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Defect-promoted photo-electrochemical performance enhancement of orange-luminescent ZnO nanorod-arrays

Abstract

Intentionally defect-rich zinc oxide (ZnO) nanorod-arrays were grown from solution by carefully adjusting the concentration ratio of the growth-precursors used followed by various post-deposition thermal treatments. Post-deposition rapid thermal annealing (RTA) at moderate temperatures (350 °C - 550 °C) and in various atmospheres was applied to vary the defect composition of the grown nanorod-arrays. It is demonstrated that, intense, defect-related orange emission occurs solely upon RTA around 450 °C and is essentially independent of the atmosphere used. Extensive materials characterization was carried out in order to evaluate the origin of the orange-luminescent defects and what influence they have on the ZnO material properties. It is concluded that the oxygen vacancy-zinc interstitial defect complex (VO-Zni) is responsible for the orange luminescence in the prepared materials. A kinetic formation mechanism of the VO-Zni complex dependent on the RTA temperature is proposed and shown to be in accordance with the experimental findings. Furthermore it is shown that this bulk deep-level defect could act as a trap state for photo-generated electrons prolonging the charge carrier lifetime of photo-generated holes and therefore improving the charge carrier separation in the material. As a result the photo-current density under simulated sunlight is found to increase by almost 150 % over as-grown samples. The potential use of this defective material in applications such as solar water splitting is outlined.

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Publication details

The article was received on 13 Mar 2017, accepted on 19 Apr 2017 and first published on 19 Apr 2017


Article type: Paper
DOI: 10.1039/C7CP01606A
Citation: Phys. Chem. Chem. Phys., 2017, Accepted Manuscript
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    Defect-promoted photo-electrochemical performance enhancement of orange-luminescent ZnO nanorod-arrays

    J. Kegel, F. R. Laffir, I. M. Povey and M. E. Pemble, Phys. Chem. Chem. Phys., 2017, Accepted Manuscript , DOI: 10.1039/C7CP01606A

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