Organic Light Emitting Diode


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Organic Light Emitting Diode

  1. 1. OLED (Organic Light Emitting Diode) Presented by: Rehan Fazal 1171110180 Submitted to: Mrs.K.A.Sunitha mam
  2. 2. What is an OLED? OLED - Organic Light Emitting Diode An OLED is any light emitting diode (LED) which emissive electroluminescent layer is composed of a film of organic compounds. This layer of organic semiconductor is situated between two electrodes. Generally, at least one of these electrodes is transparent. OLEDs are used to create digital displays in devices such as television screens, computer monitors, portable systems.
  3. 3. History of OLEDs • First developed in the early 1950s in France • Early technology would emmite a short burst of light when a voltage was applied • This early form applied high-voltage alternating current field to crystalline thin films of acridine orange and quinacrine. • 1960s - AC-driven electroluminescent cells using doped anthracene was developed • In a 1977 paper, Shirakawa et al. Reported high conductivity in similarly oxidized and iodine-doped polyacetylene. • In 1987 Chin Tang and Van Slyke introduced the first light emitting diodes from thin organic layers. • In 1990 electroluminescence in polymers was discovered.
  4. 4. Architecture of OLEDs Substrate (clear plastic, glass, foil) - The substrate supports the OLED. Anode (transparent) - The anode removes electrons (adds electron "holes") when a current flows through the device. Organic layer: o Conducting layer - This layer is made of organic plastic molecules that transport "holes" from the anode. One conducting polymer used in OLEDs is polyaniline. o Emissive layer - This layer is made of organic plastic molecules (different ones from the conducting layer) that transport electrons from the cathode; this is where light is made. One polymer used in the emissive layer is polyfluorene. Cathode (may or may not be transparent depending on the type of OLED) - The cathode injects electrons when a current flows through the device.
  5. 5. Working of OLEDS: • A typical OLED is composed of a layer of organic materials situated between two electrodes, the anode and cathode, all deposited on a substrate. The organic molecules are electrically conductive as a result of delocalization of pi electrons caused by conjugation over all or part of the molecule. These materials have conductivity levels ranging from insulators to conductors, and therefore are considered organic semiconductors. The highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) of organic semiconductors are analogous to the valence and conduction bands of inorganic semiconductors.
  6. 6. • During operation, a voltage is applied across the OLED such that the anode is positive with respect to the cathode. Anodes are picked based upon the fact of how good their optical transparency, electrical conductivity, and chemical stability are. A current of electrons flows through the device from cathode to anode, as electrons are injected into the LUMO of the organic layer at the cathode and withdrawn from the HOMO at the anode. This latter process may also be described as the injection of electron holes into the HOMO. Electrostatic forces bring the electrons and the holes towards each other and they recombine forming an exciton, a bound state of the electron and hole. This happens closer to the emissive layer, because in organic semiconductors holes are generally more mobile than electrons. The decay of this excited state results in a relaxation of the energy levels of the electron, accompanied by emission of radiation whose frequency is in the visible region.
  7. 7. • As electrons and holes are fermions with half integer spin, an exciton may either be in a singlet state or a triplet state depending on how the spins of the electron and hole have been combined. Statistically three triplet excitons will be formed for each singlet exciton. Decay from triplet states (phosphorescence) is spin forbidden, increasing the timescale of the transition and limiting the internal efficiency of fluorescent devices. Phosphorescent organic light- emitting diodes make use of spin–orbit interactions to facilitate intersystem crossing between singlet and triplet states, thus obtaining emission from both singlet and triplet states and improving the internal efficiency
  8. 8. Types of OLEDs Passive OLEDs • The organic layer is between strips of cathode and anode that run perpendicular • The intersections form the pixels • Easy to make • Use more power • Best for small screens Active OLEDs • Full layers of cathode and anode • Anode over lays a thin film transistor (TFT) • Requires less power • Higher refresh rates • Suitable for large screens
  9. 9. Current Research for OLEDs • Manufacturers focusing on finding a cheap way to produce o "Roll-to-Roll" Manufacturing • Increasing efficiency of blue luminance • Boosting overall lifespan
  10. 10. Applications of OLEDs • TVs • Cell Phone screens • Computer Screens • Keyboards (Optimus Maximus) • Lights • Portable Divice displays
  11. 11. OLEDs as a Light Source
  12. 12. OLED Televisions • Released XEL-1 in February 2009. • First OLED TV sold in stores. • 11'' screen, 3mm thin • $2,500 MSRP • Weighs approximately 1.9 kg • Wide 178 degree viewing angle • 1,000,000:1 Contrast ratio Sony
  13. 13. Optimus Maximus Keyboard • Small OLED screen on every key • 113 OLED screens total • Each key can be programmed to preform a series of functions • Keys can be linked to applications • Display notes, numerals, special symbols, HTML codes, etc... • SD card slot for storing settings
  14. 14. Advantages of OLEDs • Much faster response time • Consume significantly less energy • Able to display "True Black" picture • Wider viewing angles • Thinner display • Better contrast ratio • Safer for the environment • Has potential to be mass produced inexpensively • OLEDs refresh almost 1,000 times faster then LCDs OLED Displays Vs. LCD and Plasma OLED Lighting Vs. Incandescent and Fluorescent • Cheaper way to create flexible lighting • Requires less power • Better quality of light (ie. no "Cold Light") • New design concepts for interior lighting
  15. 15. Disadvantages of OLEDs OLED Displays Vs. LCD and Plasma • Cost to manufacture is high • Overall luminance degradation • Constraints with lifespan • Easily damaged by water • Limited market availability OLED Lighting Vs. Incandescent and Fluorescent • Not as easy as changing a light bulb
  16. 16. Future Uses for OLED Lighting • Flexible / bendable lighting • Wallpaper lighting defining new ways to light a space • Transparent lighting doubles as a window Cell Phones • Nokia 888
  17. 17. Future Uses for OLED Transparent Car Navigation System on Windshield • Using Samsungs' transparent OLED technology • Heads up display • GPS system Scroll Laptop • Nokia concept OLED Laptop
  18. 18. References • • • • ml#keep-your-eye-on-flexible-displays-coming-soon • http://www.pocket- ready.phtml • ng_market/ • • • pitched-as-automotive-hud
  19. 19. Thank you
  20. 20. Video link: v=mTcYva_rrzc