The February 10, 2010 EE Times article 'IBM increases low-cost solar cell efficiency' states, 'Thin-film solar cells hold the promise of a cheap, renewable energy source that could make fossil fuels obsolete, but thus far the cells' reliance on rare elements and expensive vacuum deposition manufacturing has impeded their progress.'
Thus, the problem so far has been with the materials used'”indium (chemical symbol In) and tellurium (Te) are expensive elements'”and the process used'”a vacuum deposition manufacturing method that is expensive to perform.
Chalcogenides are used to make thin-film solar cells.
They are combinations of either (1) the elements copper, indium, gallium, and selenium (CIGS, general chemical formula CuInxGa(1-x)Se2, with the value of x depending on the relative amount of indium and gallum used) or (2) cadmium telluride (CdTe).
And, Indium and telluride are expensive elements because of their rarity on Earth, along with them being used in other applications.
However, IBM Research has come up with a solution to the problem of making inexpensive thin-film solar cells.
Read page two for more on their exciting advance in solar cell technology.