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The optical band gap (see below) determines what portion of the solar spectrum a photovoltaic cell absorbs. [18] Strictly, a semiconductor will not absorb photons of energy less than the band gap; whereas most of the photons with energies exceeding the band gap will generate heat. Neither of them contribute to the efficiency of a solar cell.
Thus, extrapolating this linear region to the abscissa yields the energy of the optical bandgap of the amorphous material. A similar procedure is adopted to determine the optical bandgap of crystalline semiconductors. [5] In this case, however, the ordinate is given by (α) 1/r, in which the exponent 1/r denotes the nature of the transition: [6 ...
[1] [3] E g is the optical energy band gap of the material. A, B, and C depend on the band structure of the material. They are positive constants such that 4C − B 2 > 0. Finally, n(∞), a constant greater than unity, represents the value of n at E = ∞.
In a semiconductor or band insulator, the Fermi level is surrounded by a band gap, referred to as the band gap (to distinguish it from the other band gaps in the band structure). The closest band above the band gap is called the conduction band, and the closest band beneath the band gap is called the valence band.
In semiconductors, the band gap of a semiconductor can be of two basic types, a direct band gap or an indirect band gap. The minimal-energy state in the conduction band and the maximal-energy state in the valence band are each characterized by a certain crystal momentum (k-vector) in the Brillouin zone. If the k-vectors are different, the ...
The model has been used to fit the complex refractive index of amorphous semiconductor materials at frequencies greater than their optical band gap. The dispersion relation bears the names of Jan Tauc and Hendrik Lorentz, whose previous works [1] were combined by G. E. Jellison and F. A. Modine to create the model.
A detailed theoretical study of one-dimensional optical structures was performed by Vladimir P. Bykov, [12] who was the first to investigate the effect of a photonic band-gap on the spontaneous emission from atoms and molecules embedded within the photonic structure.
The wavelength of the light produced depends on the energy band gap of the semiconductors used. Since these materials have a high index of refraction, [note 1] design features of the devices such as special optical coatings and die shape are required to efficiently emit light. A LED is a long-lived light source, but certain mechanisms can cause ...