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Step-like enhancement of luminescence quantum yield of silicon nanocrystals

Nature Nanotechnology volume 6, pages 710–713 (2011)Cite this article

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Abstract

Carrier multiplication by generation of two or more electron–hole pairs following the absorption of a single photon may lead to improved photovoltaic efficiencies1 and has been observed in nanocrystals made from a variety of semiconductors, including silicon. However, with few exceptions2, these reports have been based on indirect ultrafast techniques3,4,5,6. Here, we present evidence of carrier multiplication in closely spaced silicon nanocrystals contained in a silicon dioxide matrix by measuring enhanced photoluminescence quantum yield. As the photon energy increases, the quantum yield is expected to remain constant, or to decrease as a result of new trapping and recombination channels being activated. Instead, we observe a step-like increase in quantum yield for larger photon energies that is characteristic of carrier multiplication7. Modelling suggests that carrier multiplication is occurring with high efficiency and close to the energy conservation limit.

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Figure 1: Experimental set-up for quantum yield determination.
Figure 2: Spectral dependence of external quantum yield of photoluminescence.
Figure 3: Effect of inter-nanocrystal separation.
Figure 4: Photovoltaic impact.

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  • 21 October 2011

    In the version of this Letter originally published online, the third sentence of the abstract should have read: "Here, we present evidence of carrier multiplication in closely spaced silicon nanocrystals contained in a silicon dioxide matrix by measuring enhanced photoluminescence quantum yield." This has been corrected in all versions of the Letter.

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Acknowledgements

This work was financially supported by Nederlandse Organisatie voor Wetenschappleijk Onderzoek (NWO), Stichting voor de Technologische Wetenschappen (STW) and Stichting der Fundamenteel Onderzoek der Materie (FOM). Part of this work (J.V.) was supported by Research Centre LC510 and Research Plan MSM0021620835 of the Ministry of Education, Youth and Sports and Project KAN400100701 of the Grant Agency of the Academy of Sciences of the Czech Republic.

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Authors and Affiliations

  1. Van der Waals-Zeeman Institute, University of Amsterdam, Science Park 904, Amsterdam, NL-1098 XH, The Netherlands

    D. Timmerman, K. Dohnalová, W. D. A. M. de Boer & T. Gregorkiewicz

  2. Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, Prague 2, CZ-12116, Czech Republic

    J. Valenta

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  1. D. Timmerman
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  4. W. D. A. M. de Boer
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Contributions

D.T. and T.G. conceived the project, co-wrote the paper and, together with J.V. and K.D., designed the experiments. D.T., J.V. and K.D. performed the experiments and contributed to data analysis. D.T. and K.D. prepared sputtered and po-Si materials, respectively. T.G. supervised the project. All authors discussed the results and commented on the manuscript.

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Correspondence to D. Timmerman.

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The authors declare no competing financial interests.

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Timmerman, D., Valenta, J., Dohnalová, K. et al. Step-like enhancement of luminescence quantum yield of silicon nanocrystals. Nature Nanotech 6, 710–713 (2011). https://doi.org/10.1038/nnano.2011.167

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