Energy-transfer luminescence of a zinc oxide/ytterbium oxide nanocomposite

Abstract

A newly structured nanocomposite material based on nanocrystalline ZnO/Yb₂O₃ has been prepared by thermal decomposition of Yb-doped zinc carbonate hydroxide. Transmission electron microscopy has revealed that the prepared nanopowder consists of ZnO nanocrystals of about 50 to 100 nm size decorated by attached smaller Yb₂O₃ nanocrystals of about 10 to 15 nm size. X-Ray absorption spectroscopy, in particular XANES and EXAFS, indicate the charge of Yb ions equals to +3 and their coordination is oxygen octahedral with the Yb–O and Yb–Yb interatomic distances the same as in bulk Yb₂O₃. Photoluminescence spectroscopy unambiguously proves an efficient excitation energy transfer from the ZnO nanocrystals to the Yb³⁺ ions. The energy transfer from the ZnO nanocrystals (absorption range from 250 to 400 nm) to the Yb³⁺ ions (emission range from 950 to 1100 nm) has been explained by a model, which considers the quantum cutting effect. The prepared nanocomposite is promising for application as a down-conversion layer for enhanced solar cells.