**5. Quantum dots solar cells**

There are many realistic quantum dots based solar cells. In this section we classify them in seven strategies just as an approach to fulfill the main objective of this chapter that is intro‐ ducing quantum dot solar cells. For example, [21] metal-semiconductor junction, polymersemiconductor, and semiconductor-semiconductor systems are well know strategies of quantum dots based solar cell. Moreover; quantum dots attached to n-C60 composite clusters see [18] or single and multi-walled carbon nanotubes based solar cells have been investigated [22,23].
