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OLED organic light emitting diode

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Organic Light Emitting Diode works on the same principle as that of a Light emitting Diode which is Electroluminescence.
Which is a result of radiative recombination of Electrons and holes in any Semiconductor Material. These organic LEDs can be classified on several basis such as on the basis of matrix control, on the basis of type of materials used, on the basis of direction in which light exits the surface of OLED,And there several other type of OLEDs such as foldable OLED, Transparent OLED etc.
There are also many methods of manufacturing OLEDs most used of which are inkjet printing and vapor phase deposition etc.
Then finally comes the applications and advantages of this technique. As like LEDs, OLEDs also have a wide area of applications such as in VDUs, PDAs, handheld devices (Like mobile Phones, handheld Gaming consoles), and its future uses include wearable electronics. But as the coin have 2 faces so this technique also have some drawbacks like it is not waterproof and few more which include life time of the device and others.

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OLED organic light emitting diode

  1. 1. ORGANIC LIGHT EMITTING DIODE(O.L.E.D.)
  2. 2. PRESENTED BY :- MOHAMMAD HAMMAD AHMAD (2K12/EE/080) DEPARTMENT OF ELECTRICAL ENGINEERING DELHI TECHNOLOGICAL UNIVERSITY , NEW DELHI-110042
  3. 3. WHAT IS A L.E.D. ? L.E.D. OR LIGHT EMITTING DIODE IS A SEMICONDUCTOR LIGHT SOURCE THAT WORKS ON THE PRINCIPLE OF ELECTROLUMINESCENCE WHICH IS A RESULT OF RADIATIVE RECOMBINATION OF ELECTRONS AND HOLES IN A MATERIAL. STRUCTURE AND WORKING
  4. 4. LED CONSISTS OF A CHIP OF SEMICONDUCTING MATERIAL DOPED WITH IMPURITIES TO CREATE A P-N JUNCTION. AS IN OTHER DIODES, CURRENT FLOWS EASILY FROM THE P- SIDE, OR ANODE, TO THE N-SIDE, OR CATHODE, BUT NOT IN THE REVERSE DIRECTION. CHARGE-CARRIERS— ELECTRONS AND HOLES—FLOW INTO THE JUNCTION FROM ELECTRODES WITH DIFFERENT VOLTAGES. WHEN AN ELECTRON MEETS A HOLE, IT FALLS INTO A LOWER ENERGY LEVEL AND RELEASES ENERGY IN THE FORM OF A PHOTON.
  5. 5. ADVANTAGES AND DISADVANTAGES ADVANTAGES 1.LEDS CONSUME LESSER POWER AS COMPARED TO NORMAL INCANDESCENT LIGHTS. 2.LEDS HAVE LONGER LIFETIME. 3.LEDS HAVE LESSER RESPONSE TIME. 4.LEDS RADIATE LESS HEAT. 5.LEDS CAN EMIT LIGHT OF ANY COLOR USING SPECIFIC FILTER. 6.LEDS CAN BE OF VERY SMALL SIZE . 7.AND MANY MORE……
  6. 6. 1.LEDs are expensive. 2.LEDs are temperature dependent and their performance is affected by temperature to a very large extent. 3.LEDs works between certain voltage and current ranges. 4.LEDs works only when they are connected with correct electrical polarity. DISADVANTAGES
  7. 7. THERE ARE MANY USES OF L.E.D.S IN PRESENT TIME FEW OF WHICH ARE :- 1.VISUAL SIGNALS WHERE LIGHT GOES MORE OR LESS DIRECTLY FROM THE SOURCE TO THE HUMAN EYE, TO CONVEY A MESSAGE OR MEANING. 2.ILLUMINATION WHERE LIGHT IS REFLECTED FROM OBJECTS TO GIVE VISUAL RESPONSE OF THESE OBJECTS. 3.MEASURING AND INTERACTING WITH PROCESSES INVOLVING NO HUMAN VISION. 4.NARROW BAND LIGHT SENSORS WHERE LEDS OPERATE IN A REVERSE- BIAS MODE AND RESPOND TO INCIDENT LIGHT, INSTEAD OF EMITTING LIGHT. 5.EMITTING WIRELESS INTERNET SIGNAL CALLED LI-FI. 6.LEDS CAN ALSO BE USED WITH CONTACT LENSES OR NORMAL EYE GLASSES MOST RECENT EXAMPLE IS GOOGLE GLASS. 7.THE LIGHT FROM LEDS CAN BE MODULATED VERY QUICKLY SO THEY ARE USED EXTENSIVELY IN OPTICAL FIBER AND FREE SPACE OPTICS COMMUNICATIONS. Applications
  8. 8. WHAT IS AN O.L.E.D. STRUCTURE,MANUFACTURING AND WORKING An OLED (organic light-emitting diode) is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compound which emits light in response to an electric current.
