A/Prof Jeffrey Funk

Division of Engineering and Technology Management

National University of Singapore

Source: Roland Haitz, Jeffrey Tsao, Solid-state Lighting: The case 10 years after and future prospects,

Phys. Solidi A 208 (1): 17-29, 2011

What do Continued Improvements in Luminosity per

Watt for LEDs Mean for Lighting?

What about Organic LEDs (OLEDs)

What do Continued Improvements in Luminosity per

Watt for OLEDs Mean for Lighting?

Source: Sheats et al, 1996, Organic Electroluminescent Devices, Science 271 (5277): 884-888 and Changhee Lee’spresentation slides; PPV: poly (p-phenylene vinylene)

Session Technology

1 Objectives and overview of course

2 When do new technologies become economically feasible?

3 Two types of improvements: 1) Creating materials that

better exploit physical phenomena; 2) Geometrical scaling

4 Semiconductors, ICs, electronic systems, big data analytics

5 MEMS and Bio-electronics

6 Lighting, Lasers, and Displays

7 Information Technology and Land Transportation

8 Human-Computer Interfaces, Biometrics

9 Superconductivity and Solar Cells

10 Nanotechnology and DNA sequencing

This is Sixth Session of MT5009

Outline

Existing state of lighting

Light emitting diodes (LEDs)

Organic light emitting diodes (OLEDs)

Laser Diodes

Applications for Laser Diodes

Bioluminescence

Type of

Specs

Incandescent

Lamp

Fluorescent

lamp

LED OLED

Thickness Very Thick Very Thick 6.9 mm (for LED

TV)

1.8 mm

Flexibility Very inflexible,

and breakable

Very inflexible,

and breakable

Some flexibility Most flexible

Danger to eyes Can’t stare at

them

Can’t stare at

them

Can’t stare at

them

Okay to stare

Lifespan 500-700 hrs >10, 000 hrs 100, 000 hrs 15, 000 hrs

Price of 60 Watt

bulb

<1 USD <5 USD 9 USD Most expensive

Efficiency/

Brightness

300 USD/Year for

800 lumens

75 USD per

year

<10 USD per year Not yet efficient

Environmental

friendliness

Low efficiency Contains

mercury

Most efficient, no

toxic chemical

Not yet efficient,

no toxic chemical

Costs of LEDs have Rapidly Dropped

Source: Group presentation in MT5016 module and http://electronics.howstuffworks.com/led4.htm

http://www.theverge.com/2013/10/3/4798602/walmart-gets-aggressive-on-led-bulb-pricing

Incandescent Lights Electricity is generated

by voltage across electrodes

Poor efficiencies (most of the power is emitted as heat or non-visible electro-magnetic radiation)

Also large size Big connector, bulbs,

filaments

Filament

Fluorescent Lighting

Electricity also generated by voltage across electrode

Better efficiencies emits about 65% in 254 nm line

(visible) and 10–20% of its light in 185 nm line (UV)

UV light is absorbed by bulb's fluorescent coating (phosphors), which re-radiates the energy at longer “visible” wavelengths

blend of phosphors controls the color of light

But still large device Bulb, Connector, gases

Outline

Existing state of lighting

Light emitting diodes (LEDs)

Organic light emitting diodes (OLEDs)

Laser Diodes

Applications for Laser Diodes

LEDs are basically a PN junction on a Semiconductor Substrate

Voltage difference

causes electrons and

holes to recombine

and thus release

photons

Amount of energy

in photons (and thus

wavelength of light)

depends on band

gap

Typical LED Characteristics

Semiconductor

MaterialWavelength Colour VF @ 20mA

GaAs 850-940nm Infra-Red 1.2v

GaAsP 630-660nm Red 1.8v

GaAsP 605-620nm Amber 2.0v

GaAsP:N 585-595nm Yellow 2.2v

AlGaP 550-570nm Green 3.5v

SiC 430-505nm Blue 3.6v

GaInN 450nm White 4.0v

Different Materials for LEDs Emit Different Wavelengths

and thus Emit Different Colors

But other changes in materials lead to improvements in efficiency

One measure of efficiency is Photons per electrons: first LEDs in 1960s generated .0001 photons/electron

But efficiency is a vague term because our eyes are more sensitive to some colors than others

More popular measure of efficiency is lumens per Watt; function of internal efficiency: amount of lumens generated

extraction efficiency: % of lumens that actually escapes

Must create the right combination of materials (and processes) to achieve high luminosity per Watt

