ELEG620_TestAndFabSiSCs_2009

ELEG620_TestAndFabSiSCs_2009 - Fabricating and Testing...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Fabricating and Testing Silicon Solar Cells ELEG620 Solar Electric Systems Silicon Solar Cell N-type contact (Ti/Pd/Ag) AR Coating N-type Si (P dopant) P-type Si (B dopant) P-type contact (Al) ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes How to tell if a solar cell is good IV Curves QE Curves How to verify processing steps Lifetime Testing IV Curves QE Curves ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes Review of Diode Equations If WL 26 s for 300 m thick Si ~34 cm2s-1 Why is lifetime important? ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes IV Curve: Measurable Metrics Open Circuit Voltage (Voc) Short Circuit Current (Isc) Fill Factor (FF) Efficiency (/Eff) Series Resistance (Rs) Shunt Resistance (Rsh) Ideality (n) ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes Pin=1000 W/m2 Vmp Voc Imp Isc ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes Series Resistance FF=.78 Rs=1 Rs=3 FF=.78 FF=.68 ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes Shunt Resistance Rsh=50 Rsh=500 FF=.58 FF=.80 Lower Voc ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes Ideality Factors Log plot of dark IV curve is used to measure ideality factors From ideal diode equation! ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes Quantum Efficiency: Surface Recombination Effects Measures conversion efficiency of discrete light spectra Plots by Paola Murcia ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes Quantum Efficiency: Lifetime Effects Plots by Paola Murcia ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes Effect of Diffusion Length on IV and QE Smaller diffusion lengths lead to smaller efficiencies Losses are due to inability of carriers far from junction to be collected Small Leff Large Leff Small Leff Large Leff Plots by Yi Wang ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes Industrial Process (using lab scale processes) 1. Phosphorus Diffusion 2. Phosphorus Glass Removal & Edge Isolation 3. Test Resistivity 4. Test Lifetime 5. Al Deposition on Rear 6. Alloy Al-Si 7. Test Voc 8. Photolithography to Define Front Contacts 9. Ti/Pd/Ag Deposition on Front 10. Test IV 11. Deposit AR Coating 12. Anneal Front Contacts 13. Test IV 14. Test QE ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. Phosphorus Glass Removal & Edge Isolation Test Resistivity Test Lifetime Al Deposition on Rear Alloy Al-Si Test Voc Photolithography to Define Front Contacts Ti/Pd/Ag Deposition on Front Test IV Deposit AR Coating Anneal Front Contacts Test IV Test QE Phosphorus Diffusion *Not used for industrial processing 4POCl3 + 3O2 -> 2P2O5 + 6Cl2 5Si + 2P2O5 -> 5SiO2 + 4P Diffusion Furnace Purpose: Form pn junction by doping Si ntype Silicon (p-type) ntype Si ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes Diffusions Temperature and time determine doping concentration of Si surface. ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes 1. Phosphorus Diffusion 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. Phosphorus Glass Removal & Edge Isolation Test Resistivity Test Lifetime Al Deposition on Rear Alloy Al-Si Test Voc Photolithography to Define Front Contacts Ti/Pd/Ag Deposition on Front Test IV Deposit AR Coating Anneal Front Contacts Test IV Test QE Phosphorus glass (P2O5) is removed to prevent delamination of module Edge isolation is performed to electrically isolate front and rear surfaces ntype Si Silicon (p-type) ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 S. Bremner 1. 2. Phosphorus Diffusion Phosphorus Glass Removal & Edge Isolation 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. Test Resistivity Test Lifetime Al Deposition on Rear Alloy Al-Si Test Voc Photolithography to Define Front Contacts Ti/Pd/Ag Deposition on Front Test IV Deposit AR Coating Anneal Front Contacts Test IV Test QE Four Point Probe A Measure of diffusion doping V t ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes 1. 2. 3. Phosphorus Diffusion Phosphorus Glass Removal & Edge Isolation Test Resistivity Al Deposition on Rear Alloy Al-Si Test Voc Photolithography to Define Front Contacts Ti/Pd/Ag Deposition on Front Test IV Deposit AR Coating Anneal Front Contacts Test IV Test QE 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. Test Lifetime Measures average time carriers move around before recombining Coil senses changes in current via induction Reference cell senses intensity and length of light pulse ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes Lifetime Results ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes 1. 2. 3. 4. Phosphorus Diffusion Phosphorus Glass Removal & Edge Isolation Test Resistivity Test Lifetime Alloy Al-Si Test Voc Photolithography to Define Front Contacts Ti/Pd/Ag Deposition on Front Test IV Deposit AR Coating Anneal Front Contacts Test IV Test QE 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. Al Deposition on Rear Electron Beam Evaporator Purpose: Deposit metal for rear contact Silicon (p-type) ntype Si Aluminum ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes 1. 