“OLED TECHNOLOGY”

A Seminar Report

Submitted in partial fulfillment of The requirements for the award of the Degree of

BACHELOR OF TECHNOLOGY

IN

Electronics and Communication Engineering

By

DEEPAK KUMAR

1101292167

DEPARTMENT OF

Electronics and Communication Engineering

GANDHI ENGINEERING COLLEGE BHUBANESWAR-752054

2014-15

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DEPARTMENT OF ELECTRONICS & COMMUNICATION

ENGINEERING

CERTIFICATE

This is to certify that the seminar report entitled “OLED

TECHNOLOGY” is presented by DEEPAK KUMAR (1101292167) in

partial fulfillment of the requirements for the award of the degree of

Bachelor of Technology in Electronics and Communication Engineering

during the academic year 2013-14. This seminar report is submitted to the

department as a part of evaluation of 7th Semester Seminar Presentation.

MANORANJAN SATAPATHY

H O D

Dept. of Electronics and Communication Engineering

Gandhi Engineering College, Bhubaneswar

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ACKNOWLEDGEMENT

My sincere thanks to Prof. Manoranjan Satapathy, Head of the

Department of ECE, Gandhi Engineering College, Bhubaneswar for his

encouragement and valuable suggestions during period of my seminar

presentation and report preparation.

No words would suffice to express my regard and gratitude to

Madhusmita Mohanty and Satyanarayan Pradhan, Department of

ECE for his inspiring guidance, and also I am gratitude to Prof.

Himansu Bh Mohapatra , Asst head of Department of ECE, Gandhi

Engineering College, Bhubaneswar for constant encouragement, immense

support and help during the seminar presentation and report preparation.

I express my heartfelt gratitude to all my teachers for his valuable

suggestion and guidance, without their cooperation this report is incomplete.

I express my thanks to all my friends for his valuable suggestion and

comments during my seminar preparation.

DEEPAK KUMAR 1101292167

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CONTENTS

Sl.No Topic Name Page No.

1. Abstract 2

2. Introduction 3

3. History 4-5

4. OLEDs structure 6

5. OLEDs working principle

5.1.Working

5.2Colour creations

7-8

6. Types of OLEDs

6.1 Passive-matrix OLED

6.2 Active-matrix OLED

6.3 Transparent OLED

6.4 Top-emitting OLED

6.5 Foldable OLED

6.6 White OLED

9-12

7. comparison with existing forms of illumination 13

8. Advantages and Disadvantages of OLEDs 14

9. Applications of OLEDs 15

10. Current research on OLEDs 15

11. The organic future of OLEDs 16

12. Conclusion

17

13. References 18

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LIST OF FIGURE

Sl.No Figure Name Fig

No.

Page

No.

1. Generation of OLED 0 4

2. Slight emitting diode 1 4

3. Multi layered OLED 2 5

4. POLED (polymer based OLED) 3 5

5. PMOLED (passive matrix OLED) 4 5

6. PHOLED (phosphorescenterent OLED) 5 5

7. Structure of OLED 6 6

8. Working of OLED 7 7

9. Colour creation 8 8

10. Passive OLED 9 9

11. Active OLED 10 10

12. Transparent OLED 11 10

13. Top emitting OLED 12 11

14. Foldable OLED 13 12

15. White OLED 14 12

16. Future of OLED 15 16

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1. ABSTRACT

OLED (Organic Light Emitting Diode) TECHNOLOGY

OLED is flat light emitting technology, composed of thin films of organic molecules that create light with the application of electricity. OLED can provide displays on electronic devices and use less power than conventional light emitting diodes i.e. (LED) used today. Like an LED, an OLED is a solid state semiconductor device that is 100 to 500 nanometers thick and 200 times smaller than the human hair. OLED can have two layers or three layers of organic material. It emits light through a process called electrophosphorescene. An OLED consists of the following parts:

Anode

Organic layers

Cathode

There are Different Types of an OLED are available:

Active matrix OLED

Passive matrix OLED

Transparent OLED

Foldable OLED

Top emitting OLED

White OLED

Currently OLED are used in many devices such as:

Display

Keyboard

Light

Portable devices screen

Research and Development in the field of OLED is proceeding rapidly now,

and may lead to future application in heads-up display and lighting.

