oleds and beyond- light sources of the future seminar

55
Light Sources of the Future – OLED and beyond Janos Veres, CTO, [email protected] www.polyphotonix.com

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Page 1: OLeds and Beyond- Light Sources of the Future Seminar

Light Sources of the Future –

OLED and beyond

Janos Veres, CTO, [email protected]

www.polyphotonix.com

Page 2: OLeds and Beyond- Light Sources of the Future Seminar

Agenda

Light

How to turn electricity into light ?

The solid state lighting revolution

The next wave: LED and OLED

New materials on the horizon

Radical concepts

Where is the lighting industry moving ?

Page 3: OLeds and Beyond- Light Sources of the Future Seminar

PolyPhotonix

Innovative SME based in the North East of England within PETEC (The UK National Centre for

Printed Electronics).

Established in early 2009

Focus on the application end of OLED technology - disruptive, radical uses in:

Architectural lighting, medical devices and automotive lighting/ambient interiors

Page 4: OLeds and Beyond- Light Sources of the Future Seminar

LightLight is electromagnetic radiation: waves and particles at the same time

Produced by exciting a substance with a variety of means

(heat, light, charged particles, chemical or biological)

Excitation and subsequent emission corresponds to transfer of energy between discrete levels

in matter

Page 5: OLeds and Beyond- Light Sources of the Future Seminar

Energy and excitation levels: gases

Sharp, discrete energy levels for individual atoms/molecules

Electrons transitioning between levels produce distinct absorption/radiation colours

Bromine

Deuterium

Helium

Hydrogen

Krypton

Mercury

Neon

Water vapour

Xenon

Emission spectrum

Absorption spectrum

Page 6: OLeds and Beyond- Light Sources of the Future Seminar

Energy and excitation levels: solids

Solids: atoms interact, energy levels start splitting, discrete levels become “energy bands”

Discreet lines are more difficult to observe

Page 7: OLeds and Beyond- Light Sources of the Future Seminar

Incandescence and blackbody radiation

Emission of light from a hot

body due to its temperature

The sensitivity of the eyeThe “Planckian Locus” in a colour space

Radiation of a blackbody

Page 8: OLeds and Beyond- Light Sources of the Future Seminar

Sunlight

Radiation of a blackbody

Solar radiation spectrum

Page 9: OLeds and Beyond- Light Sources of the Future Seminar

From incandescence to exciting gases and solids

CathodoluminescenceBeam of electrons excites a

luminescent phosphor

(television)

IncandescenceEmission of light from a hot

body due to its temperature

Thermionic emissionHeat induced flow of charge

from a surface.

Charge:

Fluorescent sourcesElectrons (thermionic) emitted ionise a gas.

The relaxation of gas molecules emit UV light.

UV is in turn used to excite a phosphor.

Page 10: OLeds and Beyond- Light Sources of the Future Seminar

Electroluminescence: LEDs

First practical visible device 1962 red

(Holonyak, GE)

p and n type layers deliver holes and

electrons to a recombination zone

Emission colour is determined by

bandgap of active layer

From Kazarinov and Pinto,

IEEE J. Quantum El.

30, 49, 1994

Page 11: OLeds and Beyond- Light Sources of the Future Seminar

White LEDs

Emission is centered around a single peak: bandgap

White is achieved either by phosphors or RGB devices combined

High colour rendering is a challenge

See http://en.wikipedia.org/wiki/Light-emitting_diode

Page 12: OLeds and Beyond- Light Sources of the Future Seminar

3–6 V

-

+

+

--

+

- - - - - -

+ + + + + +

-

+

- +- +

Visible light

OLED

Certain organic materials are semiconductors!

Photoluminescence+ electronic transport=electroluminescence

Light Emitting Diodes can be built that resemble LED

HOMO

LUMO

High workfunction

Anode

Au, ITO, Pt etc.

Low workfunction

cathode

Ca, Li, Al etc.+

+ +

- - -

+

Page 13: OLeds and Beyond- Light Sources of the Future Seminar

Organic semiconductors• Molecular solids. Intrinsic semiconductors

• Localisation is strong (especially in amorphous materials)

• bias for n or p type character due to electron donating/withdrawing groups

N

N

OO

OO

R

R

NTDI derivatives

S N

Polythienylene-

Vinylene (PTV)N N RR

O

OO

O

perylenes

PentaceneS

R R

Oligo, poly-

-thiophenes

polyfluorenes

LUMO: orbitals overlap

HOMO

e-

n-type

N

n

X X

Y

PTAA

R'R

n

R'

