# P-n junction in a thermoelectric device

Greetings,

I've just learned some of the basics about thermoelectrics, and I often come across a diagram that confuses me (see the third and fourth figures in the http://en.wikipedia.org/wiki/Thermoelectric_effect#Charge-carrier_diffusion"). All of the literature I've read refers to the top connection between the n- and p-type as a p-n junction, but physically, there's a conductor connecting the p- and n-type materials (as shown in the diagram). How does this conductor effect the physics behind power generation? Qualitatively, I'd imagine one must choose a conductor having a Fermi level in between those of the p- and n-type materials - otherwise, migration would drive carriers toward the junction, opposing the temperature-induced current on one or the other side.

But in any case, I don't see how the junction can be referred to as a p-n junction, as it often is in the literature.

I'd appreciate any insight you might have on the subject! Thank you very much.

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