Universitat estiu2011 j_ferre

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Universitat estiu2011 j_ferre

  1. 1. Numerical Modeling of Photonic Nanostructures (and Organic Solar Cells) J osep Ferré i Borrull , Mohammad Mahbubur Rahman, Pedro Granero, Josep Pallarès, Lluis F. Marsal [email_address] Universitat Rovira i Virgili Universitat d’Estiu URV. July 2011. N a n o e l e c t r o n I c and P h o t o n I c S y s t e m s
  2. 2. Universitat d’Estiu URV. July 2011. Numerical Modeling
  3. 3. OUTLINE <ul><li>Introduction to Photonic Nanostructures </li></ul><ul><ul><li>Photonic Crystals/Photonic Quasicrystals/Random Nanostructures </li></ul></ul><ul><li>Photonic Properties of Quasi-random Nanostructures </li></ul><ul><ul><li>The Quasi-Random Structure </li></ul></ul><ul><ul><li>Numerical Methods </li></ul></ul><ul><ul><li>Results </li></ul></ul><ul><li>Light Trapping in Nanostructured Organic Solar Cells </li></ul><ul><ul><li>Scattering by subwavelength-sized nanostructuring </li></ul></ul><ul><ul><li>Simulation of light absorption by finite-element </li></ul></ul><ul><ul><li>Simulation of exciton diffusion </li></ul></ul><ul><li>Conclusion </li></ul>Universitat d’Estiu URV. July 2011.
  4. 4. Introduction to Photonic Nanostructures Photonic Crystals ( More Properly: Photonic Band Gap Materials ) Universitat d’Estiu URV. July 2011.
  5. 5. Photonic Crystals Universitat d’Estiu URV. July 2011. ε ( r ) r a Band gap Band gap 0 k 2 π / a π / a -2 π / a - π / a ω - G G allowed allowed Dispersion relation for 1D photonic crystal h 
  6. 6. Photonic Crystals: The Band Structure TM TE Normalized Frequency!!! ω a/2πc=a/ λ Universitat d’Estiu URV. July 2011.
  7. 7. Introduction to Photonic Nanostructures Photonic Quasicrystals Ordered structures, but not periodic: Universitat d’Estiu URV. July 2011.
  8. 8. Introduction to Photonic Nanostructures Random Photonic Nanostructures Random Lasers Universitat d’Estiu URV. July 2011.
  9. 9. OUTLINE Universitat d’Estiu URV. July 2011. <ul><li>Introduction to Photonic Nanostructures </li></ul><ul><ul><li>Photonic Crystals/Photonic Quasicrystals/Random Nanostructures </li></ul></ul><ul><li>Photonic Properties of Quasi-random Nanostructures </li></ul><ul><ul><li>The Quasi-Random Structure </li></ul></ul><ul><ul><li>Numerical Methods </li></ul></ul><ul><ul><li>Results </li></ul></ul><ul><li>Light Trapping in Nanostructured Organic Solar Cells </li></ul><ul><ul><li>Scattering by subwavelength-sized nanostructuring </li></ul></ul><ul><ul><li>Simulation of light absorption by finite-element </li></ul></ul><ul><ul><li>Simulation of exciton diffusion </li></ul></ul><ul><li>Conclusion </li></ul>
  10. 10. Photonic Properties of Quasi-random Nanostructures Nanoporous Anodic Alumina: a quasi-random strucuture Photonic Properties??? (e.g. photonic band gap) Universitat d’Estiu URV. July 2011.
  11. 11. Photonic Properties of Quasi-random Nanostructures Numerical Method Computational Domain FDTD L Variables: Pore (scatterer radius): r Domain Length: L Universitat d’Estiu URV. July 2011. Source Detector PML
  12. 12. Photonic Properties of Quasi-random Nanostructures Universitat d’Estiu URV. July 2011. Finite-Differnce Time-Domain Method (FDTD) Discretization of Maxwell Equations in Space and Time
  13. 13. Photonic Properties of Quasi-random Nanostructures Universitat d’Estiu URV. July 2011. Finite-Differnce Time-Domain Method (FDTD) Discretization of Maxwell Equations in Space and Time H 0 H 1 H 2 H 3 H 4 E 1/2 E 3/2 E 5/2 E 7/2 E 9/2 Important Aspect! Boundary Conditions at the Limits of The Computational Space
  14. 14. Photonic Properties of Quasi-random Nanostructures Universitat d’Estiu URV. July 2011. a  average interpore distance Averaging over N randomly chosen domains L = 12·a L = 16·a L = 20·a
  15. 15. Photonic Properties of Quasi-random Nanostructures Results: quasi-random structure on Si, r/a=0.35 TE Polarization Domain Length Universitat d’Estiu URV. July 2011.