Orton, J, 2009. Semiconductors and the Information Revolution: Magic Crystals that made IT Happen, NY: Academic Press

Must find materials that

Emit light in visible spectrum

Have short radiative lifetime (high probability of radiative recombination for electrons and holes)

Minimize non-radiative recombination with high crystal purity and structure

Maximize the possibility of radiative recombination by bringing together holes and electrons in a small space (such as double hetero-structure or quantum well)

And also design the device such that most of the light is extracted, i.e., escapes

Orton, J, 2009. Semiconductors and the Information Revolution: Magic Crystals that made IT Happen, NY: Academic Press

Improvements in Luminosity per Watt have Occurred

Source: Lima Azevedo, Granger Morgan, Fritz Morgan, The Transition to Solid-State Lighting,

Proceedings of the IEEE 97(3)

Lu

min

osi

ty p

er W

att

New Processes Also Helped

Because these materials do not naturally occur and because the processes impacted on the efficiency of an LED, scientists and engineers also created new processes for these new materials

These processes include

Liquid phase epitaxy

MOVPE (metal organic vapor phase epitaxy)

MBE (molecular beam epitaxy)

Electron beam irradiation

MBE allowed better control over the ratio of materials and the structures of the devices

Orton, J, 2009. Semiconductors and the Information Revolution: Magic Crystals that made IT Happen, NY: Academic Press

Most Recent Color is Blue

Bottleneck for making white LEDs for many years was in blue lasers (need red, blue, and green lights)

Efficient blue lasers did not exist until Shuji Nakamura improved the efficiency of blue LEDs in late 1990s by using GaInN

Blue LEDs enabled white LEDs and thus the use of LEDs for lighting

Second, blue lasers enabled smaller memory storage areas in CDs because shorter wavelength than red lasers

Finally, he developed a new growth technique called epitaxial lateral over growth, which enabled lower dislocation densities in blue lasers

Orton, J, 2009. Semiconductors and the Information Revolution: Magic Crystals that made IT Happen, NY: Academic Press

How to achieve White Color LED

Mixture of Red, Green & Blue color to get white color LED.

Involved electro-optical design to control blending & diffusion of different colors

Involved coating of an blue LED with phosphor of different colors to produce white light.

Fraction of blue light undergoes the Stokes Shift being transformed shorter wavelength to longer wavelength.

RGB White LED Phosphor Based White LED

LED Die

Phosphor

Phosphor Based White LED Spectrum of Phosphor LEDRGB Color Chart

Warm white

Cool white

Daylight white

Both Phillips and Samsung have created LEDs that emit 200 lumens and they have concluded that maximum theoretical efficiency is 400 lumens per Watt.

http://www.greentechmedia.com/articles/read/philips-ups-led-ante-with-200lumens-per-watt-tube. http://www.ledinside.com/node/16905

Further Improvements in Efficiency Have

Continued to Occur and More are Still Possible

According to DoE, Phillips, and Samsung

DoE’s Projected Increases in Efficiency of LEDs

Fluorescent

Source: Lima Azevedo, Granger Morgan, Fritz Morgan, The Transition to Solid-State Lighting,

Proceedings of the IEEE 97(3), March 2009

More Detailed Projections for LEDs by DoE

Source: Roland Haitz, Jeffrey Tsao, Solid-state Lighting: The case 10 years after and future prospects,

Phys. Solidi A 208 (1): 17-29, 2011

Costs are also Falling (Dotted Line) due

to Greater Efficiencies and Changes in Scale

Through-hole LED

Lead frame based

Advantages Low cost & easy rework

Higher mechanical shock resistant

Better light extraction with optic designed viewing angle

Disadvantage Size

Printed Circuit Board based

Advantages Size, thickness

SMT process, more popular

Disadvantage Less immunity to environmental

No optic design, customized viewing angle

Complicated process

Surface Mount LED

Both reductions (smaller LEDs) and increases in scale (bigger wafers/equipment) drive Cost Reductions

*See fourth session on ICs and discussion of displays for more details on why costs fall as substrates

and equipment are made larger. Wafers for ICs are now 12” and will soon be 18”Source of figure: http://www.electroiq.com/articles/sst/2012/02/led-manufacturing-highlights-from-strategies-in-light-day-2.html

