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

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 publication2017 IEEE 44th Photovoltaic Specialist Conference, PVSC 2017
PublisherInstitute of Electrical and Electronics Engineers Inc.
Pages1-5
Number of pages5
ISBN (Electronic)9781509056057
DOIs
StatePublished - May 25 2018
Event44th IEEE Photovoltaic Specialist Conference, PVSC 2017 - Washington, United States
Duration: Jun 25 2017Jun 30 2017

Other

Other44th IEEE Photovoltaic Specialist Conference, PVSC 2017
CountryUnited States
CityWashington
Period6/25/176/30/17

Keywords

  • Carrier-selective contact
  • Crystalline silicon solar cell
  • Electrode
  • Passivation
  • TiO

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Electrical and Electronic Engineering
  • Electronic, Optical and Magnetic Materials

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  • Cite this

    Boccard, M., Yang, X., Weber, K., & Holman, Z. (2018). Passivation and carrier selectivity of TiO2 contacts combined with different passivation layers and electrodes for silicon solar cells. In 2017 IEEE 44th Photovoltaic Specialist Conference, PVSC 2017 (pp. 1-5). Institute of Electrical and Electronics Engineers Inc.. https://doi.org/10.1109/PVSC.2017.8366554