Roll-to-Roll deposition for Organic p gLight Emitting Diodes (OLED)

Stefan Mogck, Christian May, Jörg AmelungFraunhofer-Institut für Photonische Mikrosysteme IPMSCenter for Organic Materials and Electronic Devices Dresden COMEDDCOMEDD

AIMCAL FALL TECHNICAL CONFERENCE, Amelia Island, Florida, Mogck 21st October 2009

OUTLINE

OLED introductionFraunhofer IPMS and COMEDDWhy OLED for Lighting?Processing on glass substrates Motivation for continuous metal strip coatingThe ROLLEX projectTop emitting OLED on rough metal substratesThin film encapsulationRoll-to-Roll CoaterSummary and Outlook

2

WHY OLED FOR LIGHTING?

Very thin and light weightTotal thickness < 2mm

Broad perspective (wide view angle)Diff Li h i L b i iDiffuse Lighting, Lambert emission

Huge selectivity of materialsPolymer (Spin-Coated) and Small-Molecule (Evaporated) Material(Evaporated) Material

Non toxic materials

Low cost manufacturing with simple structureL iblLarge area possibleLow power consumptionHighly efficient

Green (130 lm/W)( )White (64 lm/W)

Low material consumption (~1 gr. material/m²)Low surface heating

3

g

PILOT SYSTEM FOR OLED LIGHTING AND OPV ON RIGID SUBSTRATES

Modular and fully automated systemcycle time down to 3 minsupplier: Sunic System, Ltd. (Korea)

and Aixtron AG (Germany)( y)

Substrate size 370 x 470 mm²Plasma pretreatmentOrganic film deposition

Organic Vapour Phase Deposition OVPD (up to 6 layer*)

Vacuum Thermal Evaporation (up to 6 layer*)

fMetal film depositione.g. Aluminium and Silver

Connection to encapsulation system

*Including dopand and host material

4

5

MOTIVATION

Roadmap of the US Display Consortium forOLED-lighting

Absolutely not possible to reach by usingOLED display materials and techniquesp y q

New technologies for high efficient andsimultaneously low-priced OLEDs neededto meet special requirements of general lightingto meet special requirements of general lighting market:

Roll-to-roll-concept: noticeable lower coating costs in comparison to cluster or inline concepts

Glass encapsulated metal sheetLow-priced metal foil as substrate for very efficient OLED

Target: energy-saving and economical alternative

Glass encapsulated metal sheet processed in the VES400

to electric light bulb or fluorescent tube in a medium term: S. Reinicke et. Al., Nature 459, 234 (2009)

6

Bottom emission Top emission

OLED-Layer structure

transparent top contact

organic layers

reflective bottom contact

reflective top contact

organic layers

transparent bottom contact

opaque substrate

transparent bottom contact

glass substrate

7

OLED-STACK: P-I-N-TYPEHigh efficiency OLEDs require pin-structure:

p-type doped hole transport layer

intrinsic emission layer (may be emitter doped)

n-type doped electron transport layer LUMO

p i n

EF

-----

Benefits of doping charge carrier transport layerslow voltage drop

low operating voltage HOMO

EF

+ + + + + +

highest power efficiency

easy charge carrier injection

easy OLED integration on arbitrary electrode materials 7 Cathode

6 Electron Transport Layer (ETL)efficient top emission

thick transport layer

flattening substrate roughness

p y ( )

5 Hole Blocking Layer (HBL)

4 Emission Layer (EL)

3 Electron Blocking Layer (EBL)

2 Hole Transport Layer

V

stable production, higher yield

Concept of electrical doping can be applied to organic semiconductors

1 Anode

Light

8

g

e.g.: M. Pfeiffer, K. Leo, X. Zhou, J.S. Huang, M. Hofmann, A. Werner, J. Blochwitz-Nimoth, Organic Electronics 4, 89 (2003)

