Efficient Light Trapping in Inverted Nanopyramid Thin Crystalline Silicon Membranes for Solar Cell Applications

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MAVROKEFALOS A., HAN S. E. , Yerci S. , Branham M. S. , CHEN G.

NANO LETTERS, vol.12, no.6, pp.2792-2796, 2012 (Journal Indexed in SCI) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 12 Issue: 6
  • Publication Date: 2012
  • Doi Number: 10.1021/nl2045777
  • Title of Journal : NANO LETTERS
  • Page Numbers: pp.2792-2796
  • Keywords: Light trapping, photovoltaics, optical absorption, inverted pyramids, thin-film solar cells, ABSORPTION ENHANCEMENT, OPTICAL-ABSORPTION, NANOWIRE ARRAYS, LIMIT, SI, LITHOGRAPHY


Thin-film crystalline silicon (c-Si) solar cells with light-trapping structures can enhance light absorption within the semiconductor absorber layer and reduce material usage. Here we demonstrate that an inverted nanopyramid light-trapping scheme for c-Si thin films, fabricated at wafer scale via a low-cost wet etching process, significantly enhances absorption within the c-Si layer. A broadband enhancement in absorptance that approaches the Yablo-novitch limit (Yablo-novitch, E. J. Opt. Soc. Am. 1987, 72, 899-907) is achieved with minimal angle dependence. We also show that c-Si films less than 10 pm in thickness can achieve absorptance values comparable to that of planar c-Si wafers thicker than 300 pm, amounting to an over 30-fold reduction in material usage. Furthermore the surface area increases by a factor of only 1.7, which limits surface recombination losses in comparison with other nanostructured light-trapping schemes. These structures will not only significantly curtail both the material and processing cost of solar cells but also allow the high efficiency required to enable viable c-Si thin-film solar cells in the future.