Semiconductor quantum dots behave like molecules

The persistent spectral hole burning (PSHB) phenomena were discovered in many kinds of nanocrystalline semiconductors, such as CdSe, CdS, CuCl, CuBr and CuI, embedded in crystals, glass or polymers. Hole burning in the luminescence spectrum was also observed. The observed PSHB phenomena are explained by the ionization of nanocrystals. The photoionization of nanocrystals takes place by tunneling through potential barriers with broadly distributed barrier height and thickness. The energy of photoionized nanocrystals is changed from the original energy and their new energies depend on the spatial arrangement of trapped carriers. Quantum confinement of carriers and resulting strong Coulomb interaction between confined carriers and trapped carriers cause the energy change