Übergangsband

Übergangsband is a term used in solid-state physics and materials science to describe a specific type of electronic transition within a material. It refers to the movement of electrons between different energy bands that are close in energy. These transitions are often responsible for the optical and electrical properties of materials.

In crystalline solids, electrons occupy distinct energy bands. The valence band is typically filled with electrons, while the conduction band is mostly empty. For an electron to move from the valence band to the conduction band, it needs to gain sufficient energy, usually in the form of a photon of light or thermal energy. The energy difference between the top of the valence band and the bottom of the conduction band is called the band gap.

Übergangsband specifically describes transitions where the energy difference is relatively small or where the bands involved are not completely separated. This can occur in materials with narrow band gaps or in cases where there are intermediate, localized energy levels within the band gap, often due to defects or impurities. These states within the band gap can facilitate transitions that would otherwise require more energy.

The probability and nature of these übergangsband transitions are crucial for understanding phenomena like light absorption and emission, electrical conductivity, and the behavior of semiconductors. For example, materials exhibiting strong übergangsband transitions in the visible spectrum are often colored. The study of these transitions is fundamental to the design and development of optoelectronic devices such as LEDs, solar cells, and photodetectors.