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CHAROTAR INSTITUTE OF TECHNOLOGY,CHANGA

CHAROTAR INSTITUTE OF TECHNOLOGY,CHANGA. ORGANIC LIGHT EMITTING DIODE SAGARKUMAR .B. PATEL 1 ST SEMESTER P.G.C.S.E. (08PGEC13). What is an OLED?.

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CHAROTAR INSTITUTE OF TECHNOLOGY,CHANGA

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  1. CHAROTAR INSTITUTE OF TECHNOLOGY,CHANGA ORGANIC LIGHT EMITTING DIODE SAGARKUMAR .B. PATEL 1ST SEMESTER P.G.C.S.E. (08PGEC13)

  2. What is an OLED? • OLED (Organic Light-Emitting Diode) is a self light-emitting technology composed of a thin, multi-layered organic film placed between an anode and cathode. In contrast to LCD/TFT technology, OLED does not require a backlight.

  3. Why Organic Electronics? •Tunability •Low-cost •Abundant •New functions •New form factors •Performance

  4. Motivation • Provide brighter, crisper displays on electronic devices • Very thin multilayer devices that do not require a backlight • Printed on plastic making displays flexible and lightweight • Use less power than conventional LEDs or liquid crystal displays (LCDs) • Much less costly to fabricate than traditional LCD displays

  5. ADVANTAGE OF MATERIAL Materials • Soluble in common solvents • Inexpensive in volume of organic material used [layers of < 100nm] • Environment friendly [i.e. etching processes] and low power consumption through low driving voltages

  6. ADVANTAGE OF MATERIAL Applications • The organic material emits light when a voltage is applied, wide viewing angle, high resolution and fast response times, as in solar cells where light is transferred in a electrical current • Possibility of using plastic substrates to create, thin, light-weight, bendable, foldable etc. devices Processing • Cheap to manufacture through a variety of printing technologies

  7. ADVANTAGES OVER LCDs • Self-emissive • Thin form factor • High luminance • High contrast • Fast response time • Wide viewing angle • Low power consumption • Wide temperature operation range • Potential of flexible substrate

  8. Basic OLED Structure

  9. Basic OLED Structure Substrate - The substrate is made of glass and supports the OLED. Anode - The anode removes electrons (adds electron "holes") when a current flows through the device. Conducting Layer(s) - One layer made of organic plastic molecules that transport "holes" from the anode. (HTL) Another layer made of organic plastic molecules (different from those in hole transport layer) that transport electrons from the cathode. (ETL) Emissive Layer – This organic layer is where light is made. (EL) Cathode - The cathode injects electrons when a current flows through the device

  10. LAYER OF OLED

  11. Materials Used • Anode: indium tin oxide (ITO) 150nm • Organic layers: HTL:a copolymer based on NN’-biphenyl-N-N’ bis(3-methylphenyl)-[1-1’-biphenyl]-4-4’-diamine (TPD) 40 nm ETL: tris-(8-hydroxyquinoline)aluminum (AlQ3) 40 nm EL: siloles derivatives blended with polystyrene (4:1 weight ratio) 40 nm • Cathode: Lithium Fluoride (LiF) 1nm and Aluminum 300 nm

  12. FIVE LAYER OF OLED

  13. Substrate Preparation • Substrate can be glass or plasticity coated glass sheets could be purchased Another option is to deposit ITO on glass or plastic Substrates are ultrasonically cleaned in detergent solution, followed by thorough rinsing in deionizer water • Then, they get ultrasonically cleaned in organic solvents and dried in pure nitrogen gas Immediately prior to deposition • The substrate would get subject to an oxygen treatment either using UV ozone or oxygen plasma to improve hole-injection Cleaning is very critical and it effects the performance significantly

  14. PASSIVE OLED DISPLAY • Passive Matrix OLED display • Low-cost and low-information-content applications– e.g. Alphanumeric displays • Array of OLED pixels connected by intersecting anode and cathode conductors. –Arib structure is pre-formed on patterned ITO anode lines – Advantage of this method is that all patterning steps use conventional lithography • Application of a voltage to rows and columns results in electrical current through selected pixels

  15. PASSIVE OLED DISPLAY

  16. ACTIVE OLED DISPLAY • Advantages in active matrix OLED displays – Low voltage and power consumption – High resolution – Large area – Robust pixel design – Integrated drivers • An active matrix OLED has an integrated electronic backplane made from thin film transistors (TFTs) – Each pixel addressed independently – A defective pixel produces only a dark defect, which is considered to be much less objectionable than a bright point defect (such as in LCD panels), or a line defect

  17. Active vs. Passive Matrix • AMOLED, the array is divided into a series of row and column lines, with each pixel formed at the intersection of a row and column line, just as in a passive-matrix display. • Each pixel now consists of an OLED in series with a thin-film transistor (TFT). The TFT is a switch that can control the amount of current flowing through the OLED.

  18. Active vs. Passive Matrix • In AMOLED, information is sent to the transistor in each pixel, dictating the brightness of the pixel. The TFT then stores this information and continuously controls the current flowing through the OLED. In this manner the OLED is operating continuously, avoiding the need for the very high currents necessary in a passive-matrix display. • In PMOLED to illuminate any particular pixel line a passive-matrix display, electrical signals reapplied to the row line and column line. The more current pumped through each pixel diode, the brighter the pixel.

  19. Advantages of AMOLED 1.High CONTRAST RATIO 2.Wide Temperature Operation 3.Fast Response 4.High and Constant colour Gamut 5.Wide Viewing Angle 6.Peak Brightness 7.Low Power Consumption 8.Very Slim design

  20. High Contrast RatioOLED TFT-LCD

  21. Constant Contrast Ratio (wide viewing angle)

  22. High Ambient Contrast Ratio

  23. FAST Response Time

  24. HOW FAST IT IS?TEMP(-40 to 80°c ) <> (-20 to 75°c)

  25. Power Consumption

  26. How to Lower Power Consumption • AMOLED power consumption can be decreased by: • 1. Black background. ( 50%~80% ) • 2. Lower full white brightness. Ex.200 nits 160 nits. ( 20% ) • 3. Auto current limit driving method.(20% ) • 4. OLED material & device efficiency increase. (30% )

  27. Mobile Phone

  28. Market Status • Displays market is high growth • OLEDs are now biting • Flexible OLEDs will be disruptive

  29. Future improvements

  30. ALL OF YOU THANK YOU

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