PV cells are made of semi-conductors materials
and they can be divided generally in different aspects
concerning the manufacturing technology, the energy conversion efficiency,
as well as the absorbance light efficiency and so
we can divide them in two categories, that are: crystalline cells and thin film
cells. The more reliable, but less cost effective,
are the crystalline cells while thin film are more promising for the future.
The first one is divided in monocrystalline and polycrystalline cells.
Monocrystalline cells are more reliable and old category
and they are mainly performed using the Czochralski method,
that is a special and patented method used for the growth of a single crystal
and then the single crystal ingot is cut in wafers of 200 to 400 micrometers
and these cells interconnect working as a module
that can be used for PV or BIPV applications. While the polycrystalline method is different,
less efficient and the cells can be ribbon -growth????
or sliced (from blocks of cast polycrystalline silicon ). And it generates less cost for
the modules even if still there is less efficiency
but in the market you can find this two different type of modules
at the same power and more or less the same cost
even if in the monocrystalline case, the efficiency can rise
up to 20% while in the second case, the efficiency is around 16 to 17%.
The other category is the thin film and we have the amorphous thin film
that is always silicon but in a disordered structure
The thin film modules are less semi conductor consuming, that is
the most expensive part of the module, because they are made by deposition of layers
of semi-conductive material on a substrate, like glass or plastic,
and it’s very cheap. Then, in this concern, we can have amorphous silicon
as I said before, or gallium arsenide or gallium telluride
or copper indium selenide known as CIS and this one is very promising because the
module in the market can reach 11% of efficiency.
At the end there are very promising technologies like graphene or organic PV like cotton
or oil, also vegetables or fruits. They can be used for different applications
and even if they have very low efficiency, the can
reach really interesting cost and they can be deposited on coats
or bags or wherever is needed a small energy supply.