On the double-band luminescence of ZnO nanoparticles

Multidisciplinary Nanotechnology Centre, College of Engineering, Swansea University Bay Campus, SA1 8EN, Swansea, UK

Received: 8 March 2017
Accepted: 2 May 2017

Abstract

Two luminescence bands from zinc oxide (ZnO) nanoparticles are known and have been experimentally observed previously. The unanswered question concerns the mechanism leading to the visible spectrum in the blue or green region. So far there have been many postulations trying to elucidate this phenomenon, but none of them gives a mathematical expression that simultaneously explain these two spectra. Here we interpret this phenomenon as the combination of distribution functions and the density of states of electrons and holes, precisely the product of both. From the analysis, the narrow UV emission is predominantly attributed to the quantum confinement, and the product of the density of states and the distribution functions determines the visible spectrum. We find that varying the density and the effective mass of holes causes a pronounced effect on both UV and visible emissions, which reflects the fact that acceptors take the main responsibility in the experimental observations.