Skip to main content

Thank you for visiting 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.

Passivating contacts for crystalline silicon solar cells


The global photovoltaic (PV) market is dominated by crystalline silicon (c-Si) based technologies with heavily doped, directly metallized contacts. Recombination of photo-generated electrons and holes at the contact regions is increasingly constraining the power conversion efficiencies of these devices as other performance-limiting energy losses are overcome. To move forward, c-Si PV technologies must implement alternative contacting approaches. Passivating contacts, which incorporate thin films within the contact structure that simultaneously supress recombination and promote charge-carrier selectivity, are a promising next step for the mainstream c-Si PV industry. In this work, we review the fundamental physical processes governing contact formation in c-Si. In doing so we identify the role passivating contacts play in increasing c-Si solar cell efficiencies beyond the limitations imposed by heavy doping and direct metallization. Strategies towards the implementation of passivating contacts in industrial environments are discussed.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Historical progression of notable c-Si solar cell efficiencies.
Fig. 2: Conceptual schematic of the operation of a solar cell.
Fig. 3: Motivation for, and characteristics of, heavily doped contacts.
Fig. 4: Solar cells featuring passivating contacts.
Fig. 5: Materials for passivating contacts.
Fig. 6: Comparison of silicon solar cell contacting approaches.

Data availability

The data from plots in Figs. 1a,b, 3f,g, 5 and 6a are available in the Supplementary Data.


  1. 1.

    BP Statistical Review of World Energy, June 2018 (BP, 2018).

  2. 2.

    Jager-Waldau, A. PV Status Report 2018 (European Union, 2018).

  3. 3.

    International Technology Roadmap for Photovoltaic (ITRPV) - Ninth Edition (ITRPV, 2018).

  4. 4.

    Richter, A., Hermle, M. & Glunz, S. W. Reassessment of the limiting efficiency for crystalline silicon solar cells. IEEE J. Photovolt. 3, 1184–1191 (2013).

    Google Scholar 

  5. 5.

    Min, B. et al. A roadmap toward 24% efficient PERC solar cells in industrial mass production. IEEE J. Photovolt. 7, 1541–1550 (2017).

    Google Scholar 

  6. 6.

    Berney Needleman, D. et al. Economically sustainable scaling of photovoltaics to meet climate targets. Energy Environ. Sci. 9, 2122–2129 (2016).

    Google Scholar 

  7. 7.

    Basore, P. A. Paths to future growth in photovoltaics manufacturing. Prog. Photovolt. Res. Appl. 24, 1024–1031 (2016).

    Google Scholar 

  8. 8.

    Baker-Finch, S. C., McIntosh, K. R., Yan, D., Fong, K. C. & Kho, T. C. Near-infrared free carrier absorption in heavily doped silicon. J. Appl. Phys. 116, 063106 (2014).

    Google Scholar 

  9. 9.

    Yan, D. & Cuevas, A. Empirical determination of the energy band gap narrowing in highly doped n+ silicon. J. Appl. Phys. 114, 044508 (2013).

    Google Scholar 

  10. 10.

    Yan, D. & Cuevas, A. Empirical determination of the energy band gap narrowing in p+ silicon heavily doped with boron. J. Appl. Phys. 116, 194505 (2014).

    Google Scholar 

  11. 11.

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

  12. 12.

    Green, M. A. The path to 25% silicon solar cell efficiency: history of silicon cell evolution. Prog. Photovolt. Res. Appl. 17, 183–189 (2009). Outlines the historical development of silicon solar cells, with specific reference to the PERC cells that continue to hold the efficiency record for silicon devices with heavily doped, directly metallized contacts.

    Google Scholar 

  13. 13.

    Zhao, J., Wang, A. & Green, M. A. 24·5% Efficiency silicon PERT cells on MCZ substrates and 24·7% efficiency PERL cells on FZ substrates. Prog. Photovolt. Res. Appl. 7, 471–474 (1999).

    Google Scholar 

  14. 14.

    Smith, D. D. et al. Toward the practical limits of silicon solar cells. IEEE J. Photovolt. 4, 1465–1469 (2014).

    Google Scholar 

  15. 15.

    Smith, D. D. et al. Silicon solar cells with total area efficiency above 25 %. In Proc. IEEE 43rd Photovoltaic Specialists Conference (PVSC) 3351–3355 (IEEE, 2016).

  16. 16.

    Adachi, D., Hernández, J. L. & Yamamoto, K. Impact of carrier recombination on fill factor for large area heterojunction crystalline silicon solar cell with 25.1% efficiency. Appl. Phys. Lett. 107, 233506 (2015).

    Google Scholar 

  17. 17.

    Masuko, K. et al. Achievement of more than 25% conversion efficiency with crystalline silicon heterojunction solar cell. IEEE J. Photovolt. 4, 1433–1435 (2014).

    Google Scholar 

  18. 18.

    Glunz, S. W. et al. The irresistible charm of a simple current flow pattern – 25% with a solar cell featuring a full-area back contact. In Proc. 31st European Photovoltaic Solar Energy Conference and Exhibition 259–263 (2015).

  19. 19.

    Richter, A. et al. n-Type Si solar cells with passivating electron contact: identifying sources for efficiency limitations by wafer thickness and resistivity variation. Sol. Energy Mater. Sol. Cells 173, 96–105 (2017).

    Google Scholar 

  20. 20.

    Yoshikawa, K. et al. Silicon heterojunction solar cell with interdigitated back contacts for a photoconversion efficiency over 26%. Nat. Energy 2, 201732 (2017). Current world record efficiency for c-Si solar cells with an amorphous silicon SHJ passivating contact in an IBC configuration.

    Google Scholar 

  21. 21.

    Green, M. A. et al. Solar cell efficiency tables (version 50). Prog. Photovolt. Res. Appl. 25, 668–676 (2017).

    Google Scholar 

  22. 22.

    Cuevas, A. & Macdonald, D. Measuring and interpreting the lifetime of silicon wafers. Sol. Energy 76, 255–262 (2004).

    Google Scholar 

  23. 23.

    Cuevas, A. The recombination parameter J0. Energy Procedia 55, 53–62 (2014).

    Google Scholar 

  24. 24.

    Schmidt, J., Peibst, R. & Brendel, R. Surface passivation of crystalline silicon solar cells: present and future. Sol. Energy Mater. Sol. Cells 187, 39–54 (2018).

    Google Scholar 

  25. 25.

    Bonilla, R. S., Hoex, B., Hamer, P. & Wilshaw, P. R. Dielectric surface passivation for silicon solar cells: A review. Phys. Status Solidi A 214, 1700293 (2017).

    Google Scholar 

  26. 26.

    Tung, R. T. The physics and chemistry of the Schottky barrier height. Appl. Phys. Rev. 1, 011304 (2014).

    Google Scholar 

  27. 27.

    Schroder, D. K. & Meier, D. L. Solar cell contact resistance: a review. IEEE Trans. Electron Devices 31, 637–647 (1984).

    Google Scholar 

  28. 28.

    Melskens, J. et al. Passivating contacts for crystalline silicon solar cells: from concepts and materials to prospects. IEEE J. Photovolt. 8, 373–388 (2018).

    Google Scholar 

  29. 29.

    Glunz, S. W. & Feldmann, F. SiO2 surface passivation layers—a key technology for silicon solar cells. Sol. Energy Mater. Sol. Cells 185, 260–269 (2018).

    Google Scholar 

  30. 30.

    Würfel, U., Cuevas, A. & Würfel, P. Charge carrier separation in solar cells. IEEE J. Photovolt. 5, 461–469 (2015). Conceptual solar cell modelling demonstrating the physical basis by which contacts separate charge carriers in solar cells.

    Google Scholar 

  31. 31.

    Cuevas, A. et al. Skin care for healthy silicon solar cells. In Proc. IEEE 42nd Photovoltaic Specialist Conference (PVSC) 1–6 (IEEE, 2015).

  32. 32.

    De Wolf, S., Descoeudres, A., Holman, Z. C. & Ballif, C. High-efficiency silicon heterojunction solar cells: a review. Green 2, 7–24 (2012).

    Google Scholar 

  33. 33.

    Würfel, P. Physics of Solar Cells: From Principles to New Concepts (Wiley, 2008).

  34. 34.

    Messmer, C., Bivour, M., Schön, J., Glunz, S. W. & Hermle, M. Numerical simulation of silicon heterojunction solar cells featuring metal oxides as carrier-selective contacts. IEEE J. Photovolt. 8, 456–464 (2018).

    Google Scholar 

  35. 35.

    Bullock, J. et al. Efficient silicon solar cells with dopant-free asymmetric heterocontacts. Nat. Energy 1, 15031 (2016).

    Google Scholar 

  36. 36.

    Green, M. A. & Godfrey, R. B. MIS silicon solar cells. Jpn. J. Appl. Phys. 17, 295–298 (1978).

    Google Scholar 

  37. 37.

    Battaglia, C. et al. Hole selective MoOx contact for silicon solar cells. Nano Lett. 14, 967–971 (2014).

    Google Scholar 

  38. 38.

    Allen, T. G. et al. Calcium contacts to n-type crystalline silicon solar cells. Prog. Photovolt. Res. Appl. 25, 636–644 (2017).

    Google Scholar 

  39. 39.

    Wolf, A. et al. Status and perspective of emitter formation by POCl3-diffusion. In Proc. 31st European Photovoltaic Solar Energy Conference and Exhibition 414–419 (2015).

  40. 40.

    Lu, H., Guo, Y., Li, H. & Robertson, J. Modeling of surface gap state passivation and Fermi level de-pinning in solar cells. Appl. Phys. Lett. 114, 222106 (2019).

    Google Scholar 

  41. 41.

    Yablonovitch, E., Gmitter, T., Swanson, R. M. & Kwark, Y. H. A 720 mV open circuit voltage SiOx:c‐Si:SiOx double heterostructure solar cell. Appl. Phys. Lett. 47, 1211–1213 (1985). Early demonstration of the surface passivation potential of doped poly-silicon or SIPOS-based contacts, which would form the basis of extensive recent research, for example in so-called TOPCon contacts.

    Google Scholar 

  42. 42.

    Liu, Y., Stradins, P., Deng, H., Luo, J. & Wei, S.-H. Suppress carrier recombination by introducing defects: the case of Si solar cell. Appl. Phys. Lett. 108, 022101 (2016).

    Google Scholar 

  43. 43.

    Brendel, R. & Peibst, R. Contact selectivity and efficiency in crystalline silicon photovoltaics. IEEE J. Photovolt. 6, 1413–1420 (2016).

    Google Scholar 

  44. 44.

    MacDonald, D., Cuevas, A., McIntosh, K., Barbosa, L. & De Ceuster, D. Impact of Cr, Fe, Ni, Ti and W surface contamination on diffused and oxidised a-type crystalline silicon wafers. In Proc. 20th European Photovoltaic Solar Energy Conference 1–4 (WIP Renewable Energies, 2005).

  45. 45.

    Nagamatsu, K. A. et al. Titanium dioxide/silicon hole-blocking selective contact to enable double-heterojunction crystalline silicon-based solar cell. Appl. Phys. Lett. 106, 123906 (2015).

    Google Scholar 

  46. 46.

    Ponpon, J. P. & Siffert, P. Open‐circuit voltage of MIS silicon solar cells. J. Appl. Phys. 47, 3248–3251 (1976).

    Google Scholar 

  47. 47.

    Tarr, N. G., Pulfrey, D. L. & Iles, P. A. Induced back‐surface field solar cells on p‐type silicon substrates. Appl. Phys. Lett. 39, 83–85 (1981).

    Google Scholar 

  48. 48.

    Godfrey, R. B. & Green, M. A. High-efficiency silicon minMIS solar cells—design and experimental results. IEEE Trans. Electron Devices 27, 737–745 (1980).

    Google Scholar 

  49. 49.

    Godfrey, R. B. & Green, M. A. 655 mV open‐circuit voltage, 17.6% efficient silicon MIS solar cells. Appl. Phys. Lett. 34, 790–793 (1979). Early demonstration of an archetypal silicon passivating contact solar cell using a thin silicon oxide layer to separate the absorber material from the metal contact, resulting in a record open circuit voltage at the time of publication.

    Google Scholar 

  50. 50.

    Hezel, R. Recent progress in MIS solar cells. Prog. Photovolt. Res. Appl. 5, 109–120 (1997).

    Google Scholar 

  51. 51.

    Hezel, R. Plasma Si nitride—a promising dielectric to achieve high-quality silicon MIS/IL solar cells. J. Appl. Phys. 52, 3076 (1981).

    Google Scholar 

  52. 52.

    Jager, K. & Hezel, R. Optical stability of silicon nitride MIS inversion layer solar cells. IEEE Trans. Electron Devices 32, 1824–1829 (1985).

    Google Scholar 

  53. 53.

    Metz, A., Meyer, R., Kuhlmann, B., Grauvogl, M. & Hezel, R. 18.5% efficient first-generation MIS inversion-layer silicon solar cells. In Proc. Conference Record of the 26 th IEEE Photovoltaic Specialists Conference 31–34 (IEEE, 1997).

  54. 54.

    Hezel, R., Meyer, R. & Metz, A. A new generation of crystalline silicon solar cells: simple processing and record efficiencies for industrial-size devices. Sol. Energy Mater. 6 (2001).

  55. 55.

    Blakers, A. W. & Green, M. A. 678‐mV open‐circuit voltage silicon solar cells. Appl. Phys. Lett. 39, 483–485 (1981).

    Google Scholar 

  56. 56.

    Blakers, A. W. et al. 18-percent efficient terrestrial silicon solar cells. IEEE Electron Device Lett. 5, 12–13 (1984).

    Google Scholar 

  57. 57.

    Zielke, D. et al. Contact passivation in silicon solar cells using atomic-layer-deposited aluminum oxide layers. Phys. Status Solidi RRL—Rapid Res. Lett. 5, 298–300 (2011).