R

n

PPVs

HOMO

LUMO

h+

ambipolar

e-

HOMO: orbitals overlap

LUMO

h+p-type

Adopted from J. Veres, MRS Spring 2006

Page 14: OLeds and Beyond- Light Sources of the Future Seminar

HOMO

Organics are disorderedMolecular orientation, surrounding of molecules influences them

1. molecular energies vary

due to local orientation & polarisation effectsLow dipole moment, symmetry

Reduce impurities

Transition probability

p = n exp(–2R/r – DE/kT)

Extended state

May be a molecule, chain segment or domaine-

n-type

LUMO

DEh

2. molecular relaxation introduces further

energy differenceLarger molecules (i.e. extended states) help

e-

3. Orbital size and shape

4. Charge in orbitals

Adopted from J. Veres, MRS Spring 2006

Page 15: OLeds and Beyond- Light Sources of the Future Seminar

Cathode

ETL (Electron Transport layer)

HBL (hole blocking layer)

Host:Dopant

HTL 2 (Hole Transport Layer)

HTL 1

HIL (Hole Injection Layer)

Anode ITO

Glass

Low work function metal

Alq3

Various dyes

Triarylamines

Copper-Phthalocyanine /

PEDOT PANI

Evaporated OLEDMultilayer structures for dedicated tasks

Electrode mathcing, emission colour, carrier confinement

Page 16: OLeds and Beyond- Light Sources of the Future Seminar

triplet excitonsinglet exciton

p+

recombination

radiative

decay

radiative

decay

non-radiative decaynon-radiative decaynon-radiative

decay

non-radiative

decay

(((( ))))↓↑↓↑↓↑↓↑−−−−↑↓↑↓↑↓↑↓2

1 (((( ))))↓↑↓↑↓↑↓↑++++↑↓↑↓↑↓↑↓2

1

↑↑↑↑↑↑↑↑

↓↓↓↓↓↓↓↓

p-

Excited stated decay following spin statistics:

singlet: triplet ratio is 1:3, allowing only 25% efficiency by luminescence

Phosphorescence:

Certain metal complexes allow radiative emission from triplet states

Excited states in organic LEDs

Page 17: OLeds and Beyond- Light Sources of the Future Seminar
Page 18: OLeds and Beyond- Light Sources of the Future Seminar

Source: Universal Display OLED review

Page 19: OLeds and Beyond- Light Sources of the Future Seminar

Source: Universal Display OLED review

Page 20: OLeds and Beyond- Light Sources of the Future Seminar

Quantum dots

Semiconductor nanoparticles that exhibit quantum confinement (typically <10nm)

Nanoparticle: inorganic material (e.g. CdSe) with a diameter less than 1nm

Properties are tuned by the size of crystalline dots

Can be functionalised

Source: Evident Technologies & AIST Today Vol.6, No 6 (2006)

Page 21: OLeds and Beyond- Light Sources of the Future Seminar

Quantum confinement

ZnO

3

4

Eg (

eV

)

250

300

350

400

λo

nse

t (n

m)

0 5 10

d (nm)

ZnO

3

4

Eg (

eV

)

250

300

350

400

λonset

(nm

)

0 5 10

d (nm)

TiO2

TiO2

ZnO has small effective masses and quantum effects can be observed for particle sizes <8nm

TiO2 has large effective masses thus quantum effects are difficult to observe

Source: J. Galloway, Johns Hopkins univ. 2007

Page 22: OLeds and Beyond- Light Sources of the Future Seminar

Surface functionalisation

Surface states need to be terminated

Particles need to be separated to stop interacting

Inorganic shell grown

Polymeric functionalisation- solubility, dispersibility!

Specific binding sites: sensing/medical applications

Voura, E. B., Jaiswal, J. K., Mattoussi, H. & Simon, S. M. Nature Med.

2004(10), 993–998 Source: Evident Technologies

Page 23: OLeds and Beyond- Light Sources of the Future Seminar

QD fabrication

E-beam lithography

Etch pillars in quantum well heterostructures

1D vertical confinement due to mismatch of

bandgaps (potential energy well)

Pillars provide confinement in the other 2

dimensions

Disadvantages: Slow, low density, defects

Growth on patterned substrates

Grow QDs in pyramid-shaped recesses

Recesses formed by selective ion

etching

Disadvantage: density of QDs limited

by mask pattern

Epitaxy, patterned growth

A.Scherer and H.G. Craighead.

Appl. Phys. Lett., Nov 1986.

