Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Article
  • Published:

Understanding the role of selenium in defect passivation for highly efficient selenium-alloyed cadmium telluride solar cells

Nature Energy volume 4, pages 504–511 (2019)Cite this article

Subjects

An Author Correction to this article was published on 28 May 2019

This article has been updated

Abstract

Electricity produced by cadmium telluride (CdTe) photovoltaic modules is the lowest-cost electricity in the solar industry, and now undercuts fossil fuel-based sources in many regions of the world. This is due to recent efficiency gains brought about by alloying selenium into the CdTe absorber, which has taken cell efficiency from 19.5% to its current record of 22.1%. Although the addition of selenium is known to reduce the bandgap of the absorber material, and hence increase the cell short-circuit current, this effect alone does not explain the performance improvement. Here, by means of cathodoluminescence and secondary ion mass spectrometry, we show that selenium enables higher luminescence efficiency and longer diffusion lengths in the alloyed material, indicating that selenium passivates critical defects in the bulk of the absorber layer. This passivation effect explains the record-breaking performance of selenium-alloyed CdTe devices, and provides a route for further efficiency improvement that can result in even lower costs for solar-generated electricity.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on SpringerLink
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: CdTe luminescence efficiency improved by selenium alloying.
Fig. 2: Hyperspectral CL imaging shows that selenium is associated with a sub-bandgap emission peak.
Fig. 3: CdTe diffusion lengths improved by selenium alloying.
Fig. 4: Mapping selenium-induced bandgap changes in the absorber.

Similar content being viewed by others

Data availability

The data that support the plots within the paper and other findings of this study are available in the repository at Loughborough University (https://repository.lboro.ac.uk/) or from the corresponding author on reasonable request.

Change history

  • 28 May 2019

    An amendment to this paper has been published and can be accessed via a link at the top of the paper.

References

  1. Gloeckler, M., Sankin, I. & Zhao, Z. CdTe solar cells at the threshold to 20% efficiency. IEEE J. Photovolt. 3, 1389–1393 (2013).

    Article  Google Scholar 

  2. Green, M. A. et al. Solar cell efficiency tables (version 51). Prog. Photovolt. Res. Appl. 26, 3–12 (2018).

    Article  Google Scholar 

  3. Lazard’s Levelized Cost of Energy Analysis—Version 11.0 (Lazard, 2017).

  4. Balderelli, J. Public Utilities Commission of Nevada Electronic Filing (2015).

  5. Hagenorf, C. et al. Assessment of Performance, Environmental, Health and Safety Aspects of First Solar’s CdTe Photovoltaic Technology (Cener, 2016).

  6. Paudel, N. R. & Yan, Y. Enhancing the photo-currents of CdTe thin-film solar cells in both short and long wavelength regions. Appl. Phys. Lett. 105, 183510 (2014).

    Article  Google Scholar 

  7. Swanson, D. E., Sites, J. R. & Sampath, W. S. Co-sublimation of CdSexTe1− x layers for CdTe solar cells. Sol. Ener. Mater. Sol. Cells 159, 389–394 (2017).

    Article  Google Scholar 

  8. Poplawsky, J. D. et al. Structural and compositional dependence of the CdTexSe1−x alloy layer photoactivity in CdTe-based solar cells. Nat. Commun. 7, 12537 (2016).

    Article  Google Scholar 

  9. Munshi, A. H. et al. Polycrystalline CdSeTe/CdTe absorber cells with 28 mA/cm2 short-circuit current. IEEE J. Photovolt. 8, 310–314 (2018).

    Article  Google Scholar 

  10. Kephart, J. M. et al. Sputter-deposited oxides for interface passivation of CdTe photovoltaics. IEEE J. Photovoltaics 8, 587–593 (2018).

    Article  Google Scholar 

  11. Kuciauskas, D. et al. Recombination velocity less than 100 cm/s at polycrystalline Al2O3/CdSeTe interfaces. Appl. Phys. Lett. 112, 263901 (2018).

    Article  Google Scholar 

  12. Dharmadasa, I. Review of the CdCl2 treatment used in CdS/CdTe thin film solar cell development and new evidence towards improved understanding. Coatings 4, 282–307 (2014).

    Article  Google Scholar 

  13. Barnard, E. S. et al. 3D lifetime tomography reveals how CdCl2 improves recombination throughout CdTe solar cells. Adv. Mater. 29, 1603801 (2017).

    Article  Google Scholar 

  14. Fiducia, T. A. M. et al. 3D distributions of chlorine and sulphur impurities in a thin-film cadmium telluride solar cell. MRS Adv. 3, 3287–3292 (2018).

    Article  Google Scholar 

  15. Abbas, A. et al. The effect of cadmium chloride treatment on close-spaced sublimated cadmium telluride thin-film solar cells. IEEE J. Photovolt. 3, 1361–1366 (2013).

    Article  Google Scholar 

  16. Munshi, A. H. Polycrystalline CdTe photovolaics with efficiency over 18% through improved absorber passivation and current collection. Sol. Ener. Mater. Sol. Cells 176, 9–18 (2018).

    Article  Google Scholar 

  17. Munshi, A. H. et al. Effect of CdCl2 passivation treatment on microstructure and performance of CdSeTe/CdTe thin-film photovoltaic devices. Sol. Ener. Mater. Sol. Cells 186, 259–265 (2018).

