Passivating electron-selective contacts for silicon solar cells based on an a-Si: H/TiOx stack and a low work function metal

Jinyoun Cho, Jimmy Melskens, Maarten Debucquoy, Maria Recamán Payo, Shruti Jambaldinni, Twan Bearda, Ivan Gordon, Jozef Szlufcik, W.M.M. Kessels, Jef Poortmans

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In this work, the ATOM (intrinsic a-Si:H/TiOx/low work function metal) structure is investigated to realize high-performance passivating electron-selective contacts for crystalline silicon solar cells. The absence of a highly doped Si region in this contact structure is meant to reduce the optoelectrical losses. We show that a low contact resistivity (ρc) can be obtained by the combined effect of a low work function metal, such as calcium (Φ 2.9 eV), and Fermi-level depinning in the metal-insulator-semiconductor contact structure (where in our case TiOx acts as the insulator on the intrinsic a-Si:H passivating layer). TiOx grown by ALD is effective to achieve not only a low ρc but also good passivation properties. As an electron contact in silicon heterojunction solar cells, inserting interfacial TiOx at the i-a-Si:H/Ca interface significantly enhances the solar cell conversion efficiency. Consequently, the champion solar cell with the ATOM contact achieves a VOC of 711 mV, FF of 72.9%, JSC of 35.1 mA/cm2, and an efficiency of 18.2%. The achievement of a high VOC and reasonable FF without the need for a highly doped Si layer serves as a valuable proof of concept for future developments on passivating electron-selective contacts using this structure.

Original languageEnglish
Pages (from-to)835-845
Number of pages11
JournalProgress in Photovoltaics: Research and Applications
Issue number10
Early online date28 May 2018
Publication statusPublished - 1 Oct 2018


  • Calcium
  • Carrier-selective
  • Electron-selective
  • Heterojunction
  • Low work function metal
  • Passivating contact
  • TiO
  • calcium
  • heterojunction
  • electron-selective
  • low work function metal
  • passivating contact
  • carrier-selective
  • TiOx


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