Seminar Reportpdf

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SEMINAR REPORTON

Organic Light Emitting DiodeSubmitted for the partial fulfilment of award

OFDegree of Bachelors of Technology

(Electronics and Communication Engineering)

BY: Jimmy Joy(ROLL NO:1013231049)

Department of Electronics and CommunicationG.N.I.T. GREATER NOIDA

Session 2012-2013


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CERTIFICATE

This is to certify thatJimmy Joy has carried out training work presentedin this report entitled Organic Light Emitting Diodefor the award ofBachelor of technology Degreefrom Mahamaya TechnicalUniversity, Noida.

Mr. Dhiraj Gupta Seminar CommitteeH.O.D (ECE) (1) Mr. Vivek Gupta

(2) Mr. S.S khalid(3) Ms. Richa Chanana


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ACKNOWLEDGEMENT

I take this opportunity to express my sincere thanks to Mr. Vivek Guptaand Mr. SS Khalid for their valuable guidance for the success of this

seminar.

I also thank Mr. DHIRAJ GUPTA(HOD, ECE) and all other staff of thedepartment for their kind co-operation extended to me.

I am thankful to all my friends who helped me in making my seminar agrand success. I am also thankful to all the people who were directly orindirectly involved in helping to complete my seminar report.

JIMMY JOY(1013231049)

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ABSTRACT

Organic light-emitting devices (OLEDs) operate on the principle of

converting electrical energy into light, a phenomenon known aselectroluminescence. They exploit the properties of certain organic materials whichemit light when an electric current passes through them.

An OLED consists of a layer of this luminescent material sandwichedbetween two electrodes. When an electric current is passed between the electrodes,through the organic layer, light is emitted with a color that depends on the

particular material used. In order to observe the light emitted by an OLED, at leastone of the electrodes must be transparent.

Although the commercialization of the OLED technology in FPDs is growingand appears to be just around the corner for SSL, there are still several key issuesthat need to be addressed: (1) the cost of OLEDs is very high, largely due to thecostly current manufacturing process; (2) the efficiency of OLEDs needs to be

improved.This is vital to the success of OLEDs in the FPD and SSL industries; (3)the lifetime of OLEDs, especially blue OLEDs, is the biggest technical challenge.All these issues raise the demand for new organic materials, new device structures,and continued lower-cost fabrication methods.

Electronically, OLED is similar to old-fashioned LEDs -- put a low voltageacross them and they glow. But instead of being made out of semiconductingmetals, OLEDs are made from polymers, plastics or other carbon-containingcompounds. These can be made very cheaply and turned into devices without allthe expensive palaver that goes with semiconductor fabrication. Light-emittingdiodes, based upon semiconductors such as Gallium Arsenide, Gallium Phosphide.They are mostly used as indicator lamps, although they were used in calculators

before liquid crystals, and are used in large advertising signs, where they are

valued for very long life and high brightness. Such crystalline LEDs are notinexpensive, and it is very difficult to integrate them into small high-resolution

displays.

