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IMPROVING EFFICIENCY OF ORGANIC PHOTOVOLTAICS

IMPROVING EFFICIENCY OF ORGANIC PHOTOVOLTAICS. Nanjia Zhou Northwestern University. 11/08/12. 1. http://econews.com.au/news-to-sustain-our-world/un-takes-hard-look-at-20-years-since-rio-earth-summit / http :// planetark.org / enviro -news/item/53111

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IMPROVING EFFICIENCY OF ORGANIC PHOTOVOLTAICS

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  1. IMPROVING EFFICIENCY OF ORGANIC PHOTOVOLTAICS Nanjia Zhou Northwestern University 11/08/12

  2. 1 http://econews.com.au/news-to-sustain-our-world/un-takes-hard-look-at-20-years-since-rio-earth-summit/ http://planetark.org/enviro-news/item/53111 http://thecityfix.com/blog/choking-on-smog/ NanjiaZhou Chang/Marks Group

  3. 2 NanjiaZhou International Energy Outlook 2011 Chang/Marks Group

  4. 3 03/23/2012 International Energy Outlook 2011

  5. 4 Clean, renewable Reduced dependence on Fossil Fuels Distributed generation Proven, reliable Modularity and Scalability Photo courtesy: NREL 03/23/2012 Department of Materials Science

  6. 5 Photo courtesy: NREL NanjiaZhou http://www.heliatek.com/technologie/organische-photovoltaik/?lang=en Chang/Marks Group

  7. 6 Photo courtesy: NREL NanjiaZhou National Renewable Energy Laboratory (NREL) Chang/Marks Group

  8. 7 Mitsubishi Chemical announced a certified 10.0% cell Photo courtesy: NREL NanjiaZhou National Renewable Energy Laboratory (NREL) Chang/Marks Group

  9. 8 Photo courtesy: NREL NanjiaZhou Chang/Marks Group

  10. 9 Photo courtesy: NREL 03/23/2012 Department of Materials Science

  11. 10 The Nobel Prize in Chemistry 2000 Alan J. Heeger, Alan G. MacDiarmid and Hideki Shirakawa "for the discovery and development of conductive polymers". Photo courtesy: NREL NanjiaZhou http://www.nobelprize.org/nobel_prizes/chemistry/laureates/2000/press.html Chang/Marks Group

  12. 11 Common conducting polymers Soliton Polaron Bipolaron NanjiaZhou Chang/Marks Group

  13. 12 1. Organic Field Effect Transistor (OFET) Source Drain Organic layer + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Insulating layer - - - - - - - - - - - - - - - - - - - Gate -30V NanjiaZhou Chang/Marks Group

  14. 13 1. OFET NanjiaZhou Chang/Marks Group

  15. 14 1. OFET Photo courtesy: NREL NanjiaZhou Chang/Marks Group

  16. 15 2. Organic Light Emitting Diode (OLED) 07 08 09 10 14-15.4’’ WXGA 21-23’’ UXGA 40’’/42’’ Full HD 3.5’’ WQVGA*3D 4.8’’WVGA 7.0’’ WSVGA 4.1’’ WQVGA 2.0，2.2，2.4，2.6’’ QVGA 2.5’’ QVGA(Landscape) 2.6，2.8，3.0’’ LQVGA 3.1’’ WVGA NanjiaZhou Chang/Marks Group

  17. 16 2. OLED 1. Brighter, thinner, lighter, faster 2. Bright from all viewing angles 3. Need less power to run 4. A lot cheaper to produce 5. Expanding memory capability - coating new layer on top of existing one 6. Wider temperature range OLED is a display device that sandwiches carbon based films between the two electrodes and when voltage is applied creates light. NanjiaZhou Chang/Marks Group

  18. 17 2. OLED NanjiaZhou Chang/Marks Group

  19. 18 3. OPV NanjiaZhou Chang/Marks Group

  20. 19 3. OPV NanjiaZhou HolgerSpanggaard, Frederik C. Krebs, Solar Energy Materials and Solar Cells, Volume 83, Issues 2–3, 15 June 2004, Pages 125-146 Chang/Marks Group

  21. 20 OPV vs. Silicon Cell Photo courtesy: NREL NanjiaZhou Harvard Science in the News: https://sitn.hms.harvard.edu/sitnflash_wp/2012/03/issue113/ Chang/Marks Group

  22. 21 OPV vs. Silicon Cell Narrower absorption range than silicon cell Lower current output Donor: Electron rich material Acceptor: Electron poor material Bulk Heterojunction: Blend of D/A materials forming a heterogeneous mixture Domain size NanjiaZhou Li et al. Nature Photonics 6, 153–161, (2012) Chang/Marks Group

  23. 22 Characterization Short circuit Open circuit Forward bias Reverse bias NanjiaZhou Kietzke, Advances in OptoElectronics Volume 2007 (2007), Article ID 40285 Chang/Marks Group

