What is bandgap?

Some articles on bandgap, bandgaps:

Multijunction Photovoltaic Cell - Description - Increasing Efficiency
... only exists if one considers a material with a single bandgap ... If you build a cell with multiple bandgaps, and tune each one to a different wavelength, then it is possible to capture the energy that would otherwise be lost through relaxation, without sacrificing ... For instance, if one had a cell with two bandgaps in it, one tuned to red light and the other to green, then the extra energy in green, cyan and blue light would be ...
Thermophotovoltaic - Active Components and Materials Selection - Photovoltaic Cells - Indium Gallium Arsenide
... When lattice-matched to an InP substrate, InGaAs has a bandgap of 0.74 eV, which is not an improvement on traditional GaSb ... to absorb higher wavelength photons, the bandgap may be engineered by changing the ratio of In to Ga ... The range of bandgaps for this system is from about 0.4 to 1.4 eV ...
Wide Bandgap Semiconductors - Material Properties - Bandgap
... The magnitude of the coulombic potential determines the bandgap of a material, and the size of atoms and electronegativities are two factors that determine the bandgap ... with small atoms and strong, electronegative atomic bonds are associated with wide bandgaps ... Elements high on the periodic table are more likely to be wide bandgap materials ...
Shockley–Queisser Limit - Exceeding The Limit - Photon Upconversion
... above, photons with energy below the bandgap are wasted in ordinary single-junction solar cells ... or material that can absorb two or more below-bandgap photons and then emit one above-bandgap photon ...
Bandgap Voltage Reference
... A bandgap voltage reference is a temperature independent voltage reference circuit widely used in integrated circuits, usually with an output voltage around 1.25 V ...