    Article  Google Scholar 

  18. Harrison, L. G. Influence of dislocations on diffusion kinetics in solids with particular reference to the alkali halides. Trans. Faraday Soc. 57, 1191–1199 (1961).

    Article  Google Scholar 

  19. Moutinho, H. R. et al. Grain boundary character and recombination properties in CdTe thin films. In 2013 IEEE 39th Photovoltaic Specialists Conference 3249–3254 (IEEE, 2013).

  20. Moseley, J. et al. Cathodoluminescence analysis of grain boundaries and grain interiors in thin-film CdTe. IEEE J. Photovolt. 4, 1671–1679 (2014).

    Article  Google Scholar 

  21. Moseley, J. et al. Recombination by grain-boundary type in CdTe. J. Appl. Phys. 118, 025702 (2015).

    Article  Google Scholar 

  22. Stechmann, G. et al. A correlative investigation of grain boundary crystallography and electronic properties in CdTe thin film solar cells. Sol. Ener. Mater. Sol. Cells 166, 108–120 (2017).

    Article  Google Scholar 

  23. Lane, D. W. A review of the optical band gap of thin film CdSxTe1−x. Sol. Ener. Mater. Sol. Cells 90, 1169–1175 (2006).

    Article  Google Scholar 

  24. Mendis, B. G., Bowen, L. & Jiang, Q. Z. A contactless method for measuring the recombination velocity of an individual grain boundary in thin-film photovoltaics. Appl. Phys. Lett. 97, 092112 (2010).

    Article  Google Scholar 

  25. Mendis, B. & Bowen, L. Cathodoluminescence measurement of grain boundary recombination velocity in vapour grown p-CdTe. J. Phys. Conf. Ser. 326, 012017 (2011).

    Article  Google Scholar 

  26. Lee, J., Giles, N. C., Rajavel, D. & Summers, C. J. Room-temperature band-edge photoluminescence from cadmium telluride. Phys. Rev. B 49, 1668–1676 (1994).

    Article  Google Scholar 

  27. Yang, J.-H., Yin, W.-J., Park, J.-S., Ma, J. & Wei, S.-H. Review on first-principles study of defect properties of CdTe as a solar cell absorber. Semicond. Sci. Technol. 31, 83002 (2016).

    Article  Google Scholar 

  28. Yang, J. H., Shi, L., Wang, L. W. & Wei, S. H. Non-radiative carrier recombination enhanced by two-level process: a first-principles study. Sci. Rep. 6, 21712 (2016).

    Article  Google Scholar 

  29. Abbas, A. The Microstructure of Thin Film Cadmium Telluride Photovoltaic Materials. PhD thesis, Loughborough Univ. (2014).

Download references

Acknowledgements

The authors at Loughborough University are grateful to the EPSRC CDT in New and Sustainable Photovoltaics for providing T.F. with a studentship, RCUK for providing funding through the EPSRC SUPERGEN SuperSolar Hub (EP/J017361/1), and the Loughborough Materials Characterisation Centre for use of equipment. The authors at Colorado State University acknowledge support from NSF AIR, NSF I/UCRC and DOE SIPS programmes. The work at Colorado State University was supported by NSF award 1540007, NSF PFI:AIR-RA programme 1538733 and DOE SIPS award DE-EE0008177. K.L. acknowledges support from EPSRC grant M018237/1.

Author information

Authors and Affiliations

  1. Centre for Renewable Energy Systems Technology, Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Loughborough, UK

    Thomas A. M. Fiducia, Lewis D. Wright, Ali Abbas, Jake W. Bowers & John M. Walls

  2. Department of Physics, Durham University, Durham, UK

    Budhika G. Mendis

  3. Materials Department, Oxford University, Oxford, UK

    Kexue Li & Chris R. M. Grovenor

  4. Colorado State University, Fort Collins, CO, USA

    Amit H. Munshi, Kurt Barth & Walajabad S. Sampath

Authors
  1. Thomas A. M. Fiducia
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Budhika G. Mendis
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Kexue Li
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Chris R. M. Grovenor
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Amit H. Munshi
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Kurt Barth
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. Walajabad S. Sampath
    View author publications

    You can also search for this author in PubMed Google Scholar

  8. Lewis D. Wright
    View author publications

    You can also search for this author in PubMed Google Scholar

  9. Ali Abbas
    View author publications

    You can also search for this author in PubMed Google Scholar

  10. Jake W. Bowers
    View author publications

    You can also search for this author in PubMed Google Scholar

  11. John M. Walls
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

T.A.M.F. conceived this study and planned it along with J.M.W., K.L., C.R.M.G. and B.G.M. A.H.M. made the cells with assistance from K.B. and W.S.S. A.A. performed the TEM. T.A.M.F. prepared the samples for CL and SIMS characterization. B.G.M. carried out the CL measurements. K.L. performed the SIMS characterization with assistance from C.R.M.G. T.A.M.F. and L.D.W. performed the data analysis. T.A.M.F. wrote the manuscript with help from J.W.B. and J.M.W.

Corresponding author

Correspondence to John M. Walls.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Figs. 1–4

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Fiducia, T.A.M., Mendis, B.G., Li, K. et al. Understanding the role of selenium in defect passivation for highly efficient selenium-alloyed cadmium telluride solar cells. Nat Energy 4, 504–511 (2019). https://doi.org/10.1038/s41560-019-0389-z

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41560-019-0389-z

This article is cited by

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing