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Optical Simulation of External Quantum Efficiency Spectra

  • Prakash Koirala
  • Abdel-Rahman A. Ibdah
  • Puruswottam Aryal
  • Puja Pradhan
  • Zhiquan Huang
  • Nikolas J. PodrazaEmail author
  • Sylvain Marsillac
  • Robert W. Collins
Chapter
Part of the Springer Series in Optical Sciences book series (SSOS, volume 214)

Abstract

Applications of ex situ spectroscopic ellipsometry (SE) are presented for determination of the parameters that describe the dielectric function and structure of thin film solar cells. Complete optical models of solar cells developed using least squares regression analysis of the SE data enable external quantum efficiency (EQE) simulations for comparison with measurements. Through this comparison, it becomes possible to understand in detail the origins of optical and electronic collection and losses in thin film photovoltaics technologies and, as a result, the underlying performance limitations. Examples of this approach are presented for the three commercialized thin film technologies of hydrogenated amorphous silicon (a-Si:H), cadmium telluride (CdTe), and copper indium-gallium diselenide (CuIn1–xGaxSe2; CIGS). In the studies of a-Si:H solar cells, a comparison between the EQE simulation based on the SE model and the measured EQE suggests electrical losses from photo-generated carriers near the p/i and i/n interfaces, the latter caused by an i-layer thickness greater than the hole collection length. Also demonstrated here through comparisons of EQE measurements and simulation is enhanced carrier collection near the p/i interface when a protocrystalline Si:H i-layer of improved electrical quality is incorporated at the interface. For a CdS/CdTe heterojunction solar cell in the superstrate configuration, SE is performed through the glass, and simulations of the EQE spectra have been generated on the basis of comprehensive optical property and multilayer analysis by SE. In this case, observed deviations between simulated and measured EQE can assist in refining the optical model of the cell. Applying these methods, the optical losses that occur when photons with above-bandgap energies are not absorbed within the cell’s active layers can be distinguished from electronic losses that occur when electrons and holes photo-generated within these active layers are not collected. CIGS/CdS heterojunction solar cells incorporating both standard thickness and thin absorbers are also studied using SE. Data analysis is more challenging for CIGS because of the need to extract absorber layer Ga profiles for accurate optical models. For cells with standard thickness absorbers, excellent agreement is found between the simulated and measured EQE, the latter under the assumption of 100% collection from the active layers. For cells with thin absorbers, however, the difference observed between the simulated and measured EQE can be assigned to losses via electron-hole recombination near the Mo back contact. When a probability profile for carrier collection is introduced into the EQE simulation, closer agreement between this simulation and the measurement is observed. In addition to a single spot capability of SE as presented in this study, a capability also exists for high resolution mapping of multilayer thicknesses and component layer characteristics that provide short-circuit current density predictions. The mapping capability is made possible due to the high speeds [<1 s per measurement of (ψ, Δ) spectra] of multichannel ellipsometers.

