Why are Si and GaAs are preferred materials for solar cells?

Explanation

For the solar radiation spectrum recieved by us, the maxima is near 1.5 eV, hence semiconductor with balad gap 1.5 eV or lower is likely to give better solar conversion efficiency. Silicon has 1.1 eV while for GaAs it is 1.53 eV. In fact, GaAs is better (in spite of its higher band gap) than Si because of its relatively higher absorption coefficient.