1. Nanophotonics Class 9 Nanophotovoltaics

2. The world’s present sources of energy

3. Different sources of energy: future oil coal gas nuclear power hydroelectricity biomass (traditional) biomass (advanced) solar power (photovoltaics (PV) & solar thermal generation (CSP) solar thermal (heat only) other renewables geothermal wind energy German Advisory Council on Global Change, 2003, www.wbgu.de year 2000 2020 2040 200 600 1000 1400 2100 EJ/a PV & CSP gas coal oil sun

4. + The greenhouse effect!

5. Available renewable energy sources

6. Black dots: area of solar panels needed to generate all of the worlds energy assuming 8% efficient photovoltaics Solar irradiance on earth Average solar irradiance, W/m 2.

7. Solar flux distribution on earth in kWh/m 2. day source: ABB, 1998

8. … © Ron Tandberg

9. Production costs of electricity US DOE (2002)

10. Explosive growth in PV manufacturing P. Maycock, PV News (2005)

11. Price per solar Watt vs. installed power P. Maycock

12. CHALLENGE How to reduce the price/Watt of photovoltaic energy ???? 1.Increase efficiency 2.Reduce materials costs

13. Solar cell basic geometry electron ( hole(+) front contact n-typesemiconductor p-typesemiconductor back contact anti reflection coating _ + generation electron (-) gat (+) front contact n-typesemiconductor p-typesemiconductor back contact anti reflection coating _ +

14. Current-Voltage characteristics

15. The first practical solar panel (1954) Bell Laboratories (1954)

17. Si solar cell efficiencies

18. Efficiency/cost of photovoltaic technology M. Green, UNSW Crystalline Silicon cells

19. Efficiency/cost of photovoltaic technology M. Green, UNSW Organic, thin- film cells

20. Improvements in solar cell efficiencies US DOE 2006

21. Third-generation photovoltaics M. Green, UNSW

22. H. Atwater (CALTECH) “Quantum defect” problem

23. H. Atwater (CALTECH)

25. Record efficiency solar cell NREL data (2005)

26. Efficiency/cost of photovoltaic technology M. Green, UNSW tandem cells

27. Efficiency/cost of photovoltaic technology M. Green, UNSW Thin- film cells

28. Thin-film solar cells

29. Poor IR absorption in (thin-film) Si solar cells solar spectrum EgEg Poor absorption just below bandgap

30. (a) (b) Absorption ~ r 3 Scattering ~ r 6 increased absorption in Si f subs f f air Goal: Ultra-thin-film solar cell Kylie Catchpole Albedo Ag Possible solution: light trapping

31. H. Atwater (CALTECH) “Quantum defect” problem

32. Semiconductor nanocrystals / quantum dots Increasing particle size single atoms Many open fundamental questions regarding multiple-exciton generation

33. Quantum dot tandem solar cell (science fiction!) 3.0 V2.0 V 1.0 V Plasmonic quantum dot solar cell

34. Upconversion from infrared to visible exc = 1490 nm 10 µm Ewold Verhagen, Kobus Kuipers transmission Nano Lett. 7, 334 (2007) 550 nm exc = 1480 nm Guiding and concentration observed to /16 Plasmonic hot-spot

35. Plasmonic nano-solar cell (science fiction!) E Small active semiconductor volume = low cost Small size  low minority carrier lifetime required p n

36. The Energy Problem: Needed: Large Area Cost-Effective Photovoltaics

37. k E x z New third-generation solar cell concepts f 3.0 V2.0 V 1.0 V YOU CAN HELP MAKE IT WORK !!