  9. 9. . 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 such as mobile phones, handheld games consoles and PDAs. A major area of research is the development of white OLED devices for use in solid-state lighting applications.
  10. 10. HISTORY AND DEVELOPMENT  THE FIRST OBSERVATIONS OF ELECTROLUMINESCENCE IN ORGANIC MATERIALS WERE IN THE EARLY 1950S BY ANDRÉ BERNANOSE AND CO-WORKERS AT THE NANCY- UNIVERSITÉ, FRANCE.  THEY APPLIED HIGH-VOLTAGE ALTERNATING CURRENT (AC) FIELDS IN AIR TO MATERIALS SUCH AS ACRIDINE ORANGE, EITHER DEPOSITED ON OR DISSOLVED IN CELLULOSE OR CELLOPHANE THIN FILMS.  IN 1960, MARTIN POPE AND CO-WORKERS AT NEW YORK UNIVERSITY DEVELOPED OHMIC DARK-INJECTING ELECTRODE CONTACTS TO ORGANIC CRYSTALS. THEY FURTHER DESCRIBED THE NECESSARY ENERGETIC REQUIREMENTS (WORK FUNCTIONS) FOR HOLE AND ELECTRON INJECTING ELECTRODE CONTACTS.  ALSO IN 1965, W. HELFRICH AND W. G. SCHNEIDER OF THE NATIONAL RESEARCH COUNCIL IN CANADA PRODUCED DOUBLE INJECTION RECOMBINATION
  11. 11. OF MODERN DOUBLE INJECTION DEVICES. IN THE SAME YEAR, DOW CHEMICAL RESEARCHERS PATENTED A METHOD OF PREPARING ELECTROLUMINESCENT CELLS USING HIGH VOLTAGE (500–1500 V) AC-DRIVEN (100–3000 HZ) ELECTRICALLY INSULATED ONE MILLIMETRE THIN LAYERS OF A MELTED PHOSPHOR CONSISTING OF GROUND ANTHRACENE POWDER, TETRACENE, AND GRAPHITE POWDER.
  12. 12. WORKING PRINCIPLE
  13. 13. OLED Components Like an LED, an OLED is a solid-state semiconductor device that is 100 to 500 nanometers thick or about 200 times smaller than a human hair. OLEDs can have either two layers or three layers of organic material,the third layer helps transport electrons from the cathode to the emissive layer. Thus, the organic material must serve all the three main functions: electron transport, hole transport and emission. The injection rates of both carriers should be almost equal for high efficiency. Otherwise, the surplus electrons or holes will not recombine, which results in low operation efficiency An OLED consists of the following parts: 1. 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. 2. Organic layers - These layers are made of organic molecules or polymers. Conducting layer - This layer is made of organic plastic molecules that transport "holes“ from the anode. One conducting polymer used in OLEDs is polyaniline.
  14. 14. 3. 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. 4. Cathode (may or may not be transparent depending on the type of OLED) - The cathode injects electrons when a current flows through the device.