SUBMITTED BY: - DEEPAK KUMAR REG.NO:- 1101292167

DEPARTMENT OF “ECE” GANDHI ENGINEERING COLLEGE

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2. INTRODUCTION

An organic light emitting diode (OLED) is simply a light emitting diode (LED)

whose emissive electro luminescent layer is composed of a film of organic

compounds. The layers are made up of small organic molecules or macro

polymers that conduct electricity. They have conductivity levels ranging from

insulators to conductors, so OLEDs are considered as organic

semiconductors. The layer of organic semiconductor material is formed

between two electrodes, where at least one of the layers is transparent.

An organic light emitting diode (OLED), also organic electro

luminescent device (OELD), is a light-emitting diode (LED) whose emissive

electroluminescent layer is composed of a film of organic compounds. This

layer of organic semiconductor material is formed between two electrodes,

where at least one of the electrodes is transparent.

Such devices can be used in television screens, computer monitors,

small, portable system screens such as cell phones and PDAs, watches,

advertising, information and indication. OLEDs can also be used in light

sources for general space illumination, and large-area light-emitting elements.

Due to the younger stage of development, OLEDs typically emit less light per

unit area than inorganic solid-state based LEDs which are usually designed

for use as point-light sources.

In the context of displays, OLEDs have certain advantages over

traditional liquid crystal displays (LCDs). OLED displays do not require a

backlight to function. Thus, they can display deep black levels and can be

thinner and lighter than LCD panels. OLED displays also naturally achieve

higher contrast ratios than either LCD screens using cold cathode fluorescent

lamps (CCFLs) or the more recently developed LED backlights in conditions

of low ambient light such as dark rooms.

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3. HISTORY

© Fig-0 Generation of OLED (www.oled-display.net)

In the era of Adam and Eve, i.e. in the first generation, people used to rub

stones to produce light. One day electricity was discovered and everything is

revolutionized. Bulbs were used at that time .In the third generation bulbs

were replaced by incandescent light and fluorescent light. In the fourth

generation the © Fight began for the cheapest material which could consumes

less power and give high efficiency. Thus we were here in the era of “LED”

and “OLED”. now a day’s LED is very popular but is going to be replaced by

OLED which will emerges as a leading next generation technology.

• In 1987 Chin Tang and Steven van slyke introduced the first Slight

emitting diodes from thin organic layers.

(Chin tang) (Van slyke)

© Fig-1 Slight emitting diode (www.oled-display.net)

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• In 1988 Chihaya Adachi and Tetsuo Tsutsui developed first multi

layered OLED .

(Chihaya Adachi) (Tetsuo Tsutsui)

© Fig-2 Multi layered OLED (www.oled-display.net)

• In 1990 Germy Burroughes and Richard Friend and Donal Bradely

developed first polymer based OLED(PLED).

(Germy Burroughes) ( Richard Friend) ( Donal Bradely)

© Fig-3 POLED (www.oled-display.net)

• In 1997 Teruo Tohma developed first passive matrix organic light

emitting diode (PMOLED) .

(Teruo Tohma)

© Fig-4 PMOLED (www.oled-display.net)

• In 1998 Mark Thompson and Stephen Forrest developed first

phosphorescent OLED (PHOLED) .

(Mark Thompson) (Stephen Forrest)

© Fig-5 PHOLED (www.oled-display.net)

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4. OLED STRUCTURE

It consists of an emissive layer, a conductive layer, a substrate, and both

anode and cathode terminals. The emissive layer, where light is made by the

emission of radiation whose frequency is in the visible region is made up of

organic plastic molecules that transport electrons from the cathode and the

polymer used is polyfluorene. The conductive layer is made up of organic

plastic molecules that transport holes from the anode and the conducting

polymer used is polyaniline. The substrate that supports OLED is made up of

flexible plastic, inexpensive glass or metal foil. Anode, that removes electrons

when a current flows through the device, is generally made up of Indium tin

oxide and it is transparent and cathode that injects electrons when a current

flows through the device is made up of metals like aluminum and calcium,

which may or may not be transparent depending on the type of OLED.

