THE NEXT GENERATION DISPLAY TECHNOLOGY

A Research Paper

In

English 2 - B11 (College English II)

English Department, CASS

MSU-IIT, Iligan City

Submitted to

Prof. Lynnie Ann Deocampo

By

Gil Michael E. Regalado

March 2009

THE NEXT GENERATION DISPLAY TECHNOLOGY

MAIN TOPIC

Organic Light Emitting Diodes Display Technology

THESIS STATEMENT

Despite having several inherent shortcomings recent studies on Organic Light

Emitting Diode display technology have shown promising developments in addition to its

inherent advantages and thus have become the next generation’s display technology.

OUTLINE

I. Introduction

A. There are different kinds of display technology on the consumer

electronics market.

B. However, scientists from Kodak have discovered a new display

technology that will eclipse them all.

II. Body

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

whose emissive electroluminescent layer is composed of a film of organic

compounds.

1. A typical OLED is composed of an emissive layer, a conductive

layer, a substrate, and both anode and cathode terminals.

2. There are three different material technologies used in organic

light emitting diodes.

3. Organic light emitting diodes can be made into four different

structures.

a. Bottom emission uses a transparent electrode to get the

light through a transparent substrate.

b. Transparent organic light-emitting device use transparent

contacts on both sides of the device to create displays that

can be made to be both top and bottom emitting.

c. Stacked OLED uses a pixel architecture that stacks the red,

green, and blue subpixels on top of one another instead of

next to one another, leading to substantial increase in gamut

and color depth, and greatly reducing pixel gap.

d. In contrast to a conventional OLED, in which the anode is

placed on the substrate, an Inverted OLED uses a bottom

cathode that can be connected to the drain end of an n-

channel TFT.

B. Organic light emitting diodes have several shortcomings.

1. Currently, organic light emitting diode technology is expensive.

2. Organic light emitting diode has a short life time, especially of the

blue color.

3. Organic light emitting diode is problematic in direct sunlight

4. Water can easily damage organic light emitting diodes.

C. There have been several research conducted on OLEDs in order to

overcome its inherent shortcomings.

1. Scientists from Japan found a way inexpensively manufacture

OLEDs.

2. New materials have been found that improve the power efficiency

of blue OLEDs.

3. New OLED encapsulation method reduces water intrusion and

increases lifetime.

D. Despite the tradeoffs, organic light emitting diode has significant

advantages.

1. Organic light emitting diode displays are brighter than LEDs.

2. Organic light emitting diode displays do not require backlighting

like LCDs.

3. Organic light emitting diodes consume much less power.

4. Organic light emitting diodes are easier to produce.

5. Organic light emitting diodes have large fields of view, about 170

degrees.

6. Plastic, organic layers of an organic light emitting diode displays

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

an LED or LCD.

E. Organic light emitting diode displays will become the next generation’s

display technology if it becomes as cheap as it was intended to be.

1. After it surpasses prototype stage companies can invest on

dedicated manufacturing facilities.

2. Wide acceptance among major electronics companies will lower

manufacturing cost.

3. Competition between manufacturers will lower OLEDs per unit

cost.

III. Conclusion.

A. Gadgets will have longer battery life.

B. Displays will consume less energy.

C. Large displays will have crispier colors and deeper blacks.

D. Displays like laptops will have larger viewing angles.

INTRODUCTION

Cathode Ray Tube technology (CRT) has dominated the display industry since its

commercialization in 1922 up until the late 20th century. However, the demand for

displays that rival and surpass CRTs in areas such as picture quality, size, and power

consumption has been triggered by the increased desire for mobile electronics. Due to the

lightweight, low operating power, and compact design, Liquid Crystal Displays (LCD),

became the latest technology likely to replace CRT. (Gurski, 2005)

Watches, cell phones, laptops, and any small screened electronics were then made

possible by LCDs. Then LCDs expanded into areas previously monopolized by CRTs

such as computer monitors and televisions despite the fact that LCDs were initially

created for handheld and portable devices. However another display technology is taking

the lead. Surpassing even the LCD technology’s potential. (Gurski, 2005)

It was year 1987 when Kodak first published a technical paper about high

efficiency organic led (OLED). The event triggered the increasing interest on OLED

research and development efforts. (Kruger, 2001)

THE OLED

OLED STRUCTURE AND OPERATION

A typical and well-established design of an OLED consists of a number of thin

organic layers. These thin layers are either solution-processed or vacuum-deposited.

