Size Control Over Semiconducting Materials for Organic Electronics

Collen Leng1, Jeffrey M. Mativetsky1, John E. Anthony2, Yueh-Lin Loo1

1.Chemical and Biological Engineering, Princeton University2.Chemistry, University of Kentucky

Why Organic Electronics?

• Low cost solution processing

• Mechanical flexibility

• Lightweight

http://images.sciencedaily.com/2008/02/080206154631-large.jpg

http://ww1.prweb.com/prfiles/2009/10/04/167139/FlexibleOrganicElectronicsdisplay.jpg

Increasing Efficiencies of Organic Solar Cells

• Increase charge transport – molecular packing and orientation

• Increase surface area between donor and acceptor materials

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

Project Goal

Scanning electron micrographs of aluminum oxide membrane

Cross-section of membrane Top view of membraneCross-section (zoomed in)

300 μm 2 μm 2 μm

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

I-tubemembrane

Viton O-rings

Teflon gasket

solution

closed air

rubber stopperElectron donor: ethyl-TES-ADT

Nanowires Inside Porous Membrane

Cross-sectional views

15 μm 2 μm

10 μm15 μm

Extracting Nanowires

NaOH: dissolve membrane, free nanowires

Options for removing NaOH and alumina:

1.Vacuum filtration

2. Centrifuge

Nanowire mixture

Viton O-rings

Air out

Polycarbonate filter

Fritted glass

Extracted Nanowires

10 μm

Bundles of ethyl-TES-ADT nanowires

Close-up of ethyl-TES-ADT nanowires

1 μm

Nanowires on Glass

High-density nanowires on glass:

Close-up of wires:

30 μm

100 μm

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

PCBM and P3HT Nanowires?

Nanowires of other materials can be made.

[6,6]phenyl-C61-butyric acid methyl ester (PCBM) nanowires:

- the most commonlyused electron acceptor

3 μm

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

Acknowledgements

• Professor Loo

• Jeff Mativetsky

• Gerry Poirier

• Loo Lab

• PEI/Siebel Energy Grand Challenge