    Google Scholar 

  58. 58.

    Bullock, J. et al. Amorphous silicon enhanced metal-insulator-semiconductor contacts for silicon solar cells. J. Appl. Phys. 116, 163706 (2014).

    Google Scholar 

  59. 59.

    Bullock, J. et al. Simple silicon solar cells featuring an a-Si:H enhanced rear MIS contact. Sol. Energy Mater. Sol. Cells 138, 22–25 (2015).

    Google Scholar 

  60. 60.

    Tarr, N. G. A polysilicon emitter solar cell. IEEE Electron Device Lett. 6, 655–658 (1985).

    Google Scholar 

  61. 61.

    Kwark, Y. H. & Swanson, R. M. N-type SIPOS and poly-silicon emitters. Solid-State Electron. 30, 1121–1125 (1987).

    Google Scholar 

  62. 62.

    Kwark, Y. H., Sinton, R. & Swanson, R. M. SIPOS Heterojunction contacts to silicon. In Proc. 1984 International Electron Devices Meeting 742–745 (IEEE, 1984).

  63. 63.

    Post, I. R. C., Ashburn, P. & Wolstenholme, G. R. Polysilicon emitters for bipolar transistors: a review and re-evaluation of theory and experiment. IEEE Trans. Electron Devices 39, 1717–1731 (1992).

    Google Scholar 

  64. 64.

    Gan, J. Y. & Swanson, R. M. Polysilicon emitters for silicon concentrator solar cells. In Proc. IEEE Conference on Photovoltaic Specialists 245–250 (IEEE, 1990).

  65. 65.

    Tetzlaff, D. et al. A simple method for pinhole detection in carrier selective POLO-junctions for high efficiency silicon solar cells. Sol. Energy Mater. Sol. Cells 173, 106–110 (2017).

    Google Scholar 

  66. 66.

    Peibst, R. et al. Working principle of carrier selective poly-Si/c-Si junctions: is tunnelling the whole story? Sol. Energy Mater. Sol. Cells 158, 60–67 (2016).

    Google Scholar 

  67. 67.

    Feldmann, F. et al. Charge carrier transport mechanisms of passivating contacts studied by temperature-dependent J-V measurements. Sol. Energy Mater. Sol. Cells 178, 15–19 (2018).

    Google Scholar 

  68. 68.

    Mack, S. et al. Metallisation of boron‐doped polysilicon layers by screen printed silver pastes. Phys. Status Solidi Rapid Res. Lett. 11, 1700334 (2017).

    Google Scholar 

  69. 69.

    Rienäcker, M. et al. Junction resistivity of carrier-selective polysilicon on oxide junctions and its impact on solar cell performance. IEEE J. Photovolt. 7, 1–8 (2016).

    Google Scholar 

  70. 70.

    Larionova, Y. et al. On the recombination behavior of p+-type polysilicon on oxide junctions deposited by different methods on textured and planar surfaces. Phys. Status Solidi A 214, 1700058 (2017).

    Google Scholar 

  71. 71.

    Hollemann, C. et al. 26.1%-efficient POLO-IBC cells: quantification of electrical and optical loss mechanisms. Prog. Photovolt. Res. Appl. 1–9 (2019).

  72. 72.

    Okuda, K., Okamoto, H. & Hamakawa, Y. Amorphous Si/polycrystalline Si stacked solar cell having more than 12% conversion efficiency. Jpn. J. Appl. Phys. 22, L605 (1983).

    Google Scholar 

  73. 73.

    Pankove, J. I. & Tarng, M. L. Amorphous silicon as a passivant for crystalline silicon. Appl. Phys. Lett. 34, 156–157 (1979).

    Google Scholar 

  74. 74.

    Taguchi, M. et al. Improvement of the conversion efficiency of polycrystalline silicon thin film solar cell. In Proc. Technical Digest of the International PVSEC-5, Kyoto, Japan 689–692 (1990). Initial demonstration of a-Si-based heterojunction contacts to c-Si, initially for application in a-Si/poly-Si tandem cells, which would form the basis of the silicon heterojunction (SHJ) device architecture.

  75. 75.

    Taguchi, M. et al. HIT cells—high-efficiency crystalline Si cells with novel structure. Prog. Photovolt. Res. Appl. 8, 503–513 (2000).

    Google Scholar 

  76. 76.

    Nogay, G. et al. Nanocrystalline silicon carrier collectors for silicon heterojunction solar cells and impact on low-temperature device characteristics. IEEE J. Photovolt. 6, 1654–1662 (2016).

    Google Scholar 

  77. 77.

    Schulze, T. F., Korte, L., Conrad, E., Schmidt, M. & Rech, B. Electrical transport mechanisms in a-Si:H/c-Si heterojunction solar cells. J. Appl. Phys. 107, 023711 (2010).

    Google Scholar 

  78. 78.

    Tomasi, A. et al. Transparent electrodes in silicon heterojunction solar cells: influence on contact passivation. IEEE J. Photovolt. 6, 17–27 (2016).

    Google Scholar 

  79. 79.

    Procel, P., Yang, G., Isabella, O. & Zeman, M. Theoretical evaluation of contact stack for high efficiency IBC-SHJ solar cells. Sol. Energy Mater. Sol. Cells 186, 66–77 (2018).

    Google Scholar 

  80. 80.

    Holman, Z. C. et al. Current losses at the front of silicon heterojunction solar cells. IEEE J. Photovolt. 2, 7–15 (2012).

    Google Scholar 

  81. 81.

    Taguchi, M. et al. 24.7% record efficiency hit solar cell on thin silicon wafer. IEEE J. Photovolt. 4, 96–99 (2014).

    Google Scholar 

  82. 82.

    Seif, J. P. et al. Amorphous silicon oxide window layers for high-efficiency silicon heterojunction solar cells. J. Appl. Phys. 115, 024502 (2014).

    Google Scholar 

  83. 83.

    Boccard, M. & Holman, Z. C. Amorphous silicon carbide passivating layers for crystalline-silicon-based heterojunction solar cells. J. Appl. Phys. 118, 065704 (2015).

    Google Scholar 

  84. 84.

    Ingenito, A. et al. A passivating contact for silicon solar cells formed during a single firing thermal annealing. Nat. Energy 3, 800 (2018).

    Google Scholar 

  85. 85.

    Wernerus, H., Bivour, M., Kroely, L., Hermle, M. & Wolke, W. Characterization of ultra-thin μc-Si:H films for silicon heterojunction solar cells. Energy Procedia 55, 310–319 (2014).

    Google Scholar 

  86. 86.

    Mazzarella, L. et al. p-type microcrystalline silicon oxide emitter for silicon heterojunction solar cells allowing current densities above 40 mA/cm2. Appl. Phys. Lett. 106, 023902 (2015).

    Google Scholar 

  87. 87.

    Morales-Masis, M., De Wolf, S., Woods-Robinson, R., Ager, J. W. & Ballif, C. Transparent electrodes for efficient optoelectronics. Adv. Electron. Mater. 3, 1600529 (2017).

