Optical properties of nanocrystal lattices
Colloidal nanocrystals for optoelectronics

The first advantage of nanocrystals is that their electronic properties can be controlled by modulating their geometric properties rather than the composition of the material. . For this to be possible, the characteristic size of the nanocrystal must be smaller than the Bohr radius of the exciton in the bulk material. The exciton is the quasi-particle made up of the electron-hole pair photogenerated by absorption, dressed up with the Coulombic interaction between the two. The Bohr radius is given by