References

  1. 1.
    H. Fujiwara, Spectroscopic Ellipsometry: Principles and Applications (Wiley, Chichester, UK, 2007)CrossRefGoogle Scholar
  2. 2.
    J. Li, R.W. Collins, M.N. Sestak, P. Koirala, N.J. Podraza, S. Marsillac, A.A. Rockett, in Advanced Characterization Techniques for Thin Film Solar Cells, 2nd edn, ed. by D. Abou-Ras, T. Kirchartz, U. Rau, (Wiley-VCH, Weinheim, Germany, 2016), Chapter 9, pp. 215–256Google Scholar
  3. 3.
    R.W. Collins, A.S. Ferlauto, in Handbook of Ellipsometry, ed. by H.G. Tompkins, E.A. Irene, (William Andrew, Norwich, NY, 2005), Chapter 2, pp. 93–235Google Scholar
  4. 4.
    J. Chen, J. Li, C. Thornberry, M.N. Sestak, R.W. Collins, J.D. Walker, S. Marsillac, A.R. Aquino, A. Rockett, in Proceedings of the 34th IEEE Photovoltaic Specialists Conference, Philadelphia, PA, 7–12 June 2009, (IEEE, New York, NY, 2009), pp. 1748–1753Google Scholar
  5. 5.
    P. Aryal, J. Chen, Z. Huang, L.R. Dahal, M.N. Sestak, D. Attygalle, R. Jacobs, V. Ranjan, S. Marsillac, R.W. Collins, in Proceedings of the 37th IEEE Photovoltaic Specialists Conference, Seattle, WA, 19–24 June 2011, (IEEE, New York, NY, 2011), pp. 2241–2246Google Scholar
  6. 6.
    A.S. Ferlauto, G.M. Ferreira, C. Chen, P.I. Rovira, C.R. Wronski, R.W. Collins, X. Deng, G. Ganguly, in Photovoltaics for the 21st Century II, ed. by R.D. McConnell, V.K. Kapur, (Electrochemical Society, Pennington, NJ, 2001), pp. 199–228Google Scholar
  7. 7.
    G.M. Ferreira, A.S. Ferlauto, P.I. Rovira, C. Chen, H.V. Nguyen, C.R. Wronski, R.W. Collins, in Amorphous and Heterogeneous Silicon-Based Films - 2001, Materials Research Society Symposium Proceedings, vol. 664, ed. by M. Stutzmann, J.B. Boyce, J.D. Cohen, R.W. Collins, J. Hanna, (MRS, Warrendale, PA, 2001), A24.6: pp. 1–6Google Scholar
  8. 8.
    A.-R. Ibdah, Optical Physics of Cu(In, Ga)Se2 Solar Cells and Their Layer Components, Ph.D. Dissertation, (University of Toledo, Toledo, OH, 2016)Google Scholar
  9. 9.
    P. Aryal, Z. Huang, S. Marsillac, N. J. Podraza, R. W. Collins, in Proceedings of the 42nd IEEE Photovoltaic Specialists Conference, New Orleans, LA, 14–19 June 2015, (IEEE, New York, NY, 2015), Art. No. 735-6311: pp. 1–4Google Scholar
  10. 10.
    P. Koirala, J. Li, H.P. Yoon, P. Aryal, S. Marsillac, A.A. Rockett, N.J. Podraza, R.W. Collins, Prog. Photovolt. Res. Appl. 24, 1055 (2016)CrossRefGoogle Scholar
  11. 11.
    A.-R.A. Ibdah, P. Pradhan, P. Aryal, N.J. Podraza, S. Marsillac, R.W. Collins, in Proceedings of the 43rd IEEE Photovoltaic Specialists Conference, Portland, OR, 5–10 June 2016, (IEEE, New York, NY, 2016), pp. 2184–2187Google Scholar
  12. 12.
    A. Shah (ed.), Thin Film Silicon Solar Cells (CRC, Boca Raton, FL, 2010)Google Scholar
  13. 13.
    R.W. Collins, A.S. Ferlauto, G.M. Ferreira, C. Chen, J. Koh, R.J. Koval, Y. Lee, J.M. Pearce, C.R. Wronski, Sol. Energy Mater. Sol. Cells 78, 143 (2003)CrossRefGoogle Scholar
  14. 14.
    K. von Rottkay, M. Rubin, in Thin Films for Photovoltaic and Related Device Applications, Materials Research Society Symposium Proceedings, vol. 426, ed. by A. Catalano, C. Eberspacher, D.S. Ginley, T.M. Peterson, H.W. Schock, T. Wada, (MRS, Warrendale, PA, 1996), pp. 449–454Google Scholar
  15. 15.
