0
$\begingroup$

Why can't electrons in a semiconductor move for the redox process (instead of dye electrons in a dye-sensitized solar cell)?

$\endgroup$

2 Answers 2

0
$\begingroup$

Because the energy of the sunlight does not fit to the band gap of the semiconductor that is the sunlight cannot excite an electron from the valence to the conduction band of the semiconductor. For example, titania is one of the most commonly used material for DSSC, mostly because it's price, has a band gap of 3.05 eV. The wavelength of visible light is in 400-700 nm range which corresponds to an energy range of 3.09-1.77 eV.

$\endgroup$
4
  • $\begingroup$ So absorption region of a material mainly depends on bandgap right....and why we always interest to IR region in solar cell why not UV? because of long wavelength or anything else? so that it increase the optical path length $\endgroup$
    – Abynaya
    Commented Aug 10, 2016 at 9:05
  • $\begingroup$ Yes, you are right, the absorption region of a material mainly depends on the band gap. If you look at the solar spectrum (en.wikipedia.org/wiki/Sunlight#/media/…) you see that intensity (that is, number of photons) of the UV light coming from sun is relatively low. By the way this is a good thing because otherwise we would all get skin cancer. $\endgroup$ Commented Aug 10, 2016 at 12:29
  • $\begingroup$ Thank you so much @linuxick ....Can you please explain why does triiodide take part in redox process? why not diiodide like that? also electrons from pt:FTO is 2..why not 1electron? $\endgroup$
    – Abynaya
    Commented Aug 15, 2016 at 9:08
  • $\begingroup$ That you should ask a chemist $\endgroup$ Commented Aug 15, 2016 at 19:01
0
$\begingroup$

It is due to because the semiconductor used for example Tio2 or ZnO has a high bandgap energy ( higher energy than visible range ),so that it not absorbs the incoming visible radiation.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.