10 november 2011

Foil technology for conformable electronics

Margreet de Kok TNO/ Holst Centre10 november 2011

10 november 2011

1. Holst Centre

2. Introduction OLED

3. Application of OLED

4. Lifetime of OLEDs

5. Conformable technology

6. Conclusions

Contents

� 3

1. Holst Centre

� 4

Holst Centre Fingerprint

Who we are

What we do

How we work

� Creating generic technologies, time to market 3..10 years

� Research Focus on wireless, autonomous micro-systems

and flexible electronics

� Independent research organization co-founded by IMEC (1300 fte,

Belgium) and TNO (4500 fte, the Netherlands) in 2005

� Global network of industrial and academic partners

� 150 researchers and 60 resident researchers from industry and university

� Open Innovation through precompetitive research programs

� Roadmaps defined along with partners

� Day to day interaction with industrial residents

� Results are shared between partners

� 5� 5

OLEDs

Disposable bio-sensors

Electronic textiles

Plastic solar cells

Smart bandage

Smart

packaging

Sensors

RFID tags

Flexible displays

Touch

screens

Signage

Plastic batteries

Large Area Electronics market applications

� 6

Soluble Semiconductors

Inkjet printing

Roll to Roll coating

New ways of

processing

Important Enabler:

Organic Semiconductors

MicroDrop

� 7

Access to Unique Set of Infrastructures and Process Labs

Materials Analysis

Electronic

measurement

Thin Film

clean room

OLED Device

Processing

Reliability lab

Photonics

cleanroom

Electronic

Prototyping

� 8000 m2 cleanroom

Equipment

Engineering

Life Sciences

facilities

EMC lab

Holst

R2R lab

Holst

Offices

High Tech Campus, Eindhoven

Düsseldorf

Eindhoven

Aachen

Amsterdam

Leuven

IMEC 2 & 3offices and labs

CafeteriaTraining

infrastructure

IMEC 1Main entrance

IMECEXPO visitor center

Offices and labs

IMEC 4Office building

cleanroomNano-

elektronicalab

Clean room 2

3200 m2 clean room

2200 m2 vibration controlled

300 mm pilot line

Ball room, clean sub-FAB

FOUP wafer transport

cleanroomNano-

elektronicalab

Clean room 2

3200 m2 clean room

2200 m2 vibration controlled

300 mm pilot line

Ball room, clean sub-FAB

FOUP wafer transport

Cleanroom200mm silicium

pilootlijn

Clean room 1

5200 m2 clean room

1750 m2 class 1

200 mm pilot line

Continuous operation:

24hrs / 7 days

Cleanroom200mm silicium

pilootlijn

Clean room 1

5200 m2 clean room

1750 m2 class 1

200 mm pilot line

Continuous operation:

24hrs / 7 days

Netherlands

Belgium

� 8� 8

Industrial partners from across the value chain

� 9

2. Introduction to OLED

� 10

OLED Basics

Two types of OLEDs:

Polymer LEDSmall molecule LED

cathode

Organic layers

anode

� 11

OLED: Electroluminescence

Typical Light Emitting Polymers:

PPV (polyphenylene vinylene)

PF (polyfluorene)

(Fluorescent emitter)

� 12

OLED: Injection scheme

4

5

6

Li,K

Ni Au

Ag

Ba

Mg

AlIn

Pt

Hf

BaO

SrO

2

3

4

TiO2

TiN

GdB6

Ca

LiF

Se

PEDOT

Cs

ITO

High workfunction Low workfunction

anode materials cathode materials

Work function (eV)

� 13

IVL

• Vbi ~Vturnon• Dependent on band gap material

• Dependent on work function difference of the contacts

• Blue and white 5-10 lum/W

• Record: 100 lum/W

HOMOHT (5.2 eV)

LUMOPF (2.2 eV)PEDOT:

PSS

(5.1 eV)

Ba/Al

(2.7 eV)

Energies with respect to the vacuum level

-2 0 2 4 6 81E-4

1E-3

0.01

0.1

1

10

100

1000

10000BL102

J (A/m

2)

Bias (V)

-2 0 2 4 6 80

1

2BL102

Efficacy (lm/W

)

Bias (V)

