> Or is there a silicon junction that can convert 40% of the light energy that is incident on it? This. The main benefit of concentrated solar power is that th

> Or is there a silicon junction that can convert 40% of the light energy that is incident on it? This. The main benefit of concentrated solar power is that the area of the photovoltaic cells can be a lot smaller than the area of the collector (on the order of 100-1000 times). This in turn allows having expensive, but highly efficient PV cells, so you can convert 40% of the insolation on a given area to electricity, instead of only 20%. A side-benefit is that you can actually use the waste heat from cooling the cells. The ETH Zürich is doing research on this, I think.