Tunnel Oxide Passivated Contacts Formed by Ion Implantation for Applications in Silicon Solar Cells

Christian Reichel, Frank Feldmann, Ralph Müller, Robert C. Reedy, Benjamin G. Lee, David L. Young, Paul Stradins, Martin Hermle, Stefan W. Glunz

Research output: Contribution to journalArticlepeer-review

64 Scopus Citations

Abstract

Passivated contacts (poly-Si/SiOx/c-Si) doped by shallow ion implantation are an appealing technology for high efficiency silicon solar cells, especially for interdigitated back contact (IBC) solar cells where a masked ion implantation facilitates their fabrication. This paper presents a study on tunnel oxide passivated contacts formed by low-energy ion implantation into amorphous silicon (a-Si) layers and examines the influence of the ion species (P, B, or BF2), the ion implantation dose (5 × 1014cm-2 to 1 × 1016cm-2), and the subsequent high-temperature anneal (800 °C or 900 °C) on the passivation quality and junction characteristics using double-sided contacted silicon solar cells. Excellent passivation quality is achieved for n-type passivated contacts by P implantations into either intrinsic (undoped) or in-situ B-doped a-Si layers with implied open-circuit voltages (iVoc) of 725 and 720 mV, respectively. For p-type passivated contacts, BF2 implantations into intrinsic a-Si yield well passivated contacts and allow for iVoc of 690 mV, whereas implanted B gives poor passivation with iVoc of only 640 mV. While solar cells featuring in-situ B-doped selective hole contacts and selective electron contacts with P implanted into intrinsic a-Si layers achieved Voc of 690 mV and fill factor (FF) of 79.1%, selective hole contacts realized by BF2 implantation into intrinsic a-Si suffer from drastically reduced FF which is caused by a non-Ohmic Schottky contact. Finally, implanting P into in-situ B-doped a-Si layers for the purpose of overcompensation (counterdoping) allowed for solar cells with Voc of 680 mV and FF of 80.4%, providing a simplified and promising fabrication process for IBC solar cells featuring passivated contacts.

Original languageAmerican English
Article number205701
Number of pages9
JournalJournal of Applied Physics
Volume118
Issue number20
DOIs
StatePublished - 28 Nov 2015

Bibliographical note

Publisher Copyright:
© 2015 AIP Publishing LLC.

NREL Publication Number

  • NREL/JA-5J00-65649

Keywords

  • amorphous semiconductors
  • ion implantation
  • passivation
  • silicon doping
  • silicon solar cells

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