On the photoluminescence emission of ZnO nanocrystals

Photoluminescence emission (PL) behaviour of ZnO nanocrystals capped by different organic molecules and dispersed in solvents with increasing dielectric constant is studied. PL energy is observed to red shift or blue shift or even remains invariant with increasing dielectric constant of the dispersing medium depending on the capping agent. The effective dielectric constant of the dispersing medium shifts the surface defect levels energetically and governs the interfacial charge re-organisation. Further, solvent relaxation effects also cause lowering of the energy levels. Defects located at the surface of nanocrystals profoundly influence the luminescence behaviour.