A coating made of nanocrystal semiconductors can be used in discharge, filament or solid state lamps as spectrum shifter of the excitation source, either for up or down conversion, replacing fluorescent powders in fluorescent lamps or as photons energy converter from UV to visible radiation (stokes shift) in LEDs or from IR to visible radiation (anti stokes shift) in incandescent bulbs. Such a new phosphors replacement may improve the energy efficacy of those light sources by 200% or more with relevant advantages in terms of energy savings and enviromental benefits.