The efficiency of solar cells is in the 10% range. Yes, one could use these, but right now, the cost per installed megawatt is still about 4 to 10 times that of fossil powered electrical plants. yes, there are technologies that can reduce that cost (low cost solar concentrators, see US Patent #5,727,108, they reduce greatly to amount of silicon and increase the conversion efficiency and should, in principle bring the cost to only a 50% to a factor of 2 premium on fossil fuel plants), but I am having great difficulties finding interested parties to exploit the technology.
Zeev