  15. 15. The biggest part of manufacturing OLEDs is applying the organic layers to the substrate. This can be done in three ways: 1. Vacuum deposition or vacuum thermal evaporation (VTE) - In a vacuum chamber, the organic molecules are gently heated (evaporated) and allowed to condense as thin films onto cooled substrates. This process is expensive and inefficient. 2. Organic vapor phase deposition (OVPD) - In a low-pressure, hot-walled reactor chamber, a carrier gas transports evaporated organic molecules onto cooled substrates, where they condense into thin films. Using a carrier gas increases the efficiency and reduces the cost of making OLEDs. 3. Inkjet printing - With inkjet technology, OLEDs are sprayed onto substrates just like inks are sprayed onto paper during printing. Inkjet technology greatly reduces the cost of OLED manufacturing and allows OLEDs to be printed onto very large films for large displays like 80-inch TV screens or electronic billboards. MANUFACTURING TECHNIQUE
  16. 16. MATERIALS USED 1.POLYMER(S)  POLYMER LIGHT-EMITTING DIODES (PLED), ALSO LIGHT-EMITTING POLYMERS (LEP), INVOLVE AN ELECTROLUMINESCENT CONDUCTIVE POLYMER THAT EMITS LIGHT WHEN CONNECTED TO AN EXTERNAL VOLTAGE. THEY ARE USED AS A THIN FILM FOR FULL-SPECTRUM COLOUR DISPLAYS. POLYMER OLEDS ARE QUITE EFFICIENT AND REQUIRE A RELATIVELY SMALL AMOUNT OF POWER FOR THE AMOUNT OF LIGHT PRODUCED.  TYPICAL POLYMERS USED IN PLED DISPLAYS INCLUDE DERIVATIVES OF
  17. 17. 1.PHOSPHORESCENT MATERIALS  PHOSPHORESCENT ORGANIC LIGHT EMITTING DIODES USE THE PRINCIPLE OF ELECTROPHOSPHORESCENCE TO CONVERT ELECTRICAL ENERGY IN AN OLED INTO LIGHT IN A HIGHLY EFFICIENT MANNER, WITH THE INTERNAL QUANTUM EFFICIENCIES OF SUCH DEVICES APPROACHING 100%.  TYPICALLY, A POLYMER SUCH AS POLY(N-VINYLCARBAZOLE) IS USED AS A HOST MATERIAL TO WHICH AN ORGANOMETALLIC COMPLEX IS ADDED AS A DOPANT. IRIDIUM COMPLEXES SUCH AS IR(MPPY)3. 3.FLUOROSCENT THESE TYPE OF ORGANIC L.E.D.S HAVE FLOUROSCENT MATERIAL AS THEIR MAIN CONSTITUENT AND THESE TYPE OF ORGANIC LIGHT EMITTING DIODES ARE THE MOST WIDELY USED ONES. EXAMPLE:- PERYLENE
  18. 18. 4. SMALL MOLECULE OLED  MOLECULES COMMONLY USED IN OLEDS INCLUDE ORGANOMETALLIC CHELATES (FOR EXAMPLE ALQ3, USED IN THE ORGANIC LIGHT-EMITTING DEVICE REPORTED BY TANG ET AL.),  FLUORESCENT AND PHOSPHORESCENT DYES AND CONJUGATED DENDRIMERS.  A NUMBER OF MATERIALS ARE USED FOR THEIR CHARGE TRANSPORT PROPERTIES, FOR EXAMPLE TRIPHENYLAMINE AND DERIVATIVES ARE COMMONLY USED AS MATERIALS FOR HOLE TRANSPORT LAYERS.  FLUORESCENT DYES CAN BE CHOSEN TO OBTAIN LIGHT EMISSION AT DIFFERENT WAVELENGTHS, AND COMPOUNDS SUCH AS PERYLENE, RUBRENE AND QUINACRIDONE DERIVATIVES ARE OFTEN USED.
