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.

Low-temperature and effective ex situ group V doping for efficient polycrystalline CdSeTe solar cells

Abstract

CdTe solar cell technology is one of the lowest-cost methods of generating electricity in the solar industry, benefiting from fast CdTe absorber deposition, CdCl2 treatment and Cu doping. However, Cu doping has low photovoltage and issues with instability. Doping group V elements into CdTe is therefore a promising route to address these challenges. Although high-temperature in situ group V doped CdSeTe devices have demonstrated efficiencies exceeding 20%, they face obstacles including post-deposition doping activation processes, short carrier lifetimes and low activation ratios. Here, we demonstrate low-temperature and effective ex situ group V doping for CdSeTe solar cells using group V chlorides. For AsCl3 doped CdSeTe solar cells, the dopant activation ratio can be 5.88%, hole densities reach >2 × 1015 cm3 and carrier lifetime is longer than 20 ns. Thus, ex situ As doped CdSeTe solar cells show open-circuit voltages ~863 mV, compared to the highest open-circuit voltage of 852 mV for Cu doped CdSeTe solar cells.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Fig. 1: Schematic of low-temperature ex situ doping in polycrystalline CdSeTe solar cells.
Fig. 2: Characterizations of dopant distribution and the formation of shallow acceptor states.
Fig. 3: Improvement of AsCl3 doped Cu-free CdSeTe device performances.
Fig. 4: Absorber hole lifetime and hole densities.

Data availability

All data generated or analysed during this study are included in the published article and its Supplementary Information. Source data are provided with this paper.

References

  1. 1.

    Green, M. A. et al. Solar cell efficiency tables (version 54). Prog. Photovolt. Res. Appl. 27, 565–575 (2019).

    Article  Google Scholar 

  2. 2.

    Grover, S. et al. Characterization of arsenic doped CdTe layers and solar cells. In Proc. 2017 IEEE 44th Photovoltaic Specialist Conference (PVSC) 1193–1195 (IEEE, 2017).

  3. 3.

    Leading the World’s Sustainable Energy Future (First Solar, 2019); http://www.firstsolar.com/-/media/First-Solar/Documents/Corporate-Collaterals/FS_Corporate_Factsheet.ashx

  4. 4.

    Burst, J. M. et al. CdTe solar cells with open-circuit voltage breaking the 1 V barrier. Nat. Energy 1, 16015 (2016).

    Article  Google Scholar 

  5. 5.

    Metzger, W. K. et al. Exceeding 20% efficiency with in situ group V doping in polycrystalline CdTe solar cells. Nat. Energy 4, 837–845 (2019).

    Article  Google Scholar 

  6. 6.

    Fiducia, T. A. M. 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).

    Article  Google Scholar 

  7. 7.

    McCandless, B. E. et al. Overcoming carrier concentration limits in polycrystalline CdTe thin films with in situ doping. Sci. Rep. 8, 14519 (2018).

    Article  Google Scholar 

  8. 8.

    Dzhafarov, T. D., Yesilkaya, S. S., Yilmaz Canli, N. & Caliskan, M. Diffusion and influence of Cu on properties of CdTe thin films and CdTe/CdS cells. Sol. Energy Mater. Sol. Cells 85, 371–383 (2005).

    Article  Google Scholar 

  9. 9.

    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. Tech. 31, 083002 (2016).

    Article  Google Scholar 

  10. 10.

    Ma, J. et al. Dependence of the minority-carrier lifetime on the stoichiometry of CdTe using time-resolved photoluminescence and first-principles calculations. Phys. Rev. Lett. 111, 067402 (2013).

    Article  Google Scholar 

  11. 11.

    Nagaoka, A. et al. Growth and characterization of arsenic doped CdTe single crystals grown by Cd-solvent traveling-heater method. J. Cryst. Growth 467, 6–11 (2017).

    Article  Google Scholar 

  12. 12.

    Kartopu, G. et al. Study of thin film poly-crystalline CdTe solar cells presenting high acceptor concentrations achieved by in-situ arsenic doping. Sol. Energy Mater. Sol. Cells 194, 259–267 (2019).

