What is the most efficient solar electrical energy generator?

Solar thermal energy technology is more efficient than photovoltaics. So when you want to heat water it’s not a good idea to use electricity generated by photovoltaics. If you want to use a computer during daylight photovoltaics is a good idea. At night solar thermal energy technology can use heated oil also at night. This technology has been proposed for the Desertec project in the Sahara.

Recently, Popsci featured several extremely talented and innovative young scientists. One was named William Yuan. Here’s an excerpt from his mini-bio:
“At age 11, he began studying nanoimaging at Portland State University, where he hit upon his idea for a three-dimensional solar cell that absorbs both visible and ultraviolet light by trapping it between two concave surfaces.”

While they’ve yet to be manufactured and may still be less efficient than other forms of energy, these cells will certainly be the most efficient within the category of photovoltaics.