Impact of Na Doping on the Carrier Transport Path in Polycrystalline Flexible Cu2ZnSn(S,Se)4 Solar Cells

Woo Lim Jeong, Kyung Pil Kim, Juran Kim, Ha Kyung Park, Jung Hong Min, Je Sung Lee, Seung Hyun Mun, Sung Tae Kim, Jae Hyung Jang, William Jo, Dong Seon Lee

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31 Scopus citations


It is well-known that the alkali doping of polycrystalline Cu2ZnSn(S,Se)4 (CZTSSe) and Cu(In,Ga)(Se,S)2 has a beneficial influence on the device performance and there are various hypotheses about the principles of performance improvement. This work clearly explains the effect of Na doping on the fill factor (FF) rather than on all of the solar cell parameters (open-circuit voltage, FF, and sometimes short circuit current) for overall performance improvement. When doping is optimized, the fabricated device shows sufficient built-in potential and selects a better carrier transport path by the high potential difference between the intragrains and the grain boundaries. On the other hand, when doping is excessive, the device shows low contact potential difference and FF and selects a worse carrier transport path even though the built-in potential becomes stronger. The fabricated CZTSSe solar cell on a flexible metal foil optimized with a 25 nm thick NaF doping layer achieves an FF of 62.63%, thereby clearly showing the enhancing effect of Na doping.

Original languageEnglish
Article number1903085
JournalAdvanced Science
Issue number21
StatePublished - 1 Nov 2020

Bibliographical note

Publisher Copyright:
© 2020 The Authors. Published by Wiley-VCH GmbH


  • CZTSSe
  • carrier transport
  • doping
  • flexible electronics
  • thin-film solar cells


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