Handling, Assembly, and Electrical Interconnection of 2 nd Generation SLIVER Solar Cells

1. Handling, Assembly, and Electrical Interconnection of 2nd Generation SLIVER Solar Cells Vernie Everett, Andrew Blakers, Klaus Weber, Evan Franklin

2. 3D 2D

3. Grooves formed through the wafer 0.04 to 0.1mm pitch 100mm • Silicon wafer • single crystal • 150mm Ø • 1-3mm thick Following grooving, wafer processing proceeds: Diffusions, oxidations, depositions, metallisation.

4. ~1,000 completed bifacial SLIVER solar cells, each ~ 2 cm2 Illumination Cuts 100mm 2mm 0.1mm

5. Sliver Solar CellCross-Section Illumination Illumination Perfectly bifacial Phosphorus diffusion Boron diffusion 1-2mm 20-50m Metal (n-electrode) Metal (p-electrode) • Surface texturing • Phosphorus diffusion • AR coating

6. A 2nd Generation SLIVER Technology 1. SLIVER cell fabrication • Reduce Grooving Pitch and SLIVER Thickness • Strong cost driver • Major challenges • Advantage: with 40 micron pitch, 2.5X surface area increase over 100 micron pitch, at near-zero cost increase. • Reduce SLIVER Cell Fabrication Complexity • 1st Generation SLIVER cell fabrication required 59 steps • 2nd Generation SLIVER cell fabrication requires only 32 steps • Simplify texturing, improve light-trapping and AR-coating • Broaden Process Windows and Improve Yield and Efficiency • Robust processes with broad process windows • Improve yield: essential for simplified handling and assembly • Improve efficiency. Long term, efficiency will be the deciding factor

7. A 2nd Generation SLIVER Technology 2. SLIVER handling and assembly • A fundamental change in handling philosophy • Abandoned individual, sequential linear processes. • Moved to group handling modular parallel processes. • Improved yield through simplified separation, “bulk” handling, and a simplified structure. • Improved throughput with modular process line, with input and output buffers. • Modular sub-assemblies • Conventional cell “analogues” • Avoid individual testing and binning • Versatility through modularity • Two main sub-assembly types: “Rafts”, and “Sheets”. • Separation and handling processes are common for both. • Applications are common for both: cost and efficiency are the only differences. • Rafts and Sheets can be the building blocks of all SLIVER applications.

8. A SLIVER Raft

9. A Flexible SLIVER Raft

10. Flexible SLIVER Raft Assembly

11. Soldered electrical interconnections SLIVER cells A 2nd Generation SLIVER Technology 3. SLIVER electrical interconnections • Simplified process • Eliminated stencilling • Eliminated dispensing • Eliminated cleaning and waste • Eliminated machine vision • Eliminated complex automation • Robust process • Simplified alignment requirements • “Automatic” solder volume and location and distribution • Conventional materials • reliability, durability, warranty Advantages: • Equipment: low-cost, low-tech, industry-standard. • Process: robust, modular, buffered. • Materials: conventional, low-cost, reliable. • Throughput: 500 – 1,000 connections per second.

12. A 2nd Generation SLIVER Technology 3. SLIVER electrical interconnections (ctd.)

13. A 2nd Generation SLIVER Technology A SLIVER module constructed using Raft Sub-module Technology

14. A 2nd Generation SLIVER Technology • Reduces silicon consumption by a factor of 10 - 20 • Reduces wafer starts by a factor of 20 – 40 • Reduces cell fabrication steps from 59 to 32 • Simplifies cell fabrication equipment requirements • Exceeds 20% cell efficiency [world first for thin production cells] • Reduces assembly equipment cost by a factor of 10 • Increases assembly line throughput by a factor of 10 • Increases rate of electrical connection by factor of 100 • Modularises the entire assembly process • Establishes an entire assembly process using only conventional materials

15. A 2nd Generation SLIVER Technology Conclusion • Reduce present PV costs by two-thirds • Rapidly grow market share • Play a significant role in ameliorating climate change Mature SLIVER Technology can:

16. Thank You!