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Organic Semiconductors. ECEN 3913 Cherwa Vang. What are Organic Semiconductors. Organic material with semiconductor properties. http://perepichka-group.mcgill.ca/images/organics2.png. https://en.wikipedia.org/wiki/File:Flexible_display.jpg. What are Organic Materials?.
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Organic Semiconductors ECEN 3913 Cherwa Vang
What are Organic Semiconductors • Organic material with semiconductor properties. http://perepichka-group.mcgill.ca/images/organics2.png https://en.wikipedia.org/wiki/File:Flexible_display.jpg
What are Organic Materials? • Chemical compounds that include carbon. Often also includes H, O, N. https://en.wikipedia.org/wiki/File:Methane-2D-stereo.svg https://en.wikipedia.org/wiki/File:Glucose_chain_structure.svg
History • 1862 - Henry Letheby obtained a partly conductive material • 1950s - researchers discovered that polycyclic aromatic compounds formed semi-conducting salts • 1954 - perylene-iodine complex discovered, conductivity of 0.12 S/cm • 1972 - researchers found metallic like conductivity in Tetrathiafulvalene and Tetracyanoq http://www.nature.com/nature/journal/v453/n7198/fig_tab/453996a_F1.html
History (cont) • 1977 - Shirakawa et al. reported high conductivity in oxidized and iodine-doped polyacetylene. Received the 2000 Nobel prize in Chemistry for "The discovery and development of conductive polymers“ • 1987 - The first diode device was reported at Eastman Kodak by Ching W. Tang and Steven Van Slyke • 1987, Koezuka and co-workers reported the first organic field-effect transistor (OFET) • 1990s - J. H. Burroughes, high efficiency green light emitting polymer (OLED)
Applications • Biodegradable electronics • Organic Field effect transistor (OFET) • Organic Light Emitting Diodes (OLED) https://en.wikipedia.org/wiki/File:OLED_EarlyProduct.JPG
Materials • Common organic transistors are made of aromatic and conjugated pi-electron systems • Examples • Benzene • Pentacene • Pentadiene https://en.wikipedia.org/wiki/File:Pentacene-3D-balls.png https://en.wikipedia.org/wiki/File:1,3-pentadien.svg https://en.wikipedia.org/wiki/File:Benzene-6H-delocalized.svg
Mechanics • Why aromatic and conjugated molecules?
Mechanics • Non aromatic molecules Ethylene Acetylene Ethane http://www.inorganicventures.com/element/hydrogen http://www.inorganicventures.com/element/carbon https://en.wikipedia.org/wiki/File:Ethan_Lewis.svg https://en.wikipedia.org/wiki/File:Ethylene-CRC-MW-dimensions-2D.png https://en.wikipedia.org/wiki/File:Acetylene-CRC-IR-dimensions-2D.png
Mechanics Benzene molecule • Aromatic molecules • Electrons move around carbon atoms, similar to silicon • More efficient with longer chains of benzene rings. https://en.wikipedia.org/wiki/Aromatic https://en.wikipedia.org/wiki/File:Benzene-aromatic-3D-balls.png
Electron Flow • Electron flows through the carbon chain
Rubrene • Used in OLED, and OFET • Highest organic mobility 40 cm2/(V·s) https://en.wikipedia.org/wiki/File:Rubrene-3D-spacefill.png https://en.wikipedia.org/wiki/File:Rubrene.svg
Pentacene • Five Benzene Rings fused together • Higher mobility than amorphous silicon 5.5 cm2/(V·s) • Most studied organic transistor • Why so popular? https://en.wikipedia.org/wiki/File:Pentacene.svg
Pentacene mixed compounds • Pentacene-quinone – oxidized insulating material • Buckminsterfullerene - Organic Photovotaic cells • Terphenyl – Doping material, proved successful in MASERs. https://en.wikipedia.org/wiki/File:Buckminsterfullerene-perspective-3D-balls.png http://www.caslab.com/6-13-pentacenequinone_CAS_3029-32-1/
OFETs • Similar functions to MOSFETs (A) & MESFETs (B) • Takes on the Thin Film Transistor (TFT) model (C) https://en.wikipedia.org/wiki/File:3_FET_strucutre.png
TFT Architecture • Why use TFT architecture? https://en.wikipedia.org/wiki/File:TFT_DIA_BIAS.png
OLED • TFT Architecture • Different Organic materials for different colors http://electronics.howstuffworks.com/oled3.htm
OLED • Different Layers http://www.nature.com/nmat/journal/v12/n7/fig_tab/nmat3622_F1.html http://provideocoalition.com/aadams/story/sony_the_non-technical_technical_guide_to_oled_technology/
Why Organic transistors? http://hyperphysics.phy-astr.gsu.edu/hbase/solids/sili2.html http://www.inorganicventures.com/element/germanium http://www.inorganicventures.com/element/arsenic http://www.inorganicventures.com/element/gallium http://www.inorganicventures.com/element/silicon http://www.inorganicventures.com/element/oxygen
Organic Transistors Pros: • Future material/production cost • Flexible & lightweight • Higher viewing angle • Brighter • Better Darker colors • Higher response time http://www.engadget.com/2013/05/19/lg-5-inch-flexible-oled/ http://www.smh.com.au/digital-life/hometech/tvs-get-bigger-bolder-smarter-at-ces-20130109-2cg2a.html
Organic Transistors Cons: • Present production cost • Color balance • Life expectancy • Water damage https://en.wikipedia.org/wiki/File:Oled_display_alterung.jpg https://en.wikipedia.org/wiki/File:Nexus_one_screen_microscope.jpg