Electrodeposited CuIn(S, Se)2 films for low cost high efficiency solar cell applications: microstructural analysis

This paper describes the detailed microstructral characterisation of S-rich CuIn(S,Se)₂ absorbers fabricated by single step electrodeposition (ED) of nanocrystalline CuInSe₂ precursors followed by rapid thermal annealing under sulphurising conditions. This has allowed identifying the main secondary phases in the precursors as elemental Se, CuSe and Cu₂Se. The Raman spectra from these precursors also show the presence of Cu-poor OVC domains, which contrasts with the Cu-rich conditions used in the ED growth. This has been related to the presence in the annealed layers of In rich secondary phases, which lead to a slightly Cu poor composition. Moreover, the used sulphurising conditions also lead to the formation of a relatively thick MoS₂ layer between the absorber and the Mo back contact. The high microcrystalline quality of the layers is likely responsible of the relatively high efficiency value of 11% of the solar cells fabricated with these absorbers.