesis of CuInSe₂. Existence of different growth stages during the process determines a non-homogeneous in-depth distribution of the secondary phases in the deposited layers that are determining for the final efficiency of the devices.