    Article  Google Scholar 

  13. 13.

    Ghandhi, S. K., Taskar, N. R. & Bhat, I. B. Arsenic-doped P-CdTe layers grown by organometallic vapor-phase epitaxy. Appl. Phys. Lett. 50, 900–902 (1987).

    Article  Google Scholar 

  14. 14.

    Nagaoka, A., Nishioka, K., Yoshino, K., Kuciauskas, D. & Scarpulla, M. A. Arsenic doped Cd-rich CdTe: equilibrium doping limit and long lifetime for high open-circuit voltage solar cells greater than 900 mV. Appl. Phys. Express 12, 081002 (2019).

    Article  Google Scholar 

  15. 15.

    Krasikov, D. & Sankin, I. Beyond thermodynamic defect models: a kinetic simulation of arsenic activation in CdTe. Phys. Rev. Mater. 2, 103803 (2018).

    Article  Google Scholar 

  16. 16.

    Li, D.-B. et al. Maximize CdTe solar cell performance through copper activation engineering. Nano Energy 73, 104835 (2020).

    Article  Google Scholar 

  17. 17.

    Artegiani, E. et al. Analysis of a novel CuCl2 back contact process for improved stability in CdTe solar cells. Prog. Photovolt. Res. Appl. 27, 706–715 (2019).

    Google Scholar 

  18. 18.

    Mao, D., Wickersham, C. E. & Gloeckler, M. Measurement of chlorine concentrations at CdTe grain boundaries. IEEE J. Photovolt. 4, 1655–1658 (2014).

    Article  Google Scholar 

  19. 19.

    Colegrove, E. et al. Phosphorus diffusion mechanisms and deep incorporation in polycrystalline and single-crystalline CdTe. Phys. Rev. Appl. 5, 054014 (2016).

    Article  Google Scholar 

  20. 20.

    Colegrove, E. et al. Experimental and theoretical comparison of Sb, As, and P diffusion mechanisms and doping in CdTe. J. Phys. D Appl. Phys. 51, 075102 (2018).

    Article  Google Scholar 

  21. 21.

    Kraft, C. et al. Phosphorus implanted cadmium telluride solar cells. Thin Solid Films 519, 7153–7155 (2011).

    Article  Google Scholar 

  22. 22.

    Romeo, N., Bosio, A. & Rosa, G. The back contact of CdTe/CdS thin film solar cells. In Proc. ISES Solar World Congress 2017 (International Solar Energy Society Selection, 2017).

  23. 23.

    Hu, S. et al. Band diagrams and performance of CdTe solar cells with a Sb2Te3 back contact buffer layer. AIP Adv. 1, 042152 (2011).

    Article  Google Scholar 

  24. 24.

    Kumar, S. G. & Rao, K. S. R. K. Physics and chemistry of CdTe/CdS thin film heterojunction photovoltaic devices: fundamental and critical aspects. Energy Environ. Sci. 7, 45–102 (2014).

    Article  Google Scholar 

  25. 25.

    Huang, J. et al. Copassivation of polycrystalline CdTe absorber by CuCl thin films for CdTe solar cells. Appl. Surf. Sci. 484, 1214–1222 (2019).

    Article  Google Scholar 

  26. 26.

    Bastola, E. et al. Doping of CdTe using CuCl2 solution for highly efficient photovoltaic devices. In Proc. 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) 1846–1850 (IEEE, 2019).

  27. 27.

    Major, J. D., Treharne, R. E., Phillips, L. J. & Durose, K. A low-cost non-toxic post-growth activation step for CdTe solar cells. Nature 511, 334–337 (2014).

    Article  Google Scholar 

  28. 28.

    Abbas, A. et al. The effect of a post-activation annealing treatment on thin film CdTe device performance. In Proc. 2015 IEEE 42nd Photovoltaic Specialist Conference (PVSC) 1–6 (IEEE, 2015).

  29. 29.