  16. 16. Photonic Properties of Quasi-random Nanostructures Results: quasi-random structure on Si, r/a=0.35 TM Polarization Domain Length Universitat d’Estiu URV. July 2011.
  17. 17. Photonic Properties of Quasi-random Nanostructures Results: quasi-random structure on Si, L=19a Scatterer radius TE Polarization TM Polarization Universitat d’Estiu URV. July 2011.
  18. 18. Photonic Properties of Quasi-random Nanostructures Decreasing trend of the transmittance with  : Simulation of a fully random structure TE Polarization TM Polarization Universitat d’Estiu URV. July 2011.
  19. 19. Photonic Properties of Quasi-random Nanostructures Quasi-random crystals with metallic components. Au – Drude-Lorentz Model Good fit between λ=500nm-1000nm Vial et al., PRB 71, 085416 (2005) No scale invariance Universitat d’Estiu URV. July 2011.
  20. 20. Photonic Properties of Quasi-random Nanostructures Quasi-random crystals with metallic components. Triangular Lattice.  X Direction Quasi-random. r/a=0.05 Universitat d’Estiu URV. July 2011.
  21. 21. OUTLINE Universitat d’Estiu URV. July 2011. <ul><li>Introduction to Photonic Nanostructures </li></ul><ul><ul><li>Photonic Crystals/Photonic Quasicrystals/Random Nanostructures </li></ul></ul><ul><li>Photonic Properties of Quasi-random Nanostructures </li></ul><ul><ul><li>The Quasi-Random Structure </li></ul></ul><ul><ul><li>Numerical Methods </li></ul></ul><ul><ul><li>Results </li></ul></ul><ul><li>Light Trapping in Nanostructured Organic Solar Cells </li></ul><ul><ul><li>Scattering by subwavelength-sized nanostructuring </li></ul></ul><ul><ul><li>Simulation of light absorption by finite-element </li></ul></ul><ul><ul><li>Simulation of exciton diffusion </li></ul></ul><ul><li>Conclusion </li></ul>
  22. 22. Light Trapping in Nanostructured Organic Solar Cells Planar Heterojunction Universitat d’Estiu URV. July 2011. Organic Solar Cells: Morphologies h + e - h + e - h + e - ? h + e - Bulk Heterojunction Nanostructured Heterojunction Donor Acceptor Ex Ex Ex
  23. 23. Light Trapping in Nanostructured Organic Solar Cells Universitat d’Estiu URV. July 2011. Diffraction: a possible way for light trapping Incident Light Wavelength:  Diffracted Light Period: p p  
  24. 24. Light Trapping in Nanostructured Organic Solar Cells Universitat d’Estiu URV. July 2011. Diffraction: a possible way for light trapping Incident Light Wavelength:  Trapped Light Period: p p <    >90º
  25. 25. Light Trapping in Nanostructured Organic Solar Cells Universitat d’Estiu URV. July 2011. Nanostructuring Organic Solar Cells with Templates: Nanoporous Anodic Alumina 500nm 2µm
  26. 26. Light Trapping in Nanostructured Organic Solar Cells Universitat d’Estiu URV. July 2011. Nanostructuring Organic Solar Cells with Templates: Nanoporous Anodic Alumina 1 µm
  27. 27. Light Trapping in Nanostructured Organic Solar Cells Universitat d’Estiu URV. July 2011. Numerical Modeling: COMSOL ® <ul><li>RF Module: Maxwell Equations </li></ul><ul><li>Time-dependent and stationary </li></ul><ul><li>Possibility of evaluating absorption as a function of position </li></ul><ul><li>Connection with drift-diffusion and Poisson equations </li></ul><ul><li>1-D Periodicity (period 2  ) </li></ul><ul><li>P3HT and PCBM optical constants n and k . </li></ul><ul><li>Width: 4  m </li></ul>