  19. 19. ON THE BASIS OF PIXEL CONTROL/DRIVING METHOD 1. A.M.O.L.E.D.-IN A.M.O.L.E.D. OR ACTIVE MATRIX ORGANIC LIGHT EMITTING DIODE THE PIXELS ARE CONTROLLED DIRECTLY.THIS TECHNIQUE IS USED TO MAKE LARGER AND MORE EFFICIENT DISPLAYS BUT IS EXPENSIVE. 2. P.M.O.L.E.D.-IN P.M.O.L.E.D. OR PASSIVE MATRIX ORGANIC LIGHT EMITTING DIODE THE DISPLAY IS CONTROLLED BY SWITCHING A CERTAIN ROW AND COLUMN - IN EFFECT LIGHTING THE PIXEL AT THE INTERSECTION. THE PIXELS ARE TURNED ON AND OFF QUICKLY, AND THE SEQUENCE CREATES THE IMAGE. BUT IT ONLY ALLOW FOR SMALL SIZED DISPLAYS (UP TO 3", TYPICALLY) AND IS CHEAP. Classification
  20. 20. ON BASIS OF DIRECTION LIGHT EXITS O.L.E.D. 1. TOP EMISSION- . TOP EMISSION DEVICES ARE CLASSIFIED BASED ON WHETHER OR NOT THE LIGHT EMITTED FROM THE OLED DEVICE EXITS THROUGH THE LID THAT IS ADDED FOLLOWING FABRICATION OF THE DEVICE. TOP-EMITTING OLEDS ARE BETTER SUITED FOR ACTIVE-MATRIX APPLICATIONS AS THEY CAN BE MORE EASILY INTEGRATED WITH A NON-TRANSPARENT TRANSISTOR BACKPLANE. 2. BOTTOM EMISSION-. OLED DEVICES ARE CLASSIFIED AS BOTTOM EMISSION DEVICES IF LIGHT EMITTED PASSES THROUGH THE TRANSPARENT OR SEMI-TRANSPARENT BOTTOM ELECTRODE AND SUBSTRATE ON WHICH THE PANEL WAS MANUFACTURED.
  21. 21. ON BASIS OF MANUFACTURING MATERIAL 1. SMALL MOLECULE-SMALL MOLECULES' OLEDS ARE MORE COMMON TODAY, WITH MOST DISPLAYS USING THOSE KIND OF MATERIALS.THIS TYPE OF O.L.E.D. IS DIFFICULT TO FABRICATE. 2. LARGE MOLECULE/POLYMER BASED-LARGE MOLECULES (ALSO CALLED POLYMER-BASED OLEDS, OR P-OLEDS) ARE LAGGING BEHIND IN LIFETIME AND EFFICIENCY SPECS. P- OLEDS MIGHT BE EASIER TO MAKE, THOUGH, BECAUSE THEY ARE MORE EASILY ADAPTED FOR PRINTING. 3. FLOURSCENT O.L.E.D.-THESE TYPE OF O.L.E.D.S HAS FLUORESCENT MATERIAL AS MAJOR CONSTITUENT.THESE ARE THE MOST USED O.L.E.D.S. 4. PHOSPHORESCENT O.L.E.D.-THESE O.L.E.D.S HAS PHOSPHORESCENT MATERIAL AS MAJOR CONSTITUENT .THEY ARE KNOWN TO GIVE A MORE EFFICIENT PICTURE.
  22. 22.  SOME OTHER O.L.E.D. 1. FOLDABLE O.L.E.D.S-SUBSTRATE IS MADE OF FLEXIBLE METALLIC FOILS OR PLASTICS. THEY ARE LIGHTWEIGHT AND CONSIDERED VERY DURABLE. 2. TRANSPARENT O.L.E.D.S-USE TRANSPARENT OR SEMI- TRANSPARENT CONTACTS ON BOTH SIDES TO CREATE DISPLAYS THAT CAN BE TOP AND BOTTOM EMITTING. OFFERS GREAT CONTRAST. 3. STACKED O.L.E.D.-UNIQUE PIXEL ARCHITECTURE THAT STACKS RED, GREEN, AND BLUE SUBPIXELS ON TOP OF ONE ANOTHER (INSTEAD OF NEXT TO EACH ANOTHER). THIS PROVIDES BETTER COLOR SCOPE AND DEPTH, AND ALSO REDUCES PIXEL GAP
  23. 23. DIFFERENCE BETWEEN LCD,PLASMA AND OLED DISPLAYS
  24. 24. APPLICATIONS ORGANIC LIGHT EMITTING DIODES HAVE A LOT OF PRACTICAL APPLICATIONS IN TODAY`S WORLD.SOME OF WHICH ARE AS FOLLOW….. THE MOST WIDE USE OF ORGANIC L.E.D.S IS IN THE FIELD OF DISPLAYS OR MORE PRECISELY VDUS(VISUAL DISPLAY UNITS) SUCH AS MONITORS , TELEVISIONS , MOBILE PHONES ETC. O.L.E.D. SCREENS HAVE A MUCH GOOD DISPLAY RESOLUTION THAN NORMAL LCD(LIQUID CRYSTAL DISPLAY) AND ALSO HAVE A LONGER LIFETIME AS COMPARED TO CRT(CATHODE RAY TUBE) DISPLAYS OR LCD. ORGANIC LEDS CAN ALSO BE USED IN THE CONSTRUCTION OF WEARABLE ELECTRONICS.