Wafer Sizes Have and Will Become Larger*

LED CFL Incandescent

Light bulb projected lifespan 50,000 hours 10,000 hours 1,200 hours

Watts per bulb (equiv. 60

watts)10 14 60

Cost per bulb $35.95 $3.95 $1.25

KWh of electricity used over

50,000 hours500 700 3000

Cost of electricity (@ 0.10per

KWh)$50 $70 $300

Bulbs needed for 50k hours

of use1 5 42

Equivalent 50k hours bulb

expense$35.95 $19.75 $52.50

Total cost for 50k hours $85.75 $89.75 $352.50

Relatively Recent Cost ComparisonBut most recent price < $10 (USD) for LEDs

Sources: http://www.tomsguide.com/us/light-bulb-guide-2014,review-1986.html;

http://www.tomsguide.com/us/light-bulb-guide-2014,review-1986.html

$9

$9

$59

Can’t

we design

and package

LED lights

any better

than this?

Two LED-based Decorative Lights

Available in Singapore

LEDs for Greenhouses?

Greenhouses enable more locally grown food, and thus lower transportation costs

Build greenhouses in cities, something like vertical farms?

LEDs make more light available for greenhouses in northern climates and thus increase their productivity

http://nextbigfuture.com/2014/06/greenhouses-will-get-more-energy.html#more

Smart Lighting and (Heating)? Easer to control LEDs via Internet with for example,

tablet or smartphone

Can set timing, adjust colors and brightness

Various hardware are needed

but getting cheaper due to better electronic components

may be economical in office or other commercial buildings

How about using electronics to sense presence and location of humans?

Lights automatically turn on and off as people move

Take this one step further: lights only illuminate spots where people are standing or looking

Lighting as a serviceSource: Technology Review, Nov 5, 2012. http://m.technologyreview.com/blog/guest/28396/

Upgrades lightings at no

upfront cost

Provides maintenance

Provide free energy audits,

technical assistance and its

new financing option

Share Electricity Savings from using LEDs

More than

120 years

in lighting

business

What is Lighting-as-a-Service?

Smart Heating with Infra-Red LEDs

Direct beams of infrared light at people using

Clever optics

Servo-motors

Infrared light heats people and reduces need for heating entire room

Large infrared lamps?

Or small infrared LEDs?

People tracked with image sensors or Wi-Fi

Useful for large open rooms (e.g., lobbies, atrium, lecture halls) or rooms rarely used

Can reduce heating costs by 90%

Economist, in the moment of the heat, economist, September 6, 2014

Market for LEDs is Changing from Industrial Applications to General

Lighting as US bans sale of 40 and 60Watt Incandescent Bulbs

Source: http://www.semiconductor-today.com/news_items/2012/AUG/LED_090812.html

http://www.ledinside.com/node/17226; April 24, 2013

Outline

Existing state of lighting

Light emitting diodes (LEDs)

Organic light emitting diodes (OLEDs)

Laser Diodes

Applications for Laser Diodes

Bioluminescence

OLEDs have many Advantages Cheaper to process than semiconductor materials

Lower temperatures required

Can be roll printed onto a substrate (see later slides in this session)

Can put multiple colors on the same substrate

Can stare at them, unlike other forms of lighting

Thinner and more flexible

These advantages enable more aesthetically appealing

designs, even more than LEDs

But they currently have higher cost, lower efficiency and shorter lifetimes than do LEDs

What about Organic LEDs (OLEDs)

Improvements in OLEDs are Occurring

Source: Sheats et al, 1996, Organic Electroluminescent Devices, Science 271 (5277): 884-888 and Changhee Lee’spresentation slides; PPV: poly (p-phenylene vinylene)

More Recent Data Improvements also continue to be made. According to a 2009

paper in Nature, a novel structural design for a white OLED is described that exhibits efficiencies of 90 lumens per watt and shows a potential for efficiencies as high as 124 lumens per watt

Panasonic announced a white OLED with 114 lumens per Watt in 2013

Philips claims that efficiencies of 150 lumens per Watt can and will likely be achieved in the near future.

http://www.technologyreview.com/news/413485/ultra-efficient-organic-leds/

http://panasonic.co.jp/corp/news/official.data/data.dir/2013/05/en130524-6/en130524-6.html

Improvements are Driven by Creating Materials…..

Creating materials that better exploit the phenomenon of electroluminescence is the main reason for the improvements shown in the previous slide

Nitrides

Polymers

Polyfluorene

Also new processes?

