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Charge Transfer Induced Photoluminescence in ZnO Nanoparticles

Abstract

The quality of solution-processed zinc oxide (ZnO) nanoparticles (NPs) is often correlated with their photoluminescence (PL) spectral characteristics. However, the reported PL spectral characteristics are lack of consistency and remained controversial. Here we report that “defect-emission free” PL spectra can be even obtained in thin films composed of as-synthesized ZnO NPs. It is found that both the PL spectral line-shape and intensity are extremely sensitive to nitrogen and oxygen. By conducting time-dependent PL (t-PL) and photothermal deflection spectroscopy (PDS) measurements in vacuum and different gases purged environments, it is proposed that both inert (N2) and reactive (O2) molecules can be absorbed on the ZnO NP surface and induce charge transfer (CT). The CT states induced by N2 are non-radiative which significantly reduces the band emission. Whereas the CT states induced by O2 are radiative at the visible region, and the exciton transfer is efficient which increases the overall PL quantum yield. Owing to such effects, the previously reported correlation between defects and PL emission becomes questionable and needs to be revisited. Particularly, the visible emission from the ZnO NPs is proved to be facilitated by external effect, instead of direct recombination from defect states.

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Publication details

The article was received on 07 Mar 2019, accepted on 05 Apr 2019 and first published on 08 Apr 2019


Article type: Communication
DOI: 10.1039/C9NR02020A
Citation: Nanoscale, 2019, Accepted Manuscript

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    Charge Transfer Induced Photoluminescence in ZnO Nanoparticles

    Y. Ma, T. Choi, S. H. Cheung, Y. Cheng, X. XU, Y. Xie, H. LI, M. Li, H. Luo, W. Zhang, S. So, S. Chen and S. W. TSANG, Nanoscale, 2019, Accepted Manuscript , DOI: 10.1039/C9NR02020A

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