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Hydrogenation of Passivated Contacts

National Renewable Energy Laboratory

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Technology Marketing Summary

Silicon solar cells have advantages over other solar cells materials in that they are generally less expensive and require fewer steps to manufacture than III-V solar cells, yet are more efficient than today’s thin film materials.  Nevertheless, the efficiency of Si solar cells has historically been limited by carrier recombination losses, particularly at the surface of the cell and at the metal contact interfaces. One approach to reduce recombination losses at the contact interface is to deposit hydrogen-doped amorphous silicon on top of a tunneling oxide layer, followed by an annealing step.  This process results in a pc-Si/metal contact region which is electrically isolated from the rest of the cell by virtue of the passivating tunneling oxide. When the a-Si:H layer is annealed, however, hydrogen gas may be released, resulting in delamination or blistering of the cell at the contact interface. Preventing this delamination of the pc-Si surface in the annealing process has been an active area of research in order to improve the efficiency of Si solar cells using a pc-Si-on-SiOx contact architecture.

Description

NREL scientists have developed a method to mitigate delamination in polycrystalline solar cells through the utilization of Aluminum Oxide (Al2O3) as a passivating layer.  This is accomplished by growing Al2O3 films on the hydrogen-doped amorphous silicon and tunneling oxide stacks, and then annealing the amorphous film onto the silicon wafer. This process ultimately densifies the Al2O3 and hydrogenates the underlying material. This method of Al2O3 hydrogenation has been shown to improve the passivation of cells with pc-Si-on-SiOx stacks while circumventing the use of expensive hydrogenation equipment, such as plasma hydrogenation vacuums.

Benefits
  • Mitigates solar cell delamination
  • Improves passivation
  • Reduces costs
Applications and Industries
  • Solar Cells and Devices
  • Solar Energy
  • Transistors
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
NREL 15-51PrototypeAvailable07/07/201607/07/2016

Contact NREL About This Technology

To: Bill Hadley<bill.hadley@nrel.gov>