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Organic Electronics

Yousof Mortazavi

VLSI Course PresentationDecember 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. SelectedTopics in Quantum Electronics, Vol. 10, No. 1, Feb. 2004.

T. Y. Winarski, Patenting bright ideas; the current state of patentedtechnology in the field of organic light emitting diodes, IEEE Circuits andDevices Magazine, Apr. 2004.

T. Shimoda, T. Kawase, All-polymer thin film transistor fabricated by high-

resolution ink-jet printing, In Proceedings IEEE International Solid-StateCircuits 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 boostperformance Macroelectronics: reduce costs in order build

ever larger devices, with acceptableperformance

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 becoated and patterned without conventionalphotolithography (e.g. spin-coaters and ink-jetprinters).

Organic TFTs may be made large or small(30 nm @ Cornell U.)

Cost/area Cost/function

Bulk Si ICs $10K/ft2100 cents/transistor

a-Si TFTs onglass $150/ft2

1 mcents/transistor

PrintedOrganic TFTs $30/ft2

200 cents/transistor

[Kane (ISSC04)]

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OLED Fundamentals

In 1987, Tang, et al.published Organicelectroluminescentdiodes.

Currently more than 500U.S. Patents have been

issued on organicelectronics. Challenges:

Choice of anode for ohmiccontact (for low voltagedevices)

Diffusion of In, O into HTL HIL interface betweenITO and HTL

Protection from oxygen andwater encapsulation

ITO-Covered Substrate

HTL

ETL

Metal

Cathode

Transparent Anode

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OTFT (OFET)

Typical OTFT:

Bottom gate, inverted staggeredstructure Pentacene (C22H14) active Gate dielectric

SiO2 PMMA PVP

OTFTs operation: accumulation depletion

Mobilities as high as 1 cm2/Vs hasbeen obtained with Ion/Ioff ratio of108.

Very low fabrication temperature

(

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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 (~180) Good contrast High resolution (

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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