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Title: Asymmetric band offsets in silicon heterojunction solar cells: Impact on device performance

Here, amorphous/crystalline silicon interfaces feature considerably larger valence than conduction band offsets. In this article, we analyze the impact of such band offset asymmetry on the performance of silicon heterojunction solar cells. To this end, we use silicon suboxides as passivation layers -- inserted between substrate and (front or rear) contacts -- since such layers enable intentionally exacerbated band-offset asymmetry. Investigating all topologically possible passivation layer permutations and focussing on light and dark current-voltage characteristics, we confirm that to avoid fill factor losses, wider-bandgap silicon oxide films (of at least several nanometer thin) should be avoided in hole-collecting contacts. As a consequence, device implementation of such films as window layers -- without degraded carrier collection -- demands electron collection at the front and hole collection at the rear. Furthermore, at elevated operating temperatures, once possible carrier transport barriers are overcome by thermionic (field) emission, the device performance is mainly dictated by the passivation of its surfaces. In this context, compared to the standard amorphous silicon layers, the wide-bandgap oxide layers applied here passivate remarkably better at these temperatures, which may represent an additional benefit under practical operation conditions.
 [1] ;  [2] ;  [3] ;  [3] ;  [2] ;  [1] ;  [1]
  1. Photovoltaics and Thin-Film Electronics Laboratory, Institute of Microengineering (IMT), Ecole Polytechnique Federale de Lausanne (EPFL), Neuchatel (Switzerland)
  2. Yildiz Technical University, Istanbul (Turkey). Dept. of Physics
  3. CSEM, PV-Center, Neuchatel (Switzerland)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 120; Journal Issue: 5; Journal ID: ISSN 0021-8979
American Institute of Physics (AIP)
Research Org:
Ecole Polytechnique Federale de Lausanne (Switzerland)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Country of Publication:
United States
14 SOLAR ENERGY; amorphous silicon; silicon oxide; passivation; silicon heterojunction; solar cells
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1279021; OSTI ID: 1354906