    Montgomery, A. et al. Solution-processed copper (I) thiocyanate (CuSCN) for highly efficient CdSe/CdTe thin-film solar cells. Prog. Photovolt. Res. Appl. 27, 665–672 (2019).

    Google Scholar 

  30. 30.

    Fiducia, T. 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 

  31. 31.

    Akis, R. et al. Extracting Cu diffusion parameters in polycrystalline CdTe. In Proc. 2014 IEEE 40th Photovoltaic Specialist Conference (PVSC) 3276–3281 (IEEE, 2014).

  32. 32.

    Colegrove, E. et al. Antimony diffusion in CdTe. IEEE J. Photovolt. 7, 870–873 (2017).

    Article  Google Scholar 

  33. 33.

    Flores, M. A., Orellana, W. & Menéndez-Proupin, E. Self-compensation in phosphorus-doped CdTe. Phys. Rev. B 96, 134115 (2017).

    Article  Google Scholar 

  34. 34.

    Barrioz, V. et al. Highly arsenic doped CdTe layers for the back contacts of CdTe solar cells. MRS Proc. 1012, 1208 (2007).

    Article  Google Scholar 

  35. 35.

    Murria, P. et al. Speciation of CuCl and CuCl2 thiol-amine solutions and characterization of resulting films: implications for semiconductor device fabrication. Inorg. Chem. 56, 14396–14407 (2017).

    Article  Google Scholar 

  36. 36.

    Molva, E., Saminadayar, K., Pautrat, J. L. & Ligeon, E. Photoluminescence studies in N, P, As implanted cadmium telluride. Solid State Commun. 48, 955–960 (1983).

    Article  Google Scholar 

  37. 37.

    Yun, J. H., Kim, K. H., Lee, D. Y. & Ahn, B. T. Back contact formation using Cu2Te as a Cu-doping source and as an electrode in CdTe solar cells. Sol. Energy Mater. Sol. Cells 75, 203–210 (2003).

    Article  Google Scholar 

  38. 38.

    Li, C. et al. Grain-boundary-enhanced carrier collection in CdTe solar cells. Phys. Rev. Lett. 112, 156103 (2014).

    Article  Google Scholar 

  39. 39.

    Ablekim, T. et al. Self-compensation in arsenic doping of CdTe. Sci. Rep. 7, 4563 (2017).

    Article  Google Scholar 

  40. 40.

    Guo, J. L. et al. Effect of selenium and chlorine co-passivation in polycrystalline CdSeTe devices. Appl. Phys. Lett. 115, 153901 (2019).

    Article  Google Scholar 

  41. 41.

    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 

  42. 42.

    Grecu, D. & Compaan, A. D. Photoluminescence study of Cu diffusion and electromigration in CdTe. Appl. Phys. Lett. 75, 361–363 (1999).

    Article  Google Scholar 

  43. 43.

    Corwine, C. R., Pudov, A. O., Gloeckler, M., Demtsu, S. H. & Sites, J. R. Copper inclusion and migration from the back contact in CdTe solar cells. Sol. Energy Mater. Sol. Cells 82, 481–489 (2004).

    Google Scholar 

  44. 44.

    Dobson, K. D., Visoly-Fisher, I., Hodes, G. & Cahen, D. Stability of CdTe/CdS thin-film solar cells. Sol. Energy Mater. Sol. Cells 62, 295–325 (2000).

    Article  Google Scholar 

  45. 45.

    Awni, R. A. et al. The effects of hydrogen iodide back surface treatment on CdTe solar cells. Sol. RRL 3, 1800304 (2019).

    Article  Google Scholar 

  46. 46.

    Awni, R. A. et al. Influences of buffer material and fabrication atmosphere on the electrical properties of CdTe solar cells. Prog. Photovolt. Res. Appl. 27, 1115–1123 (2019).

    Article  Google Scholar 

  47. 47.

    Perrenoud, J. et al. A comprehensive picture of Cu doping in CdTe solar cells. J. Appl. Phys. 114, 174505 (2013).

    Article  Google Scholar 

  48. 48.

