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

mono-, poly- and amorphous silicon, cadmium telluride, and copper indium gallium
selenide/sulde (CIGS) have become the most used materials.
1.2.2 Three Generations of PV cells
The major challenges faced by the PV industry are the high costs of production
for a relatively low eciency 1 . To overcome this challenge, PV cells are categorized
into three generations on their genealogical basis, and all three are being currently
investigated towards protable development. Figure 1.2 shows a consolidated representation
of the conversion eciencies and cost of the three generations of PV
cells.
tel-00916300, version 1 - 10 Dec 2013
Figure 1.2: Consolidated representation of conversion eciencies and cost of the three
generations of PV cells [Conibeer 07].
The rst generation PV cells are largely based on mono- or polycrystalline Si
and has the major share of over 85% commercial production. Laboratory eciencies
of 23-24.7% [Green 93, Green 01a] and commercial module eciencies lying between
14-19% [Parida 11] have been reported from these cells. The main drawback of rst
generation cells arises from the indirect bandgap nature of Si which necessitates a
thick active layer which is at least 50 µm thick for ecient absorption [Chopra 04].
In general, about 300-500 µm thick layer is used for a solar cell, which accounts to
about 28% of the module cost. The sophisticated procedures for high temperature
processing to obtain highly puried electronic grade silicon for a device, combined
with the need for large material area has made these solar cells expensive with about
US$ 3.50/W.
The second generation PV cells aim at reducing the production costs by
1 Eciency = Maximum electrical power/ Incident optical power
7