    Google Scholar 

  88. 88.

    Yang, X. et al. High-performance TiO2-based electron-selective contacts for crystalline silicon solar cells. Adv. Mater. 28, 5891–5897 (2016).

    Google Scholar 

  89. 89.

    Allen, T. G. et al. A low resistance calcium/reduced titania passivated contact for high efficiency crystalline silicon solar cells. Adv. Energy Mater. 7, 1602606 (2017).

    Google Scholar 

  90. 90.

    Macco, B. et al. Atomic-layer deposited Nb2O5 as transparent passivating electron contact for c-Si solar cells. Sol. Energy Mater. Sol. Cells 184, 98–104 (2018).

    Google Scholar 

  91. 91.

    Wan, Y., Bullock, J. & Cuevas, A. Passivation of c-Si surfaces by ALD tantalum oxide capped with PECVD silicon nitride. Sol. Energy Mater. Sol. Cells 142, 42–46 (2015).

    Google Scholar 

  92. 92.

    Allen, T. G. & Cuevas, A. Electronic passivation of silicon surfaces by thin films of atomic layer deposited gallium oxide. Appl. Phys. Lett. 105, 031601 (2014).

    Google Scholar 

  93. 93.

    Smit, S., Garcia-Alonso, D., Bordihn, S., Hanssen, M. S. & Kessels, W. M. M. Metal-oxide-based hole-selective tunneling contacts for crystalline silicon solar cells. Sol. Energy Mater. Sol. Cells 120, 376–382 (2014).

    Google Scholar 

  94. 94.

    Zhang, Y. et al. High efficiency hybrid PEDOT:PSS/nanostructured silicon Schottky junction solar cells by doping-free rear contact. Energy Environ. Sci. 8, 297–302 (2014).

    Google Scholar 

  95. 95.

    Shewchun, J., Burk, D. & Spitzer, M. B. MIS and SIS solar cells. IEEE Trans. Electron Devices 27, 705–716 (1980).

    Google Scholar 

  96. 96.

    Ghosh, A. K., Fishman, C. & Feng, T. SnO2 /Si solar cells—heterostructure or Schottky‐barrier or MIS‐type device. J. Appl. Phys. 49, 3490–3498 (1978).

    Google Scholar 

  97. 97.

    Yang, X., Weber, K., Hameiri, Z. & De Wolf, S. Industrially feasible, dopant-free, carrier-selective contacts for high-efficiency silicon solar cells. Prog. Photovolt. Res. Appl. 25, 896–904 (2017).

    Google Scholar 

  98. 98.

    Bullock, J. et al. Dopant-free partial rear contacts enabling 23% silicon solar cells. Adv. Energy Mater. 9, 1803367 (2019).

    Google Scholar 

  99. 99.

    Zhang, X., Wan, Y., Bullock, J., Allen, T. & Cuevas, A. Low resistance Ohmic contact to p-type crystalline silicon via nitrogen-doped copper oxide films. Appl. Phys. Lett. 109, 052102 (2016).

    Google Scholar 

  100. 100.

    Battaglia, C. et al. Silicon heterojunction solar cell with passivated hole selective MoOx contact. Appl. Phys. Lett. 104, 113902 (2014). Exemplary dopant-free hole contact—common in organic electronics—applied to silicon, spurring further research into MoO x and other high/low work function, dopant free materials, including other transition metal oxides.

    Google Scholar 

  101. 101.

    Bullock, J., Cuevas, A., Allen, T. & Battaglia, C. Molybdenum oxide MoOx: A versatile hole contact for silicon solar cells. Appl. Phys. Lett. 105, 232109 (2014).

    Google Scholar 

  102. 102.

    Bivour, M., Temmler, J., Steinkemper, H. & Hermle, M. Molybdenum and tungsten oxide: high work function wide band gap contact materials for hole selective contacts of silicon solar cells. Sol. Energy Mater. Sol. Cells 142, 34–41 (2015).

    Google Scholar 

  103. 103.

    Gerling, L. G. et al. Transition metal oxides as hole-selective contacts in silicon heterojunctions solar cells. Sol. Energy Mater. Sol. Cells 145, 109–115 (2016).

    Google Scholar 

  104. 104.

    Meyer, J. et al. Transition metal oxides for organic electronics: energetics, device physics and applications. Adv. Mater. 24, 5408–5427 (2012).

    Google Scholar 

  105. 105.

    Bullock, J. et al. Proof-of-concept p-type silicon solar cells with molybdenum oxide local rear contacts. IEEE J. Photovolt. 5, 1591–1594 (2015).

    Google Scholar 

  106. 106.

    Xu, X. et al. Chemical bath deposition of p-type transparent, highly conducting (CuS)x:(ZnS)1–x nanocomposite thin films and fabrication of Si heterojunction solar cells. Nano Lett. 16, 1925–1932 (2016).

    Google Scholar 

  107. 107.

    Yang, X. et al. Tantalum nitride electron-selective contact for crystalline silicon solar cells. Adv. Energy Mater. 8, 1800608 (2018).

    Google Scholar 

  108. 108.

    Yang, X. et al. Dual-function electron-conductive, hole-blocking titanium nitride contacts for efficient silicon solar cells. Joule 3, 1314–1327 (2019).

    Google Scholar 

  109. 109.

    Feifel, M. et al. MOVPE grown gallium phosphide-silicon heterojunction solar cells. IEEE J. Photovolt. 7, 502–507 (2017).

    Google Scholar 

  110. 110.

    He, J. et al. High-efficiency silicon/organic heterojunction solar cells with improved junction quality and interface passivation. ACS Nano 10, 11525–11531 (2016).

    Google Scholar 

  111. 111.

    Wan, Y. et al. Temperature and humidity stable alkali/alkaline-earth metal carbonates as electron heterocontacts for silicon photovoltaics. Adv. Energy Mater. 8, 1800743 (2018).

    Google Scholar 

  112. 112.

    Ishii, H., Sugiyama, K., Ito, E. & Seki, K. Energy level alignment and interfacial electronic structures at organic/metal and organic/organic interfaces. Adv. Mater. 11, 605–625 (1999).

    Google Scholar 

  113. 113.

    Bullock, J. et al. Lithium fluoride based electron contacts for high efficiency n-type crystalline silicon solar cells. Adv. Energy Mater. 6, (2016).

    Google Scholar 

  114. 114.

    Coss, B. E. et al. Near band edge Schottky barrier height modulation using high-κ dielectric dipole tuning mechanism. Appl. Phys. Lett. 95, 222105 (2009).

    Google Scholar 

  115. 115.

    Lacharme, J. P., Benazzi, N. & Sébenne, C. A. Compositional and electronic properties of Si(001)2×1 upon diatomic sulfur interaction. Surf. Sci. 433, 415–419 (1999).

    Google Scholar 

  116. 116.

    Zhang, X. et al. High-efficiency graphene/Si nanoarray Schottky junction solar cells via surface modification and graphene doping. J. Mater. Chem. A 1, 6593–6601 (2013).

