Work Function and Bandgap

Hi, sorry I was just wondering if you could please explain the difference between work function and energy band gap in relation to the photoelectric effect in PV cells? I don't understand how, if the work function of silicon is 4.6eV, silicon solar cells can absorb visible light? Thank you so much.
- Issy (age 16)
England

The work function tells you how much energy it takes to pull an electron completely out of the material. The band gap tells you how much energy it takes to pull an electron up from the mostly-occupied valence band of states into the mostly-unoccupied conduction band of states. All those are states of electrons inside the material.  So the bandgap is smaller than the work function.

Mike W.

(published on 06/10/2014)