Size Control Over Semiconducting Materials for Organic Electronics

1
Size Control Over Semiconducting Materials for
Organic Electronics

• Collen Leng1, Jeffrey M. Mativetsky1, John E.
  Anthony2, Yueh-Lin Loo1
• Chemical and Biological Engineering, Princeton
  University
• Chemistry, University of Kentucky

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Why Organic Electronics?

• Low cost solution processing
• Mechanical flexibility
• Lightweight

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Increasing Efficiencies of Organic Solar Cells

• Increase charge transport
• molecular packing and orientation
• Increase surface area between donor and acceptor
  materials

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Project Goal

• Make organic semiconducting nanowires
• Size control of electron acceptors and donors
• Increase interfacial surface area
• Wire-like structures for efficient charge
  transport
• Method templating using aluminum oxide membranes

Scanning electron micrographs of aluminum oxide
membrane
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Set-up

• Allow solution to penetrate membrane from I-tube
• Cap off I-tube to sustain internal pressure and
  prevent the solution from completely flowing
  through membrane

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Nanowires Inside Porous Membrane
Cross-sectional views
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Extracting Nanowires

• NaOH dissolve membrane, free nanowires
• Options for removing NaOH and alumina
• 1.Vacuum filtration
• 2. Centrifuge

Nanowire mixture
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Extracted Nanowires
Bundles of ethyl-TES-ADT nanowires
Close-up of ethyl-TES-ADT nanowires
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Nanowires on Glass

• High-density nanowires on glass

Close-up of wires
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TEM Electron Diffraction

• Occasional polycrystalline structures

Bundle of ethyl-TES-ADT nanowires in a
transmission electron microscope (TEM)
Electron diffraction of nanowires to the left
shows some polycrystallinity
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PCBM and P3HT Nanowires?

• Nanowires of other materials can be made.
• 6,6phenyl-C61-butyric acid methyl ester (PCBM)
  nanowires
• - the most commonly
• used electron acceptor

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Future Plans

• Structural studies
• Thinner nanowires (10 - 20 nm diameters) to
  better match exciton diffusion lengths
• Crystallization to help electron transport
• Structural characterization (Grazing Incidence
  X-ray Diffraction)
• Photovoltaic studies
• Map photoexcited charge generation at
  donor-acceptor nanowire interfaces (Kelvin Probe
  Force Microscopy, Photoluminescence)
• Nanowire-based solar cells

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Acknowledgements

• Professor Loo
• Jeff Mativetsky
• Gerry Poirier
• Loo Lab
• PEI/Siebel Energy Grand Challenge