For the thermoelectric effect, now, consider the case of uniform voltage (uniform chemical potential) with a temperature gradient. In this case, at the hotter side of the material there is more variation in the energies of the charge carriers, compared to the colder side. This means that high energy levels have a higher carrier occupation per state on the hotter side, but also the hotter side has a lower occupation per state at lower energy levels.
Can somebody explain this statement to me. What's the meaning of "higher carrier occupation per state" and "lower occupation per state" . And why does hot side has both of them?
Edit: Source of the quoted material-