© Fig-6 Structure of OLED (www.oled-display.net)

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5. OLED WORKING PRINCIPLE

5.1 Working:

OLEDs emit light in a similar manner to LEDs, through a process called

electro-phosphorescence. An electrical current flows from the cathode to the

anode through the organic layers. When a voltage is applied to OLED, the

holes and the electrons are generated from each of the two electrodes, which

have a positive and negative electric charge respectively. When they

recombine in the emissive layer, organic materials make the emissive layer to

turn into a high energy state termed “excitation”. The light is emitted when the

layer returns to its original stability. The molecular structure of organic

materials has limitless combinations, each of which varies in its colour and

durability. Within these limitless combinations, identifying organic materials

that provide high efficiency and long life will determine its practical application.

A semi-conducting material such as silicon has an energy gap

between its lower, filled electrons state called as valence band and its upper,

unfilled electrons state called as conduction band. As electrons drop to the

lower state and occupy holes, photons of visible light are emitted. The colour

of the light depends on the type of organic molecule in the emissive layer and

the intensity or brightness of the light depends on the amount of electrical

current applied.

© Fig-7 Working of OLED (www.oled-display.net)

The device does not work when the anode is put at a negative potential with

respect to the cathode. In this condition, holes move to the anode and

electrons to the cathode, so they are moving away from each other and do not

recombine. Indium tin oxide is commonly used as the anode material. It is

transparent to visible light and has a high work function which promotes

injection of holes into the polymer layer. Metals such as aluminum and

calcium are often used for the cathode as they have low work functions which

promote injection of electrons into the polymer layer.

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5.2 CREATION OF COLOUR: OLED has more control over colour expression because it only expresses

pure colours when electric current stimulates the relevant pixels. The primary

colour matrix is arranged in red, green and blue pixels which are mounted

directly to a printed circuited board. Each individual OLED element is housed

in a special micro cavity structure designed to greatly reduce ambient light

interference that also improves overall colour contrast. The thickness of the

organic layer is adjusted to produce the strongest light to give a colour picture.

Further, the colours are refined with a filter and purified without using a

polarizer to give outstanding colour purity.

© Fig-8 Colour creation (www.oled-display.net)

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6. TYPES OF OLEDs

Passive-matrix OLED

Active-matrix OLED

Transparent OLED

Top-emitting OLED

Foldable OLED

White OLED

6.1 PASSIVE-MATRIX OLED (PMOLED):

PMOLEDs have strips of cathode, organic layers and strips of anode. The

anode strips are arranged perpendicular to the cathode strips. The

intersections of the cathode and anode make up the pixels where light is

emitted. External circuitry applies current to selected strips of anode and

cathode, determining which pixels get turned on and which pixels get turned

off. The brightness of each pixel is proportional to the amount of applied

current. PMOLEDs are easy to make, but they consume more power than

other types of OLED, mainly due to the power needed for the external

circuitry. They are most efficient and are used in cell phones, PDAs and MP3

players.

© Fig-9 Passive matrix OLEDs (www.oled-display.net)

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6.2 ACTIVE-MATRIX OLED (AMOLED):

AMOLEDs have full layers of cathode, organic molecules and anode, but the

anode layer overlays a thin film transistor (TFT) array that forms a matrix. The

TFT array itself is the circuitry that determines which pixels get turned on to

form an image.

AMOLEDs consume less power than PMOLEDs because the TFT array

requires less power than external circuitry, so they are efficient for large

displays. They are used in computer monitors, large-screen TVs and

electronic signs or billboards. The life expectancy of it is 30,000 hours.

© Fig-10 Active matrix OLED (www.oled-display.net)

6.3 TRANSPARENT OLED: Transparent OLEDs have only transparent components that are substrate,

cathode and anode. When turned off, they are 85% as transparent as their

substrate. When a transparent OLED display is turned on, it allows light to

pass in both directions. This can be either active or passive matrix. This

technology can be used for heads-up displays.

