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Organic light emitting diodes for display technology Shamna - - PowerPoint PPT Presentation

Dec 22, 2023 847 likes •1.09k views

Organic light emitting diodes for display technology Shamna Shamsudeen MScTI - ZITI-Heidelberg University OLED ZITI, Uni Heidelberg Page1 Whats Light Light : Visible part of EM spectra . Ref:[1] Thermoluminescence: Eg: luminescence

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Organic light emitting diodes for display technology

Shamna Shamsudeen MScTI - ZITI-Heidelberg University

OLED ZITI, Uni Heidelberg Page1

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What’s Light

OLED ZITI, Uni Heidelberg Page2

Light:

Visible part of EM spectra .

  • Thermoluminescence: Eg:

luminescence produced due to the re-emission of previously absorbed energy.

  • Electroluminescence: Eg:

luminescence produced electrically, especially by the application of a voltage.

  • Photoluminescence: Eg:

luminescence produced due to the absorption of EM radiation.

  • Chemiluminescence:

luminescence produced due to energy released during a chemical reaction of a substance.

Ref:[1]

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OLED ZITI, Uni Heidelberg Page3

What is an LED(Light Emitting Diode)? & How it works?

  • Two-lead semiconductor light source.
  • Current flows (forward Bias) - the free Negative electrons are drawn to the

positive electrode. The holes move the other way.

  • The holes exist at a lower energy level than the free electrons. When electrons fall

into holes, it losses energy .

  • This energy is emitted in a form of a photon, which causes light.

Hole injection

Electron injection Light emission

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SLIDE 4

OLED ZITI, Uni Heidelberg Page4

Organic Semiconductors

  • In Organic semiconductors the emission of light occurs in organic(Carbon based)

semiconducting layers.

  • The organic semiconductors are used in Organic LEDs (OLED).

Alq3- Trisaluminium Phenylene vinylene HTL:Hole transporting layer ETL:Electron transporting EML:Emissive layer (EML). LUMO : lowest unoccupied molecular orbital HOMO: highest occupied molecular orbital

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SLIDE 5

OLED ZITI, Uni Heidelberg Page5

What’s OLED

  • An OLED is an electronic device made by placing a series of organic thin films

between two conductors.

  • A device that is 100 to 500 nanometers thick or about 200 times smaller than a

human hair.

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SLIDE 6

OLED ZITI, Uni Heidelberg Page6

Electro optic comparison of LED & OLED

Efficiency (utilization)

100% 50%

Maximum Brightness

Display Color Gamut Big Range Smaller than OLED

LED OLED

Pixels active- when needed Active always – waste of energy

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OLED Page7

Color Gamuts

The Color Gamut is the range of colors that a display can produce.

LED OLED

ZITI, Uni Heidelberg

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SLIDE 8

OLED ZITI, Uni Heidelberg Page8

Branches of OLEDs

There are two Principle Branches

1.Small molecular OLEDs:

Electron transport layer Hole transport layer Anode Substrate Emissive layer Electron Injection layer Cathode Hole Injection layer

  • Electrons injected from cathode, Holes injected

from anode.

  • Transport and radiative recombination of

electron hole pairs at emissive layer .

Light

Substrate Small molecules Vacuum Heater

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SLIDE 9

OLED ZITI, Uni Heidelberg Page9

Cathode Conducting polymer Anode Substrate Emissive polymer

  • Polymer light-emitting diodes (PLED), also light-emitting polymers

(LEP), involve an electroluminescent conductive polymer that emits light when connected to an external voltage.

2.Polymer light-emitting diodes :

Branches of OLEDs

WS-400 spin coater used to apply photoresist to the surface of a silicon wafer.

