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Organic Electronics

Organic Electronics. Yousof Mortazavi VLSI Course Presentation December 2004. References. L. Ficke,M. Cahay, “The bright future of organic LEDs”, IEEE Potentials , Jan. 2004.

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Organic Electronics

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  1. Organic Electronics Yousof Mortazavi VLSI Course Presentation December 2004

  2. 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.

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

  4. 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. • Can’t 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 @ Cornell U.) [Kane (ISSC’04)]

  5. 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

  6. 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 (<60°C) allows use of cheap plastics. • Conventional MOSFET equations are used to model OTFTs however, mobility is voltage dependent. Pentacene:Formula: C22H14Metling Point: 300°COptical 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.

  7. 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 (<5 µm pixel size) • Fast switching (1-10 µs) • Low bill of materials and fabrication cost [Bardsley, 2004] Dupont Thermal Multilayer Transistor Process

  8. 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

  9. OLEDs for Color Displays [Forrest, et al.]

  10. Challenges • Choice of electrodes • Encapsulation • Reliability and yield • Lifetime • Brightness control with feedback • Particle migration control with AC driver A. Giraldo, et al.

  11. Thank You

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