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

Abstract

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.