On the “atomic/electronic” level, what is actually happening that causes the transport of heat from one side to another via the Peltier effect(?)

Question

I get the principle of the Peltier effect. But what is *actually* happening on the atomic level when currect goes through a N- and P-doped semiconductor. Sure, this causes one side to heat up by releasing heat, and the other to cool down by absorbing heat. But why do the materials behave that way? How does the filling of electrons (when they re-combine with the “holes”) cause a heating on one side, but cooling on the other and not necessarily vice-versa?

In: Chemistry

Answer 1

Every atomic nucleus creates a kind of “gravity well” that electrons can fall into. Electrons can spontaneously fall into an atom/nucleus, but need energy input to leave a particular atom and enter a conduction band. For electrons to travel, they need to have enough energy to escape their atoms, which means they need to absorb heat energy. Electrons travel within the N-doped semiconductor, so that layer heats up with absorbed energy from the P-doped layer. The heat from the P-layer is needed to make the electrons mobile in the N-layer.