Black silicon solar cells with interdigitated back-contacts achieve 22.1% efficiency


The nanostructuring of silicon surfaces—known as black silicon—is a promising approach to eliminate front-surface reflection in photovoltaic devices without the need for a conventional antireflection coating. This might lead to both an increase in efficiency and a reduction in the manufacturing costs of solar cells. However, all previous attempts to integrate black silicon into solar cells have resulted in cell efficiencies well below 20% due to the increased charge carrier recombination at the nanostructured surface. Here, we show that a conformal alumina film can solve the issue of surface recombination in black silicon solar cells by providing excellent chemical and electrical passivation. We demonstrate that efficiencies above 22% can be reached, even in thick interdigitated back-contacted cells, where carrier transport is very sensitive to front surface passivation. This means that the surface recombination issue has truly been solved and black silicon solar cells have real potential for industrial production. Furthermore, we show that the use of black silicon can result in a 3% increase in daily energy production when compared with a reference cell with the same efficiency, due to its better angular acceptance.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Structure and reflectance of b-Si.
Figure 2: Lifetimes and corresponding surface recombination velocities.
Figure 3: Structure of the IBC cell.
Figure 4: EQE and J–V and P–V characteristics for the selected b-Si solar cell.
Figure 5: Angle-dependent EQE and daily/yearly energy production enhancement.


  1. 1

    Clapham, P. B. & Hutley, M. C. Reduction of lens reflection by the ‘moth eye’ principle. Nature 3, 281–282 (1973).

    Article  Google Scholar 

  2. 2

    Zhu, J. et al. Optical absorption enhancement in amorphous silicon nanowire and nanocone arrays. Nano Lett. 9, 279 (2008).

    Article  Google Scholar 

  3. 3

    Garnett, E. & Yang, P. Light trapping in silicon nanowire solar cells. Nano Lett. 10, 1082–1087 (2010).

    CAS  Article  Google Scholar 

  4. 4

    Kelzenberg, M. D. et al. Enhanced absorption and carrier collection in Si wire arrays for photovoltaic applications. Nature Mater. 9, 239–244 (2010).

    CAS  Article  Google Scholar 

  5. 5

    Oh, J., Yuan, H-C. & Branz, H. M. An 18.2%-efficient black-silicon solar cell achieved through control of carrier recombination in nanostructures. Nature Nanotech. 7, 743–748 (2012).

    CAS  Article  Google Scholar 

  6. 6

    Zhu, J., Hsu, C-M., Yu, Z., Fan, S. & Cui, Y. Nanodome solar cells with efficient light management and self-cleaning. Nano Lett. 10, 1979–1984 (2010).

    CAS  Article  Google Scholar 

  7. 7

    De Boer, M. J. et al. Guidelines for etching silicon MEMS structures using fluorine high-density plasmas at cryogenic temperatures. J. Micromech. Microeng. 11, 385–401 (2002).

    CAS  Article  Google Scholar 

  8. 8

    Gesemann, B., Wehrspohn, R., Hackner, A. & Müller, G. Large-scale fabrication of ordered silicon nanotip arrays used for gas ionization in ion mobility spectrometers. IEEE Trans. Nanotechnol. 10, 50–52 (2011).

    Article  Google Scholar 

  9. 9

    Hoyer, P., Theuer, M., Beigang, R. & Kley, E-B. Terahertz emission from black silicon. Appl. Phys. Lett. 93, 091106 (2008).

    Article  Google Scholar 

  10. 10

    Sainiemi, L. et al. Rapid fabrication of high aspect ratio silicon nanopillars for chemical analysis. Nanotechnology 18, 505303 (2007).

    Article  Google Scholar 

  11. 11

    Huang, Z. et al. Microstructured silicon photodetector. Appl. Phys. Lett. 89, 033506 (2006).

    Article  Google Scholar 

  12. 12

    Ivanova, E. P. et al. Bactericidal activity of black silicon. Nature Commun. 4, 2838 (2013).

    Article  Google Scholar 

  13. 13

    Jeong, S., McGehee, M. D. & Cui, Y. All-back-contact ultra-thin silicon nanocone solar cells with 13.7% power conversion efficiency. Nature Commun. 4, 2950 (2013).

    Article  Google Scholar 

  14. 14

    Zhong, S. et al. Influence of the texturing structure on the properties of black silicon solar cell. Sol. Energ. Mater. Sol. Cells 108, 200–204 (2013).

