Enhancing blue luminescence from Ce-doped ZnO nanophosphor by Li doping
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NANO EXPRESS
Open Access
Enhancing blue luminescence from Ce-doped ZnO nanophosphor by Li doping Qiang Shi1,2*, Changzheng Wang2,3*, Shuhong Li1,2, Qingru Wang1,2, Bingyuan Zhang1,2, Wenjun Wang1,2, Junying Zhang4 and Hailing Zhu5
Abstract Undoped ZnO, Ce-doped ZnO, and (Li, Ce)-codoped ZnO nanophosphors were prepared by a sol-gel process. The effects of the additional doping with Li ions on the crystal structure, particle morphology, and luminescence properties of Ce-doped ZnO were investigated by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, electron paramagnetic resonance spectroscopy and photoluminescence spectroscopy. The results indicate that the obtained samples are single phase, and a nanorod shaped morphology is observed for (Li, Ce)-codoping. Under excitation with 325 nm light, Ce-doped ZnO phosphors show an ultraviolet emission, a green emission, and a blue emission caused by Zn interstitials. The spectrum of the sample codoped with a proper Li concentration features two additional emissions that can be attributed to the Ce3+ ions. With the increase of the Li doping concentration, the Ce3+ blue luminescence of (Li, Ce)-codoped ZnO is obviously enhanced, which results not only from the increase of the Ce3+ ion concentration itself but also from the energy transfer from the ZnO host material to the Ce3+ ions. This enhancement reaches a maximum at a Li content of 0.02, and then decreases sharply due to the concentration quench. These nanophosphors may promise for application to the visible-light-emitting devices. Keywords: (Li, Ce)-codoped ZnO; Blue luminescence; Phosphors; Sol-gel PACS: 78.55.Et; 81.07.Wx; 81.20.Fw
Background ZnO is an n-type semiconductor material with a wide band gap of 3.3 eV and a large exciton binding energy of 60 meV. Room temperature photoluminescence (PL) spectra from ZnO can exhibit an ultraviolet (UV) emission and possibly one or more visible emissions caused by defects and/or impurities [1]. It has been reported that doping a ZnO host crystal structure with rare earth elements such as Tb, Er, and Ce can lead to excellent luminescence properties [2-4]. Especially, the blue lightemitting Ce-doped ZnO has received particular attention because of its high chemical stability, excellent optoelectronic properties, avirulence behavior, and biological compatibility, resulting in potential applications in the field of visible-light-emitting devices and biological fluorescence * Correspondence: [email protected]; [email protected] 1 School of Physical Science and Information Engineering, Liaocheng University, Shandong 252059, People's Republic of China 2 Shandong Provincial Key Laboratory of Optical Communication Science and Technology, Shandong 252059, People's Republic of China Full list of author information is available at the end of the article
labeling [5]. Therefore, a further enhancement of the emission intensity in the blue emission band of Ce-doped ZnO phosphor is highly desirable. It is well known that Li+ ions, as dopants, even in very
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