Preparation and characterization of ZnS based nano-crystalline particles for polymer light-emitting diodes

Nano-crystalline ZnS:Mn and its derivatives are promising as a novel luminescent center because of its high quantum efficiency at room temperature. In this work, three different kinds of ZnS based nano-crystalline particles were synthesized and characterized in order to be utilized for polymer light-emitting diodes; ZnS:Mn, ZnS:CuCl, and ZnS:AgCl. Some of the ZnS based nanocrystals were either hybridized with poly(acrylic acid)(PAA) or doped to poly(9-vinyl carbazole)(PVCz)). The XRD analysis showed that the diameter of the ZnS based particles was in the range of 11.8-23.4 nm. In all the ZnS based nanocrystals hybridized with PAA, the photoluminescence (PL) was enhanced in comparison to the ZnS:Mn regardless of the metal ion. It was found that the ZnS:AgCl hybridized with PAA showed the highest PL and the ZnS:CuCl hybridized with PAA showed the lowest PL among the three ZnS based nanocrystals hybridized with PAA. The PL of PVCz doped with the ZnS based nanocrystals, however, was lower in comparison to the ZnS:Mn regardless of the metal ion though the differences were not large.