Are solar cells more efficient for specific frequencies of light?

[qazwsxedc]

my understanding is that energy is wasted in a solar cells when light with more frequency than necessary to make an electron cross the band gap comes along and the excess energy is converted to heat. does this mean if you only shined blue light at a solar cell which had a perfect electron gap material for blue light that it would be 100% efficient. Why don't they just separate natural light into its different colors and then direct it towards the appropriate solar cell. Wouldnt this be 100% efficient?

 

[thopsy]

The first part of what you said is true. If you had blue light hitting a perfect cell with a blue bandgap, you would get a very high efficiency. However you would never get 100% due to radiative recombination under the conditions of detailed balance. Basically some of the electron-hole pairs generated will recombine and emit photons thereby losing some useful energy.

The reason spectral splitting it is not done is because it is expensive (glass prisms).

Triple-junction cells are designed to use nearly all of the solar spectrum efficiently. Commercially available cells have efficiencies approaching 40% under concentrated light.