JESUS GUARDADO, LEAH NATION, HUY NGUYEN, TINA RO

1. JESUS GUARDADO, LEAH NATION, HUY NGUYEN, TINA RO The Effect of Carbon Nanotubes in Polymer Photovoltaic Cells May 13, 2010

2. Overview of Market • Goal of Project • Science & Design of Cell • Fabrication Procedures • Results • Analysis • Future Work Agenda

3. Current Market Projection for Photovoltaics • Investments on the rise • Photovoltatic capacity is increasing • Avg growth rate >40% for past 5 years

4. Increased market focus on diversifying solar technologies • Potential fabrication advantages • Low processing temperature • Printable • Unique application possibilities • Light weight • Flexible • Current disadvantages • Lifetime instability • Lower efficiency Our Focus: Polymer Photovoltaic Cells (PPC)

5. Polymer Photovoltaic Cell Efficiency Growth 24.7% 20.3% Crystalline Si Cells (Single and Multi-crystalline) 12.1% Thin-Film Technologies (Amorphous Si:H) Organic Photovoltaics 5.4%

6. Project Goals • Add carbon nanotubes (CNTs) to increase cell photovoltaic response • Make functional cells to validate photoresponse mechanism • Match current polymer photovoltaic cell (PPC) cell efficiency

7. SWCNT at 80,000x • Single-walled carbon nanotubes • Large surface area • High e- affinity • Aids cells • Improve carrier transport • Induces crystallinity • Cost: +$8 per m2 Focus: sw-CNTs

8. Cell Design • Based on past research • Cell parts: • Active layer (with CNTs) • Charge acceptors • Electrodes FTO – Fluoride Tin Oxide

9. How It Works: • Photons => Exitons • Carbon Nanotubes: • Charge transport • Facilitate disassociation

10. How It Works: Electron => TiO2 Hole => PEDOT

11. How It Works: Electrodes accept charges

12. 1 2 3 Procedures Prepare Solutions Fabricate Samples Test Samples

13. Preparing the Solutions Evolution of the solutions Mix P3HT and solvent Add varying conc. of CNTs CNTs => main variable Sonicate & centrifuge to debundle CNTs

14. Device Fabrication Taping pix here Prepare substrate Clean FTO substrate Separate layers with tape Spin Coat Must optimize rpm 800 rpm for thick layers 1200 rpm for thin layers Deposit top electrode Thermal vapor deposition

15. Fabricated Cell

16. Tests UV-Vis on solutions Confirms semiconductor properties Open circuit voltage No light vs desk lamp Tests for photoresponse IV-Curve Determines cell performance

17. UV-Vis Spectroscopy • samples with CNTs show increased photo-response compared to control cells • absorption increases as the wt% CNTs increases

18. CNT Concentration vs. Voc Trend

19. I-V Curves • Observed Behavior • Resistors • Short circuit • Desired Behavior • Diode

20. Typical IV curve of our samples • The symmetry about the 0V axis implies there is no bias in electron/hole travel IV Curves: Round I Sample 4, Concentration 1 Fabrication: 4/6 Testing: 4/14, 4/27

21. IV Curve: Round II

22. Verified Expectations Summary Sources of Error Geng, J.; Zeng, T. Journal of the American Chemical Society2006, 128, 16827-16833.  

23. Future Work • Materials • Investigate the effects of the TiO2 layer • Study alternative materials to P3HT • Explore different materials for the heterostructure’s layers Fabrication & Testing • Experiment with the engineering parameters for fabrication • Standardize testing

24. Acknowledgements Helen Zeng  Yin-lin Xie   Jill Rowehl Prof. Yet-Ming Chiang 3.042 – Materials Project Laboratory Staff Facilities: Institute of Soldier Nanotechnologies (ISN) Organic Nanostructure Electronics (ONE) Lab

25. Thank you. Questions?You may reach us at nanosol@mit.eduhttp://web.mit.edu/course/3/3.042/team1_10

26. Appendix

27. Renewable Energy Comparison

28. Current Progress & Future Schedule

29. Cost Estimation $/gram mg/mL L/slide slides/meter $/meter 100 0.1875 0.0001 4444.44 8.33 PRODUCTION COSTS, to be added to other company's approximation of $/meter CNT $ 15-20% cnts

30. Profilometry: Ag/TiO2 Border Image Silver TiO2

31. Profilometry: Active Layer/PEDOT Image ACTIVE LAYER PEDOT