© Fig-11 Transparent OLED (www.oled-display.net)

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6.4 TOP-EMITTING OLED:

Top-emitting OLEDs have a substrate that is either opaque or reflective. The

top-emitting OLED display includes providing a handling substrate. A

composite layer is formed on the handling substrate. An organic light emitting

unit is formed on the composite layer. A top electrode is formed on the

organic light emitting unit. A reflective type display and fabrication method

thereof is provided. The reflective type display includes providing a handling

substrate. A composite layer is formed on the handling substrate; a thin film

transistor array is formed on the composite layer.

They are best suited to active-matrix design. These displays are used in smart

cards. The efficiency is 500 cd/m2 and the life span is 17,000 hours.

© Fig-12 Top emitting OLED (www.oled-display.net)

6.5 FOLDABLE OLED: Foldable OLEDs have substrates made of very flexible metallic foils or

plastics. They are very light-weight and durable. Their use in devices such as

cell phones and PDAs can reduce breakage, a major cause for return or

repair. Potentially, these displays can be attached to fabrics to create smart

clothing, such as outdoor survival clothing with an integrated computer chip,

cell phone, GPS receiver and OLED display sewn into it.

They are less breakable and more impact resistant – than other displays. With

glass breakage a major cause of display-containing product returns, this is a

highly desirable commercial alternative. They are very flexible i.e., they may

be manufactured on a variety of substrates. Such displays may be made to

bend, flex and conform to many surfaces. The luminance is 200 cd/m2.

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© Fig-13 Foldable OLED (www.oled-display.net)

6.6 WHITE OLED: White OLEDs emit white light that is brighter, more uniform and more energy

efficient than that emitted by fluorescent lights. They also have the true-colour

qualities of incandescent lighting. They can replace fluorescent lights that are

currently used in homes and buildings because they can be made in large

sheets. Their use could potentially reduce energy costs for lighting. Its

efficiency is 90 lm/W at a brightness of 1000 cd/m2 .

© Fig-14 White OLED (www.oled-display.net)

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7. COMPARISON WITH EXISTING FORMS OF ILLUMINATION:

OLED lighting Incandescent

light bulbs

Fluorescent

lamps

LED

Illustration

Principle of

light emission

Emits light by applying a voltage to organic matter

Emits light by sending an electric current to a metallic filament

Ultraviolet rays generated by an electric current collide with fluorescent material to produce visible light

Emits light by applying a voltage to an inorganic semiconductor

Characteristics Illuminates large area (surface light source)

Energy efficient Low heat-

generation Slim,

lightweight Flexible (when

plastic substrate used)

Environmentally sound

Illuminates small area (point light source) High power

consumption High heat-

generation Closely

approximates natural light

Size of area illuminated is between point light source and surface light source (linear light source)

Energy efficient Uses

hazardous substance (mercury)

Illuminates small area (point light source)

Energy efficient

Long life Easy to

reduce size

Environmentally sound

Uses Anticipated applications include living spaces, offices, decorative illumination, car interior lighting, and POP lighting

Photographic lighting, living spaces such as dining rooms or bedrooms, etc.

Living spaces, offices, commercial premises, etc.

Indirect lighting, floor level lighting, spotlights for retail spaces, etc.

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8. ADVANTAGES:

OLEDs are thinner, lighter and more flexible than the crystalline layers in

an LED or LCD. The plastic, organic layers of an OLED are 100 to 500

nanometers thick or about 200 times smaller than a human hair.

They are brighter than LEDs because the organic layers of an OLED are

much thinner than the corresponding inorganic crystal layers of an LED.

Also they do not require glass for support which absorbs some light.

It has ability to emit light from a surface, low heat generation, and

environmentally sound compared to fluorescent lamps.

They do not require backlighting like LCDs as they generate light

themselves, so they consume much less power than LCDs.

They are easier to produce and can be made to large sizes because they

are essentially plastics, which can be made into large, thin sheets.

They can enable a greater artificial contrast ratio that is measured in

purely dark conditions and have better viewing angle compared to LCDs

because OLED pixels directly emit light.

They have a faster time response than standard LCD screens.

