Abstract
M.Sc.
Thin film solar cells based on polycrystalline indium diselenide (CulnSe₂) and
amorphous silicon (a-Si:H) are promising candidates for the efficient conversion of
sunlight into useable, cheap electrical energy. However, typical device structures are
rather complex and consists of semiconductor/metal contacts as well as complicated
p - n and p - i - n heterojunctions. In this study, CulnSe₂ absorber layers with
excellent material properties were prepared by the selenization of metallic alloys. The
a-Si:H thin films were deposited by radio frequency (RF) glow discharge in vacuum.
The polycrystalline and amorphous absorber layers were deposited on glass and
flexible substrates. In each case, a systematic study was conducted in which all the
relevant processing parameters were varied over a broad range. These studies
indicated that the structural features of the substrate significantly influence the
structural features of the semiconductor thin films. The flexible substrate (kapton) was
characterized by the presence of ridges, which distorted the growth behavior of the
films. Deposition of ln/Cu/ln metallic alloys onto Mo coated glass (kapton) resulted in
discontinuous metallic alloys, which were characterized by the presence of separated
elongated island structures. The structural features of the precursors were maintained
in the absorber film after selenization in elemental Se vapor. The morphological
features of the CulnSe₂ absorber films were also critically influenced by the reaction
temperature And reaction period to Se. The structural features on a-Si:H was
significantly influenced by the structural features of the particular substrate used.
Atomic force microscopy (AFM) imaging in combination with statistical analysis
revealed higher roughness values when the amorphous semiconductor materials were
deposited onto kapton, which negatively impacts on the device properties of solar cell
devices.