Civil Engineering Reference
In-Depth Information
smaller amounts of material, in addition to the lower manufacturing process
cost. It was theorized that the ideal solar panel would not utilize the wafer
principle as it uses a lot of material, hence the development of the thin fi lm
principle. The thin fi lm was created by using various inexpensive deposition
methods to produce thin layers of silicon, micrometres thick, which enable
approximately 90-95% of the solar light spectrum to be absorbed, compa-
red to the fi rst generation which would need to be 200-400
m thick for
the same amount of absorption. The difference in this silicon material is it
contains almost no crystal structure, hence can neither be referred to as
crystalline nor multi-crystalline. Rather, it is named amorphous silicon
(a-Si).
The main issue with this material is its low electrical properties, hence
not improving overall effi ciency. Many interesting structures and processes
have enabled such PVs to reach approximately 10% effi ciency, but this is
anticipated to improve. One of the largest issues with the a-Si is the Staeb-
ler-Wronski phenomenon (Kolodziej, 2004), which basically causes degra-
dation when the panel is exposed to sunlight. So, although this component
of the second generation technology has good potential due to its low cost,
more research and development is required to ensure a stable and effi cient
device. One of the most interesting principles associated with this techno-
logy is it has the ability to be either fl exible or semi-transparent, leading
the way to further installation options. If no fl exibility is required, it is
placed between two pieces of glass with no frame, but if fl exibility is needed
then it can be deposited onto plastic fi lm. This thin fi lm technology is nor-
mally connected with the second generation, but silicon is not the only
material that can be linked with this group of PV technologies.
Panels are also commonly associated with materials that include cadmium
telluride and cadmium sulphide layers (CdTe/CdS) or members of the
chalcopyrite family, copper indium gallium selenide and copper indium
diselenide (CIGS/CIS), which offer high-effi ciency possibilities. As can be
seen, the difference between these two initial types of PVs is the material
used and the manufacturing methods, rather than a difference in the method
of conversion.
One further technology that is sometimes considered under this second
generation umbrella is the PVs made from organic materials, which cur-
rently (2012) have a very low effi ciency of 1-8%, but have potential because,
not only is the material accessible, but it is reasonably priced to further
support easy and cheap manufacturing methods. These organic devices,
which operate in a similar way to the photosynthesis process, could in the
future offer an alternative to inorganic materials.
It has been anticipated that not only will this second generation techno-
logy have the market share by 2015 but also by this year it will be able to
provide power at a lower cost than fossil fuel. It is only with time that we
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