Evolution of the band structure of β-In2S3-3xO3x buffer layer with its oxygen content

The evolution of the band structure of beta-In2S3-3xO3x (BISO) thin films grown by physical vapor deposition, with composition x, is investigated using x-ray photoelectron spectroscopy. It is shown that the energy difference between the valence-band level and the Fermi level remains nearly constant as the optical band gap of the films increases. As a consequence, the difference between the conduction band level and the Fermi level increases as much as the optical band gap of the films. The calculation of the electronic affinity chi of the BISO thin films shows that it decreases linearly from 4.65 to 3.85 eV when x varies from 0 to 0.14. This will facilitate fabrication of efficient Cu(InGa)Se-2-based solar cells having different absorber layer band gap. (C) 2003 American Institute of Physics.