Organic Electronics

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Organic Electronics

• Yousof Mortazavi
• VLSI Course Presentation
• December 2004

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References

• L. Ficke,M. Cahay, The bright future of organic
  LEDs, IEEE Potentials, Jan. 2004.
• J. N. Bardsley, International OLED technology
  roadmap, IEEE J. Selected Topics in Quantum
  Electronics, Vol. 10, No. 1, Feb. 2004.
• T. Y. Winarski, Patenting bright ideas the
  current state of patented technology in the field
  of organic light emitting diodes, IEEE Circuits
  and Devices Magazine, Apr. 2004.
• T. Shimoda, T. Kawase, All-polymer thin film
  transistor fabricated by high-resolution ink-jet
  printing, In Proceedings IEEE International
  Solid-State Circuits Conference, 2004.
• S. Forrest, P. Burrows, M. Thompson, The dawn of
  organic electronics, IEEE Spectrum, Aug. 2000.
• G. Schmid, et al., Organic electronics
  perspectives towards applications, ISSCC 2004.
• K. Nomoto, et al., A bottom-contact
  organic-thin-film-transistor for flexible display
  application, ISSCC 2004.
• M. G. Kane, Organic electronics what is it good
  for?, ISSCC 2004.
• D. Gundlach, et al., High-mobility, low voltage
  organic thin film transistors, IEDM 1999.

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Outline

• Motivations
• OLED Fundamentals
• OTFTs
• Advantages of Organic Electronics
• Applications
• OLEDs for Color Displays
• Challenges

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Motivations

• Microelectronics vs. Macroelectronics
• Microelectronics try to make smaller transistors
  to reduce cost and boost performance
• Macroelectronics reduce costs in order build
  ever larger devices, with acceptable performance
• Thin Film Transistors
• Active layer is silicon (a-Si) deposited on glass
  .
• For high mobilities, a-Si can be crystallized
  (p-Si) by laser-pulses at high temperatures.
• Cant easily use flexible substrates, such as
  plastics
• Organic Thin Film Transistors
• Organic semiconductors were discovered in 1987.
• Organic compounds are a natural match for plastic
  substrates.
• Use of polymers allows large-areas to be coated
  and patterned without conventional
  photolithography (e.g. spin-coaters and ink-jet
  printers).
• Organic TFTs may be made large or small (30 nm _at_
  Cornell U.)

Kane (ISSC04)
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OLED Fundamentals

• In 1987, Tang, et al. published Organic
  electroluminescent diodes.
• Currently more than 500 U.S. Patents have been
  issued on organic electronics.
• Challenges
• Choice of anode for ohmic contact (for low
  voltage devices)
• Diffusion of In, O into HTL ? HIL interface
  between ITO and HTL
• Protection from oxygen and water ? encapsulation

Cathode
Metal
ETL
HTL
ITO-Covered Substrate
Transparent Anode
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OTFT (OFET)

• Typical OTFT
• Bottom gate, inverted staggered structure
• Pentacene (C22H14) active
• Gate dielectric
• SiO2
• PMMA
• PVP
• OTFTs operation
• accumulation
• depletion
• Mobilities as high as 1 cm2/Vs has been obtained
  with Ion/Ioff ratio of 108.
• Very low fabrication temperature (lt60C) allows
  use of cheap plastics.
• Conventional MOSFET equations are used to model
  OTFTs however, mobility is voltage dependent.

PentaceneFormula C22H14Metling Point
300COptical Bandgap 2.8 eV
SAM dielectric to reduce gate thickness to 2.5
nm Schmid et al.
W/L 240 µm/44 µm Tgate 1700 Å.
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Advantages of Organic Electronics

• Thin, lightweight, flexible displays
• Low voltage, low power, emissive source
• High brightness
• Broad color gamut
• Wide viewing angle (180º)
• Good contrast
• High resolution (lt5 µm pixel size)
• Fast switching (1-10 µs)
• Low bill of materials and fabrication cost
• Bardsley, 2004

Dupont Thermal Multilayer Transistor Process
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Applications

• Flexible Displays
• PM-OLED
• AM-OLED
• Wearable Displays
• Sensor Arrays
• Artificial Skin
• Gas Sensors
• RF ID Tags
• Inductors
• Capacitors
• X-ray imaging panels
• Solid-State Lighting

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OLEDs for Color Displays
Forrest, et al.
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Challenges

• Choice of electrodes
• Encapsulation
• Reliability and yield
• Lifetime
• Brightness control with feedback
• Particle migration control with AC driver

A. Giraldo, et al.
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Thank You