� 14

Possibilities to prevent voltage drop

• Metal grid

12x12 cm2 top emission white OLED on SS

12x6 cm2 top emission white OLED on SS

� 15

Application in OLED

144 cm2 white PLED without ITO using high conductivity PEDOT with Ag printed shunting lines (submitted for SPIE 2009)

� 16

3. Applications for OLEDs

� 17

OLED Applications & Expectations

Signaling Signage

Lighting

Displays

� 18

But also:

Advertising

Company logo AutomotiveAdd-Vision

Automotive

Healthcare

� 19

Flexible OLEDs

• Only prototypes, no commercial products

� Add-Vision

� Sony

� Samsung

� Novaled/Assilor-Mital

� UDC

� GE

• Showstopper: barrier films

� 20

Next Application for OLED: Solid State Lighting

LED

(SM/P)OLED

� 21

Solid State Lighting

OSRAM

InorganicOrganic

Small-molecular

Macromolecular

� 22

Comparison Inorganic – Organic LEDs

• Inorganic LEDs

• Products on the market with high efficiency and long lifetime

• Small area and high luminance (no large area possible)

• Thermal management needs attention

• (Colour stability of production leads to binning of LEDs)

• Organic LEDs

• First lighting products on the market

• Large area possible and therefore low luminance enough

• Thin

• Thermal management less problematic

• Colour better controllable

• Cost per area effective

Application and design freedom (and price) make the difference

� 23

Organic light sources and detectors: opportunities and challenges

• Form freedom

• Large area possible

• Flexibility (bendability)

• Very thin features

• Fine tuning of optical properties possible

• Integration with multiple functionalities possible in foil

• Production technology versatile

• Cost aspect positive

• Challenges:

• Processing thin layers - shorts

• Encapsulation and intrinsic lifetime

• Efficiency

• Current density distribution

• Design of combination of building blocks

� 24

Why flexible?

• Enhanced functionality for the end user: bendable, rollable devices

But also

• Integration of foil devices in products & systems: conformal application?; convenient feeding into assembly system

• Efficient large area production of foil devices (e.g. roll-to-roll; no manual assembly) -> cost aspect

Source: GE Source: Metsuo

� 25

State-of-the-art in white OLED

� 26

OLED Trends

� Materials

� Substrates: flexible plastic or metal substrates combined with R2R processing

� Barrier: strong focus on developing flexible thin film barriers (Holst Centre, Vitex, General Electrics, Dow, ..) with WVTR < 10-6 g/m2.day

� Emitters: phosphorescent emitters (UDC, Sumation, Merck, Novaled, ..)

� Transport layers: doping of transport layers (Novaled, ..)

� Cathodes: top emitting/transparent OLEDs with transparent cathodes

� Anodes: high conductive organic materials and/or or introduction of support structures (evaporated or other) (GE, OLLA, Holst Centre, ..)

� Processing:

� Roll-to-roll processing on flexible plastic or metallic substrates

� Printing or coating of functional materials in general (as opposed to spin-coating)

� Printing or coating of small molecules (Dupont, UDC, ..)

� Devices:

� Innovative OLED designs / Intelligent Lighting

� >100 cm2 lighting tiles (Lumiotec, GE, Philips, OSRAM, UDC, Konica Minolta, ..)

� OLED display driving: AMOLED as opposed to PMOLED (SDI, LGE, SONY, ..)

� TFT towards oxide TFT as opposed to OTFT / LTPS (Dai Nippon Printing)

� Place-it: conformable electronic systems comprising OLEDs

� 27

4. Lifetime of OLEDs

� 28

OLED Degradation

time

0

50

100

150

0 50 100luminance (%)

intrinsic

time

0

50

100

150

0

50

100

150

0

50

100

150

0 50 1000 50 100luminance (%)

intrinsic

voltage (%)

time

0

50

100

150

500 100

voltage increase

voltage (%)

time

0

50

100

150

500 100

voltage increase

time

0

50

100

150

0

50

100

150

500 1000 100

voltage increase

luminance (%)

time

0

50

100

150

0 50 100

short

luminance (%)

time

0

50

100

150

0 50 100

short

time

0

50

100

150

0

50

100

150

0

50

100

150

0 50 1000 50 100

short

time

0

50

100

150

0 50 100

luminance (%)