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CONTENTS

1. Introduction 1

2. What is OLED? 23. History of OLED 3

4. Features of OLED 4

5. Structure of OLED 5

6. Making of OLED 6

7. Working of OLED 7-8

8. Types of OLED 9-10

7.1. Passive-matrix OLED

7.2. Active-matrix OLED

7.3. Flexible OLED

9. OLED Advantages 11

10. OLED Disadvantages 12

11. Applications 13-16

11.1. Television

11.2. Lights

11.3. Cell phones

12. Comparison With other Technology 17

13. Current and Future OLED Applications 17

14. Conclusion 18

15. References 19

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INDEX OF FIGURE

1. Figure (2.a) 22. Figure (5.a) 5

3. Figure (6.a) 6

5. Figure (7.a) 7

6. Figure (7.b) 8

7. Figure (8.a) 9

8. Figure (8.b) 10

9. Figure (8.c) 11

10. Figure (8.d) 11

11. Figure (9.a) 12

12. Figure (11.a) 14

13. Figure (11.b) 15

14. Figure (11.c) 1615. Figure (11.d) 16

16. Figure (11.e) 17

17. Figure (11.f) 17

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INDEX OF TABLE

1. Table1 18

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1. INTRODUCTION

OLEDs constitute a new and exciting emissive display technology. Ingeneral, the basic OLED structure consists of a stack of fluorescent organic layerssandwiched between a transparent conducting anode and metallic cathode . Whenan appropriate bias is applied to the device, holes are injected from the anode andelectrons from the cathode; some of the recombination events between the holesand electrons result in electroluminescence (EL).

An OLED (organic light-emitting diode) is a light-emitting diode (LED) in

which the emissive electroluminescent layer is a film of organic compound whichemits light in response to an electric current. This layer of organic semiconductoris situated between two electrodes. Generally, at least one of these electrodes is

transparent. OLEDs are used to create digital displays in devices such as televisionscreens, computer monitors, portable systems such as mobile phones, handheldgames consoles and PDAs.

In 1987, Tang et al. reported OLEDs based on small organic molecules bythermal vacuum deposition and in 1990, at Cambridge University, Friend et al.reported OLEDs based on solution-processed semiconducting polymers. These

two pioneering works made a breakthrough in the OLED areas, and since then lotsof papers on this subject were published. According to the materials used forOLEDs, OLEDs can be divided into two types: small-molecular OLEDs and

polymer light-emitting diodes (PLEDs).

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2. What is Organic LED?

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 anelectric current. This layer of organic semiconductor is situated between two electrodes.Generally, at least one of these electrodes is transparent. OLEDs are used to create digitaldisplays in devices such as television screens, computer monitors, portable systems such asmobile phones, handheld games consoles and PDAs.

There are two main families of OLEDs: those based on small molecules and those employingpolymers. Adding mobile ions to an OLED creates a light-emitting electrochemical cell or LEC,which has a slightly different mode of operation. OLED displays can use either passive-matrix(PMOLED) or active-matrix addressing schemes. Active-matrix OLEDs (AMOLED) require athin-film transistor backplane to switch each individual pixel on or off, but allow for higher

resolution and larger display sizes

An OLED display works without a backlight. Thus, it can display deep black levels and can bethinner and lighter than a liquid crystal display (LCD). In low ambient light conditions such as adark room an OLED screen can achieve a higher contrast ratio than an LCD, whether the LCDuses cold cathode fluorescent lamps or LED backlight.

Fig (2.a)

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3. HISTORY

The first observations of electroluminescence in organic materials were inthe early 1950s by Andr Bernanose and co-workers at the Nancy-Universit,

France. They applied high-voltage alternating current (AC) fields in air tomaterials such as acridine orange, either deposited on or dissolved in cellulose orcellophane thin films. The proposed mechanism was either direct excitation of thedye molecules or excitation of electrons.

Also in 1965, W. Helfrich and W. G. Schneider of the National ResearchCouncil in Canada produced double injection recombination electroluminescencefor the first time in an anthracene single crystal using hole and electron injecting

electrodes,[10] the forerunner of modern double injection devices. In the sameyear, Dow Chemical researchers patented a method of preparingelectroluminescent cells using high voltage (5001500 V) AC-driven (1003000Hz) electrically insulated one millimetre thin layers of a melted phosphorconsisting of ground anthracene powder, tetracene, and graphite powder.[11] Their

proposed mechanism involved electronic excitation at the contacts between thegraphite particles and the anthracene molecules.

Electroluminescence from polymer films was first observed by RogerPartridge at the National Physical Laboratory in the United Kingdom. The device

consisted of a film of poly(n-vinylcarbazole) up to 2.2 micrometres thick locatedbetween two charge injecting electrodes. The results of the project were patented in1975[12] and published in 1983.