  24. 23 NU Characterization • Class A Solar Cell Analyzer • AM 1.5G simulated light • Scan area: 5 x 5 cm • Light and dark evaluation • Series resistance evaluation • Xenon lamp with an adjustable intensity of 850 - 1150 W/m2 • Calibrated with KG3-filtered Si standard from NREL. Spectral mismatch = 1.00 • Spectral Response • Examines wavelengths from 400 - 1100 nm • Includes 15 filters in this range • Circulating Bath • Cell test temperature variable from -15C to +75C NanjiaZhou Chang/Marks Group

  25. 24 ORGANIC PHOTOVOLTAICS Cathode – Conventional cell Low work function metal: Ca/Al (Anode – Inverted Cell High work function metal: Ag/Au) Cathode IFL – LiF, n-type semiconductors: ZnO, TiO2 Active Layer: blend of donor and acceptor materials Anode IFL: PEDOT:PSS P-type semiconductor: NiO, WO3, MoO3, V2O5 graphene oxide Transparent conductive substrate – ITO, Carbon based material NanjiaZhou Chang/Marks Group

  26. 25 ORGANIC PHOTOVOLTAICS μED μCT μCC NanjiaZhou Chang/Marks Group

  27. 26 ORGANIC PHOTOVOLTAICS STRATEGIES FOR EFFICIENCY ENHANCEMENT • Band Gap Tuning: • Lower band gap to raise Jsc. • Higher IP polymers and lower EA acceptors to reduce energy loss during charge separation. • Morphology Control: • Domain sizes comparable to exciton diffusion length • Efficient carrier transport • Experimentally: solvent, additive, processing conditions, and self organizing properties of materials • Photon Management: • Alter device architecture to focus photo absorption in active layer • Potentially reduce active layer thickness for higher IQE • Ordered Heterojunction: • Donor/acceptor form interdigitated morphology within nanometer scale • Direct pathways of donor/acceptor to electrodes Decrease LUMO-LUMO offset Nelson, J. Materials Today2011, 14, 462–470. Li, G.; Zhu, R.; Yang, Y. 2012, 1–9. Kang, M.-G.; Xu, T.; Park, H. J.; Luo, X.; Guo, L. J. Adv. Mater.2010, 22, 4378. NanjiaZhou Chang/Marks Group

  28. 27 RESEARCH OUTLINE Band Gap Tuning Morphology Control Photon Management Novel Device Architecture Materials Development Morphology-Carrier Transport Relationship Nanowire, Tandem, Hybrid, etc. Plasmonic Structure Novel high efficiency donor-type polymers, study of device characteristics Processing conditions; Solvent choice; Polymer stacking; Characterization Nanoscale patterning of polymer active layer surface. Photonic and plasmonic enhancement of photocurrent Tandem device to enhance light harvesting; Optimize electron/hole transport NanjiaZhou Chang/Marks Group

  29. Morphology Carrier Transport Relationship Control of nanoscale morphology: Domain size variation NanjiaZhou Chang/Marks Group

  30. 28 BILAYER VS. BHJ NanjiaZhou Chang/Marks Group

  31. 29 EFFECT OF PROCESSING CONDITIONS Annealing Treat, N. D., Brady, M. A., Smith, G., Toney, M. F., Kramer, E. J., Hawker, C. J. and Chabinyc, M. L. (2011), Interdiffusion of PCBM and P3HT Reveals Miscibility in a Photovoltaically Active Blend. Adv. Energy Mater., 1: 82–89. doi: 10.1002/aenm.201000023 NanjiaZhou Chang/Marks Group

  32. 30 EFFECT OF PROCESSING CONDITIONS Solvent choice NanjiaZhou Lee et al. J. Am. Chem. Soc. 130, 3619 (2008) Chang/Marks Group

  33. 31 CRYSTALLINITY AND PACKING NanjiaZhou Huang et al. J. Phys. Chem. C, 2012, 116 (18), pp 10238–10244 Chang/Marks Group

  34. 32 CHARACTERIZATION Atomic Force Microscope (AFM), Transmission Electron Microscope (TEM) Grazing Incidence Wide Angle X-ray Scattering (GIWAXS) NanjiaZhou Lu et al. Nature Communications 3, Article number: 795 Chang/Marks Group

  35. 33 PRECISE MANIPULATION OF DOMAIN SIZES High sensitivity of DIO PC71BM BTIBDT Increase DIO concentration 0 0.5% 1.0% 3.0% 10.0% NanjiaZhou N. Zhou, A. Guerrero, H. Heitzer, S. Lou et. al. Chang/Marks Group

  36. High Performance Donor Materials NanjiaZhou Chang/Marks Group

  37. 34 NanjiaZhou Li et al. Nature Photonics 6, 153–161, (2012) Chang/Marks Group

