2. Physical phenomena and optical processes in nanotubes

2.1 Light emission process

The emission of light from a semiconductor is called luminescence. It results from the recombination of an excited electron in the conduction band with a hole in the valence band. In the case of photoluminescence, the semiconductor is put into a non-equilibrium state after absorption of a photon at an energy greater than its electronic gap (figure 5 ). Photoluminescence is a more complicated phenomenon than optical absorption. It involves energy relaxation processes, particularly within electronic bands. On the other hand, the process of light emission is a pathway back to equilibrium that competes with non-radiative mechanisms. In the case...