We can predict the light wavelength that the material can absorb with the help of a bandgap. The transition of the electron into the conduction band is possible due to lower energy requirements, the narrow bandgap materials will absorb in the wide visible range of wave duration.
The variation is known as the bandgap or energy gap between the valence and conduction bands.
Due to increasing temperature, the band-gap energy of semiconductors continues to decrease. The amplitude of atomic motions changes as the temperature increases, resulting in greater interatomic spacing. The energy required to pass an electron from the valence band to the conduction band, the essential external energy, is equal to the prohibited energy difference.
Its unit is electron volt (eV).
Si (Silicon) has a bandgap of 1.12 eV.