  38. 35 BTIBDT BASEDCOPOLYMERS • R1=2-hexyldecyl, R2=2-ethylhexyl; PCE=3.4% • R1=2-butyloctyl, R2=2-ethylhexyl; PCE=4.8% • R1=2-hexyldecyl, R2=n-dodecyl; PCE=5.5% • R1=2-butyloctyl, R2=n-decyl;PCE=3.3% • R1=n-octyl, R2=2-butyloctyl;PCE=1.6% NanjiaZhou Zhouet al. Adv. Mater., 24: 2242–2248 Chang/Marks Group

  39. 36 BTIBDT BASEDCOPOLYMERS Bithiophene Imide (BTI) and Benzodithiophene (BDT) Copolymers Inverted OPVs The electron deficiency of the BTI units leads to polymers with a low-lying HOMOs (~-5.6 eV). Inverted solar cells are fabricated to investigate the OPV performance of the BTI-based polymers and achieve power conversion efficiencies up to 5.5%, with substantial Vocs above 0.9 V which are among the highest Vocs reported to date for polymer/PCBM solar cells. NanjiaZhou Zhouet al. Adv. Mater., 24: 2242–2248 Chang/Marks Group

  40. 37 BTIBDT BASEDCOPOLYMERS Bithiophene Imide (BTI) and Benzodithiophene (BDT) Copolymers Inverted OPVs • Inverted architectures: ITO/ZnO/polymer:PC71BM/MoOx/Ag • Inverted structures avoid oxidation of low work-function cathodes, such as Al or Ca, and acidic PEDOT:PSS etching of ITO, both of which limit conventional devices. • ZnO is an excellent cathode interfacial layer due to its high electron mobility, excellent thermal stability, and hole-blocking properties. • MoOx conduction band (-2.60 eV) lies sufficiently above the donor LUMOs (-3.7 eV, estimated from the HOMOs and optical band gaps), to block electrons, while the low work function (-5.6 eV) forms a good anode contact with the donor polymers NanjiaZhou Zhouet al. Adv. Mater., 24: 2242–2248 Chang/Marks Group

  41. 38 BTIBDT BASEDCOPOLYMERS Device Performance Stability Stability J-V Curve EQE and UV-vis • Best deviceachievedwithout thermal annealing • Initial drop due tomicrostructuralreorganization NanjiaZhou Zhouet al. Adv. Mater., 24: 2242–2248 Chang/Marks Group

  42. 39 BTIBDT BASEDCOPOLYMERS Conventional Device and SCLC measurement Conventional Device Performance Space charged limited current (SCLC) measurement ITO/PEDOT:PSS/polymer/Au Hole mobilities OTFT: 1.2 × 10-4and2.8 × 10-4 cm2V-1s-1 SCLC: 5.5 × 10-5 and 1.9 × 10-4 cm2V-1s-1 forP1andP2-based OTFTs and hole onlydevices, respectively NanjiaZhou Zhouet al. Adv. Mater., 24: 2242–2248 Chang/Marks Group

  43. 40 BTIBDT BASEDCOPOLYMERS Morphology Optimization • Without DIO, predominantly phase-segregated morphologies for the P1/PC71BM and P2/PC71BM blends. • The dark regions in the TEM images confirm large PC71BM domain sizes -- far larger than typical exciton diffusion lengths (~10 nm). Consequently, poor exciton dissociation and low current density are expected. • Significantly more homogeneous morphologies are found for P1/PC71BM and P2/PC71BM films processed with DIO. • nanosacle phase separation and bicontinuous interpenetrating networks result in more efficient charge separation and transport, leading to more than doubled Jsc. NanjiaZhou Zhouet al. Adv. Mater., 24: 2242–2248 Chang/Marks Group

  44. 41 BTIDTS BASEDCOPOLYMERS BTI and Dithienosilole (DTS) Copolymers Inverted OPVs NanjiaZhou X. Guo, N. Zhou, et al. JACS (2012) Chang/Marks Group

  45. 42 BTI BASEDCOPOLYMERS NanjiaZhou X. Guo, N. Zhou, et al. JACS (2012) Chang/Marks Group

  46. 43 BTI BASEDCOPOLYMERS NanjiaZhou X. Guo, N. Zhou, et al. JACS (2012) Chang/Marks Group

  47. 44 BTI BASEDCOPOLYMERS NanjiaZhou X. Guo, N. Zhou, et al. JACS (2012) Chang/Marks Group

  48. 45 BTIDTG COPOLYMERS NanjiaZhou X. Guo, N. Zhou, et al. JACS (2012) Chang/Marks Group

  49. 46 BTI/TPD-DTS COPOLYMERS NanjiaZhou X. Guo, N. Zhou, et al. JACS (2012) Chang/Marks Group

  50. 48 BTIDTS BASEDCOPOLYMERS BTI and Dithienosilole (DTS) Copolymers Inverted OPVs polymer/PC71BM DCB:DIO=100:0 polymer/PC71BM DCB:DIO=98:2 neat polymer P1 P2 π-π stacking distances are 3.6 Å and 3.5 Å for P1 and P2, respectively NanjiaZhou X. Guo, N. Zhou, et al. JACS (2012) Chang/Marks Group

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