1. Design & Fabrication of a High- Voltage Photovoltaic Device Jennifer Felder North Carolina State University Project Advisor: Chris Kenney

2. Outline Brief Review Motivation Unique Features of Design (Mask) Design Simulation Fabrication Conclusion

3. A Brief Review Photoelectric Effect Photovoltaic (PV) Effect/Devices Image courtesy of: http://amazingdata.com/mediadata8/Image/amazing_fun_science_technology_20090729124730244.jpg

4. Project Motivation High-Voltage PV EXO Experiment Power Source Unique Features of Device – Wavelength – Temperature – Float-zone Si wafers Impurities Cost

5. Wavelength Matching Band gap & efficiency Band gap of Si = 1.12 eV λ=hc/E  1.12 eV ~ 1100 nm Solar cells?

6. Temperature & Efficiency η drops 0.1% per °C above 25°C Ex: If it were 105°F (40.5°C)  -1.55% Liquid Xe Solar cells?

7. 100 μm Individual Cell Designs (Mask)

8. Preliminary Calculations 1. Known Parameters 2. Modeling Equations 3. Calculated Parameters

9. Mask Design: PV Device Series Connections Various Voltages (50-2000 V) From Calculations:

10. 3 Basic Cell Designs Simulated SOI Layer P Diffusion N Diffusion

11. Optimized Cell Design N-type diffusion area Constraints on area size

12. Built-in Potential High built-in potential  fewer number cells Φ j ≈ 0.97 V (± 0.01 V between designs) Not a deciding factor

13. SRH Recombination Low recombination  high photovoltage generation

14. Other Simulation Results

15. Fabrication Stanford Nanofabrication Facility (SNF) Wet oxidation process – Remove organic materials – Remove metal ions – Oxidation Other steps to be finished in future work…

16. Conclusions Feasibility/Proof of Concept Test Significant Impact – Experiments (EXO) Noise – SLAC – Extended to other PV/solar cell technology, many others!

17. Acknowledgments Chris Kenney Jasmine Hasi Astrid Tomada Julie Segal DOE SLAC & SNF Staff

18. Questions, Comments, Concerns? Feel free to e-mail me at jkfelder@ncsu.edu