Does the semiconductor in a photovoltaic cell need to be silicon? Are there cheaper materials that can be used

Question

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Answer 1

Silicon is made from sand. How much cheaper can you get?

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Answer 2

well the only other element used in semi conductors to my knowledge is germanium.  i have never heard of a germanium solar cell.  semi conductors occupy a certain place on the periodic table of elements.  it's the atomic structure that gives them this special property.