During operation, holes are injected from a transparent anode called “indium tin oxide”

hence referred to as anode ITO layer. A hole injection and transport layer (HTL) is found

adjacent to this anode layer. HTL is normally applied to allow for a well balanced hole

transport to the next layer. The next layer is the doped emission layer (EML) followed by

the electron transport layer (ETL) then the electron injection and protection layer and

lastly the cathode metal layer (CML). (Yertsin, 2008)

If a power supply of a device containing OLED applies a voltage across the

OLED, an electrical current flows from the cathode (CML) via the OLEDs organic layers

to the anode (ITO). The cathode gives electrons to the EML while the anode (ITO) gives

holes or positive charges to the EML. In the EML the process of electron (-) and hole (+)

recombination will occur. As a result, the electron gives up energy in the form of a

photon of light. (Freudenrich, N.d.)

There are three different materials used in the construction of OLEDs. One is the

use of small molecules, however the production of small molecules involves a very

expensive process called vacuum deposition. Organo-metallic chelates and conjugated

dendrimers are few of the commonly used molecules in small molecule OLEDs.

(Wikipedia-OLED, n.d.)

Another material is the polymer. An electroluminescent conductive polymer emits

light when connected to an external voltage source. Derivatives of poly (p-phenylene

vinylene) and polyfluorene are the typical polymers used. Last is the use of

phosphorescent materials, wherein electrophosphorescence converts electrical energy in

an OLED into light in a highly efficient manner. (Wikipedia-OLED, n.d.)

OLEDs can be made in to different structures. To get the light through a

transparent substrate, a bottom emission structure uses a transparent or semi-transparent

bottom electrode while a top emission structure uses a transparent or semi-transparent top

electrode to emit light directly. Top emitting OLEDs are well suited for active-matrix

applications because they are easily integrated to non-transparent transistor backplanes.

Likewise, transparent OLED structure use transparent or semitransparent contact on both

sides of the device to create displays that can be made transparent ideal for Head-up

displays, smart windows or augmented reality applications. (Wikipedia-OLED, n.d.)

On the other hand, using pixel architecture that stacks the red, green, and blue

subpixels on top of one another instead of next to one another, stacked OLED structure

can have substantial increase in gamut and color depth, and greatly reducing pixel gap.

And lastly, inverted OLEDs use a bottom cathode that can be connected to the drain end

of an n-channel TFT. Stacked OLED structure is very efficient for the low cost

amorphous silicon TFT backplane useful in the manufacturing of active matrix OLED

displays. (Wikipedia-OLED, n.d.)

ADVANTAGES AND SHORTCOMINGS

Since the earliest phase of the development of OLED several key advantages have

been found compared to today’s generation of LCD displays. In year 1989 Pioneer found

that OLED could resolve LCD’s weaknesses and started their own research and

development efforts. (Krüger, 2001)

According to Hagen Klauk (2001, p368) an OLED’s brightness is proportional to the

current, hence it’s also called current driven device and increasing the current will

increase the brightness of the OLED. In addition, the organic layers of an OLED are

much thinner than the corresponding inorganic crystal layers of an LED, the conductive

and emissive layers of an OLED can be multi-layered and since OLED does not require

glass which usually absorbs light OLEDs brightness is significantly increased. (Klauk,

2006) OLEDs can achieve deeper black colors in the absence of backlighting.

(Freudenrich, N.d.)