The first diode device was reported at Eastman Kodak by Ching W. Tangand Steven Van Slyke in 1987.[17] This device used a novel two-layer structurewith separate hole transporting and electron transporting layers such thatrecombination and light emission occurred in the middle of the organic layer. Thisresulted in a reduction in operating voltage and improvements in efficiency and ledto the current era of OLED research and device production.

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4 . FEATURES OF OLED

Organic LED has several inherent properties that afford unique possibilities

High brightnessis achieved at low drive voltages / current densities Operating life time exceeding 10,000 hour s Materials do not need to be crystalline, so easy to fabricate Possible to fabricate on glass and flexible substrates Self luminescent so no requirement of backlighting Higher brightness Low operating and turn-on voltage

High contrast Low power consumption Wide operating temperature range Long operating lifetime A flexible, thin and lightweight Cost effective manufacturability

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5 . STRUCTURE OF OLED

Structure of OLED consist of

Substrate(glass) - The substrate supports the OLED. Anode(transparent) - The anode removes electrons (adds electron "holes") when a

current flows through the device.

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.

Emissive layer : This layer is made of organic plastic molecules (different onesfrom 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 (transparent depending on the type of OLED) - The cathode injects electronswhen a current flows through the device.

Fig (5.a)

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6. Making of OLED

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 very expensive and inefficient.

2.Organic vapour phase deposition

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.

Fig (6.a)

The OVPD process employs an inert carrier gas to a precisely transfer films of organic materialonto a cooled substrate in a hot-walled, low pressure chamber. The organic materials are storedin external, separate, thermally-controlled cells .Once evaporated from these heated cells, thematerials are entrainedand transported by an inert carrier gas such as nitrogen, using gas flowrate, pressure and temperature as process control variables. The materials deposit down onto thecooled substrate from a manifold located only several centimeters above the substrate.

3. Inkjet printing

With inkjet technology, OLEDs are sprayed onto substrates just like inks are sprayed onto paperduring printing. Inkjet technology greatly reduces the cost of OLED manufacturing and allowsOLEDs to be printed onto very large dims for large displays like 80 inch TV screens orelectronic billboards.

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7. OLED: WORKING

The process is as follows:

1. The battery or power supply of the device containing the OLED applies a voltage across theOLED.

2. An electrical current flows from the cathode to the anode through the organic layers (anelectrical current is a flow of electrons).

3. The cathode gives electrons to the emissive layer of organic molecules.4. The anode removes electrons from the conductive layer of organic molecules. (This is the

equivalent to giving electron holes to the conductive laye).5. At the boundary between the emissive and the conductive layers, electrons find electron holes.6. When an electron finds an electron hole, the electron fills the hole (it falls into an energy level

of the atom that's missing an electron).7. The OLED emits light.

8. The color of the light depends on the type of organic molecule in the emissive layer.Manufacturers place several types of organic films on the same OLED to make color displays.

9. The intensity or brightness of the light depends on the amount of electrical current applied: themore current, the brighter the light.

Fig (7.a)

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Fig (7.b)

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8. TYPES OF OLED

There are six different types of OLEDs. They are: Passive-matrix OLED Active-matrix OLED

Transparent OLED Foldable OLED Top-emitting OLED White OLED

8.1 PASSIVEMATRIX OLED

Passive-matrix OLEDs are particularly well suited for small-area display applications,such as cell phones and automotive audio applications.

PMOLEDs have strips of cathode, organic layers and strips of anode. The anode strips arearranged perpendicular to the cathode strips. The intersections of the cathode and anode make up

the pixels where light is emitted. Sandwiched between the orthogona column and row lines, thinfilms of organic material are activated to emit light by applying electrical signals to designatedrow and column lines. The more current that is applied, the more brighter the pixel becomes.PMOLEDs are easy to make, but they consume more power than other types of OLED. mainlydue to the power needed for the external circuitry.

Fig (8.a)

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8.2 ACTIVE MATRIX OLED

AMOLED have full layers of cathode, organic molecule and anode, but the anode layeroverlays a thin film transistor(TFT) array that forms a matrix. The TFT array itself is thecircuitry that determines which pixels get turned on to form an image.

