Nitride Layer Screening as Carrier-Selective Contacts for Silicon Heterojunction Solar Cells

Angela N. Fioretti, Mathieu Boccard, Adele C. Tamboli, Andriy Zakutayev, Christophe Ballif

Research output: Contribution to conferencePaperpeer-review

9 Scopus Citations

Abstract

A three-architecture method for screening new materials' viability as carrier-selective contacts for silicon solar cells is presented. Test-structure solar cells were fabricated with a standard silicon heterojunction contact for the front side, and one of three treatments on the back: bare silicon, intrinsic amorphous silicon (i-aSi:H), or n-type amorphous silicon on an i-aSi:H passivation layer. Then, the candidate contact material of interest was deposited on the back of each test structure and the cells were finished with evaporated Al. By analysing the current-voltage characteristics of each type of architecture, the carrier selectivity and surface passivation quality of novel contact materials or material stacks can be rapidly screened. To demonstrate the utility of this method, we present a preliminary investigation of nitride compounds as electron-selective contacts in silicon solar cells, in particular zinc tin nitride (ZnSnN2), which is naturally n-type and has favourable band alignments with c-Si. ZnSnN2 was deposited by reactive sputtering as an electron contact on each test structure. No passivation was observed, but decent electron-selectivity was observed when in direct contact with the silicon wafer. When combined with intrinsic amorphous silicon, poor performances were obtained with poor selectivity and the occurrence of an S-shape, likely due to insufficient selectivity of the ZTN. Similar results were obtained for 2 nm and 20 nm thick layers, indicating selectivity did not result from the Al over-layer, but was in fact due to the ZTN itself. Overall, this work shows the three-architecture screening method is a useful tool for assessing novel contact materials for silicon heterojunction solar cells.

Original languageAmerican English
Number of pages8
DOIs
StatePublished - 10 Aug 2018
EventSiliconPV 2018: The 8th International Conference on Crystalline Silicon Photovoltaics - Lausanne, Switzerland
Duration: 19 Mar 201821 Mar 2018

Conference

ConferenceSiliconPV 2018: The 8th International Conference on Crystalline Silicon Photovoltaics
Country/TerritorySwitzerland
CityLausanne
Period19/03/1821/03/18

Bibliographical note

Publisher Copyright:
© 2018 Author(s).

NREL Publication Number

  • NREL/CP-5900-71249

Keywords

  • chemical elements
  • educational assessment
  • heterostructures
  • I-V characteristics
  • leptons passivation
  • materials purification
  • nitrides
  • solar cells
  • sputter deposition

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