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Open Access Publications from the University of California

Spectroscopic evidence for a surface layer in CuInSe2 : Cu deficiency

  • Author(s): Han, Sung-Ho
  • Hasoon, Falah S.
  • Hermann, Allen M.
  • Levi, Dean H.
  • et al.

Published Web Location

The near-surface region of thin-film polycrystalline (PX) CuIn1-xGaxSe2 (CIGS) is considered important because it is the region where the electrical junction forms in a CIGS photovoltaic device. Spectroscopic ellipsometry measurements of polycrystalline CuInSe2 films reveal that there is a thin layer at the surface which has different optical and electronic properties from those of the bulk film. This surface layer of thin-film CIGS has a larger band gap and greater spin-orbit interaction energy than the bulk film. These properties indicate that the surface layer is more Cu deficient than the bulk in the nearly stoichiometric thin-film PX-CIGS used in photovoltaic devices. This work provides an insight into the importance of surface layer engineering for photovoltaic device design. (C) 2007 American Institute of Physics.

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