    CAS  Article  Google Scholar 

  15. 15

    Koynov, S., Brandt, M. S. & Stutzmann, M. Black multi-crystalline silicon solar cells. Phys. Status Solidi RRL 1, R53–R55 (2007).

    CAS  Article  Google Scholar 

  16. 16

    Hoex, B., Schmidt, J., Pohl, P., van de Sanden, M. C. M. & Kessels, W. M. M. Silicon surface passivation by atomic layer deposition Al2O3 . J. Appl. Phys. 104, 044903 (2008).

    Article  Google Scholar 

  17. 17

    Repo, P. et al. Effective passivation of black silicon surfaces by atomic layer deposition. IEEE J. Photovolt. 3, 90–94 (2013).

    Article  Google Scholar 

  18. 18

    Otto, M. et al. Extremely low surface recombination velocities in black silicon passivated by atomic layer deposition. Appl. Phys. Lett. 100, 191603 (2012).

    Article  Google Scholar 

  19. 19

    Neuhaus, D. & Münzer, A. Industrial silicon wafer solar cells. Adv. Optoelectron. 2007, 24521 (2007).

    Article  Google Scholar 

  20. 20

    Halbwax, M. et al. Micro and nano-structuration of silicon by femtosecond laser: application to silicon photovoltaic cells fabrication. Thin Solid Films 516, 6791–6795 (2008).

    CAS  Article  Google Scholar 

  21. 21

    Toor, F., Branz, H. M., Page, M. R., Jones, K. M. & Yuan, H-C. Multi-scale surface texture to improve blue response of nanoporous black silicon solar cells. Appl. Phys. Lett. 99, 103501 (2011).

    Article  Google Scholar 

  22. 22

    Sainiemi, L. et al. Non-reflecting silicon and polymer surfaces by plasma etching and replication. Adv. Mater. 23, 122–126 (2011).

    CAS  Article  Google Scholar 

  23. 23

    Huang, Y-F. et al. Improved broadband and quasi-omnidirectional anti-reflection properties with biomimetic silicon nanostructures. Nature Nanotech. 2, 770–774 (2007).

    CAS  Article  Google Scholar 

  24. 24

    Richter, A., Glunz, S. W., Werner, F., Schmidt, J. & Cuevas, A. Improved quantitative description of Auger recombination in crystalline silicon. Phys. Rev. B 86, 165202 (2012).

    Article  Google Scholar 

  25. 25

    Carrio, D. et al. Rear contact optimization based on 3D simulations for IBC solar cells with point-like doped contacts. Energy Procedia 55, 47 (2014).

    CAS  Article  Google Scholar 

  26. 26

    Hoex, B., van de Sanden, M. C. M., Schmidt, J., Brendel, R. & Kessels, W. M. M. Surface passivation of phosphorus-diffused n+-type emitters by plasma-assisted atomic-layer deposited Al2O3 . Phys. Status Solidi RRL 6, 4–6 (2012).

    CAS  Article  Google Scholar 

  27. 27

    Masters, G. M. Renewable and Efficient Electric Power Systems (Wiley, 2004).

    Google Scholar 

Download references


This work was supported by the network ‘Nanophotonics for Energy Efficiency’ (grant agreement no. 248855), the Effinano-project (funded by the School of Electrical Engineering at Aalto University) and the Tekes-funded project PASSI. The authors acknowledge The Centre for Research in NanoEngineering (CRnE) and Aalto University Micronova Nanofabrication Centre for providing facilities. The authors thank T. Trifonov for help and comments on performing reflectance measurements and V. Vähänissi for providing valuable comments regarding writing the manuscript.

Author information




H.S. and R.A. conceived and designed the experiments. P.R., G.G., P.O. and E.C. performed the experiments. P.O. and H.S. analysed the data. M.G. performed the angle-dependent simulations. H.S. wrote the paper. All authors discussed the results and commented on the manuscript.

Corresponding author

Correspondence to Hele Savin.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary information

Supplementary information (PDF 577 kb)

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Savin, H., Repo, P., von Gastrow, G. et al. Black silicon solar cells with interdigitated back-contacts achieve 22.1% efficiency. Nature Nanotech 10, 624–628 (2015).

Download citation

Further reading


Find nanotechnology articles, nanomaterial data and patents all in one place. Visit Nano by Nature Research