T. Fukui et al.

Appl. Phys. Lett. May, 1991

Page 24: OLeds and Beyond- Light Sources of the Future Seminar

Self-organized QDs through epitaxial growth strains

Stranski-Krastanov growth mode (use MBE, MOCVD)

Islands formed on wetting layer due to lattice mismatch (size ~10s nm)

Disadvantage: size and shape fluctuations, ordering

Control island initiation

Induce local strain, grow on dislocation, vary growth conditions, combine with patterning

QD fabrication

P. Petroff, A. Lorke, and A. Imamoglu. Physics Today, May 2001.

Page 25: OLeds and Beyond- Light Sources of the Future Seminar

Reactions engineered to precipitate quantum dots from solutions or a host material (e.g. polymer)

Surface is capped so the dot remains chemically stable

Can form “core-shell” structures, by sequential growth

Typically group II-VI materials (e.g. CdS, CdSe)

Disadvantage: Size variations ( “size dispersion”)

QD fabrication

C. B. Murray, et al Annual Rev. Mater. Sci. 30, 545, 2000.

Page 26: OLeds and Beyond- Light Sources of the Future Seminar

Quantum dots - properties

High quantum yield

Narrower and more symmetric emission spectra

100-1000 times more stable to photobleaching than organics

High resistance to photo-/chemical degradation

Tunable wave length range 400-4000 nm CdTe

J. Am. Chem. Soc. 2001, 123, 183-184

Page 27: OLeds and Beyond- Light Sources of the Future Seminar

Quantum dots for white LED

Evident, QD Vision, Nanoco

Page 28: OLeds and Beyond- Light Sources of the Future Seminar

Quantum dot electroluminescent devices

The next step in solid state devices!

Direct injection of holes and electrons into the quantum dots

Challenges: surface states on dots

Balancing carrier transport and isolation of quantum dots for their optical properties

Potentially coatable, printable like OLED !

J.M. Caruge et al, Nature Photonics, 2, 247, 2008

Page 29: OLeds and Beyond- Light Sources of the Future Seminar

QD for biology & sensing

Source: Justin Galloway, Johns Hopkins

Page 30: OLeds and Beyond- Light Sources of the Future Seminar

Lighting today

Lighting is a $90B industry and growing

rapidly

2/3 of all artificial light is generated by

fluorescent area lights

Quality of light, glare, efficacy, and toxic

mercury are fluorescent’s shortcomings

Page 31: OLeds and Beyond- Light Sources of the Future Seminar

31

Tomorrow

LED and OLED will dominate

inefficient environmental impact

Today

LED: efficient spot light OLED: efficient area light

?

Towards LED and OLED

Page 32: OLeds and Beyond- Light Sources of the Future Seminar

LED growth

Strong growth despite high prices and recession in 2008-2009

Source: Strategies Unlimited)

Page 33: OLeds and Beyond- Light Sources of the Future Seminar

The Haitz Law

1) Luminous flux per package increases 30 times each decade

2) Cost per lumen decreases by a factor of 10 each decade.

Source: Roland Haitz, Hewlett-Packard Labs, 1998

Page 34: OLeds and Beyond- Light Sources of the Future Seminar

34

OLED is real: displays and lighting

Displays

Lihgting

Page 35: OLeds and Beyond- Light Sources of the Future Seminar

Picture or graphic here

Incandescent

CFL

LED

Source: DOE Round 9 CALiPER Report

Real energy efficiency depends on the luminaire!

OLED has the opportunity to be the luminaire itself

Page 36: OLeds and Beyond- Light Sources of the Future Seminar

LED and OLED development expectations –DOE roadmaps

Both are predicted to offer important solutions to energy efficiency in the next 10 years

Both can achieve similar power efficiencies.

OLED is approximately 3 years behind LED

Source: DOE Roadmaps

Page 37: OLeds and Beyond- Light Sources of the Future Seminar

OLED lighting today

Source: DisplaySearch

Page 38: OLeds and Beyond- Light Sources of the Future Seminar

OLED lighting today – commercial devices

Page 39: OLeds and Beyond- Light Sources of the Future Seminar

OLED lighting today -demos

Source: Philips, GE, Add-Vision, Osram

Page 40: OLeds and Beyond- Light Sources of the Future Seminar

40

Inherently large area and low glare light source

Potentially ½ the power consumption of fluorescent

Warm, pleasing color

Green technology – no mercury

Innovative form factors in the future

Long term vision

Source: Osram, Konica Minolta, Acuity Brands

Page 41: OLeds and Beyond- Light Sources of the Future Seminar

It involves the printing of materials to create electronics.

