A band is a small section of the spectrum of radio communication frequencies, in which channels are usually used or set aside for the same purpose. Examples include:
Note that as a matter of physics, bands are divided at wavelengths of 10nmetres, or frequencies of 3×10n hertz. For example, 30MHz or 10m divides shortwave (lower and longer) from VHF (shorter and higher). These are the parts of the radio spectrum, and not its frequency allocation.
In solid state physics, the electronicband structure (or simply band structure) of a solid describes ranges of energy that an electron is "forbidden" or "allowed" to have.
The uppermost occupied band in an insulator or semiconductor is called the valence band by analogy to the valence electrons of individual atoms.
Because one of the main mechanisms for electrons to be excited to the conduction band is due to thermal energy, the conductivity of semiconductors is strongly dependent on the temperature of the material.
Electrons and holes are then injected from the electrodes, and the recombination of these charge carriers results in luminescence.
Electronic polymers are plastic materials with metallic and semiconductor characteristics, a combination of properties not exhibited by any other known material.
Applications of these materials in light-emitting devices, field effect transistors, as well as other molecular electronic devices have been fuelled by the improved solubility and ease of processing of mono-, di-, and ring-substituted polythiophenes, while simultaneously allowing the electronicband gap to be tuned.
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