ECN publication
Superior light trapping in thin film silicon solar cells through nano imprint lithography
Published by: Publication date:
ECN Solar Energy 30-9-2013
ECN report number: Document type:
ECN-M--13-037 Conference Paper
Number of pages: Full text:
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ECN and partners have developed a fabrication process based on nanoimprint lithography (NIL) of textures for light trapping in thin film solar cells such as thin-film silicon, OPV, CIGS and CdTe. The process can be applied in roll-to-roll mode when using a foil substrate or in roll-to-plate mode when using a glass substrate. The lacquer also serves as an electrically insulating layer for cells if steel foil is used as substrate, to enable monolithic series interconnection. In this paper we will show the superior light trapping in thin film silicon solar cells made on steel foil with nanotextured back contacts. We have made single junction a-Si and uc-Si and a-Si/?c-Si tandem cells, where we applied several types of nano-imprints with random and periodic structures. We will show that the nano-imprinted back contact enables more than 30% increase of current in comparison with non-textured back contacts and that optimized periodic textures outperform state-of-the-art random textures. For a-Si cells we obtained Jsc of 18 mA/cm2 and for ?c-Si cells more than 24 mA/cm2. Tandem cells with a total Si absorber layer thickness of only 1350 nm have an initial efficiency of 11%.

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