The plastic and organic layers of an OLED are thinner and lighter hence the

substrate of an OLED can be flexible instead of rigid. OLED substrates can be plastic

rather than the glass that is required for LEDs and LCDs and therefore providing

opportunities for commercialization of OLED lighting and display technologies that

aren’t possible today. (Freudenrich, N.d.)

Most of LCD power goes to backlighting since they work by selectively blocking

areas of the backlight to make the images that is displayed. However OLEDs generate

light by themselves hence they do not require backlighting and consume significantly less

power.

OLEDs are also easier to produce and are very scalable in size. They can be made

into large thin sheets because they are essentially made of plastic organic materials. Thus

OLEDs are more efficient economically compared to today’s generation of displays.

Additionally, according to Sanderson (2008, p175)

OLEDs also have larger viewing angles at 170 degrees. Compared to current

display technologies that work by blocking light, they have an inherent viewing obstacle

from certain angles. OLEDs also have much wider viewing range since they produce

their own light. (Freudenrich, N.d.)

However, OLED technology is not without its shortcomings. There are several

key shortcomings on OLED technology. Red and green OLED films have long lifetimes

from 46,000 to 230,000 hours however blue OLED currently have significantly lower

lifetime around 14,000 hours. OLED is also susceptible to water and oxygen intrusion

making manufacturing more difficult. Despite being bright, providing great image

quality, OLEDs have readability problem when viewed under direct sunlight or any

strong light source because of its emissive nature. (OLED-Info, N.d.)

Generally this only shows that OLED technology is still premature making

commercialization today unfeasible and very expensive. This has been to the extent that

as described by OLED-Info (N.d.), companies are selling very expensive prototypes than

real commercial products.

RECENT DEVELOPMENTS

There have been recent developments in OLED technology in order to overcome

their inherent shortcomings. These developments have contributed significant

improvements to OLED technology. Among them is one from Pacific Northwest

National Laboratory scientists where PNNL scientist Asanga Padmaperuma and his

colleagues designed, synthesized and tested new materials that improve the power

efficiency of blue OLEDs by at least 25 percent. Padmaperuma himself also presented

design strategies developed through computational and experimental chemistry for

engineering blue OLED materials efficiently. (Haas, 2009)

From Physorg Website sourced from Georgia Institute of Technology reports

another significant development in OLED technology (PhysOrg, 2008). Senior research

scientist Wusheng Tong from Georgia Tech Research Institute presented a high-density,

pinhole-free thin silicon oxynitride film on an organic light emitting diode surface

produced using ion assisted deposition to reduce moisture intrusion on OLED displays.

Displays are sealed commonly by manufacturers in an inert atmosphere or in a

vacuum environment. By gluing a glass lid on top of the display substrate with a powder

inside the display moisture that diffuses through the glue are absorbed. However, these

seals are expensive and labor-intensive to assemble. Tong and his GTRI collaborators –

senior research scientist Hisham Menkara and principal research scientist Brent Wagner –

have replaced the glass enclosure with a thin-film barrier formed by a less expensive

conventional deposition method. (PhysOrg, 2008)

Scientists from Japan also found a way for cost efficient manufacturing of

OLEDs. In the report from OLED-Info (2009), sourced from NanoWerk, using

electrospray-deposited polymer films, a new way to make OLEDs, have been found by

Scientists from the RIKEN center in Japan. According to Yutaka Yamagata of the

RIKEN Center, “Using this technology these devices could be manufactured as

inexpensively as printing newspapers.” (OLED-Info, 2009)

In addition, algorithms for longer OLED lifetime was also developed by

Eisenbrand (2007, p338) and colleagues. According to their research paper submitted to

the 6th International Workshop on Experimental Algorithms, current flowing through

OLED have a direct impact on its lifetime. By minimizing the amplitude of the electrical

current flowing though the diodes the lifetime of OLED can be increased. In order to

lower the display driver’s stress on the diodes, the optimization required finding a

decomposition of an image displayed into sub frames with special structural properties.