    Google Scholar 

  117. 117.

    Tune, D. D., Flavel, B. S., Krupke, R. & Shapter, J. G. Carbon nanotube-silicon solar cells. Adv. Energy Mater. 2, 1043–1055 (2012).

    Google Scholar 

  118. 118.

    Tsai, M.-L. et al. Monolayer MoS2 heterojunction solar cells. ACS Nano 8, 8317–8322 (2014).

    Google Scholar 

  119. 119.

    Wang, D. et al. Tuning back contact property via artificial interface dipoles in Si/organic hybrid solar cells. Appl. Phys. Lett. 109, 043901 (2016).

    Google Scholar 

  120. 120.

    Zhang, Y. et al. Heterojunction with organic thin layers on silicon for record efficiency hybrid solar cells. Adv. Energy Mater. 4, 1300923 (2014).

    Google Scholar 

  121. 121.

    Reichel, C. et al. Electron-selective contacts via ultra-thin organic interface dipoles for silicon organic heterojunction solar cells. J. Appl. Phys. 123, 024505 (2018).

    Google Scholar 

  122. 122.

    Zielke, D. et al. Organic-silicon solar cells exceeding 20% efficiency. Energy Procedia 77, 331–339 (2015).

    Google Scholar 

  123. 123.

    He, L., Jiang, C., Rusli, Lai, D. & Wang, H. Highly efficient Si-nanorods/organic hybrid core-sheath heterojunction solar cells. Appl. Phys. Lett. 99, 021104 (2011).

    Google Scholar 

  124. 124.

    Zielke, D. et al. Large-area PEDOT:PSS/c-Si heterojunction solar cells with screen-printed metal contacts. Sol. RRL 2, 1700191 (2018).

    Google Scholar 

  125. 125.

    Gogolin, R. et al. Demonstrating the high Voc potential of PEDOT:PSS/c-Si heterojunctions on solar cells. Energy Procedia 124, 593–597 (2017).

    Google Scholar 

  126. 126.

    Liu, R., Lee, S.-T. & Sun, B. 13.8% Efficiency hybrid Si/organic heterojunction solar cells with MoO3 film as antireflection and inversion induced layer. Adv. Mater. 26, 6007–6012 (2014).

    Google Scholar 

  127. 127.

    Bullock, J. et al. Stable dopant-free asymmetric heterocontact silicon solar cells with efficiencies above 20%. ACS Energy Lett. 3, 508–513 (2018).

    Google Scholar 

  128. 128.

    Um, H.-D. et al. Dopant-free all-back-contact Si nanohole solar cells using MoOx and LiF Films. Nano Lett. 16, 981–987 (2016).

    Google Scholar 

  129. 129.

    Wu, W. et al. 22% efficient dopant-free interdigitated back contact silicon solar cells. AIP Conf. Proc. 1999, 040025 (2018).

    Google Scholar 

  130. 130.

    Yoshikawa, K. et al. Exceeding conversion efficiency of 26% by heterojunction interdigitated back contact solar cell with thin film Si technology. Sol. Energy Mater. Sol. Cells 173, 37–42 (2017).

    Google Scholar 

  131. 131.

    Altermatt, P. P. et al. Learning from the past to look beyond the roadmap of PERC Si solar cell mass production. In Proc. 35th European Photovoltaic Solar Energy Conference and Exhibition 1–7 (2018).

  132. 132.

    Bivour, M., Reichel, C., Hermle, M. & Glunz, S. W. Improving the a-Si:H(p) rear emitter contact of n-type silicon solar cells. Sol. Energy Mater. Sol. Cells 106, 11–16 (2012).

    Google Scholar 

  133. 133.

    Davidsson, S. & Höök, M. Material requirements and availability for multi-terawatt deployment of photovoltaics. Energy Policy 108, 574–582 (2017).

    Google Scholar 

  134. 134.

    Kavlak, G., McNerney, J., Jaffe, R. L. & Trancik, J. E. Metal production requirements for rapid photovoltaics deployment. Energy Environ. Sci. 8, 1651–1659 (2015).

    Google Scholar 

  135. 135.

    Morales-Vilches, A. B. et al. ITO-free silicon heterojunction solar cells with ZnO:Al/SiO2 front electrodes reaching a conversion efficiency of 23%. IEEE J. Photovolt. 9, 34–39 (2019).

    Google Scholar 

  136. 136.

    Tomasi, A. et al. Simple processing of back-contacted silicon heterojunction solar cells using selective-area crystalline growth. Nat. Energy 2, 17062 (2017).

    Google Scholar 

  137. 137.

    Haschke, J. et al. The impact of silicon solar cell architecture and cell interconnection on energy yield in hot & sunny climates. Energy Environ. Sci. 10, 1196–1206 (2017).

    Google Scholar 

  138. 138.

    Holman, Z. C., Descoeudres, A., De Wolf, S. & Ballif, C. Record infrared internal quantum efficiency in silicon heterojunction solar cells with dielectric/metal rear reflectors. IEEE J. Photovolt. 3, 1243–1249 (2013).

    Google Scholar 

  139. 139.

    Essig, S. et al. Raising the one-sun conversion efficiency of III–V/Si solar cells to 32.8% for two junctions and 35.9% for three junctions. Nat. Energy 2, 17144 (2017).

    Google Scholar 

  140. 140.

    Cariou, R. et al. III-V-on-silicon solar cells reaching 33% photoconversion efficiency in two-terminal configuration. Nat. Energy 3, 326–333 (2018).

    Google Scholar 

  141. 141.

    Bush, K. A. et al. 23.6%-efficient monolithic perovskite/silicon tandem solar cells with improved stability. Nat. Energy 2, 17009 (2017).

    Google Scholar 

  142. 142.

    Sahli, F. et al. Fully textured monolithic perovskite/silicon tandem solar cells with 25.2% power conversion efficiency. Nat. Mater. 17, 820 (2018).

    Google Scholar 

  143. 143.

    Zhao, Y. et al. Monocrystalline CdTe solar cells with open-circuit voltage over 1 V and efficiency of 17%. Nat. Energy 1, 16067 (2016).

    Google Scholar 

  144. 144.

    Vermang, B. et al. Employing Si solar cell technology to increase efficiency of ultra-thin Cu(In, Ga)Se2 solar cells. Prog. Photovolt. Res. Appl. 22, 1023–1029 (2014).

    Google Scholar 

  145. 145.

    Tan, H. et al. Efficient and stable solution-processed planar perovskite solar cells via contact passivation. Science 355, 722–726 (2017).

    Google Scholar 

  146. 146.

    Peng, J. et al. Interface passivation using ultrathin polymer–fullerene films for high-efficiency perovskite solar cells with negligible hysteresis. Energy Environ. Sci. 10, 1792–1800 (2017).

    Google Scholar 

  147. 147.

    Young, R. T., van der Leeden, G. A., Sandstrom, R. L., Wood, R. F. & Westbrook, R. D. High‐efficiency Si solar cells by beam processing. Appl. Phys. Lett. 43, 666–668 (1983).