What are the limits?

To what extent can efficiencies be improved?

costs be reduced?

thinness be achieved?

Lifetimes be increased?

Are these limits determined by materials or processes?

Can roll printing dramatically reduce costs; can increasing scale of roll printing equipment lead to much lower costs?

Where will be the first application for OLEDs Ones that require thinness, flexibility, and/or

multiple colors on a single substrate?

Household lighting?

Retail lighting?

Clothing?

Displays?

How many improvements are needed before these applications become economically feasible?

Household Lighting

Retail Lighting Display

New forms of eye

catching layouts

New types of Signs

Clothing

Flexible light panels sewn on clothing can provide

brighter luminance compared to conventional

safety clothing

OutlineExisting state of lighting

Light emitting diodes (LEDs)

Organic light emitting diodes (OLEDs)

Laser Diodes

they are similar to LEDs

They are basically an LED with a cavity and a mirror to enable “optical amplification based on stimulated emission of photons”

Applications for Laser Diodes Bioluminescence

Semiconductor Lasers also benefit from the two mechanisms mentioned earlier

Creating materials (and their associated processes) that better exploit physical phenomenon Creating combinations of materials that better exploit

phenomenon of optical amplification based on stimulated emission of photons

Helped by new processes that enable higher purity, better crystal structure, and better control over composition of materials

Also better materials for heat sinks, solder, and mirrors

Geometrical scaling Increases in scale: larger wafers/production equipment

Reductions in scale: smaller sizes generally lead to lower threshold current densities (helped by new technologies)

Different materials emit light at different wavelengths

Laser types shown above the wavelength bar emit light with a specific

wavelength while ones below the bar emit in a wavelength range. Non-

semiconductor lasers (many kinds of lasers) are also shown in this figure

Many Improvements to Lasers

Reductions in threshold current, i.e., minimum current needed for lasing

Reductions in Pulse Width of Lasers for faster switching

Increases in Power of Lasers

Improvements in cost and power for one type of laser (GaAs)

Source: Materials Today 14(9) September 2011, Pages 388–397

Reductions in Threshold Current, i.e., Minimum Current Needed for

Lasing to Occur, enable lower power consumption

Reductions in Threshold Current Driven By:

New structures

Double hetero-structure

Quantum wells

Quantum dots

Reductions in scale

These new structures involve smaller dimensions

Reductions in scale for a specific structure (along with other changes) also led to reductions in threshold current density

Reductions in scale also lead to lower costs in the long run

Double Heterostructure Quantum Well

(edge emitter) (edge emitter)

Vertical Cavity Surface Emitting Laser (VCSEL) (emits from the top and

emits perpendicular to the top surface), cheaper to fabricate than others

Source: NTT develops current-injection photonic-crystal laser

http://www.physorg.com/news/2012-02-ntt-current-injection-photonic-crystal-laser.html

DFB: Diffraction

Feedback Laser

VCSEL: Vertical

Cavity Surface

Emitting Laser

Lower operating currents also for VCSEL

Reductions in Threshold Current (2)

Creating new combinations of materials; enabled both

new emission wavelengths and

better lasing at a single wavelength (purity and crystal strength are important: see next slide)

New processes supported the reductions in scale and the creation of better materials

Liquid phase epitaxy

Vapor phase epitaxy

Molecular beam epitaxy

Metal organic vapor phase epitaxy

Low pressure chemical vapor deposition

Reductions

in Pulse

Width

of Lasers

http://www.nature.com/

nature/

journal/v424/n6950/fig

_tab/nature

01938_F2.html

Improvements in Power of Other Lasers for Defense, Medical

(without affecting

eyes)

Yb: Ytterbium

Tm: Thallium

Er:Yb: Ytterbium-

sensitized erbium

http://spie.org/x26003.xml

Source: Ultrafast fiber lasers, Marting Fermann and Ingmar Hart, Nature Photonics, 20 Octobers 2013, 868-874

Using Multiple Fibers can Enable Even Higher Power Output

Many Improvements to Lasers

Reductions in threshold current, i.e., minimum current needed for lasing

Reductions in Pulse Width of Lasers

Increases in Power of Lasers

Improvements in cost and power for one type of laser (GaAs)

For a specific type of laser, e.g., GaAs laser diode

Improvements are largely driven by creation of new materials

and processes for making those materials

Heat sink: heat must be removed in order to prevent overheating

of laser

Mirror: contaminants in mirror cause light to be focused on a

spot and thus burn up the mirror

Processes

Fewer defects can have large impact on maximum power because

small reduction in defects can lead to much higher power

Faster processes leads to lower costs come from faster processing

Also increases in scale of wafers and associated production

equipment

Source: Martinson R 2007. Industrial markets beckon for high-power diode lasers, Optics, October: 26-27. and

conversations with Dr. Aaron Danner, NUS

Improvements in Average Selling Price (ASP) and Power of Semiconductor Lasers

Source: Martinson R 2007. Industrial markets beckon for high-power

diode lasers, Optics, October: 26-27.

