The phrase
"band gap" refers to the energy difference between the highest occupied electron energy level and the lowest unoccupied electron energy level in a material. It represents the energy range that electrons cannot have within a solid material, either they are in the valence band (lower energy level) or the conduction band (higher energy level). This
band gap determines the conductivity and optical properties of the material, with different
band gaps leading to different abilities to conduct electricity or transmit light.
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