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SLIDE 10

OLED ZITI, Uni Heidelberg Page10

AMOLED TEOLED,TOLED PMOLED TOLED Addressing

Active

Passive

Types of OLED

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SLIDE 11

OLED ZITI, Uni Heidelberg Page11

Passive-Matrix OLED (PMOLED)

  • Perpendicular cathode/anode strip orientation.
  • Light emitted at intersection (pixels)
  • External circuitry

Turns on/off pixels

  • Large power consumption

Used on 1-3 inch screens

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SLIDE 12

Active-Matrix OLED (AMOLED)

OLED ZITI, Uni Heidelberg Page12

  • Layers of cathode, anode, organic molecules.
  • Thin Film Transistor matrix (TFT) on top of

anode. Internal circuitry to determine which pixels to turn on/off

  • Less power consumed than PMOLED.

Used for larger displays

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SLIDE 13

OLED ZITI, Uni Heidelberg Page13

Transparent OLED (TOLED)

  • Transparent substrate, cathode and anode
  • Bi-direction light emission
  • Passive or Active Matrix OLED
  • Useful for heads-up display.

Eg: Transparent projector screen glasses

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SLIDE 14

OLED ZITI, Uni Heidelberg Page14

Top-emitting OLED (TEOLED)

  • Non-transparent or reflective substrate
  • Transparent Cathode
  • Used with Active Matrix Device

Eg: Smart card displays

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SLIDE 15

OLED ZITI, Uni Heidelberg Page15

Flexible - OLED

  • Deposition of the organic layer onto the substrate using a method derived from

inkjet printing.

  • Used in the production of rollable displays, electronic paper, or bendable

displays.

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Comparison Study

OLED ZITI, Uni Heidelberg Page16

Source of light Thermal Fluorescent LED OLED Usage Over all Efficiency 2% 15% 22% 84% Black level/ contrast 0 -- ∞ 0 -- ∞ 1/1000 0 -- ∞ Resolution in dpi

  • 40

300-800 1000 Refresh rate 60fms 120fms

LED < OLED

Viewing angle Lambertian Lambertian Non- Lambertian Lambertian

Plasma TV LED Back Lighting Display Pixels 1000 Not used for displays

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SLIDE 17

OLED Page

OLED TVs ,Tablets, Mobile phones

OLED ZITI, Uni Heidelberg Page17

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SLIDE 18

OLED ZITI, Uni Heidelberg Page18

Devices with OLED

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Case Study

OLED ZITI, Uni Heidelberg Page19

Devices Companies OLED Mobile phones Samsung,Motorola,LG…. YES Televisions Panasonic ,LG…. YES Digital Cameras Sony,Canon,Olympus... YES Tablets Samsung,Dell,Fujitsu… YES Wearable Devices LG,Samsung,Acer…. YES OLED Lamps Acuity,LG.. YES Other Devices(binoculars, Car audio Systems, remote Controllers…) Sony… YES

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SLIDE 20
  • Lifespan
  • Large quantity production of large-size screens is not available.
  • Water can easily damage OLED.
  • Sunlight Effect: Another disadvantage of OLED display is that they are

hard to see in direct sunlight.

  • Expensive.

OLED ZITI, Uni Heidelberg Page20

Drawbacks of OLED

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SLIDE 21

OLED ZITI, Uni Heidelberg Page21

1.http://kaffee.50webs.com/Science/activities/Chem/Activity.Light.html 2.http://www.provideocoalition.com/sony_the_non- technical_technical_guide_to_oled_technology 3.http://www.microtipsusa.com/blog/the-new-era-of-flexible-and-oled/

4.Wikipedia

  • 5. http://de.slideshare.net/Ananthkrishn/oled-38063680?next_slideshow=5

http://www.necdisplay.com/Documents/WhitePapers/OLED.pdf

  • 6. http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/report_oled_august_2002_1.pdf
  • 7. https://www.cdtltd.co.uk/pdf/p-oled-materials-device-operation.pdf
  • 8. http://www.trustedreviews.com/opinions/oled-vs-led-lcd
  • 9. http://gizmodo.com/which-is-a-better-tv-screen-lcd-or-oled-

1732313764?trending_test_three_e&utm_expid=66866090- 68.Rvuykf2qT9qOAx_axtw3_w.2&utm_referrer=https%3A%2F%2Fwww.google.de 10.Books:

References

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SLIDE 22

OLED ZITI, Uni Heidelberg Page22

Thank you