A method and apparatus for solar cell having graded energy wells is provided. The active region of the solar cell comprises nanostructures. The nanostructures are formed from a material that comprises a III-V compound semiconductor and an element that alters the band gap of the III-V compound semiconductor. For example, the III-V compound semiconductor could be gallium nitride (GaN). As an example, the "band gap altering element" could be indium (In). The concentration of the indium in the active region is non-uniform such that the active region has a number of energy wells, separated by barriers. The energy wells may be "graded", by which it is meant that the energy wells have a different band gap from one another, generally increasing or decreasing from one well to another monotonically.