leak

time

0

50

100

150

0

50

100

150

0

50

100

150

0 50 1000 50 100

luminance (%)

leak

time

0

50

100

150

0 50 100

voltage (%)

time

0

50

100

150

0 50 100

voltage (%)

time

0

50

100

150

0

50

100

150

0

50

100

150

0 50 1000 50 100

voltage (%)

voltage (%)

time

0

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0 50 100

voltage (%)

time

0

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100

150

0

50

100

150

0

50

100

150

0 50 1000 50 100

� 29

OLED Degradation

� 30

OLED Degradation: black spots

• Intrinsic: homogeneous degradation

• Cathode oxidation: local degradation leading to black spots

H2O, not O2

Right after processing ~10h at 20 °C / 50% RH

� 31

Focus is on water penetration, not oxygen

• oxygen analysis (RBS)

• exposed calcium layer

• DA = dry air

• AA = atmospheric

Cros et al. Nucl. Instr. Meth. Phys. Res. B 2006, 251, 257-260

� 32

EL vs PL

• black spots visible in EL, not in PL

• no degradation of the active (emitting) material(s)

• formation of a charge injection barrier due to cathode interface oxidation

• light spots in PL: enhanced out-coupling due to scattering

electroluminescence (EL) photoluminescence (PL)

� 33

black spot formation: pinholes in Al

� ~106-107 pinholes / m2 in cathode

� Al-cathode = very good intrinsic barrier properties

� Linear growth of circular black spots: diffusion controlled process

� Shelf Effect

cathodecathode21

organics

- shelf effect !!E3140201, SiN shelf

0

10

20

30

40

50

60

70

80

90

100

0 200 400 600 800 1000 1200

time (hrs)

black spot area (a.u.)

- shelf effect !!E3140201, SiN shelf

0

10

20

30

40

50

60

70

80

90

100

0 200 400 600 800 1000 1200

time (hrs)

black spot area (a.u.)

E3140201, SiN shelf

0

10

20

30

40

50

60

70

80

90

100

0 200 400 600 800 1000 1200

time (hrs)

black spot area (a.u.)

� 34

Standard Encapsulation

� State-of-the-art encapsulation using metal or glass lid with cavity containing getters

� no hermetic seal (getter!)

� 40,000 hrs at 80 °°°°C without black spot formation

But, it is not applicable for:

� Fast production

� Large area devices

� Flexible (foil-based) devices

cathodeorganics

ITO

substrate

getter

� 35

Requirements for (TF) barrier/encapsulation

• Intrinsic WVTR < 10-6 g.m-2.day-1

• No black spots

� >5 years @ 20/50

� >504 h @ 60/90

• Feasibility for R2R

� Barriers should be rollable over d=20cm

• Low cost

� High deposition rates

Barrier on foil specific:

• Transparency for visible light >90%

• Uniform light output

� Extremely uniform layers over large areas

• Light outcoupling

• Abrasion resistance, UV protection, etc.

� 36

Multilayer approach

• Stacks of inorganic and organic layer used to decouple pinholes and get full coverage => time delay of black spot formation

• Holst approach: SiN – OCP – SiN

• OCP = organic coating for planarisation

4

planarizationlayer

321

4

planarizationlayer44

planarizationlayer

planarizationlayer

321

3321 21 21

0.1

1

10

100

10 100 1000 10000

time (hrs)

black spot area (a.u.)

SiN

SiN-org-SiN

� 37

State of the Art for encapsulation

• Wvtr: 10-6 g/m2day

• >5000 hrs at 20/50 black spot free and still running

Side leakage Black spots by pin holes

� 38

Advanced systems by combined functionalities in Foil

• Organic LEDs

• Organic Photodetectors

• Organic Photovoltaics

• Embedded circuitry

• Embedded chips

• RFID

• Memories

• Sensors

� Electrochemical

� Optochemical

� Optical

� 39

Device Design - laminated foil approach

• Foil

� Double side processing

� Modular: diodes and LEDs printed on separate foils

• Top emissive PLEDs, Bottom receptive OPDs:

• Bottom emissive PLEDs, Top receptive OPDs:

• Etc.

