Thermoelectric generators: How they are made?

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Usually, semiconductors (n-type and p-type) are used to make generators. The n-type and p-type semiconductors (called ‘thermoelectric legs’) are coupled together to make a p-n junction. This type of configuration adds the thermo-voltage of n-type and p-type legs and hence results in higher output voltage.

Several p-n junctions are further connected to each other to make a thermoelectric generator. 

Commercially available generators are usually consisting of hundreds of thermoelectric junctions in order to get sufficient voltage generation.