DISADVANTAGES: Limited lifetime of the organic materials. While red and green OLED

films have longer lifetimes, blue organics currently have much

shorter lifetimes. However, the lifespan of OLED displays can be

increased by improving light out coupling.

The intrusion of water into displays can damage the organic

materials and limit the longevity of more flexible displays. Therefore,

improved sealing processes are important for practical

manufacturing.

The fabrication of the substrate is complex and expensive process in

the production of TFT LCD, so flexible substrates such as roll-up

displays and displays embedded in fabrics or clothing can be used.

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9. APPLICATIONS:

Light sources made from organic materials are of immense potential value for

a range of applications. Large area, flat light sources with surface brightness

have potential applications such as space lighting, back lighting or advertising

displays. Organic light emitting devices(OLEDs) offer the potential for such a

source. OLEDs promise a cheap, light weight source which potentially can be

made any size and on to a range of substrates (including flexible plastic).

Due to its light-weight, they can be used in cellular phones, PDAs,

notebooks, digital cameras, DVD players, car stereos, televisions, etc.,

They can be used as solid-state light sources.

In heads-up displays, automotive dashboards, billboard-type displays,

home and office lighting and flexible displays.

Due to its faster response than LCDs almost 1000 times faster, a device

with an OLED display could change information almost in real time.

In video images for more realistic and constant updates.

10. CURRENT RESEARCH ON OLEDs

Manufacturers focusing on finding a cheap way to produce OLEDs.

"Roll-to-Roll" Manufacturing Increase the efficiency of blue luminance.

Focusing to increase overall lifespan of OLEDs.

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11. THE ORGANIC FUTURE

The first products using organic displays are already being introduced into

the market place. And while it is always difficult to predict when and what

future products will be introduced, many manufacturers are now working to

introduce cell phones and personal digital assistants with OLED displays

within the next one or two years. The ultimate goal of using high-efficiency,

phosphorescenct, flexible OLED displays in lap top computers and even for

home video applications may be no more than a few years into future.

However, there remains much to be done if organics are to establish a

foothold in the display market. Achieving higher efficiencies, lower operating

voltages, and lower device life times are all challenges still to be met. But,

given the aggressive worldwide efforts in this area, emissive organic thin

films have an excellent chance of becoming the technology of choice for the

next generation of high-resolution, high-efficiency flat panel displays.

In addition to displays, there are many other opportunities for

application of organic thin-film semiconductors, but to date these have

remained largely untapped. Recent results in organic electronic technology

that may soon find commercial outlets in display black planes and other low-

cost

electronics

© Fig-15 Future of OLED(www.oled-display.net)

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12. CONCLUSION

Organic light emitting diodes promise to make electronic viewing more

convenient and ubiquitous as they are more energy efficient. OLED is so

revolutionary that in the field of illumination it is being hailed as “the first

discovery since Edison”. Today, OLED technology is widely seen as a next

generation component for flat panel displays and is expected to become a key

technology in the development of flexible displays.

Performance of organic LEDs depend upon many parameters such as

electron and hole mobility, magnitude of applied field, nature of hole and

electron transport layers and excited life-times. Organic materials are poised

as never before to transform the world IF circuit and display technology.

Major electronics firms are betting that the future holds tremendous

opportunity for the low cost and sometimes surprisingly high performance

offered by organic electronic and optoelectronic devices.

Organic Light Emitting Diodes are evolving as the next generation of

light sources. Presently researchers have been gong on to develop a 1.5

emitting device. This wavelength is of special interest for telecommunications

as it is the low-loss wavelength for optical fibre communications. Organic full-

colour displays may eventually replace liquid crystal displays for use with lap

top and even desktop computers. Researches are going on this subject and it

is sure that OLED will emerge as future solid state light source.

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13. REFERENCE

1. Electronics for You ; Volume 35

2. www.universaldisplay.com

3. www.edtn.com

4. www.emagin.com

5. www.pearsonptg.com

6. http://www.edisontechcenter.org/LED.html

7. www.google.com/oled-technology

8. www.wikipedia.com/oled

9. www.electronics.howstuffworks.com/oled

10. www.oled-info.com

11. www.oled-display.net