2. 3. 4. 5. Phosphorus Diffusion Phosphorus Glass Removal & Edge Isolation Test Resistivity Test Lifetime Al Deposition on Rear 6. 7. 8. 9. 10. 11. 12. 13. 14. Alloy Al-Si Test Voc Photolithography to Define Front Contacts Ti/Pd/Ag Deposition on Front Test IV Deposit AR Coating Anneal Front Contacts Test IV Test QE Annealing Furnace Purpose: Dopes rear surface ptype. Forms back surface field. ntype Si Silicon (p-type) Aluminum ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes 1. 2. 3. 4. 5. 6. Phosphorus Diffusion Phosphorus Glass Removal & Edge Isolation Test Resistivity Test Lifetime Al Deposition on Rear Alloy Al-Si Voc 7. 8. 9. 10. 11. 12. 13. 14. Photolithography to Define Front Contacts Ti/Pd/Ag Deposition on Front Test IV Deposit AR Coating Anneal Front Contacts Test IV Test QE Test Voc Purpose: Verify quality of processing before further processing V ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes 1. 2. 3. 4. 5. 6. 7. Phosphorus Diffusion Phosphorus Glass Removal & Edge Isolation Test Resistivity Test Lifetime Al Deposition on Rear Alloy Al-Si Test Voc Ti/Pd/Ag Deposition on Front Test IV Deposit AR Coating Anneal Front Contacts Test IV Test QE Spinner 8. 9. 10. 11. 12. 13. 14. Photolithography to Define Front Contacts Mask Aligner Purpose: Allows selective deposition of metal ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes 1. 2. 3. 4. 5. 6. 7. 8. Phosphorus Diffusion Phosphorus Glass Removal & Edge Isolation Test Resistivity Test Lifetime Al Deposition on Rear Alloy Al-Si Test Voc Photolithography to Define Front Contacts 9. 10. 11. 12. 13. 14. Ti/Pd/Ag Deposition on Front Test IV Deposit AR Coating Anneal Front Contacts Test IV Test QE Electron Beam Evaporator Purpose: Form ntype contact Ti/Pd/Ag ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes 1. 2. 3. 4. 5. 6. 7. 8. 9. 11. 12. 13. 14. Phosphorus Diffusion Phosphorus Glass Removal & Edge Isolation Test Resistivity Test Lifetime Al Deposition on Rear Alloy Al-Si Test Voc Photolithography to Define Front Contacts Ti/Pd/Ag Deposition on Front Deposit AR Coating Anneal Front Contacts Test IV Test QE 10. Test IV Estimating characteristics of a completed solar cell Super positioning IV curves Adjust light source so solar cell has expected Isc with AR coating (not illuminating at 1 sun) ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 12. 13. 14. Phosphorus Diffusion Phosphorus Glass Removal & Edge Isolation Test Resistivity Test Lifetime Al Deposition on Rear Alloy Al-Si Test Voc Photolithography to Define Front Contacts Ti/Pd/Ag Deposition on Front Test IV Anneal Front Contacts Test IV Test QE 11. Deposit AR Coating Optical coatings can be designed to Plasma Enhanced Chemical Vapor Deposition optimize transmission of light into Si. (PECVD) Purpose: Improve collection of light. Passivate front surface. AR Coating Ti/Pd/Ag ntype Si Silicon (p-type) Al ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 13. 14. Phosphorus Diffusion Phosphorus Glass Removal & Edge Isolation Test Resistivity Test Lifetime Al Deposition on Rear Alloy Al-Si Test Voc Photolithography to Define Front Contacts Ti/Pd/Ag Deposition on Front Test IV Deposit AR Coating Test IV Test QE 12. Anneal Front Contacts Rapid Thermal Processor (RTP) A single wafer can have many solar cells when using microelectronic processing. Purpose: Improves electrical connection between metal and Si. AR Coating Ti/Pd/Ag ntype Si Silicon (p-type) Al ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 14. Phosphorus Diffusion Phosphorus Glass Removal & Edge Isolation Test Resistivity Test Lifetime Al Deposition on Rear Alloy Al-Si Test Voc Photolithography to Define Front Contacts Ti/Pd/Ag Deposition on Front Test IV Deposit AR Coating Anneal Front Contacts Test QE 13. Test IV Slope deviating from vertical indicates series resistance Slope deviating from horizontal indicates shunt resistance ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. Phosphorus Diffusion Phosphorus Glass Removal & Edge Isolation Test Resistivity Test Lifetime Al Deposition on Rear Alloy Al-Si Test Voc Photolithography to Define Front Contacts Ti/Pd/Ag Deposition on Front Test IV Deposit AR Coating Anneal Front Contacts Test IV 14. Test QE Light absorbed near the front Light absorbed near rear ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes Summary Testing techniques are used to identify processing problems Reviewed fabrication techniques for lab grade solar cells Reviewed information that can and cannot be measured by common techniques Lifetime IV QE Viewed effects of key parameters on solar cells ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes More Tests Metal Resistance Contact Resistance L ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 C. Kerestes ...
View Full Document

Ask a homework question - tutors are online