Passivation and carrier selectivity of TiO2 contacts combined with different passivation layers and electrodes for silicon solar cells

Mathieu Boccard, Xinbo Yang, Klaus Weber, Zachary C. Holman

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

18 Scopus citations

Abstract

Titanium dioxide (TiO2) films have previously been demonstrated to function as electron-selective contacts to silicon solar cells, and an efficiency of 21.6% has been reported for a cell featuring a full-area TiO2 contact. However, the passivation quality of TiO2 contacts still falls short of that possible with best-in-class contacts based on, e.g., hydrogenated amorphous silicon (a-Si:H). We investigate here the performance of a-Si:H/TiO2 stacks as electron-selective, passivating contacts. We show that combining a-Si:H with TiO2 can result in excellent surface passivation (lifetime close to 3 ms for textured CZ wafers), especially for 7.5-nm-thick TiO2 capping layers. However, initial cell results show that such a-Si:H/TiO2 stacks give poorer efficiencies than TiO2 only, with extremely low fill factors due to S-shaped current-voltage curves. Also, the role of the rear electrode becomes apparent when substituting Al for an ITO/Ag stack: the latter has significantly lower open-circuit voltage and fill factor than the former. Combining a TiO2/Al rear electron contact (with no a-Si:H) and an intrinsic a-Si:H/p-type a-Si:H front hole contact, we demonstrate a double heterojunction silicon solar cell with an efficiency of approximately 15%. Furthermore, a full metal-oxide heterojunction cell that combines a molybdenum oxide (MoOx)/ITO hole contact with the TiO2/Al electron contact achieves an efficiency of 11%.

Original languageEnglish (US)
Title of host publication2016 IEEE 43rd Photovoltaic Specialists Conference, PVSC 2016
PublisherInstitute of Electrical and Electronics Engineers Inc.
Pages2403-2407
Number of pages5
ISBN (Electronic)9781509027248
DOIs
StatePublished - Nov 18 2016
Event43rd IEEE Photovoltaic Specialists Conference, PVSC 2016 - Portland, United States
Duration: Jun 5 2016Jun 10 2016

Publication series

NameConference Record of the IEEE Photovoltaic Specialists Conference
Volume2016-November
ISSN (Print)0160-8371

Other

Other43rd IEEE Photovoltaic Specialists Conference, PVSC 2016
Country/TerritoryUnited States
CityPortland
Period06/5/1606/10/16

Bibliographical note

Funding Information:
We acknowledge Kate Fisher for wafer preparation and Laura Ding for MoOx deposition. The information, data, or work presented herein was funded in part by the U.S. Department of Energy, Energy Efficiency and Renewable Energy Program, under Award Number DE-EE0006335. Support was also provided by the Research Corporation for Science Advancement through Scialog Collaborative Innovation Award Number 23460

Publisher Copyright:
© 2016 IEEE.

Keywords

  • TiO2
  • carrier-selective contact
  • crystalline silicon solar cell
  • electrode
  • passivation

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Industrial and Manufacturing Engineering
  • Electrical and Electronic Engineering

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