An electron-hole is just a free electron state in a quantum system. Is this right? For example, let's say that there are 2 electrons with opposite spins in the fundamental state of a quantum well. If one electron with spin up is excited to the first excited state now you have a free spin up spot at the fundamental level an electron can take, which can be interpreted as an electron-hole with spin up.
Now let me change the scenario to that of a quantum dot. If you have a quantum dot operating with electrons in a quantum well you may load 1 electron into it. If you irradiate it with an appropriate photon it might get enough energy to jump from the valence band to the conduction one.
If you have, however, a quantum dot operating with electron-holes and you irradiate it with a photon, what happens to the hole? The quantum dot in this case is a region of the crystal which a perfect balance between positive and negative charges except for one open spot for an electron of a particular energy, which we call a hole. If you give energy to the system through light irradiation you might send an electron to the conduction band and just place one more hole in your quantum dot. So what happens to the hole in the quantum dot if you irradiate it?
And a follow up question... what happens to the electron in the first case? If you give it energy enough to go to the conduction band wouldn't it just scape from the quantum dot? So why is the energy band gap important at all other than a way to know how to empty your quantum dot thought light irradiation?
Thank you very much for your time.