    Google Scholar 

  148. 148.

    Mulligan, W. P. & Swanson, R. M. High efficiency, one-sun solar cell processing. In Proc. 13th NREL Workshop on Crystalline Silicon Solar Cell Materials and Processes: Extended Abstracts and Papers (Ed. Sopori, B. L.) 30–37 (NREL, 2003).

  149. 149.

    Mulligan, W. P. et al. Manufacture of solar cells with 21% efficiency. In Proc.19th European Photovoltaic Solar Energy Conference 1–4 (2004).

  150. 150.

    Green, M. A., Emery, K., King, D. L., Hishikawa, Y. & Warta, W. Solar cell efficiency tables (version 28). Prog. Photovolt. Res. Appl. 14, 455–461 (2006).

    Google Scholar 

  151. 151.

    Cousins, P. J. et al. Generation 3: improved performance at lower cost. In Proc. 35th IEEE Photovoltaic Specialists Conference 275–278 (IEEE, 2010).

  152. 152.

    Green, M. A., Emery, K., Hishikawa, Y., Warta, W. & Dunlop, E. D. Solar cell efficiency tables (version 44). Prog. Photovolt. Res. Appl. 22, 701–710 (2014).

    Google Scholar 

  153. 153.

    Tanaka, M. et al. Development of new a-Si/c-Si heterojunction solar cells: ACJ-HIT (artificially constructed junction-heterojunction with intrinsic thin-layer). Jpn. J. Appl. Phys. 31, 3518 (1992).

    Google Scholar 

  154. 154.

    Sawada, T. et al. High-efficiency a-Si/c-Si heterojunction solar cell. In Proc. 1994 IEEE 1 st World Conference on Photovoltaic Energy Conversion - WCPEC (A Joint Conference of PVSC, PVSEC and PSEC) 1219–1226 (IEEE, 1994).

  155. 155.

    Taguchi, M. et al. An approach for the higher efficiency in the HIT cells. In Conference Record of the Thirty-first IEEE Photovoltaic Specialists Conference 866–871 (IEEE, 2005).

  156. 156.

    Sakata, H. et al. 20.7% highest efficiency large area (100.5 cm2) HIT/TM/ cell. In Conference Record of the 28th IEEE Photovoltaic Specialists Conference 7–12 (IEEE, 2000).

  157. 157.

    Taguchi, M. et al. High-Efficiency HIT Solar Cell on Thin (<100 μm) Silicon Wafer. In 24th European Photovoltaic Solar Energy Conference 1690–1693 (2009).

  158. 158.

    Dullweber, T. & Schmidt, J. Industrial silicon solar cells applying the passivated emitter and rear cell (PERC) concept:a review. IEEE J. Photovolt. 6, 1366–1381 (2016).

    Google Scholar 

  159. 159.

    Gatz, S. et al. 19.4%-efficient large-area fully screen-printed silicon solar cells. Phys. Status Solidi RRL – Rapid Res. Lett. 5, 147–149 (2011).

    Google Scholar 

  160. 160.

    Metz, A. et al. Industrial high performance crystalline silicon solar cells and modules based on rear surface passivation technology. Sol. Energy Mater. Sol. Cells 120, 417–425 (2014).

    Google Scholar 

  161. 161.

    Colthorpe, A. SolarWorld touts 21.7% PERC world record efficiency. PV Tech (2015)

  162. 162.

    Ye, F. et al. 22.13% Efficient industrial p-type mono PERC solar cell. In Proc. 2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC) 3360–3365 (IEEE, 2016).

  163. 163.

    Weiwei, D. et al. 22.61% efficient fully screen printed perc solar cell. In IEEE 44th Photovoltaic Specialist Conference (PVSC) (2017).

  164. 164.

    Trina Solar sets new 22.61% mono PERC efficiency record. pv magazine (2016)

  165. 165.

    JinkoSolar claims new 22. 78% PERC efficiency record. pv magazine (2017)

  166. 166.

    Parnell, J. Jinko beats its own mono PERC efficiency record. PV Tech (2017)

  167. 167.

    Kenning, T. LONGi hits record 23.6% conversion efficiency for mono PERC solar cells. PV Tech (2018)

  168. 168.

    Feldmann, F., Bivour, M., Reichel, C., Hermle, M. & Glunz, S. W. Passivated rear contacts for high-efficiency n-type Si solar cells providing high interface passivation quality and excellent transport characteristics. Sol. Energy Mater. Sol. Cells 120, 270–274 (2014).

    Google Scholar 

  169. 169.

    Feldmann, F., Reichel, M. B. C., Hermle, M. & Glunz, S. W. A passivated rear contact for high efficiency n-type silicon solar cells enabling high Vocs and FF > 82%. In Proc. 28th European Photovoltaic Solar Energy Conference and Exhibition (2013).

  170. 170.

    Feldmann, F. et al. Tunnel oxide passivated contacts as an alternative to partial rear contacts. Sol. Energy Mater. Sol. Cells 131, 46–50 (2014).

    Google Scholar 

  171. 171.

    Rienäcker, M. et al. Recombination behavior of photolithography-free back junction back contact solar cells with carrier-selective polysilicon on oxide junctions for both polarities. Energy Procedia 92, 412–418 (2016).

    Google Scholar 

  172. 172.

    Haase, F. et al. Interdigitated back contact solar cells with polycrystalline silicon on oxide passivating contacts for both polarities. Jpn. J. Appl. Phys. 56, (2017).

    Google Scholar 

  173. 173.

    Hernández, J. L. et al. High efficiency silver-free heterojunction silicon solar cell. Jpn. J. Appl. Phys. 51, (2012).

  174. 174.

    Hernández, J. L. et al. High efficiency copper electroplated heterojunction solar cells. In Proc. 27th European Photovoltaic Solar Energy Conference and Exhibition 655–656 (WIP Renewable Energies, 2012).

  175. 175.

    Yamamoto, K. et al. High-efficiency heterojunction crystalline Si solar cell and optical splitting structure fabricated by applying thin-film Si technology. Jpn. J. Appl. Phys. 54, (2015).

    Google Scholar 

  176. 176.

    Green, M. A. et al. Solar cell efficiency tables (version 49): Solar cell efficiency tables (version 49). Prog. Photovolt. Res. Appl. 25, 3–13 (2017).

    Google Scholar 

  177. 177.

    Blakers, A. W. & Green, M. A. 20% efficiency silicon solar cells. Appl. Phys. Lett. 48, 215–217 (1986).

    Google Scholar 

  178. 178.

    Blakers, A. W., Wang, A., Milne, A. M., Zhao, J. & Green, M. A. 22.8% efficient silicon solar cell. Appl. Phys. Lett. 55, 1363–1365 (1989).

    Google Scholar 

  179. 179.

    Green, M. A. et al. Characterization of 23-percent efficient silicon solar cells. IEEE Trans. Electron Devices 37, 331–336 (1990).

    Google Scholar 

  180. 180.