Outline

Existing state of lighting

Light emitting diodes (LEDs)

Organic light emitting diodes (OLEDs)

Laser Diodes

Applications for Laser Diodes

Bioluminescence

Applications for Lasers

Telecom is a big one: covered in Session 10

But many others Information storage (e.g., CDs and DVDs)

Processing of metals and other materials

Printing, Surgery

High power lasers for military, fusion

Agriculture

Automated vehicles

Virtual reality games

Some of these applications use laser diodes while other applications use other forms of lasers (gas and solid state lasers)

Agriculture

Laser leveled fields facilitate irrigation

Better control of water

GPS equipped tractors facilitate harvesting and seeding

Remember prescriptive planting in session 4?

Helps farmers plant seeds with greater precision using GPS and special seed drills

Cost of Autonomous Vehicles (Google Car) Falls as Improvements

in Lasers and Other “Components” Occur

Source: Wired Magazine, http://www.wired.com/magazine/2012/01/ff_autonomouscars/3/

Better Lasers, Camera chips, MEMS, ICs, GPS Making these Vehicles

Economically Feasible1 Radar: triggers alert when something

is in blind spot

2 Lane-keeping: Cameras recognize lane

markings by spotting contrast between road

surface and boundary lines

3 LIDAR: Light Detection and Ranging

system depends on 64 lasers, spinning at

upwards of 900 rpm, to generate a 360-

degree view

4 Infrared Camera: camera detects

objects

5 Stereo Vision: two cameras build a

real-time 3-D image of the road ahead

6 GPS/Inertial Measurement: tells us

location on map

7 Wheel Encoder: wheel-mounted

sensors measure wheel velocity

ICs interpret and act on this data

What an Autonomous Vehicle Sees

Underwater Automated Vehicles

For better oil exploration and fisheries

For fish farms

More than 50% of consumed fish are from fish farming

But feeding the fish is costly and the waste damages the local environment

Self propelled submersible fish pens can move fish to food and disperse waste

Many sensors help make this more economically feasible

Virtual Reality is becoming economically feasible partly

because lasers are getting better and cheaper. Lasers sense

the head movements so that the field of view changes.

Outline

Existing state of lighting

Light emitting diodes (LEDs)

Organic light emitting diodes (OLEDs)

Laser Diodes

Applications for Laser Diodes

Bioluminescence

Biological Materials Emit Light!

How it Works

71

Applications Lighting

Can we use trees to provide street

lighting?

Or to provide indoor lighting?

In-vivo imaging

A noninvasive insight into living

organisms

Understand disease related changes in

the body

Food industry

Can help detect pathogens

Challenges

Very expensive to extract luciferase from fire flies

Can we make better sources of bioluminescence through sequencing DNA, adjusting DNA, synthesizing DNA?

Discussed in next session

Can we put DNA into another living organism like has been done with spider silk?

Or will the cost of luciferase as we scale up production?

Just as cost of chemicals dropped as scale was increased

Conclusions and Relevant Questions for Your Group Projects (1)

The luminosity per Watt and their costs continue to be improved for LEDs and OLEDs because Scientists and engineers create new materials that better exploit

the relevant phenomenon

Also benefits from changes in scale

How many further improvements are likely to occur?

When will their costs become low enough or performance high enough to be economical for specific applications?

Can we identify those applications, order in which they will become economical, and specific needs of each application?

What does this tell us about the future?

Conclusions and Relevant Questions for Your Group Projects (2)

Improvements in lasers continue to occur Lower threshold current density

Higher power

Shorter pulse widths

How many further improvements are likely to occur?

When will their costs become low enough or performance high enough to be economical for specific applications?

Can we identify those applications, order in which they will become economical, and specific needs of each application?

What does this tell us about the future?