According to the paper the algorithm was shown to compute near optimal solution of

real-world instances in real-time. (Eisenbrand, 2007)

NEXT GENERATION DISPLAY TECHNOLOGY

A report by Alex Tullo (2002, p10) from the Chemical and Engineering News

Magazine shows that large firms have been positioning themselves in the new display

technology. A newcomer to OLEDs, BASF purchased a stake in Taiwanese OLED

display maker Teco Optronics Corp. A research partnership was also established by Teco

with BASF where BASF will develop light-emitting dyes. While OLED displays made at

RiTdisplays’ new plant in Hsinchu, Taiwan will be marketed by DuPont. (Tullo, 2002)

The size of the OLED market was estimated by Display consultancy

iSuppli/Stanford Resources (Tullo, 2002) as $112 million worldwide in 2002, growing to

$2.3 billion by 2008. However, today OLEDs are still expensive, much of the

investments have been allotted on the development of efficient manufacturing of OLEDs

by manufacturing companies.

Today, large Asian firms are also speeding up OLED developments. As reported

by Reuters (July 2008), according to the Nikkei business daily, the Japanese government

and major Japanese companies have teamed up to speed up OLED development. Aiming

to cut development costs, Sony, Toshiba, Matsushita Electric and Sharp join hands in the

mass-production of OLED displays and clear hurdles such as cutting production costs and

maximizing screen size in order to begin mass-producing OLEDs. It was also reported

that Japan’s Ministry of Economy, Trade and Industry is to pitch in 3.5 billion yen (PHP

1.76 billion) to help with the project, which would run from this year through 2012.

(Reuters, July 2008)

However in another part of Asia, as reported by Kim from The Korea Times,

(Yoo-chul, 2009) Samsung Electronics and LG Electronics of Korea are spending sizable

amounts of money for initial investments. Samsung Mobile Display (SMD), a joint

venture between Samsung Electronics and Samsung SDI in organic panels allocated an

initial investment amount of 1.5 trillion won (PHP 60.42 billion). A move that follows up

Korea’s stacking of 50% share of all patents on OLED technology worldwide as reported

from OLED-Info Website (OLED-Info, May 2007).

LG Electronics on the other hand will increase research and development

spending by 25% and direct them to OLED development, a move described by OLED-

Info to increase market share by taking advantage of the economic downturn. For future

growth of their business they will be investing roughly around USD 2 billion (91.13

billion PHP). (OLED-Info, March 2007)

Hence the continued funding by large companies on the research and

development on OLED technology will hasten the development stage of OLED,

combined with competition between these large companies, the cost of OLED will be

significantly reduced. OLEDs will then become as cheap as it was intended to be and will

truly become the next generation display technology.

CONCLUSION

Originally it has been the CRT technology that dominated the display industry.

However, by the increased demand for mobile consumer electronics, LCD display

technology replaced CRTs dominance. LCD display expanded to areas previously

monopolized by CRT and hence becoming today’s dominant display technology. But,

when Kodak published a paper about OLED it has since been the subject of major

interest among the largest electronics manufacturer.

Despite having several shortcomings, OLEDs potential is outstanding. And there

have been recent developments aimed at reducing the impact of OLEDs shortcomings.

Continued investment by companies for the development of OLED will increase the

acceptance of manufacturers for the mass production of OLEDs. And finally, competition

among companies will reduce the current exorbitant cost of OLED and thus truly

becoming the next generation display technology.

Because OLEDs need less energy, future laptops, handheld media players and

mobile phones will consume less energy for display and thus significantly extending

battery life while having impressive brightness and crisp colors. OLED technology will

affordably deliver significant improvements to a wide range of future consumer

electronics that needs displays.

Future consumer electronics with ultrathin, flexible, transparent, durable and

lighter weight form factors that are beyond today’s technology capabilities will be made

available by OLED technology. By Taking advantage of these incredible potentials

OLED will bring the future of consumer electronics to a whole new level of innovation.

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