    Zhao, J., Wang, A. & Green, M. A. 24% efficient PERL structure silicon solar cells. In Proc. IEEE Conference on Photovoltaic Specialists 333–335 (IEEE, 1990).

  181. 181.

    Zhang, S. et al. 335-W World-Record p-Type Monocrystalline Module With 20.6% Efficient PERC Solar Cells. IEEE J. Photovolt. 6, 145–152 (2016).

    Google Scholar 

  182. 182.

    Tsunomura, Y. et al. Twenty-two percent efficiency HIT solar cell. Sol. Energy Mater. Sol. Cells 93, 670–673 (2009).

    Google Scholar 

  183. 183.

    Mishima, T., Taguchi, M., Sakata, H. & Maruyama, E. Development status of high-efficiency HIT solar cells. Sol. Energy Mater. Sol. Cells 95, 18–21 (2011).

    Google Scholar 

  184. 184.

    Green, M. A. Solar cell fill factors: General graph and empirical expressions. Solid-State Electron. 24, 788–789 (1981).

    Google Scholar 

  185. 185.

    Plagwitz, H., Nerding, M., Ott, N., Strunk, H. P. & Brendel, R. Low-temperature formation of local Al contacts to a-Si:H-passivated Si wafers. Prog. Photovolt. Res. Appl. 12, 47–54 (2004).

    Google Scholar 

  186. 186.

    H. Plagwitz. et al. 20%-efficient silicon solar cells with local contacts to the a-Si-passivated surfaces by means of annealing (COSIMA). In Proc. 20th European Photovoltaic Solar Energy Conference and Exhibition 725–728 (WIP Renewable Energies, 2005).

  187. 187.

    Heinemeyer, F., Mader, C., Münster, D., Dullweber, T. & Brendel, R. Inline high-rate thermal evaporation of aluminum for novel industrial solar cell metallization. In Proc. 25th European Photovoltaic Solar Energy Conference Conversion (WIP Renewable Energies, 2010).

  188. 188.

    Mader, C., Müller, J., Eidelloth, S. & Brendel, R. Local rear contacts to silicon solar cells by in-line high-rate evaporation of aluminum. Sol. Energy Mater. Sol. Cells 107, 272–282 (2012).

    Google Scholar 

  189. 189.

    Rohatigi, A., Narasimha, S. & Ruby, D. S. Effective passivation of the low resistivity silicon surface by a rapid thermal oxide/PECVD silicon nitride stack and application to passivated rear and bifacial Si solar cells. In Proc. 2nd World Conference and Exhibition on Photovoltaic Solar Energy Conversion, Vienna, Austria (Georgia Institute of Technology, 1998).

  190. 190.

    Riegel, S., Mutter, F., Hahn, G. & Terheiden, B. Influence of the dopant on the contact formation to p+-type silicon. Energy Procedia 8, 533–539 (2011).

    Google Scholar 

  191. 191.

    Urrejola, E., Peter, K., Plagwitz, H. & Schubert, G. Al–Si alloy formation in narrow p-type Si contact areas for rear passivated solar cells. J. Appl. Phys. 107, 124516 (2010).

    Google Scholar 

  192. 192.

    Gatz, S., Dullweber, T. & Brendel, R. Evaluation of series resistance losses in screen-printed solar cells with local rear contacts. IEEE J. Photovolt. 1, 37–42 (2011).

    Google Scholar 

  193. 193.

    Richter, A., Hörteis, M., Benick, J., Hermle, M. & Glunz, S. W. Seed layer printed contact formation for highly doped boron emitters of n-type silicon solar cells with front side junction. In Proc. 2nd Workshop on Metallization for Crystalline Silicon Solar Cells 26–31 (2010).

  194. 194.

    Seren, S., Braun, S., Schiele, Y., Hahn, G. & Terheiden, B. Nickel plating on p+ silicon - a characterization of contact resistivity and line resistance. In Proc. 27th European Photovoltaic Solar Energy Conference and Exhibition 1777–1780 (WIP Renewable Energies, 2012).

  195. 195.

    Binder, S., Bartsch, J., Glatthaar, M. & Glunz, S. Printed contact on emitter with low dopant surface concentration. Energy Procedia 21, 32–38 (2012).

    Google Scholar 

  196. 196.

    Hörteis, M. Fine-line Printed Contacts on Crystalline Silicon Solar Cells. PhD thesis, University of Konstanz (2009).

  197. 197.

    Mette, A. New Concepts for Front Side Metallization of Industrial Silicon Solar Cells. PhD thesis, Albert-Ludwigs Univ. (2007).

  198. 198.

    Gunnar, S. Thick Film Metallisation of Crystalline Silicon Solar Cells: Mechanisms, Models and Applications. PhD thesis, University of Konstanz (2006).

  199. 199.

    Vinod, P. N. Specific contact resistance measurement of screen-printed ag metal contacts formed on heavily doped emitter region in multicrystalline silicon solar cells. J. Electron. Mater. 42, 2905–2909 (2013).

    Google Scholar 

  200. 200.

    Braun, S., Emre, E., Raabe, B. & Hahn, G. Electroless nickel and copper metallization: Contact formation on crystalline silicon and background plating behavior on PECVD silicon SiNx:H layers. In Proc. 25th European Photovoltaic Solar Energy Conference and Exhibition/5th World Conference on photovoltaic Energy Conversion 1892–1895 (WIP Renewable Energies, 2010).

  201. 201.

    Rauer, M. et al. Nickel-plated front contacts for front and rear emitter silicon solar cells. Energy Procedia 38, 449–458 (2013).

    Google Scholar 

  202. 202.

    Richter, A. et al. Towards industrial n-type PERT silicon solar cells: rear passivation and metallization scheme. Energy Procedia 8, 479–486 (2011).

    Google Scholar 

  203. 203.

    Woehl, R. et al. Evaluating the aluminum-alloyed p+-layer of silicon solar cells by emitter saturation current density and optical microspectroscopy measurements. IEEE Trans. Electron Devices 58, 441–447 (2011).

    Google Scholar 

  204. 204.

    Bullock, J. Advanced Contacts for Silicon Solar Cells. PhD thesis, The Australian National Univ. (2016).

  205. 205.

    Cuevas, A., Basore, P. A., Giroult‐Matlakowski, G. & Dubois, C. Surface recombination velocity of highly doped n‐type silicon. J. Appl. Phys. 80, 3370–3375 (1996).

    Google Scholar 

  206. 206.

    Kerr, M. J. Surface, Emitter and Bulk Recombination in Silicon and Development of Silicon Nitride Passivated Solar Cells. PhD thesis, The Australian National Univ. (2002).

  207. 207.

    Sze, S. M. & Ng, K. K. Physics of Semiconductor Devices 3rd edn (John Wiley & Sons, 2006).

  208. 208.

    McIntosh, K. R. & Altermatt, P. P. A freeware 1D emitter model for silicon solar cells. In Proc. 35th IEEE Photovoltaic Specialists Conference (PVSC) 002188–002193 (IEEE, 2010).

  209. 209.

    EDNA 2. PV Lighthouse (2018)

  210. 210.

