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

Abstract

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.

Authors:
; ;  [1]; ;  [2]; ;  [3]
  1. Photovoltaics and Thin-Film Electronics Laboratory, Institute of Microengineering (IMT), Ecole Polytechnique Fédérale de Lausanne (EPFL), Rue de la Maladière 71b, CH-2002 Neuchâtel (Switzerland)
  2. Department of Physics, Yıldız Technical University, Davutpasa Campus, TR-34210 Esenler, Istanbul (Turkey)
  3. CSEM, PV-Center, Jaquet-Droz 1, CH-2002 Neuchâtel (Switzerland)
Publication Date:
OSTI Identifier:
22597738
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 120; Journal Issue: 5; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ASYMMETRY; COMPARATIVE EVALUATIONS; ELECTRIC POTENTIAL; ELECTRONS; FIELD EMISSION; FILL FACTORS; FILMS; HETEROJUNCTIONS; HOLES; IMPLEMENTATION; INTERFACES; LAYERS; PASSIVATION; PERFORMANCE; SILICON OXIDES; SILICON SOLAR CELLS; SUBSTRATES; SURFACES; TOPOLOGY; DARK CURRENT

Citation Formats

Seif, Johannes Peter, E-mail: johannes.seif@alumni.epfl.ch, Ballif, Christophe, De Wolf, Stefaan, Menda, Deneb, Özdemir, Orhan, Descoeudres, Antoine, and Barraud, Loris. Asymmetric band offsets in silicon heterojunction solar cells: Impact on device performance. United States: N. p., 2016. Web. doi:10.1063/1.4959988.
Seif, Johannes Peter, E-mail: johannes.seif@alumni.epfl.ch, Ballif, Christophe, De Wolf, Stefaan, Menda, Deneb, Özdemir, Orhan, Descoeudres, Antoine, & Barraud, Loris. Asymmetric band offsets in silicon heterojunction solar cells: Impact on device performance. United States. doi:10.1063/1.4959988.
Seif, Johannes Peter, E-mail: johannes.seif@alumni.epfl.ch, Ballif, Christophe, De Wolf, Stefaan, Menda, Deneb, Özdemir, Orhan, Descoeudres, Antoine, and Barraud, Loris. Sun . "Asymmetric band offsets in silicon heterojunction solar cells: Impact on device performance". United States. doi:10.1063/1.4959988.
@article{osti_22597738,
title = {Asymmetric band offsets in silicon heterojunction solar cells: Impact on device performance},
author = {Seif, Johannes Peter, E-mail: johannes.seif@alumni.epfl.ch and Ballif, Christophe and De Wolf, Stefaan and Menda, Deneb and Özdemir, Orhan and Descoeudres, Antoine and Barraud, Loris},
abstractNote = {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.},
doi = {10.1063/1.4959988},
journal = {Journal of Applied Physics},
number = 5,
volume = 120,
place = {United States},
year = {Sun Aug 07 00:00:00 EDT 2016},
month = {Sun Aug 07 00:00:00 EDT 2016}
}