In contrast to a PMOLED display, where electricity is distributed row by row. the active-matrix TFT backplane acts as an array of switches that controls the amount of current flowingthrough each OLED pixel. The TFT array continuously controls the current that Hows to thepixels, signaling to each pixel how brightly to shine.

Fig (8.b)

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8.3 FLEXIBLE OLED

Foldable OLEDs have substrates made of very flexible metallic foils or plastics. FoldableOLEDs are very lightweight and durable. Their use in devices such as cellphones and PDAs canbe sewn into fabrics for "smart" clothing, such as outdoor survival clothing with an integrated

computer chip, cell phone, GPS receiver and oled display display sewn into it.

Fig (8.c)

Fig (8.d)

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9. OLED ADVANTAGES

1. Slimmer: The biggest adavantage of OLED screen is that it is slimmer than LCD display.While LCD and Plasma displays could be few inches thick, OLED advantage is that it is

only few millimeters thick.2. Faster: Another advantage of OLED is that it has much better response time than other

displays. So these screens often provide better user experience. This advantage will leadgreat use of OLEd screens in mobile phones and other handheld devices where fastresponse time is usually required.

3. Efficient in Energy: OLED displays consumes less energy as compared to LCD displaysand other display screens. No backlit is required in these screens which is the biggestOLED advantage for use in portable gadgets.

4. Good for Eyes: Another great advantage of OLED is that it pts less stains on eyes andhence are eye soothening. These screens provide better viewing experience because theyhave better contrast, brightness and color aspects.

5. Large Viewing Angle: Viewing angle is always an issue in flat screens. But with theadvent of OLED displays, viewing angle could be as large as 170 degree because theyproduce their own light which increases their viewing angle. (Fig 8. a)

6. Flexible: Now you get displays which you can bend. This is possible only through theadvent of OLED screens.

7. Durability: Another great advantage of OLED is that it is more durable than traditionalscreens. There chance of getting broken is comparitively less to LCD screens and otherdisplays.

8. Low Cost: The price of OLED screens may be much higher now but it will come down asthe technology becomes popular. OLED screens could become cheaper than LCD screensin coming times

Fig (9.a)

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10. OLED DISADVANTAGES

1. Short Lieftime: OLED's biggest disadvantage is that these screens are not forlong use. Compared with LCD, these screens are not designed to last aslong. So life time may be a critical issue and ofcourse a biggest disadvantageof OLED screens. However, these screens may find good use as mobile

phone displays as most people don't keep phone for more than a year.2. Sunlight Effect: Another disadvantage of OLED display is that they are hard

to see in direct sunlight. So if you have open lobbies where sunlight reachesdirectly, you will not get benefit of vieiwng these screens.

3. Highly Water prone: OLED screens are highly prone to water. This adds toanother disadvantage as these screens can't withstand even a small water on

display. In this regard, LCD screens are less susceptible to water damage.4. High Cost: As mentioned above, current cost is quite high which adds to

another OLED disadvantage.

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Samsung's 55" Real OLED TV

Together with LG, Samsung also announced their own 55" OLED TV. First branded as "SuperOLED TV", Samsung now calls them "Real OLED TVs" - to note the fact that Samsung areusing 'True OLED' RGB subpixels, as opposed to LG's WRGB architecture, and also to

differentiate its OLED TVs from LED TVs. The model number of Samsung's TV will be F9500,but the company did not reveal their launch plans yet.

Fig (11.b)

11.2 Lights

OLEDs offer a new way to create artistic applications with light - pure, sophisticated andbeautiful. As a unique area light source, OLEDs have strong potential for new applications invarious industries. OLEDs can also be incorporated in furniture elements such as mirrors andother surfaces, or as a part of an interior space, room or building.

OLED devices are ultra slim and emit very homogeneous light. Novaled PIN OLEDTechnology delivers high quality OLED lighting products with long lifetime and low powerconsumption. Other advantages of OLED devices are the transparency, design flexibility, color

retention and clean technology.