    Luo, W. et al. Copper thiocyanate/copper iodide based hole transport composites with balanced properties for efficient polymer light-emitting diodes. J. Mater. Chem. C. 6, 4895–4902 (2018).

    Google Scholar 

  211. 211.

    Zhao, K. et al. Solution-processed inorganic copper(i) thiocyanate (CuSCN) hole transporting layers for efficient p-i-n perovskite solar cells. J. Mater. Chem. A 3, 20554–20559 (2015).

    Google Scholar 

  212. 212.

    Steirer, K. X. et al. Solution deposited NiO thin-films as hole transport layers in organic photovoltaics. Org. Electron. 11, 1414–1418 (2010).

    Google Scholar 

  213. 213.

    Chen, T.-G., Huang, B.-Y., Chen, E.-C., Yu, P. & Meng, H.-F. Micro-textured conductive polymer/silicon heterojunction photovoltaic devices with high efficiency. Appl. Phys. Lett. 101, 033301 (2012).

    Google Scholar 

  214. 214.

    Meyer, B. K. et al. Binary copper oxide semiconductors: From materials towards devices. Phys. Status Solidi B 249, 1487–1509 (2012).

    Google Scholar 

  215. 215.

    Tanaka, Y., Kanai, K., Ouchi, Y. & Seki, K. Oxygen effect on the interfacial electronic structure of C60 film studied by ultraviolet photoelectron spectroscopy. Chem. Phys. Lett. 441, 63–67 (2007).

    Google Scholar 

  216. 216.

    Hu, C. et al. Work function variation of monolayer MoS2 by nitrogen-doping. Appl. Phys. Lett. 113, 041602 (2018).

    Google Scholar 

  217. 217.

    Jiang, Q. et al. Enhanced electron extraction using SnO2 for high-efficiency planar-structure HC(NH2)2PbI3-based perovskite solar cells. Nat. Energy 2, 16177 (2017).

    Google Scholar 

  218. 218.

    Ling, X. et al. Room-temperature processed Nb2O5 as the electron-transporting layer for efficient planar perovskite solar cells. ACS Appl. Mater. Interfaces 9, 23181–23188 (2017).

    Google Scholar 

  219. 219.

    Ho Yeon, D., Min Lee, S., Hwa Jo, Y., Moon, J. & Soo Cho, Y. Origin of the enhanced photovoltaic characteristics of PbS thin film solar cells processed at near room temperature. J. Mater. Chem. A 2, 20112–20117 (2014).

    Google Scholar 

  220. 220.

    Kirner, S. et al. Silicon heterojunction solar cells with nanocrystalline silicon oxide emitter: insights into charge carrier transport. IEEE J. Photovolt. 5, 1601–1605 (2015).

    Google Scholar 

  221. 221.

    Biron, R. et al. Window layer with p doped silicon oxide for high Voc thin-film silicon n-i-p solar cells. J. Appl. Phys. 110, 124511 (2011).

    Google Scholar 

  222. 222.

    Hamma, S. & Cabarrocas, P. R. Determination of the mobility gap of microcrystalline silicon and of the band discontinuities at the amorphous/microcrystalline silicon interface using in situ Kelvin probe technique. Appl. Phys. Lett. 74, 3218–3220 (1999).

    Google Scholar 

  223. 223.

    de Vrijer, T., Si, F. T., Tan, H. & Smets, A. H. M. Chemical stability and performance of doped silicon oxide layers for use in thin-film silicon solar cells. IEEE J. Photovolt. 9, 3–11 (2019).

    Google Scholar 

  224. 224.

    Yang, X., Chen, J., Liu, W., Li, F. & Sun, Y. Single-side heterojunction solar cell with microcrystalline silicon oxide emitter and diffused back surface field. Phys. Status Solidi A 214, 1700193 (2017).

    Google Scholar 

  225. 225.

    Spear, W. E. & Le Comber, P. G. Substitutional doping of amorphous silicon. Solid State Commun. 88, 1015–1018 (1993).

    Google Scholar 

  226. 226.

    Tsai, H., Lin, W., Sah, W. J. & Lee, S. The characteristics of amorphous silicon carbide hydrogen alloy. J. Appl. Phys. 64, 1910–1915 (1988).

    Google Scholar 

  227. 227.

    Tawada, Y., Kondo, M., Okamoto, H. & Hamakawa, Y. Hydrogenated amorphous silicon carbide as a window material for high efficiency a-Si solar cells. Sol. Energy Mater. 6, 299–315 (1982).

    Google Scholar 

  228. 228.

    Fell, A. A Free and Fast Three-Dimensional/Two-Dimensional Solar Cell Simulator Featuring Conductive Boundary and Quasi-Neutrality Approximations. IEEE Trans. Electron Devices 60, 733–738 (2013).

    Google Scholar 

  229. 229.

    Feldmann, F. et al. A study on the charge carrier transport of passivating contacts. IEEE J. Photovolt. 8, 1503–1509 (2018).

    Google Scholar 

  230. 230.

    Nogay, G. et al. Interplay of annealing temperature and doping in hole selective rear contacts based on silicon-rich silicon-carbide thin films. Sol. Energy Mater. Sol. Cells 173, 18–24 (2017).

    Google Scholar 

  231. 231.

    Wan, Y. et al. Conductive and stable magnesium oxide electron-selective contacts for efficient silicon solar cells. Adv. Energy Mater. 7, 1601863 (2016).

    Google Scholar 

  232. 232.

    Masmitjà, G. et al. V2Ox -based hole-selective contacts for c-Si interdigitated back-contacted solar cells. J. Mater. Chem. A 5, 9182–9189 (2017).

    Google Scholar 

  233. 233.

    Wan, Y. et al. Tantalum oxide electron-selective heterocontacts for silicon photovoltaics and photoelectrochemical water reduction. ACS Energy Lett. 3, 125–131 (2018).

    Google Scholar 

  234. 234.

    Tong, H. et al. Dual functional electron-selective contacts based on silicon oxide/magnesium: Tailoring heterointerface band structures while maintaining surface passivation. Adv. Energy Mater. 8, 1702921 (2018).

    Google Scholar 

  235. 235.

    Brendel, R. et al. Breakdown of the efficiency gap to 29% based on experimental input data and modeling. Prog. Photovolt. Res. Appl. 24, 1475–1486 (2016).

    Google Scholar 

Download references


The work was supported by funding from King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under award no. OSR-CRG URF/1/3383, as well as funding from Saudi Aramco. Figures 2 and 4, as well as the text box images, were created by Heno Hwang, scientific illustrator at KAUST. T.G.A. and J.B. would like to thank prof. Andres Cuevas for guidance and feedback related to the physics of passivating contacts.

Author information



Corresponding author

Correspondence to Stefaan De Wolf.

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 Data 1

Data from plots in Figs. 1a,b, 3f,g, 5 and 6a.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Allen, T.G., Bullock, J., Yang, X. et al. Passivating contacts for crystalline silicon solar cells. Nat Energy 4, 914–928 (2019).

Download citation

Further reading


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