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

andgap increases. Consequently, the absorption and emission properties are also
enhanced which are promising for photovoltaic as well as photonic applications.
The main challenge lies in optimizing the dielectric barrier thickness to provide
connement for the formation of QDs as well as carrier transport.
Prior to integration of these materials in a tandem cell device, preliminary investigations
of the Si QW or QD in each of these dielectric matrices become a necessary
part of research. In this context, this thesis aims at studying Si QW or QD in SiO 2
and Si 3 N 4 matrices in monolayered [Si-rich SiO 2 (SRSO) and Si-rich Si 3 N 4 (SRSN)]
and multilayered [SRSO/SiO 2 and SRSO/SRSN] congurations.
Major objectives of this thesis
tel-00916300, version 1 - 10 Dec 2013
For Si-based thin lms to be incorporated in a third generation solar cell device,
this thesis focuses on four major issues which are:
Material growth technique: Among the various methods available for the
fabrication of Si nanostructures, we use the sputtering technique for thin lm growth
in our laboratory. Increasing the density of Si-QDs is one of the most eective way
to enhance the optical and electrical properties required for a solar cell device that
takes advantage of Si QDs. Therefore, the rst major objective of this thesis is to
increase the Si excess incorporation in the material during the growth process that
would form Si-QDs upon suitable high temperature annealing.
Thermal budget: Decreasing the thermal budget (either the temperature or
time of annealing) required for the formation of Si-QDs would be attractive. Therefore,
the second major objective of this work is to explore ways of favoring the
formation of Si-QDs even in the as-grown state, and also to analyse various temperature/time
of annealing towards possible lowering of the thermal budget.
Material properties: Photoluminescence (PL) measurements are indicative
of the possibility to create excitons in the material that facilitate absorption and
electrical transport in a future PV device. Achieving signicant emission is a challenge,
and understanding the origin of these emission becomes the next important
challenge. Therefore, the third major objective of this work is to obtain size controlled
Si-QDs, analyse the structural properties of the material and to understand
the inuence of the materials microstructure on optical properties.
Optical and geometrical eects on emission: Besides the inherent material
properties depending on the Si-QD density, various other factors such as the angle of
incidence of the incident light, its prole inside the thin lm structure with regard to
thickness and refractive indices of the material etc., may aect the optical properties.
These eects have to be considered with a special attention during device fabrication,
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