Efficient Doping and Energy Transfer from ZnO to Eu³⁺ Ions in Eu³⁺-Doped ZnO Nanocrystals

Abstract

Successful doping of Eu3+ ions into ZnO nanocrystals has been realized by using a low temperature wet chemical doping technique. The substitution of Eu3+ for Zn2+ is shown to be dominant in the Eu-doped ZnO nanocrystals by analyzing the X-ray diffraction patterns, transmission electron microscopy images, Raman and selectively excited photoluminescence spectra. Measurement of the luminescence from the samples shows that the excited ZnO transfers the excited energy efficiently to the doped Eu3+ ions, giving rise to efficient emission at red spectral region. The red emission quantum yield is measured to be 31% at room temperature. The temperature dependence of photoluminescence and the photoluminescence excitation spectra have also been investigated, showing strong energy coupling between the ZnO host and Eu3+ ions through free and bound excitons. The result indicates that Eu3+ ion-doped ZnO nanocrystals are promising light-conversion materials and have potential application in highly distinguishable emissive flat panel display and LED backlights.

Strong luminescence and efficient energy transfer in Eu3+/Tb3+-codoped ZnO nanocrystals

“…It also indicates that successful doping of Eu 3+ and Tb 3+ ions into ZnO nanocrystals has been realized. Our previous paper reported the successful doping of Eu 3+ ions into ZnO nanocrystals and the red emission quantum yield of ZnO: Eu sample was measured to be 31% at room temperature [13]. In this paper, emission spectra of Eu 3+ /Tb 3+ -codoped ZnO show that the green emission is much stronger than that of red emission, thus the green emission quantum yield is estimated to be higher than 31% at room temperature.…”

“…ZnO is a direct gap semiconductor material with a wide band gap of 3.37 eV and a large exciton binding energy (60 meV) as well as excellent chemical and thermal stability [9][10][11]. The wide band gap of ZnO can be combined with the luminescence of rare earth ions to develop blue, green or red emitting luminescent materials with the advantages such as strong near ultraviolet absorption, high color purity, low degradation and high efficiency [12][13][14]. They are promising light-conversion materials and have potential in field emission display devices and liquid crystal display (LCD) backlights [15].…”

Toward RGB LEDs based on rare earth-doped ZnO

“…The energy of this particle could be transferred to the RE ions thanks to the lattice. [33] Their later relaxation results in the emission of photons we detect as EL emission. In contrast and as previously discussed, under reverse bias the injection of both electrons and holes is highly quenched, diminishing the possibility of RE excitation and resulting in no-observable EL emission.…”

White Light Emission from Thin-Film Samples of ZnO Nanocrystals, Eu3+ and Tb3+ Ions Embedded in an SiO2 Matrix

“…There have been substantial studies demonstrating the energy transfer specifically from ZnO-nc to Eu 3+ ions [6,7,8,9,10,11,12,13,14,15,16,17,18] and also from ZnO-nc to Tb 3+ ions [19,20,21,22,23]. Previous works by our group have also reported on the study of the energy transfer mechanism, contribution and transfer efficiency from various ZnO-nc emission centers to Eu 3+ ions [17,18,24] and Tb 3+ ions individually [23].…”