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Open Access Publications from the University of California

Dopant-Free Partial Rear Contacts Enabling 23% Silicon Solar Cells

  • Author(s): Bullock, J;
  • Wan, Y;
  • Hettick, M;
  • Zhaoran, X;
  • Phang, SP;
  • Yan, D;
  • Wang, H;
  • Ji, W;
  • Samundsett, C;
  • Hameiri, Z;
  • Macdonald, D;
  • Cuevas, A;
  • Javey, A
  • et al.

Over the past five years, there has been a significant increase in both the intensity of research and the performance of crystalline silicon devices which utilize metal compounds to form carrier-selective heterocontacts. Such heterocontacts are less fundamentally limited and have the potential for lower costs compared to the current industry dominating heavily doped, directly metalized contacts. A low temperature (≤230 °C), TiO x /LiF x /Al electron heterocontact is presented here, which achieves mΩcm 2 scale contact resistivities ρ c on lowly doped n-type substrates. As an extreme demonstration of the potential of this heterocontact, it is trialed in a newly developed, high efficiency n-type solar cell architecture as a partial rear contact (PRC). Despite only contacting ≈1% of the rear surface area, an efficiency of greater than 23% is achieved, setting a new benchmark for n-type solar cells featuring undoped PRCs and confirming the unusually low ρ c of the TiO x /LiF x /Al contact. Finally, in contrast to previous versions of the n-type undoped PRC cell, the performance of this cell is maintained after annealing at 350–400 °C, suggesting its compatibility with conventional surface passivation activation and sintering steps.

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