    Wei, S.-H. & Zhang, S. B. Chemical trends of defect formation and doping limit in II-VI semiconductors: the case of CdTe. Phys. Rev. B 66, 155211 (2002).

    Article  Google Scholar 

  49. 49.

    Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865–3868 (1996).

    Article  Google Scholar 

  50. 50.

    Hutter, J., Iannuzzi, M., Schiffmann, F. & VandeVondele, J. cp2k: atomistic simulations of condensed matter systems. Wiley Interdiscip. Rev. Comput. Mol. Sci. 4, 15–25 (2014).

    Article  Google Scholar 

  51. 51.

    VandeVondele, J. & Hutter, J. Gaussian basis sets for accurate calculations on molecular systems in gas and condensed phases. J. Chem. Phys. 127, 114105 (2007).

    Article  Google Scholar 

  52. 52.

    Li, D.-B. et al. Eliminating S-kink to maximize the performance of MgZnO/CdTe solar cells. ACS Appl. Energy Mater. 2, 2896–2903 (2019).

    Article  Google Scholar 

Download references

Acknowledgements

S.N.V., L.L. and F.Y. acknowledge funding from the National Science Foundation under contracts no. 1944374 and 2019473, the National Aeronautics and Space Administration, Alabama EPSCoR International Space Station Flight Opportunity Program (contract no. 80NSSC20M0141) and the US Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Solar Energy Technologies Office (SETO) Agreement DE-EE0009368. D.-B.L., C.Y., R.A.A., K.K.S., R.J.E. and Y.Y. acknowledge funding from the Air Force Research Laboratory, Space Vehicles Directorate (contract no. FA9453-18-2-0037), the National Science Foundation under contract no. 1711534 and the US Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under Solar Energy Technologies Office (SETO) Agreement DE-EE0008974. We thank D. Strickler from Pilkington North America Inc. for supplying us with the FTO coated substrates.

Author information

Affiliations

Authors

Contributions

D.-B.L. and S.N.V. performed film and device synthesis as well as JV, EQE and CV measurements. S.N.V. performed the XPS measurements. C.Y. performed the DFT calculations. R.A.A. carried out TAS and temperature-dependent JV measurements. K.K.S. and R.J.E. performed the PL and TRPL measurements. L.L. performed the PL mapping. Y.Y. and F.Y. directed the research.

Corresponding authors

Correspondence to Yanfa Yan or Feng Yan.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information Nature Energy thanks Gang Xiong and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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

Supplementary information

Supplementary Information

Supplementary Figs. 1–16, Tables 1–4 and references.

Reporting Summary

Supplementary Data

Supplementary Fig 1. DFT calculation for the diffusion barrier of interstitial Cd and As in CdTe. Supplementary Fig. 3. As linear profile. Supplementary Fig. 7. Statistical Source Data. Supplementary Fig. 10. JV curves under AM1.5 illumination and in the dark for CdSeTe solar cells without any intentional doping. Supplementary Fig. 12. Light soaking test of the Cu and As doped CdTe solar cells at 85 °C under 1 sun. Supplementary Fig. 14. The CV determined carrier concentration for the group V chlorides doped CdSeTe solar cells. Supplementary Fig. 15. Temperature-dependent capacitance–frequency measurement for the group V doped CdSeTe measured at temperatures from 150 to 310 K with a step size of 10 K to determine the defect states and back-barrier heights. Supplementary Fig. 16. The Arrhenius plots used to calculate the back-barriers.

Source data

Source Data Fig. 2

Characterizations of dopant distribution and the formation of shallow acceptor states.

Source Data Fig. 3

Improvement of AsCl3 doped Cu-free CdSeTe device performances.

Source Data Fig. 4

Absorber hole lifetime and hole densities.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Li, DB., Yao, C., Vijayaraghavan, S.N. et al. Low-temperature and effective ex situ group V doping for efficient polycrystalline CdSeTe solar cells. Nat Energy 6, 715–722 (2021). https://doi.org/10.1038/s41560-021-00848-z

Download citation

Further reading

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