Expert: Mike Fulcher - 1/19/2007

Question
Hi Mike.  I have read that the most efficient type of solar cell is expensive to manufacture because it is costly to produce large crystals of pure n type semiconductor material.  Could you please tell me in as much detail as possible what makes producing those crystals costly?

   Thank you,
     Mike Hebert

Answer
The ability to produce large crystals of any material is strongly impacted by the cleanliness of the operation.  Not only do you have to operate in a more expensive clean room environment, you have to ensure your starting materials are essentially pure.  For an idea of the costs of this, check out a chemical supplier catalog (e.g. Aldrich) and compare the cost differences between differenty purity levels of the same materials.  In crystal growth, even atomic levels of impurities can cause flaw sites and irregularities in crystal growth.  Polycrystalline materials, while not as efficient, are way cheaper, and thus the prefered material.  I hope this helps.