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

the values from literatures for band to band recombinations in Si-np. Therefore,
the carrier lifetime (τ 34 ) is xed as 50 µs in all the simulations. The time taken for
fast radiative transitions to reach a maximum density of excited carriers (τ 23 ) and
the time to deexcite to ground state (τ 41 ) are xed arbitrarily as 100 and 500 ps
respectively.
5.4.3 Absorption and emission wavelengths
tel-00916300, version 1 - 10 Dec 2013
Figure 5.15: Extinction coecient curves as
a function of wavelength obtained from ellipsometry
and UV-Visible spectrophotometry.
The absorption wavelength of Si-np
was estimated by tting the absorption
k (λ) curves (obtained from ellipsometry
and UV-Vis spectrophotometry
3 ) using Forouhi-Bloomer model
[Forouhi 86]. Figure 5.15 shows the typical
example of k (λ) curves, obtained
with SRSO/SRSN ML.
The maximum absorption of the material
is centered around 260 nm (4.76
eV). Similar curves were obtained also
with SRSO/SiO 2 MLs. Hence, it is valid
to link this absorption wavelength at
260 nm to Si-np absorption as the SRSO
sublayer containing Si-np is the common
sublayer in both MLs.
The emission of Si-np mostly ranges between 720-830 nm (1.5 eV-1.7 eV) as
demonstrated experimentally in our layers in the previous chapters. Hence in the
modeling, the emission wavelength is xed in this range when assuming the existence
of a single peak in the PL spectra.
As mentioned in the previous sections, the other parameters such as the electric
eld amplitude of the pump (Ar laser) and the initial population of emitters are
xed at 8x10 3 V/m and 10 26 Si-np/m 3 respectively.
5.5 Modeling SRSO/SiO 2 MLs
Figure 5.16 is shown to remind the PL spectra obtained experimentally from 50(3/3)
SRSO/SiO 2 1h-1100°C annealed (CA) ML in chapter 3. As mentioned earlier, curve
3 UV-Visible measurements were performed at Matériaux et Instrumentation Laser team of
the CIMAP laboratory
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