  28. 28. Light Trapping in Nanostructured Organic Solar Cells Universitat d’Estiu URV. July 2011. <ul><li>Taking into account the exciton diffusion length (~10nm) </li></ul><ul><li>Four different size ranges: </li></ul><ul><li>i) 1.25nm    12.5 nm </li></ul><ul><li>ii) 20nm    100 nm </li></ul><ul><li>iii) 125nm    250 nm </li></ul><ul><li>iii) 400nm    2  m </li></ul>Unit Cell 2a 10nm 20nm 10nm
  29. 29. Light Trapping in Nanostructured Organic Solar Cells Universitat d’Estiu URV. July 2011. Total Dissipated Power
  30. 30. Light Trapping in Nanostructured Organic Solar Cells Universitat d’Estiu URV. July 2011. Reference Cells Bilayer – Planar Heterojunction Effective Medium: n, k: average of P3HT and PCBM 20nm 20nm 10nm 20nm 10nm
  31. 31. Light Trapping in Nanostructured Organic Solar Cells Universitat d’Estiu URV. July 2011. Absorption Results. Features much smaller than wavelength. 100nm 1  m Effective Medium a=1.25nm a=12.5nm
  32. 32. Light Trapping in Nanostructured Organic Solar Cells Universitat d’Estiu URV. July 2011. Absorption Results. Features smaller than wavelength.
  33. 33. Light Trapping in Nanostructured Organic Solar Cells Universitat d’Estiu URV. July 2011. Absorption Results. Feature size the order of wavelength. 100nm 1  m a=200nm a=250nm a=125nm
  34. 34. Light Trapping in Nanostructured Organic Solar Cells Universitat d’Estiu URV. July 2011. Absorption Results. Features bigger than wavelength. 100nm 1  m a=400nm a=2  m Bilayer
  35. 35. Light Trapping in Nanostructured Organic Solar Cells Universitat d’Estiu URV. July 2011. Absorption Results
  36. 36. Light Trapping in Nanostructured Organic Solar Cells Universitat d’Estiu URV. July 2011. Exciton Diffusion. Ex Ex How much absorbed light contributes to current? IPCE  Excitons reaching the D/A interface vs incident photons h  h  Ex Ex
  37. 37. Light Trapping in Nanostructured Organic Solar Cells Universitat d’Estiu URV. July 2011. Exciton Diffusion. Planar Heterojunction (Reference) Exciton Concentration (  inc =540nm) 40nm 100nm
  38. 38. Light Trapping in Nanostructured Organic Solar Cells Universitat d’Estiu URV. July 2011. Exciton Diffusion. Smallest features (a=12.5nm) Exciton Concentration (  inc =540nm) 40nm 100nm
  39. 39. Light Trapping in Nanostructured Organic Solar Cells Universitat d’Estiu URV. July 2011. Exciton Diffusion. Wavelength-order features (a=250 nm) Exciton Concentration (  inc =540nm) 40nm 200nm
  40. 40. Conclusion <ul><li>Photonic Quasi-Random Nanostructures: photonic band gap  other possible photonic properties (resonant cavities, 3D structures). </li></ul><ul><li>Absorption in Nanostructured Organic Solar Cells: light trapping for wavelength-order nanostructuring sizes. </li></ul><ul><li>Exciton Diffusion in Organic Solar Cells: favored by the smallest nanostructuring sizes. </li></ul>Universitat d’Estiu URV. July 2011.
  41. 41. Acknowledgments <ul><li>Seniors: </li></ul><ul><li>Pilar Formentín </li></ul><ul><li>Students: </li></ul><ul><li>Abel Santos </li></ul><ul><li>Collaboration with: </li></ul><ul><li>Enric Garcia-Caurel </li></ul><ul><li>École Polytechnique Paris </li></ul><ul><li>Sabine Portal </li></ul><ul><li>Universitat de Barcelona </li></ul><ul><li>Mar Sánchez </li></ul><ul><li>Ignacio Moreno </li></ul><ul><li>Universidad Miguel Hernández </li></ul>Universitat d’Estiu URV. July 2011.

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