Organic Semiconductor Technology

ORGANIC TRANSISTOR TECHNOLOGY

SAMI UR REHMAN 1

Thin-film transistor (TFT) Sony Technology

• Video link: http://www.youtube.com/watch?v=mtLfJ-mFsA8

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Organic Vs Inorganic Semiconductors

• Silicon based inorganic material

• Covalently bonded crystals

Polymer based organic material

Van der Waals bonded crystals

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Advantages of organic electronics

• Organic electronics are lighter, more flexible

• Low-Cost Electronics

– No vacuum processing

– No lithography (printing)

– Low-cost substrates (plastic, paper, even cloth…)

– Direct integration on package (lower insertion costs)

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Comparison of organic and Si based technologies

Cost

Fabrication Cost

Device Size

Material

Required Conditions

Process

Organic Electronic

$5 / ft2

Low Capital

10 ft x Roll to Roll

Flexible Plastic Substrate

Ambient Processing

Continuous Direct Printing

Silicon

$100 / ft2

$1-$10 billion

< 1m2

Rigid Glass or Metal

Ultra Cleanroom

Multi-step Photolithography

Sara Saedinia

University of California, Irvine

Courtesy:

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Disadvantages of organic technology

• Conductive polymers have high resistance and therefore are not good conductors of electricity.

• Because of poor electronic behavior (lower mobility), they have much smaller bandwidths.

• Shorter lifetimes and are much more dependant on stable environment conditions than inorganic electronics would be.

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• One of the biggest applications of organic transistors right now.

Organic TFTs may be used to drive LCDs and potentially even OLEDs, allowing integration of entire displays on plastic.

• Brighter displays

• Thinner displays

• More flexible

Displays (OLED)

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Solar Cells

• The light falls on the polymer

• Electron/hole is generated

• The electron is captured C60

• The electricity is passed by the nanotube

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Organic Thin Film Transistors (OTFTs)

Organic material Organic material

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An Example of an I-V of OTFTs

Lg = 20 µm W = 220 µm 400 nm SiO2

50 nm organic

Courtesy: 10

Equipment and materials

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PEDOT:PSS

• PEDOT:PSS or Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) is a polymer mixture of two ionomers.

• Commercially available PEDOT:PSS products are produced by Heraeus with the trade name Clevios and by AGFA with the trade nameOrgacon.

• Heraeus Clevios™ P VP AI 4083 - one of the most commonly used PEDOT:PSS formulations for spin coated OPVs and OLEDs. Spins to ~40 nm at 5000 rpm.

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PEDOT:PSS

Resistivity: 500-5000 ohm cm

Solid content: 1.3 to 1.7% Na content: 400 ppm maximum Sulfate content: 40 ppm maximum Viscosity: 5-12 mPa s PEDOT:PSS ratio: 1:6 Usage: <100 μl per standard (20 mm x 15 mm) substrate.

Price: £149 per 100ml

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Encapsulation Epoxy

• Encapsulation epoxy can be used as an adhesive for organic light-emitting diodes and organic photovoltaics without damaging the polymer or cathode.

• In conjunction with a glass coverslip it can provide a robust barrier against ingress of oxygen and water to provide extended lifetimes for measurement and storage.

• Cost: £69 per 10 ml

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Glass substrate(Silicon TFT)

• Glass substrates can be used to prepare organic photovoltaic cells and organic light emitting diodes.

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Plastic Substrate

• Glass substrates (silicon TFT). are difficult to bend.

• However, a display with organic transistors on a plastic substrate would be completely flexible. Such a display could also be dropped without breaking, rolled up, or folded.

• PET, PEN or Kapton are the examples of flexible substrates

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Dimatix materials printer dmp-2800

• The DMP-3000 has a printable area of 300 x 300 mm with a positional accuracy and repeatability of ± 5 µm and ± 1 μm, respectively.

• The DMP-3000 uses a temperature controlled vacuum platen to accurately register, maintain and thermally manage substrates during printing.

• These substrates include plastic, glass, ceramics, and silicon, as well as flexible substrates from membranes, gels, and thin films to paper products.

• Cost: US 49,000$ (including shipping cost)

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