• It can be very large areas Outdoor Billboards

• It can offer new forms Flexible, Rollable and invisible

• It can be cheaper Low cost materials and manufacturing compared to

conventional electronics

• It can offer improved performance over conventional electronics

The Printed Electronics industry will eventually become

as big as the semiconductor industry

The step Printed Electronics from integrated circuits is as equally

important as that from vacuum tubes to transistors

It creates new possibilities for business, new business's and wealth creation.

Page 42: OLeds and Beyond- Light Sources of the Future Seminar

Printed, felxible light –

organic or inorganic

• Highly efficient operation

• High quality white light (and/or better colours)

• Long lifetimes

• Thin, flat, large area ‘lambertian’ light source – architects love the idea

• Low voltage, DC driven

• ‘Printable’ – sheet or ‘roll to roll’

• Resistant to shock and vibration

• Multitude of applications

• Conformable and flexible, ability to integrate into architecture

OLED automotive applications

Page 43: OLeds and Beyond- Light Sources of the Future Seminar

The Importance of Design

Animated WallpaperJonas 2006

Richard Kirk, Founder of PolyPhotonix has a recognised background creating markets in the

field of Printed Electronics

Page 44: OLeds and Beyond- Light Sources of the Future Seminar

It’s not just the Science…..

Working with artists via the creation

of an art foundation

Page 45: OLeds and Beyond- Light Sources of the Future Seminar

Printed Electronics in Architecture

Radisson Stanstead Wine Tower, UKAlcatel Boardroom, Paris, France

Page 46: OLeds and Beyond- Light Sources of the Future Seminar

British Airways, First Class Lounge

10,500 circuits

25 meters x 2.5 meters

All circuits individually addressable

Created by artists that Elumin8 sponsored in the past

Manufacture, design and install, 1/10th of the cost of an equivalent LED wall

Heathrow Terminal 5

Troika, London

Page 47: OLeds and Beyond- Light Sources of the Future Seminar

Experience with every outdoor company in Europe and North America

Delivery and installation

Integrated solutions

Examples of outdoor installations in Paris.

Advertising

Page 48: OLeds and Beyond- Light Sources of the Future Seminar

Gareth Pugh 2007The HSBC Advert was shown in 180 countries

Fashion

Page 49: OLeds and Beyond- Light Sources of the Future Seminar

Printed Electronics in Automotive

Pioneered the use of printed Electroluminescence in transport applications with:

Jaguar, Bentley, Rolls Royce, BAE, Lotus, Aston Martin, Ford, Ascari, JCB,

MOD, Nascar, Toyota, Westland, Nissan among others.

Jaguar CXF

Page 50: OLeds and Beyond- Light Sources of the Future Seminar

2x 8,000 sq ft clean rooms.

Pilot line processes developed for

•Organic Thin Film Transistors (OTFT);

•Organic Photovoltaic's (OPV);

•Solid State Lighting (SSL)

state of the art equipment set and

world class industry expertise

The UK Printable Electronics Centre

PETEC

Page 51: OLeds and Beyond- Light Sources of the Future Seminar

PolyPhotonix technology development

• Synergies with technology base for other projects at PETEC

• Secured significant grants for funded projects, over £2 M

• Working with technology providers to source, license existing materials/processes

• Building a development process line

• Exploring proprietary process technologies for follow up phase

• PolyPhotonix is aiming to be one of the first to market with an OLED product.

Page 52: OLeds and Beyond- Light Sources of the Future Seminar

What does the futurte hold ? Future concepts

Wireless lighting – Tesla experiments

Colour tuning in a single layer

Transparent devices

Photovoltaics and lighting combined

Lighting elements integral part of building elements

Page 53: OLeds and Beyond- Light Sources of the Future Seminar

Strechable LED arrays

Small LED “chiplets” connected with a wave-shaped wire mesh

Embedded in silicone plastic

Applications: surgical gloves, strechable displays

Source: Kim et al, Nature materials, 9, 929, 2010

Page 54: OLeds and Beyond- Light Sources of the Future Seminar

Lighting with trees ?

Implanting gold nanoparticles into the leaves of the Bacopa Caroliniana plants.

Under UV excitation, Au nanoparticles produce a blue-violet fluorescence to trigger a

red emission in the surrounding chlorophyll.

Source: Prof Shi-Hiu Chang, Taiwan

Page 55: OLeds and Beyond- Light Sources of the Future Seminar

Solid state lighting is undergoing a revolution

LED and OLED are both taking off fast

Initially high prices require targeting unique applications

There is plenty of opportunity to innovate:

LED/OLED developments with quantum dots will be significant!

Summary