  25. 25. ADVANTAGES • SUBSTRATE IS FLEXIBLE, WHICH OFFERS THE POSSIBILITY OF NEW DISPLAY OPTIONS • PLASTIC CAN BE USED AS OPPOSED TO GLASS, WHICH IS GOOD BECAUSE GLASS ABSORBS SOME LIGHT • SINCE MANUFACTURERS ARE WORKING MOSTLY WITH PLASTICS, OLEDS TEND TO BE EASIER TO PRODUCE • WIDER VIEWING RANGE (APPROXIMATELY 170°) • MUCH BETTER COLOR BALANCE BECAUSE MORE THAN 16 MILLION CAN BE DISPLAYED.
  26. 26. • NO PROBLEM TO OBSERVE FROM A HIGH ANGLE (AROUND 160°), WHICH MEANS BETTER READABILITY FROM DIFFERENT POSITIONS. • CLEAR AND BRIGHT IMAGE. • MORE MECHANICALLY RESISTANT - IDEAL FOR POCKET COMPUTERS AND MOBILE PHONES. • FAST RESPONSE. • LOW ENERGY CONSUMPTION. • WELL READABLE IN CASE OF DIRECT DAYLIGHT. • POSSIBILITY TO BEND OR SHAPE THE DEVICES. • ADDITIONAL SOURCE OF LIGHT IS NOT NEEDED SO THEY ARE THINNER AND LIGHTER.
  27. 27. DISADVANTAGES DESPITE OF BEING VERY MUCH ADVANTAGEOUS OLEDS ALSO HAVE SOME DISADVANTAGE WHICH ARE.. • WATER CAN DAMAGE THE DEVICE AND LIMIT FLEXIBILITY • DISPLAYS CAN BE DAMAGED BY PROLONGED EXPOSURE TO UV LIGHT • PIXEL BRIGHTNESS FADES OVER TIME AND THE VARIED LIFESPAN OF THE DYES CAN CAUSE A DISCREPANCY BETWEEN RED, GREEN, AND BLUE INTENSITY; THIS COULD, IN TURN, LEAD TO SCREEN BURN-IN. • BLUE OLEDS ARE INEFFICIENT: RED (625 NM) AND GREEN (530 NM) DIODES HAVE SHOWN EXTERNAL QUANTUM EFFICIENCY VALUES OF 20% AND 19%; BLUE DIODES (430 NM), ON THE OTHER HAND, ARE MUCH LOWER, WITH A REPORTED MAXIMUM EXTERNAL QUANTUM VALUE BETWEEN 4% AND 6%
  28. 28. FUTURE SCOPE THE FUTURE OF ORGANIC LIGHT EMITTING TECHNIQUE IS VERY “BRIGHT” INDEED AS DESPITE OF PRODUCING A VERY CLEAR AND BRIGHT IMAGE THIS TECHNIQUE ALSO HAS THE ABILITY OF PRODUCING FLEXIBLE AS WELL AS TRANSPARENT DISPLAYS WHICH CAN BE USED IN MANY FUTURE APPLICATIONS. BEING FLEXIBLE ORGANIC LIGHT EMITTING DIODES CAN ALSO BE INCORPORATED IN MANUFACTURING WEARABLE ELECTRONICS ,SUCH AS PEBBLE WATCH. THIS TECHNIQUE CAN ALSO BE USED TO MAKE MORE EFFICIENT TOUCHSCREEN DISPLAYS AS IN SMARTPHONES, ONE OF THE MOST IMPORTANT USE OF THIS TECHNIQUE IS IN MANUFACTURE OF TRANSPARENT

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