OLEDORGANIC LIGHT EMITTING DIODE

DISPLAY TECHNOLOGY

Jay Dhamsaniya

Rakesh Adroja

Department of E & C Engineering

Institute of Technology

Nirma University

Ahemedabad

OCT - 2011

INTRODUCTION

Definition :

An organic light emitting diode (OLED) is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compounds that emits light when an electric current passes through it.

WORKING 2 – layer structure

Active & In-active condition

Material used in layero Anode (+) Indium tin oxide (ITO) o Cathode (-) Metals such as aluminium (Al) and calcium (Ca)o Emissive layer Alq3 which emits radiation in the range of

green light o Conductive layer Diamine

WORKING For efficient emission recombination zone should be in the

middle of the organic emissive layer

In organic semiconductors, holes are more mobile than electrons

Recombination happens closer to the emissive layer

Problem solution : Multi layer structured OLED

MULTI-LAYER OLEDElectron-hole recombination zone is shifted in the middle of the emissive layer

TYPES OF OLEDOLED

Organic material used

Small Molecule OLED

Polymer OLED

Phosphorescent OLED

Transparency

Bottom or Top emitting OLED

Transparent OLED

Foldable OLED

Pixel Formation used

Active Matrix OLED

Passive Matrix OLED

Stacked OLED

Inverted OLED

White OLED

TYPES OF OLED[A] Classification according to Organic Material used

1. SMALL MOLECULE OLEDs:• First developed at Eastman Kodak by Dr. Ching W. Tang

• Example: Alq3

2. POLYMER MOLECULE OLEDs:• Example: poly(p-phenylene vinylene)

3. PHOSPHORESCENT MATERIALS OLEDs:

• Example: Ir(mppy)3,

• It is a phosphorescent dopant which emits green light

TYPES OF OLED[B] Classification according to Transparency

1. Bottom or top emissive OLEDs:• One of the electrode is kept transparent

TYPES OF OLED[B] Classification according to Transparency

2. Transparent OLEDs:• Both electrodes are kept transparent

TYPES OF OLED[C] FOLDABLE OLED

• Flexible substrate is used

• It is prepared by roll-to-roll patterning method

TYPES OF OLED[C] FOLDABLE OLED

FOLEDs offer Revolutionary Features for Display:

1. Flexibility

2. Ultra-lightweight, thin form

3. Durability

4. Cost-effective processing

TYPES OF OLED[D] CLASSIFICATION ACCORDING TO PIXEL FORMATION USED

1. Active Matrix OLEDs (AM-OLEDs): Display is a set of pixel Pixel is a single oled

Individual Cathode and Anode Biasing current provided to pixel, is

controlled by TFT according to information

A/D: Reduces power consumption

D/A: Patterning/Fabrication cost is high

TYPES OF OLED[D] CLASSIFICATION ACCORDING TO PIXEL FORMATION USED

2. Passive Matrix OLEDs (PM-OLEDs):

Cathode and Anode are kept common for

each rows/columns Pixel formed at the intersection

ADVANTAGES OF OLED DISPLAY

Advantages:1. Very thin panel of approximately 1mm

2. Low power consumption

3. High brightness

4. High contrast ratio of 10,000 : 1

5. Wide viewing angle of 170

6. No environmental drawbacks

7. Foldable display panel

ADVANTAGES OF OLED DISPLAY

Advantages of OLED Display over TFT-LCD Display:

1. Contrast Ratio Higher contrast ratio than TFT-LCD display Better impression for higher brightness

Contrast Ratio(Sunlight Readable)

Condition OLED TFT-LCD

Dark room > 10,000 : 1 300 : 1

Rainy 400 130

Cloudy 190 10

Sunlight 50 4

ADVANTAGES OF OLED DISPLAY

2. Viewing Angle Higher viewing angle

up to 170

for constant contrast ratio

Graph:

contrast V/S viewing angle

ADVANTAGES OF OLED DISPLAY

3. Response Time Fast time response

in order of <50 us Comparison

by graphical point of view

ADVANTAGES OF OLED DISPLAY

4. Backlight Function No backlight required in OLED display During black background OLED is turned OFF In LCD backlight is still required

ADVANTAGES OF OLED DISPLAY

4. Power Efficiency OLED display is more power efficient

than TFT-LCD display For the same power OLED display is

more brighter

DISADVANTAGES OF OLED DISPLAY

1. Limited life time

2. Color balancing issues

3. Water damage

4. Power consumption

APPLICATIONS OF OLED DISPLAY

FUTURE OF OLED Light weight Thin Unbreakable Low cost processing

potential for Roll-to-Roll

patterning New product possibility

CONCLUSIONThere are many other opportunities for application of organic

thin-film semiconductors and challenges are remain for development that is shown following table.

Challenges Opportunities

Matireals blue & white EL, low-cost ITO alternatives

Process cost high

OLED Industry still in the early stage of development

Driving Tech for AMOLED is still under development

White OLED high performance WOLED is needed

Solution Printing

tech is viable for large size and low cost

FOLED will be very attractive for application in conformal,fordable or even flexible lighting and displays

Thank you!