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Paper   IPM / P / 14597
School of Physics
  Title:   Crystalline Si Solar Cell Rear Contacts: Optical Evaluation by Coupled Electromagnetic and Statistical Ray-Optics Modelling
  Author(s): 
1.  A. Dabirian
2.  M. Morales Masis
3.  F. J. Haug
4.  S. De Wolf
5.  C. Ballif
  Status:   Published
  Journal: IEEE Journal of Photovoltaics
  Vol.:  7
  Year:  2016
  Pages:   718-726
  Supported by:  IPM
  Abstract:
High-efficiency crystalline silicon (c-Si) solar cells increasingly feature sophisticated electron and hole contacts aimed at minimizing electronic losses. At the device rear, such contacts usually consisting of stacks of functional layers ? also offer opportunities to enhance the infrared response of the solar cells. In this article, an accurate and simple modeling procedure is proposed to evaluate the infrared performance related to the rear contacting design in c-Si solar cells. The method combines full-wave electromagnetic modelling of the rear-contact with a statistical ray optics model to obtain the fraction of optical energy dissipated in the rear contact, relative to that absorbed by the Si wafer. Using this technique, the impact of refractive index, extinction coefficient, and thickness of the rear-passivating layer is studied and basic design rules are established. In addition, novel optical structures including stratified thin films, nanoparticle composites and conductive nanowires embedded in a low-index dielectric matrix are evaluated for integration in advanced rear contacts in c-Si photovoltaic devices. From optical perspective, nanowire structures preserving low contact resistance appear to be the most effective approach to mitigate dissipation losses in the rear contact.

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