Projects

Spectrolab, Inc.

Publications

Project Objective:  Identify critical paths towards achieving long-term project goals of 33% module conversion efficiency at or under $1 per Watt. Specific objectives:

1. Develop a high efficiency (>32%) monolithic multijunction concentrator cell
2. Develop an ultra-high efficiency cell (>35%) using an integrated cell approach
3. Reduce the cost of Ge wafers
4. Increase reliability of concentrator cells under continuous exposure to high concentration
5. Investigate efficient and robust receiver packaging designs.
6. Provide 100 concentrator cells to ENTECH for their near-term demonstration of a 440 sun average concentration system.

Approach/Background:  Addressing the objectives stated above, investigations are being conducted towards a 4-junction cell approach as well as a metamorphic cell structure. Both the mechanical stacking and wafer bonding are being detailed with lower-tier subcontractor University of Wisconsin, Madison. Effort is being conducted with substrate vendor Union Menier, towards feasibility of low-cost Ge wafer grades instead of the high cost, space grade wafers. Different cell metallization structures are being investigated to eliminate cell shunting under high concentration. Investigations towards a combination of finite element modeling (for thermal and thermal stress analysis) and experiments to define a robust receiver package design and build a prototype for demonstration are being pursued as well as defining a suitable test vehicle for high concentration cell and module testing. 

Status/Accomplishments:  Activities that are in progress: (a) Electrical modeling for the MJ; (b) Definition of the framework of the initial experimental plan for the demonstration of the integrated cell approach working with University of Wisconsin; Modeling for the ENTECH cell; (c) Growth and fabrication of concentrator monolithic MJ cells; (d) Experiments to address cell shunting for different cell metallization structures; (e) Thermal modeling of different receiver packages.

Planned FY 2002 Activities:

• Complete the MJ cell electrical modeling input for cell growths.
• Deliver 10 cells of different types to ENTECH for evaluation. Once completed, fabricate and deliver 100 cells for the ENTECH High Performance PV Project.
• Receive alternate low cost Ge substrates.
• Complete the growth and fabrication monolithic MJ cells optimized for terrestrial systems.
• Grow and fabricate III-V cells for integrated MJ cells, mechanically-stacked and wafer-bonded configurations.
• Fabricate silicon cells for mechanically-stacked and wafer-bonded MJ cell demonstrations.
• Demonstrate wafer bonding and substrate removal between GaInP/GaAs 2-junction cell and Si substrate.
• Grow and fabricate MJ concentrator cells on alternative low-cost Ge substrates
• Demonstrate mechanically-stacked GaInP/GaAs/Si 3-junction concentrator cell.
• Complete designs of several receiver packages, including thermal modeling, thermal stress modeling, and cost analysis.
• Procure hardware for receiver packages
• Build test-vehicles and use them to complete assessment of cell robustness under high concentration.

Spectrolab High-Performance PV Publications:
"High Performance, Low Cost Concentrator Module," (PDF 36 KB) National Center for Photovoltaics Program Review Meeting, Oct. 14-17, 2001 (Lakewood, CO).

R. A. Sherif, and R. R. King