Films minces à base de Si nanostructuré pour des cellules ...

tel-00916300, version 1 - 10 Dec 2013
Figure 1.11: Schematic representation of third generation solar cell principles.
concept was proposed [Green 06] considering the stability, compatibility and availability
of all the stacked materials required for the cell. Si nanostructures embedded
in barriers such as silicon oxide (SiO 2 ), silicon nitride (Si 3 N 4 ) and silicon carbide
(SiC) possess high absorption coecients and short diusion lengths allowing their
incorporation in a tandem cell [Green 05, Conibeer 06]. Though other approaches
promise higher theoretical eciencies, tandem cell approach is the only successfully
demonstrated approach so far.
Impurity, Intermediate and Multi bandgap solar cell : In order to absorb
the sub-bandgap photons, recent attempts have been made on Impurity Photovoltaic
eect (IPV), by introducing an impurity level in the semiconductor band
gap. Finding a suitable wide band gap semiconductor combined with a ecient
radiative impurity is the major challenge [Beaucarne 02]. Intermediate Band Solar
Cells (IBSC) is a related concept characterized by the existence of a narrow band
often called the intermediate band formed by the QD arrays within the forbidden
band gap [Luque 97]. IBSC with many bands are very promising photovoltaic devices
(theoretical maximum eciency-87%) and are known as multiband solar cells
[Green 02]. It is very dicult to produce such solar cells, because a signicantly
high quantum dot density (∼10 19 cm −3 ) is needed to form the intermediate band
and there is no successful demonstration of IBSC yet. Recently, some attempts
have been made to obtain the intermediate band structure using InAs quantum dot
arrays embedded in GaAs [Luque 05], Si/SiO 2 superlattices [Jiang 06a], and Si QDs
[Kurokawa 06, Quan 11].
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