SEMICONDUCTORS: THERMOELECTRIC EFFECT

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The potential for transforming energy generation technologies has been recognized in thermoelectric materials for several decades. Development in this field is accelerating in recent years and finding more efficient materials has been the main concern of researchers.

The thermoelectric devices are based on the fact that when certain materials are heated, they generate a significant electrical voltage. Conversely, when a voltage is applied to them, they become hotter on one side, and colder on the other. The electrons move from the hot end of the material to the cold end, creating positive and negative electrodes and thereby the electrical voltage. This effect, known as Peltier-Seebeck, is reversible. This does not occur in all materials since, for example, the filament of the incandescent bulbs produces heat by applying a voltage difference (Joule effect), but it is not a reversible effect.

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Thermoelectric Materials

The process of thermoelectricity only occurs in certain materials, especially in the semiconductors (the materials with which the chips are made). The fundamental problem for creating efficient thermoelectric materials is that they need to be very good at transmitting electricity, but not heat.

The key to making them more practical has been to create special semiconductor materials in which tiny patterns were created to alter the behavior of materials. This may include the incorporation of nanoparticles or nanowires into a matrix of another material. These nanometric structures interfere with the flow of heat but allow electricity to flow freely.

Applications

Current thermoelectric technology is only used in very specialized fields, such as solid state cooling, because the materials are not very efficient. An example is the cooling of car seats in warm climates. The seat-like devices provide comfort directly to the individual, rather than cooling the entire car, saving air conditioning and energy costs. Another curious application are the boots that use the thermoelectricity generated by the heat of the feet to charge the mobile phone.

The current internal combustion engines only take advantage of 25% of the energy released in the combustion. Photovoltaic cells have a maximum yield of 15%. However, the new materials allow substantial energy savings by being able to manufacture more efficient engines. The new hybrid photovoltaic cells allow to generate electrical and thermal energy simultaneously. Electronic devices also take advantage of heat radiated in thermoelectricity.

More details here: thermoelectric effect

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