    R.A. Synowicki, B.D. Johs, A.C. Martin, Thin Solid Films 519, 2907 (2011)ADSCrossRefGoogle Scholar
  16. 16.
    J. Koh, Y. Lee, H. Fujiwara, C.R. Wronski, R.W. Collins, Appl. Phys. Lett. 73, 1526 (1998)ADSCrossRefGoogle Scholar
  17. 17.
    J. Chen, Spectroscopic Ellipsometry Studies of II-VI Semiconductor Materials and Solar Cells, Ph.D. Dissertation, (University of Toledo, Toledo, OH, 2010)Google Scholar
  18. 18.
    A.S. Ferlauto, G.M. Ferreira, J.M. Pearce, C.R. Wronski, R.W. Collins, X. Deng, G. Ganguly, J. Appl. Phys. 92, 2424 (2002)ADSCrossRefGoogle Scholar
  19. 19.
    G.D. Cody, in Hydrogenated Amorphous Silicon Optical Properties; Semiconductors and Semimetals, vol. 21, Part B, ed. by J.I. Pankove, (Academic, New York, NY, 1984), Chapter 2, pp. 11–82Google Scholar
  20. 20.
    W.B. Jackson, S.M. Kelso, C.C. Tsai, J.W. Allen, S.-J. Oh, Phys. Rev. B 31, 5187 (1985)ADSCrossRefGoogle Scholar
  21. 21.
    Z. Huang, Spectroscopic Ellipsometry Studies of Thin Film a-Si:H/nc-Si:H Micromorph Solar Cell Fabrication in the p-i-n Superstrate Configuration, Ph.D. Dissertation, (University of Toledo, Toledo, OH, 2016)Google Scholar
  22. 22.
    R.W. Collins, I. An, C. Chen, in Handbook of Ellipsometry, ed. by H.G. Tompkins, E.A. Irene, (William Andrew, Norwich, NY, 2005), Chapter 5, pp. 329–432Google Scholar
  23. 23.
    P. Aryal, Optical and Photovoltaic Properties of Copper Indium-Gallium Diselenide Materials and Solar Cells, Ph.D. Dissertation, (University of Toledo, Toledo, OH, 2014)Google Scholar
  24. 24.
    J. Li, P. Pradhan, P. Koirala, X. Tan, B. Sang, B. J. Stanbery, N.J. Podraza, R.W. Collins, in Proceedings of the 42nd IEEE Photovoltaic Specialists Conference, New Orleans, LA, 14–19 June 2015, (IEEE, New York, NY, 2015), Art. No. 735-5642: pp. 1–4Google Scholar
  25. 25.
    H. Fujiwara, J. Koh, P.I. Rovira, R.W. Collins, Phys. Rev. B 61, 10832 (2000)ADSCrossRefGoogle Scholar
  26. 26.
    I. An, Y.M. Li, C.R. Wronski, R.W. Collins, Phys. Rev. B 48, 4464 (1993)ADSCrossRefGoogle Scholar
  27. 27.
    E.A. Schiff, in Amorphous and Polycrystalline Thin Film Silicon Science and Technology -2009, Materials Research Society Symposium Proceedings, vol. 1153, ed. by A. Flewitt, Q. Wang, J. Hou, A. Nathan, S. Uchikoga, (MRS, Warrendale, PA, 2009), A15-01: pp. 1-12Google Scholar
  28. 28.
    J. Liang, E.A. Schiff, S. Guha, B. Yan, J. Yang, Appl. Phys. Lett. 88, 063512 (2006)ADSCrossRefGoogle Scholar
  29. 29.
    M. Gloeckler, I. Sankin, Z. Zhao, IEEE J. Photovolt. 3, 389 (2013)CrossRefGoogle Scholar
  30. 30.
    B.E. McCandless, J.R. Sites, in Handbook of Photovoltaic Science and Engineering, 2nd edn, ed. by A. Luque, S. Hegedus, (Wiley, New York, NY, 2011), pp. 600–641Google Scholar
  31. 31.
    N.R. Paudel, Y. Yan, Appl. Phys. Lett. 105, 183510 (2014)ADSCrossRefGoogle Scholar
  32. 32.
    A. Gupta, A.D. Compaan, Appl. Phys. Lett. 85, 684 (2004)ADSCrossRefGoogle Scholar
  33. 33.
    X. Wu, Sol. Energy 77, 803 (2004)ADSCrossRefGoogle Scholar
  34. 34.
    C.C. Kim, M. Daraselia, J.W. Garland, S. Sivanathan, Phys. Rev. B 56, 4786 (1997)ADSCrossRefGoogle Scholar
  35. 35.
    J. Li, J. Chen, R.W. Collins, Appl. Phys. Lett. 99, 061905 (2011)ADSCrossRefGoogle Scholar
  36. 36.