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Fig (11.c) Fig (11.d)

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11.3 Cell Phones

Samsung Galaxy S4

The Galaxy S4 (Fig 10.e) is Samsung's 2013 flagship phone. It sports a 4.99" Full-HD

(1920x1080, 441 PPI) Super AMOLED display behind a Corning Gorilla Glass 3, an Octa-Core1.6Ghz Exynos CPU (some models use a QuadCore 1.9Ghz QUalcomm CPU), 2GB of memory,13 mp camera and a 2,600mAh battery. The S4 is actually a bit smaller and lighter than the S3,despite having a larger display and a larger battery.

Fig (11.e) Fig (11.f)

Nokia Lumia 505

Nokia's Lumia 505(Fig 10.f) is an entry-level Windows Phone 7.8 device that features a 3.7"ClearBlack AMOLED display (480x800), a 800 Mhz CPU, 256 MB RAM, 4GB of internal

memory (no card slot) and an 8mp camera.

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12. COMPARISON WITH OTHER TECHNOLOGY

Table1OLED VS LCD

OLED LCD

1. OLED panels need no lamps -- they are selfilluminating.

1.LCD TVs that use a fluorescent lamp forilluminating the picture. LCDs are screens ofcolored pixels. They do not create light, andas such, they require a light source.

2. OLED TVs can be thinner and lighterthanthe skinniest LCDs

2. LCDs arethickerthan OLED TVs

3. OLEDs consumeLessPOWER 3. LCDs Consume MorePower

4. OLEDs have large fields of view, about 170degrees

4. LCDs less fields of view

13. CURRENT AND FUTURE OLED APPLICATIONS

Currently, OLEDs are used in small-screen devices such as cell phones, PDAs and digitalcameras.

In September 2004, Sony Corporation announced that it was beginning mass productionof OLED screens for its CLIE PEG-VZ90 model of personal entertainment handhelds.Kodak already uses OLED displays in several of its digital camera models.

Several companies have already built prototype computer monitors and large screen TVs.In May 2005, Samsung Electronics announced that it had developed the first 40 inch,OLED based, ultra-slim TV. Research and development in the field of OLEDs isproceeding rapidly and may lead to future applications in heads up displays, automotivedashboards, billboard-type displays, home and office lighting and flexible displays.Because OLEDs refresh faster than LCDs, almost 1000 times faster , a device with anOLED display can change the information almost in real time.

Video images could be much more realistic and constantly updated. The newspaper of thefuture might be an OLED display that refreshes with breaking news and like a regularnewspaper,you could fold it up when you are done reading it and stick it in yourbackpack or briefcase

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14. CONCLUSION

OLEDs offer many advantages over both LEDs and LCDs. They are thinner, lighter andmore flexible than the crystalline layers in an LED or LCD. They have large fields ofview as they produce their own light.

Research and development in the field of OLEDs is proceeding rapidly and may lead tofuture applications in heads up displays, automotive dash boards, billboard type displaysetc. Because OLEDs refresh faster than LCDs, a device with OLED display could changeinformation almost in real time.

And this may lead to the future application in heads-up displays, automotive dashboards,billboard type displays, home and office lightings and flexible displays

In the near future, the flexible OLED display will appear in your laptop or home videoApplications.

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15. REFERENCES

C. W. Tang and S. A. Van Slyke, Organic electroluminescent diodes,Appl. Phys. Lett. 51, 913-915, 1987.

J. H. Burroughes, D. D. C. Bradely, A. R. Brown, R. N. Marks, K.Mackay, R. H. Friend, P. L. Burns, and A. B. Holmes, Light-emittingdiodes on conjugated polymers, Nature 347, 539-541, 1990.

www.howstuffworks.com www.wikipedia.org www.nytimes.com www.laserfocusworld.com www.jyi.org www.inhabitat.com www.oled-info.com www.proavmagazine.com

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