Bandpositionerna

Bandpositionerna, literally “the band positions,” is a term used in Swedish to describe the energies at which electronic states are allowed in a material. The concept is central to solid-state physics and spectroscopy, and it underpins how materials conduct electricity, absorb light, and interact at interfaces.

In crystalline solids, electrons occupy bands formed by the overlap of atomic orbitals. The most important are the valence band maximum (VBM) and the conduction band minimum (CBM); the energy difference between them is the band gap. The absolute positions of these bands relative to the vacuum level determine the work function and electron affinity, which in turn influence charge transfer at contacts and the behavior of devices such as diodes and solar cells. When two materials form an interface, their bandedges align and create band offsets that classify heterojunctions as type I, II, or III. Band bending, caused by electrostatic fields at interfaces or by doping, modifies carrier energetics near the surface.

In spectroscopy, Bandpositionerna also refer to the energies of electronic transitions that produce absorption or emission bands. These bands appear at characteristic wavelengths or wavenumbers and may exhibit vibrational structure, aiding the assignment of electronic states.

Determination of bandpositions uses experimental methods such as photoelectron spectroscopy (UPS/XPS) to anchor levels to the vacuum, inverse photoemission, and optical spectroscopy for gaps, often complemented by theoretical calculations like density functional theory.

See also: band gap, work function, band offsets, heterojunctions, photoelectron spectroscopy.