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

Chapter 1
Role of Silicon in Photovoltaics
tel-00916300, version 1 - 10 Dec 2013
1.1 Energy needs in the global scenario
The growth of industrialization and sophistications in the human life-style have
enormously increased the global energy demands. The fossil fuels such as coal, oil
and natural gas have been the major source of electricity from the last two centuries,
owing to its aordability. Though 85% of today's energy needs are satised by
burning fossil fuels, it is accompanied with two major environmental footprints: 1)
Depletion of natural resources, and 2) CO 2 emission of about 26.7 billion tons into
the atmosphere each year [Internet 01]. As a result of CO 2 emission, there is an
increase in the global mean surface temperature and the sea level. According to
a report on climate changes [IPCC 07], it is estimated that the temperature has
increased by 1.8-4.0°C in the 20th century, due to global warming. Though the
production and consumption of renewable energies like solar, wind, ocean, biomass,
geothermal resources, and biofuels have increased over the years, it accounts to only
15% of the global energy consumption as per 2007 statistics (Fig. 1.1). Hence, the
world faces an urge towards maximum utilization of renewable resources to meet the
global energy needs. The enormous quantity of non-polluting energy from the Sun
has gained attention as one of the major alternative energy source leading towards a
sustainable development. Despite being an abundant source of energy, only 0.015%
of world's electricity comes from the solar energy [Crabtree 07] due to the lack of
ecient technology to harness and store the solar radiation.
In general, solar energy can be harnessed and utilized for energy generation by
two dierent approaches [Internet 02]:
1. Solar Thermal Approach, which deals with the direct usage of Sun's radiation
as heat such as in passive water heaters.
2. Solar Photovoltaic (PV) Approach, which deals with the usage of semicon-
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