Doped nanocrystals of semiconductors - a new class of luminescent materials

We report on the unique luminescent properties of nanocrystals of Mn-doped ZnS with varying sizes from 30 to 70A˚prepared at room temperature. These nanosize quantized particles yield the best external photoluminescent quantum efficiency of about 18% at room temperature and luminescent decay time at least five orders of magnitude faster than the corresponding Mn2+ radiative transition in the bulk crystals. These luminescent measurements also suggest that the efficiency increases with decreasing size of the nanocrystalline particles. These novel properties may be attributed to electron-hole localization and hybridization of the s-p host states with d-electrons of the Mn impurity.