Though most first choice when it come to green energy, these are generally expensive and take up a lot of Sq footage and lack efficiency, about 27%
There are cheaper alternative by making them yourself with "broken" cells
They are also only very efficient when constantly pointed at the sun
You can also get more out of less cells by focusing the sun with Fresnel lenses
Nanocrystal Cell (3D Solar Cell)
Same basic concept as the normal cell but instead of a flat surface, it has nano crystal structures grown on it giving far more surface area
These cells are far more efficient, about 65%, because they absorb nearly all of the photons fun the sun vs reflecting most all of it
with this notion, these panels are most effective when not directly perpendicular with the sun, which means they get nearly the same energy all day without moving