Inorganic Solid State Solar Cell with Ultra-thin Nanocomposite Absorber based on Nanoporous TiO2 and In2S3
Date
2009Author
Herzog, Christian
Belaidi, Abdelhak
Ogacho, Alex
Dittrich, Thomas
Type
ArticleMetadata
Show full item recordAbstract
The increase of the diffusion length of a wet chemically prepared
absorber by introducing a nanocomposite morphology and the
resulting potential for reaching high energy conversion efficiencies
were demonstrated.
The basic processes of light absorption and photo-generation of
charge carriers, charge transport and charge separation are separated
in space in nanostructured solar cells. This opened up the opportunity
to applymaterials with low diffusion length which can be produced at
low temperatures and even under wet chemical conditions and raised
the hope that production costs of solar cells can be strongly reduced
by implementing nanostructured materials. In nanostructured solar
cells the absorber layer has to be folded since the local absorber
thickness is usually much less than the absorption length. For
example, for dye-sensitized solar cells the internal surface area is
increased by a factor of about 1000,1 for solar cells with extremely
thin absorber a factor of about 10 is sufficient.2
The thickness of an inorganic absorber layer has to be much larger
than the tunnelling length to avoid tunnelling recombination between
electron and hole conducting regions. From this point of view the
minimum thickness of inorganic absorber layers should be at least
about 20–30 nm in systems with solid electron and hole contacts.2
However, the diffusion length of photo-generated charge carriers is
usually of the same order or even less for wet chemically prepared
absorber layers.3 In fact, the low diffusion length limits the energy
conversion efficiency. We should mention that the diffusion length of
a given absorber is quite fixed and can hardly be increased for a given
deposition technique.