Hydrogen passivation of poly-Si/SiOx contacts for Si solar cells using Al2O3 studied with deuterium

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  • Manuel Schnabel
    National Renewable Energy Laboratory 1 , Golden, Colorado 80401, USA
  • Bas W. H. van de Loo
    Department of Applied Physics, Eindhoven University of Technology 2 , 5600 MB Eindhoven, Netherlands
  • William Nemeth
    National Renewable Energy Laboratory 1 , Golden, Colorado 80401, USA
  • Bart Macco
    Department of Applied Physics, Eindhoven University of Technology 2 , 5600 MB Eindhoven, Netherlands
  • Paul Stradins
    National Renewable Energy Laboratory 1 , Golden, Colorado 80401, USA
  • W. M. M. Kessels
    Department of Applied Physics, Eindhoven University of Technology 2 , 5600 MB Eindhoven, Netherlands
  • David L. Young
    National Renewable Energy Laboratory 1 , Golden, Colorado 80401, USA

Abstract

<jats:p>The interplay between hydrogenation and passivation of poly-Si/SiOx contacts to n-type Si wafers is studied using atomic layer deposited Al2O3 and anneals in forming gas and nitrogen. The poly-Si/SiOx stacks are prepared by thermal oxidation followed by thermal crystallization of a-Si:H films deposited by plasma-enhanced chemical vapor deposition. Implied open-circuit voltages as high as 710 mV are achieved for p-type poly-Si/SiOx contacts to n-type Si after hydrogenation. Correlating minority carrier lifetime data and secondary ion mass spectrometry profiles reveals that the main benefit of Al2O3 is derived from its role as a hydrogen source for chemically passivating defects at SiOx; Al2O3 layers are found to hydrogenate poly-Si/SiOx much better than a forming gas anneal. By labelling Al2O3 and the subsequent anneal with different hydrogen isotopes, it is found that Al2O3 exchanges most of its hydrogen with the ambient upon annealing at 400 °C for 1 h even though there is no significant net change in its total hydrogen content.</jats:p>

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