Semiconductors are used for solar energy conversion in devices called photovoltaic cells. For high efficiency, the cell should be able to utilize as...

1. Semiconductors are used for solar energy conversion in devices called photovoltaic cells. For high efficiency, the cell should be able to utilize as much light as possible. What band gap (in kJ/mole) would be needed to utilize light of 550. nm I used this formula below but I'm still not getting the right answer (about the middle of the visible spectrum) and shorter wavelengths? Answer: 217 kJ/mol

I used this formula below but I'm still not getting the right answer 

Ephoton = hν

c = λν

h = 6.626 × 10-34 J s

c = 2.998 × 108 m s-1