CVD-Based Valence-Mending Passivation for Crystalline-Si Solar Cells

Project: Research project

Description

The objective of this project is to integrate a new surface passivation technique, valencemending passivation, into crystalline-Si solar cells for significant efficiency improvement and cost reduction. Our preliminary results demonstrate a high potential for this approach to overcome several bottlenecks in crystalline-Si solar cells. One of the bottlenecks this project intends to overcome is the silver electrode in crystalline-Si solar cells. The deployment of solar cells has to reach a scale of tens of peak terawatt in order to become a noticeable source of energy in our life. The known reserve of silver on this planet, however, will limit the total wattage of crystalline-Si solar cells to just a few peak terawatts. Substitution of silver electrode with an abundant metal will allow hundreds of peak terawatts of crystalline-Si solar cells. In addition, the price of silver has more than doubled since summer 2010 and is expected to go up further. Silver paste is now the biggest contributor to cost in cell fabrication. Substitution of silver with an abundant low-cost metal will reduce the cost of crystalline-Si solar cells by $0.1/Wp. As a second example, another bottleneck this project intends to overcome is the efficiency gap between multicrystalline-Si and monocrystalline-Si solar cells, which is about 2% absolute. This efficiency gap is caused largely by grain boundaries in multicrystalline-Si. This project will investigate the passivation of dangling bonds at grain boundaries with the valencemending approach. The goal is to narrow the efficiency gap to less than 1% between multicrystalline-Si and monocrystalline-Si solar cells. The most significant deliverable of this project is a n-type base p-type emitter crystalline- Si solar cell with aluminum as both the front and back electrical contacts. The efficiency goal for this cell by the end of this project (in three years) is 18% on monocrytsalline-Si wafers, but the ultimate efficiency goal for this cell is above 20% on monocrytsalline-Si wafers. There are several milestones along the way, including recipes for passivation of monocrystalline-Si and multicrystalline-Si surfaces, a new aluminum paste for low-temperature firing, and a n-type base p-type emitter crystalline-Si solar cell with 18% efficiency. Other deliverables include a recipe for grain boundary passivation and a point back contact crystalline-Si solar cell.
StatusFinished
Effective start/end date9/1/1112/31/14

Funding

  • DOE: Golden Field Office: $1,500,000.00

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passivity
solar cells
vapor deposition
valence
silver
grain boundaries
emitters
cells
wafers
substitutes
costs
aluminum
cost reduction
electrodes
metals
summer
planets
electric contacts
fabrication