Shrinking and growing: Grain boundary density reduction for efficient polysilicon thin-film solar cells

Dong Rip Kim, Chi Hwan Lee, Jeffrey M. Weisse, In Sun Cho, Xiaolin Zheng

Research output: Contribution to journalArticle

21 Scopus citations

Abstract

Polycrystalline Si (poly-Si) thin-film, due to its low Si consumption, low substrate cost, and good stability, is an attractive candidate for cost-effective solar cells, but the as-deposited poly-Si typically has a columnar structure with grain boundaries in between, severely limiting the efficiency of the poly-Si. Here, we report a micropillar poly-Si solar cell that utilizes the columnar structure of the as-deposited poly-Si grains. We first formed submicrometer diameter poly-Si pillars, smaller than the initial grain sizes, and used these pillars as the seeds for the subsequent epitaxial growth of Si, which effectively reduces grain boundary density in the final poly-Si crystal. In addition, the vertically aligned micropillar arrays form radial p-n junctions that further mitigate the grain boundary recombination losses by improving the light absorption and charge-carrier collection efficiencies. Consequently, the maximum efficiency of micropillar poly-Si thin-film solar cells is 6.4%, that is, ∼1.5 times higher than that of the planar cells.

Original languageEnglish
Pages (from-to)6485-6491
Number of pages7
JournalNano letters
Volume12
Issue number12
DOIs
StatePublished - 2012 Dec 12

Keywords

  • Polycrystalline Si
  • light trapping
  • micropillar-seeded growth
  • radial junction
  • thin-film solar cells

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