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 Holman

Research output: Chapter in Book/Report/Conference proceedingConference contribution

12 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
Volume2016-November
ISBN (Electronic)9781509027248
DOIs
StatePublished - Nov 18 2016
Event43rd IEEE Photovoltaic Specialists Conference, PVSC 2016 - Portland, United States
Duration: Jun 5 2016Jun 10 2016

Other

Other43rd IEEE Photovoltaic Specialists Conference, PVSC 2016
CountryUnited States
CityPortland
Period6/5/166/10/16

Keywords

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

ASJC Scopus subject areas

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

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    Boccard, M., Yang, X., Weber, K., & Holman, Z. (2016). Passivation and carrier selectivity of TiO2 contacts combined with different passivation layers and electrodes for silicon solar cells. In 2016 IEEE 43rd Photovoltaic Specialists Conference, PVSC 2016 (Vol. 2016-November, pp. 2403-2407). [7750072] Institute of Electrical and Electronics Engineers Inc.. https://doi.org/10.1109/PVSC.2016.7750072