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
It is due to the conversion of that voltage and current into power, which dissipates as heat. Power is equal to the product of voltage and current. Those charge carriers bring with them the stored energy necessary to produce heat when they flow, and as you remember cold is merely the absence of heat. No charge carriers on one side means no potential for power to dissipates as heat. Or a lower potential anyway.
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.
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