� 39

skin

skin

LED

Photodiode

30

25

20

15

10

5

0

Spectral Radiance (10-3W/sr m

2 nm)

750700650600550500

wavelength (nm)

� 40

Printed devices

• Foil

� Single side processing

� Diodes and OLEDs via printing

� Arrays of different devices on one substrate

� 40

� 41

Foil Integration

• Modular approach

• Distribute functions over different layers µ-via technology combined with lamination

• Silicon in Foil embedding

� 41

� 42

First Organic Device Prototype: Proof of Principle

• OPD

� Total measured current ca. 10 µA

� Signal ca. 50 nA

• PLED

� I = 80 mA/cm2

� V = 5.2 V

� L = 520 Cd/m2

• Works!

� PPG comparable to commercial pulse-oximeter (Nelcor N200)

� 42

Signal (a.u.)

543210

Time (s)

Organic Nelcor N200

� 43

5. Conformable technology

� 44

rigid –> flexible -> conformable

Glass based OLEDPhilips Lighting

Flexible OLEDHolst Centre

Example of OLED roadmap

Conformable LEDs on foilHolst Centre

� 45

The vision: conformable electronic and photonic systems

• Featuring

� Conformable, stretchable/flexible

� Thin and light weight

� Unobtrusive integration

� Wearable

• Applications:

� Biomedical (sensors, phototherapy)

� Textile/fashion,

� Outdoor (biking, road safety)

� Architecture

� Displays

� Interior design (curtains, furniture)

• Advantages organics c.t. inorganics:

� Large area: homogeneity

� Very thin

� Temperature management

� Combination inspiring

� 46

Conformable electronics

T. Sekitani, T. Someya et al. Nature Materials 8, 2009 p. 494-499

R. Kim, J. Rogers, et al. Nature Materials 9, 2010, p. 929-937

� 47

Stretchable systems

• OLED structuring on rigid regions: printing technology

• OLED / OPV need protection by barrier technology

• Interspaces deliver stretchability and should contain electriccircuitry: Ag nanoparticles in binder matrix

cathodeanode

pedot LEP Ba/Al

foil

anode cathode

pedot Ba/Al

Bottom barrier

Top barrier

foil

� 48

Structured deposition of active materials

• Printing:

� Inkjetable ink formulation (halogen-free solvent): droplet formation

� Jetting and stable in time & speed

� Ink & substrate interaction

� Layer formation and homogeneity

� Device performance and efficiency

� 49

Ink & substrate interaction

• Pinning and de-wetting

Plasma

treatment

Temperature

treatment

� 50

Solvents selective layer formation

A 100% A:B=50:50 B 100%

� 51

Inkjet printed OLED active layer development

2007

2011

� 52

State of the art

� 53

OPV cells bonded on textile

Samples= 3 OPVs + drilled holes bondedPressure= very lowTemperature= 125°CAdhesive= CLocal encapsulation= None

3 OPVs gave 924 mV

� 54

Healing power of sunlight : wearable phototherapy

TBC treatment by sun therapy

� 55

Example - jaundice treatment of neonatals

• Old treatment

� Static light sources necessitating eye protection of neonatal

� Jaundice treatment: photochemical conversion and excretion of bilirubine (yellow colour treatment)

• New possibility

� Wearable light source

� less interfering with care

� including bonding with parents

� 55

Source flickr: 1542122226_5e43a1d008 and 2538039854_e67b67926c

Philips BilitXTM

Blue LED based

� 56

Other options for applications

• Light in safety (traffic, working conditions)

• Light harvesting (tents, outdoor sports, clothing)

• Phototherapy:

� psoriasis,

� eczema,

� jaundice,

� wound healing,

� prevention decubitus,

� pain relief,

� skin rejuvenation

• Camouflage

• Textile design – fashion!

• Bring light where no light was before

� 57

57

Platform for Large Area

Conformable Electronics

by InTegration

FP7 Place-it

� 58

6. Conclusions

� 59

Conclusions

• Organic electronics have a bright future

• Technology development indispensable

• Collaboration between disciplines necessary

• Conformable electronics will change the world

• Margreet.dekok@tno.nl

• www.holstcentre.com

• Thank you for your attention