solar energy technologies

Photovoltaics
There are generally 3 types of solar cells: mono-crystalline, poly-crystalline and amorphous. 

Basic features of each type are found below:

Mono-crystalline
Mono-crystalline cells are produced by slicing wafers from a high-purity single crystal boule.  Pure silicon can be produced using the "Czochralski" (CZ) method and the "float-zone" (FZ) method.  In the CZ method, a seed crystal is dipped into a crucible of molten silicon in an induction oven and withdrawn slowly to form a cylindrical single crystal, while in the FZ method, an induction heater travels along a silicon rod to melt the silicon and the mono-crystalline silicon originates from the cooling.  The silicon wafer is then produced by slicing the pure silicon ingot.  Mono-crystalline cell efficiency is currently about 13-16%.

Poly-crystalline
Poly-crystalline silicon cells are generally less efficient than mono-crystalline cells, but they can be less expensive to produce.  The most common production method involve a casting process in which molten silicon is directly cast into a square mold and allowed to solidify into an ingot.  The ingots are sliced into square cells that fit more compactly into a PV module.

Amorphous 
Amorphous silicon cells atoms are not arranged in any particular order.  Amorphous silicon absorbs diffuse solar radiation more efficiently than does mono-crystalline silicon, hence less material could be used and this helps to lower the cost of production.