Editing Band gap (section)

===Photovoltaic cells===
{{main | Solar cell}}
[[File:ShockleyQueisserFullCurve.svg|thumb|The [[Shockley–Queisser limit]] gives the maximum possible efficiency of a single-junction solar cell under un-concentrated sunlight, as a function of the semiconductor band gap. If the band gap is too high, most daylight photons cannot be absorbed; if it is too low, then most photons have much more energy than necessary to excite electrons across the band gap, and  the rest is wasted.<ref name="Goetzberger">{{cite book |title=Crystalline silicon solar cells |last1=Goetzberger|first1=A. |last2=Knobloch|first2=J. |last3=Voss|first3=B. |year=1998  |publisher=John Wiley & Sons | isbn=0-471-97144-8 }}</ref> The semiconductors commonly used in commercial solar cells have band gaps near the peak of this curve, as it occurs in silicon-based cells. The Shockley–Queisser limit has been exceeded experimentally by combining materials with different band gap energies to make, for example, [[tandem solar cell]]s.]]

The optical band gap (see below) determines what portion of the solar spectrum a [[photovoltaics|photovoltaic cell]] absorbs.<ref name="Goetzberger" /> 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. One way to circumvent this problem is based on the so-called photon management concept, in which case the solar spectrum is modified to match the absorption profile of the solar cell.<ref name="Zanatta1">{{cite journal |last1=Zanatta |first1=A.R. | title= The Shockley-Queisser limit and the conversion efficiency of silicon-based solar cells |journal=Results Opt. |date=December 2022 |volume=9 |pages=100320–7pp |doi=10.1016/j.rio.2022.100320 |doi-access=free |bibcode=2022ResOp...900320Z }}</ref>