Basic principle of TEC (I)

In the closed circuit with two different metals, if the temperature of the two contact points keeps different, electric potential difference will generate and at the same time, there will be current through the closed circuit, which is called Seebeck effect. Conversely, in the same closed circuit, when the direct current is supplied, one contact point becomes cold and the other one gets hot, which is called Peltier effect or thermoelectric effect. This phenomenon can directly lead to the invention of coolers, but it is not TEC. Until in the 1950s, TEC began to be used in practical applications with the development of semiconductor technology.

Actually, in the loop with any two different conductors, there are always endothermic phenomenon and exothermic phenomenon at the contact point. Why is semiconductor material used to make TEC? This is because in the metallic conductor, the average energy of the free electron participating in the conduction is very small and the effect of endothermic and exothermic is weak. However, because of the internal structure of semiconductor, it can generate temperature difference phenomenon much more obviously than other metals do. That is why semiconductor material is generally used for making TEC.

The important feature of semiconductor is that after a certain amount of some impurity seeping into semiconductor, it can not only improve the electrical conductivity greatly, but also produce many semiconductors with different nature and different uses, depending on the type and quantity of impurity. After seeping impurity into semiconductor, free electrons are released, which is called N type semiconductor. Correspondingly, P type semiconductor is conductive, which relies on “hole”. The free electrons in the N type semiconductors and something all involved in the conduction in the P semiconductor are collectively called “carriers”. Carriers are unique to semiconductorsdue to the incorporation of impurities.

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