    J. Li, J. Chen, R.W. Collins, Appl. Phys. Lett. 97, 181909 (2010)ADSCrossRefGoogle Scholar
  37. 37.
    J. Li, N.J. Podraza, R.W. Collins, Phys. Status Solidi (a) 205, 901 (2008)ADSCrossRefGoogle Scholar
  38. 38.
    P. Koirala, Multichannel Spectroscopic Ellipsometry for CdTe Photovoltaics: From Materials and Interfaces to Solar Cells, Ph.D. Dissertation, (University of Toledo, Toledo, OH, 2015)Google Scholar
  39. 39.
    J. Chen, P. Koirala, C. Salupo, R.W. Collins, S. Marsillac, K.R. Kormanyos, B.D. Johs, J.S. Hale, G.L. Pfeiffer, in Proceedings of the 38th IEEE Photovoltaic Specialists Conference, Austin, TX, 3–8 June 2012, (IEEE, New York, NY, 2012), pp. 377–381Google Scholar
  40. 40.
    B. Johs, C.M. Herzinger, Phys. Stat. Solidi (c) 5, 1031 (2008)CrossRefGoogle Scholar
  41. 41.
    R.H. Muller, in Techniques for Characterization of Electrodes and Electrochemical Processes, ed. by R. Varma, J.R. Selman, (Wiley, New York, NY, 1991), pp. 31–125Google Scholar
  42. 42.
    B. Stjerna, E. Olsson, C.G. Granqvist, J. Appl. Phys. 76, 3797 (1994)ADSCrossRefGoogle Scholar
  43. 43.
    E. Burstein, Phys. Rev. 93, 632 (1954)ADSCrossRefGoogle Scholar
  44. 44.
    T.S. Moss, Proc. Phys. Soc. London B 67, 775 (1954)ADSCrossRefGoogle Scholar
  45. 45.
    P. Koirala, X. Tan, J. Li, N.J. Podraza, S. Marsillac, A.A. Rockett, R.W. Collins, in Proceedings of the 40th IEEE Photovoltaic Specialists Conference, Denver, CO, 8–13 June 2014, (IEEE, New York, NY, 2014), pp. 674–679Google Scholar
  46. 46.
    S.S. Hegedus, W.N. Shafarman, Prog. Photovolt. Res. Appl. 12, 155 (2004)CrossRefGoogle Scholar
  47. 47.
  48. 48.
    W.N. Shafarman, S. Siebentritt, L. Stolt, in Handbook of Photovoltaic Science and Engineering, 2nd edn., ed. by A. Luque, S. Hegedus, (Wiley, New York, NY, 2011), pp. 546–599CrossRefGoogle Scholar
  49. 49.
    P. Aryal, P. Pradhan, D. Attygalle, A.-R. Ibdah, K. Aryal, V. Ranjan, S. Marsillac, N.J. Podraza, R.W. Collins, IEEE J. Photovolt. 4, 333 (2014)CrossRefGoogle Scholar
  50. 50.
    A.M. Gabor, J.R. Tuttle, M.H. Bode, A. Franz, A.L. Tennant, M.A. Contreras, R. Noufi, D.G. Jensen, A.M. Hermann, Sol. Energy Mater. Sol. Cells 41–42, 247 (1996)CrossRefGoogle Scholar
  51. 51.
    P. Pradhan, P. Aryal, A.-R. Ibdah, P. Koirala, J. Li, N.J. Podraza, A.A. Rockett, S. Marsillac, R.W. Collins, in Proceedings of the 42nd IEEE Photovoltaic Specialists Conference, New Orleans, LA, 14–19 June 2015, (IEEE, New York, NY, 2015), Art. No. 735-5890: pp. 1–4Google Scholar
  52. 52.
    P. Aryal, A.-R. Ibdah, P. Pradhan, D. Attygalle, P. Koirala, N.J. Podraza, S. Marsillac, R.W. Collins, J. Li, Prog. Photovolt. Res. Appl. 24, 1200 (2016)CrossRefGoogle Scholar

Copyright information

© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  • Prakash Koirala
    • 1
  • Abdel-Rahman A. Ibdah
    • 1
  • Puruswottam Aryal
    • 1
  • Puja Pradhan
    • 1
  • Zhiquan Huang
    • 1
  • Nikolas J. Podraza
    • 1
    Email author
  • Sylvain Marsillac
    • 2
  • Robert W. Collins
    • 1
  1. 1.Department of Physics & Astronomy and Center for Photovoltaics Innovation & CommercializationUniversity of ToledoToledoUSA
  2. 2.Virginia Institute of PhotovoltaicsOld Dominion UniversityNorfolkUSA

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