1. Plasmonic Effects in Organic Solar Cells Wei E.I. Sha, Wallace C.H. Choy, Weng Cho Chew Department of Electrical and Electronic Engineering The University of Hong Kong Speaker: Wei E.I Sha Email: wsha@eee.hku.hkwsha@eee.hku.hk PIERS 2012 in Kuala Lumpur, Malaysia

2. Plasmonic Effects in Organic Solar Cells (1) organic solar cell monocrystalline silicon solar cellamorphous/polycrystalline silicon solar cell Advance of solar cell technology

3. Plasmonic Effects in Organic Solar Cells (2) Thin-film organic solar cell low-cost processing mechanically flexible large-area application environmentally friendly Хlow exciton diffusion length Хlow carrier mobility

4. Plasmonic Effects in Organic Solar Cells (3) optical absorption exciton diffusion charge separation charge collection Working principle

5. Plasmonic Effects in Organic Solar Cells (4) Why optical enhancement? The thickness of the active layer must be smaller than the exciton diffusion length to avoid bulk recombination. As a result, the thin-film organic solar cell has poor photon absorption or harvesting. Plasmonic solar cell is one of emerging solar cell technologies to enhance the optical absorption.

6. Plasmonic Effects in Organic Solar Cells (5) Lambert’s cosine law finite-difference frequency-domain method (TE & TM) PBC PML Au PEDOT:PSS Au W.E.I. Sha, W.C.H. Choy, and W.C. Chew, Opt. Lett., 36(4), 478-480, 2011. Small molecule organic solar cell

7. Plasmonic Effects in Organic Solar Cells (6) X.H. Li, W.E.I. Sha, W.C.H. Choy, etc, J. Phys. Chem. C, 2012. In Press. doi: 10.1021/jp211237c Plasmonic band edge boosted optical enhancement (theory and experiment)

8. Plasmonic Effects in Organic Solar Cells (7) VIE-FFT method (BiCG-STAB) enhancement factors 2 fold increase in total absorption! Near-fieldFar-field directional scattering k k W.E.I. Sha, W.C.H. Choy, Y.P. Chen, and W.C. Chew, Appl. Phys. Lett., 99(11), 113304, 2011. active layer Bulk heterojunction polymer solar cell

9. Plasmonic Effects in Organic Solar Cells (8) nanoparticles in spacer layernanoparticles in active layer Comparisons to experimental results C.C.D. Wang, W.C.H. Choy, etc, J. Mater. Chem., 22, 1206-1211, 2011. D.D.S. Fung, L.F. Qiao, W.C.H. Choy, etc, J. Mater. Chem., 21, 16349-16356, 2011.

10. Plasmonic Effects in Organic Solar Cells (9) good spectral overlap Hybrid plasmonic system 4 fold increase in total absorption! W.E.I. Sha, W.C.H. Choy, and W.C. Chew, Opt. Express, 19(17), 15908-15918, 2011.

11. Plasmonic Effects in Organic Solar Cells (10) Multiphysics modeling using unified finite difference method W.E.I. Sha, W.C.H. Choy, Y.M. Wu, and W.C. Chew, Opt. Express, 20(3), 2572-2580, 2012. Maxwell’s equation generation rate semiconductor equations

12. Plasmonic Effects in Organic Solar Cells (11) Beyond optical absorption enhancement: facilitating hole collection!

13. Acknowledgement Thanks for your attention!