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Enhanced Stability of Exposed PECVD Grown Thin n+ Poly-Si/SiOx Passivating Contacts With Al2O3 Capping Layer During High Temperature Firing

Journal Article · · IEEE Journal of Photovoltaics
 [1];  [2];  [2];  [3];  [3];  [2]
  1. Georgia Institute of Technology, Atlanta, GA (United States); Georgia Institute of Technology
  2. Georgia Institute of Technology, Atlanta, GA (United States)
  3. Korea Institute of Energy Research, Daejeon (South Korea)

Carrier selective poly-Si/SiOx contacts have become a very strong contender for next generation high-efficiency Si solar cells as well as Si-based tandem cells. A thin unmetallized poly-Si/SiOx passivated contact on the top surface of the bottom Si cell provides an excellent opportunity for higher efficiency two-terminal Si-based tandem cells. However, this article shows that when the manufacturable low-cost screen-printed contacts are applied on the rear side of the Si cell, the exposed poly-Si/SiOx contact on the front undergoes appreciable degradation in J0 during high temperature contact firing without a capping layer on the front poly-Si. In this article, unmetallized n-TOPCon structures with ~10-nm poly-Si showed significant degradation after a typical simulated firing process (~750 °C), resulting in decreased implied Voc from 728 to 708 mV and increased J0 from 5 to 15 fA/cm2. Here, we found that a ~7-nm Al2O3 capping layer on poly-Si provides excellent protection with no degradation and can also be easily removed after firing for subsequent processing. For comparison, PECVD grown ~20 nm SiNx and SiOx layers were also investigated for firing stability. The SiNx capping layer was also found to be effective in preserving stability, but the SiOx failed due to lack of hydrogen supply. Large area n-type front junction Si solar cells were fabricated with a boron diffused screen-printed emitter on the front and Ag evaporated thin n-TOPCon on the rear to demonstrate ~0.3% higher absolute efficiency when the rear n-TOPCon was capped with Al2O3 during the firing of the front screen-printed contacts.

Research Organization:
Georgia Institute of Technology, Atlanta, GA (United States)
Sponsoring Organization:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Grant/Contract Number:
EE0007554
OSTI ID:
1893735
Alternate ID(s):
OSTI ID: 1848526
OSTI ID: 1893906
Journal Information:
IEEE Journal of Photovoltaics, Journal Name: IEEE Journal of Photovoltaics Journal Issue: 2 Vol. 11; ISSN 2156-3381
Publisher:
IEEECopyright Statement
Country of Publication:
United States
Language:
English

References (31)

Large area tunnel oxide passivated rear contact n -type Si solar cells with 21.2% efficiency : Large area tunnel oxide passivated rear contact journal January 2016
Tunnel oxide passivating electron contacts as full-area rear emitter of high-efficiency p-type silicon solar cells journal November 2017
26.1%‐efficient POLO‐IBC cells: Quantification of electrical and optical loss mechanisms journal October 2018
Solar cell efficiency tables (version 54) journal June 2019
Tunnel oxide passivating electron contacts for high‐efficiency n‐type silicon solar cells with amorphous silicon passivating hole contacts journal October 2019
Silicon Solar Cell Architecture with Front Selective and Rear Full Area Ion-Implanted Passivating Contacts journal June 2017
Hydrogenation Mechanisms of Poly‐Si/SiO x Passivating Contacts by Different Capping Layers journal March 2020
Carrier Selective, Passivated Contacts for High Efficiency Silicon Solar Cells based on Transparent Conducting Oxides journal January 2014
Passivated rear contacts for high-efficiency n-type Si solar cells providing high interface passivation quality and excellent transport characteristics journal January 2014
Tunnel oxide passivated contacts as an alternative to partial rear contacts journal December 2014
Rear side sphere gratings for improved light trapping in crystalline silicon single junction and silicon-based tandem solar cells journal November 2015
High efficiency n-type silicon solar cells with passivating contacts based on PECVD silicon films doped by phosphorus diffusion journal May 2019
Comparative study of different silicon oxides used as interfacial passivation layer (SiNy:H / SiOx /n+-Si) in industrial monocrystalline silicon solar cells journal October 2019
Monolithic thin-film chalcogenide–silicon tandem solar cells enabled by a diffusion barrier journal April 2020
Double-sided TOPCon solar cells on textured wafer with ALD SiOx layer journal April 2020
Sputtered indium tin oxide as a recombination layer formed on the tunnel oxide/poly-Si passivating contact enabling the potential of efficient monolithic perovskite/Si tandem solar cells journal June 2020
On the hydrogenation of Poly-Si passivating contacts by Al2O3 and SiN thin films journal September 2020
Characterization of SiNx:H thin film as a hydrogen passivation layer for silicon solar cells with passivated contacts journal April 2019
Silicon heterojunction solar cell with interdigitated back contacts for a photoconversion efficiency over 26% journal March 2017
Fully textured monolithic perovskite/silicon tandem solar cells with 25.2% power conversion efficiency journal June 2018
Etch rates for micromachining processing-part II journal December 2003
High-Efficiency Large-Area Rear Passivated Silicon Solar Cells With Local Al-BSF and Screen-Printed Contacts journal July 2011
24.7% Record Efficiency HIT Solar Cell on Thin Silicon Wafer journal January 2014
Achievement of More Than 25% Conversion Efficiency With Crystalline Silicon Heterojunction Solar Cell journal November 2014
Fabrication and Modeling of High-Efficiency Front Junction N-Type Silicon Solar Cells With Tunnel Oxide Passivating Back Contact journal September 2017
Silicon solar cells with total area efficiency above 25 % conference June 2016
Impact of Deposition of ITO on Tunnel Oxide Passivating Poly-Si Contact conference June 2019
Diffusion of Boron, Phosphorus, Arsenic, and Antimony in Thermally Grown Silicon Dioxide journal January 1999
Improving the Microstructure and Electrical Properties of Aluminum Induced Polysilicon Thin Films Using Silicon Nitride Capping Layer journal January 2014
Stress-Corrosion Cracking and Blistering of Thin Polycrystalline Silicon Films in Hydrofluoric Acid journal January 1993
Polycrystalline silicon passivated tunneling contacts for high efficiency silicon solar cells journal March 2016