TYPICAL DEFECTS ON BARE METAL SUBSTRATE

Defects and scratches on Al foil

S b t t RMS (R ) M h (R ) R h

Visible texture from the fabrication process

Cleaned and Ag coated Al sheet

Substrate RMS (Ra) Mean roughness (Ra) Roughness peak

Al foil with non-conductive smoothing dielectrical

surface

1.6 nm 1.3 nm 31.1 nmTypically OLED are deposited on very smooth ITO substrates

RMS 1Al foil with evaporated Ag at IPMS

2.5 nm 2.0 nm 24.9 nm

Glass substrate evaporated with Ag at

2.7 nm 2.1 nm 21.6 nm

RMS < 1 nm, spikes < 10 nm

9

gIPMS

RED OLED ON ROUGH METAL SUBSTRATES

15 nm AgElectron Transport Layer

Hole Blocking LayerEmission LayerOptimisation1,2

1,41,61,8

ce

Optical Simulation with ETFOSOptical simulation

Electron Blocking LayerHole Transport Layer

50 nm AgAl substrate with oxide layer

of HTL thicknessOLED in 2nd

Maximum

0 50 100 150 200 250 3000,00,20,40,60,81,0

Lum

inan

[a.u

.] Thicknessvariation

1E-30,010,1

110

100

dens

ity (m

A/cm

²)

inan

ce (c

d/m

²)

100

1000

10000

In 2nd thickness maximum:Low leakage currents !

Thickness of Hole Transport Layer[nm]

0 6

0,8

1,0

-5 -4 -3 -2 -1 0 1 2 3 41E-51E-4

a.u.

)

%)

voltage (V)voltage (V)curr

ent

lum

i

2,0 2,5 3,0 3,5 4,0

101214

High efficiencies

Low operating voltageVery sharp emission spectrum due to Electro-

400 500 600 7000,0

0,2

0,4

0,6

wavelength (nm)

inte

nsity

(

luminance (cd/m²)

EQE

(%

10 100 1k 10k02468

y p pcavity effects luminescence

10

Non-conducting passivation laye

PROCESSING OF METAL SHEET TEST SAMPLES

Processing of metal sheets in existing vacuum deposition systems for rigid substrates at Fraunhofer IPMS

Lighting (active) area

g p y

mm

Fraunhofer IPMSCleaning using a wet benchSubstrate patterning by screen printing of a non-conducting

35

50 mmprinting of a non conducting passivation layerDeposition of organic layer stack and metal top cathode by vacuum evaporation trough shadow masksEncapsulation by gluing conventional cavity glassesconventional cavity glasses

Light emission out of a 4 Quadrant test substrate during electrical test (current efficiency 6-7 cd/A)

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(current efficiency 6 7 cd/A)

2-COLOR-WHITE PIN OLED ON METAL SUBSTRATE

1024 102

10-2

10-1

100

101

10

103

104

e J

[mA

/cm

2 ]

te [c

d/m

2 ]

10-2

10-1

100

101

10

103

104

e J

[mA

/cm

2 ]

te [c

d/m

2 ]

10-6

10-5

10-4

10-3

101

102

Stro

mdi

chte

LB00017Q1 LB00014Q1LB00016Q1

Leuc

htdi

ch

10-6

10-5

10-4

10-3

10

101

102

LB00017Q2LB00014Q2

Stro

mdi

chte

Leuc

htdi

cht

-5 -4 -3 -2 -1 0 1 2 3 4 510-8

10-7

100

Spannung U [V]

LB00016Q1

-5 -4 -3 -2 -1 0 1 2 3 4 510-8

10-7

100

LB00014Q2 LB00016Q2

Spannung U [V]

Layer nmAnode 200HTL 30EBL 10EL Y 5

Thin hole transport layer usedHigh reverse leackage current

3 different deposition runs EL-Y 5EL-B 23HBL 10ETL 85

Cathode 15

3 different deposition runsdiode size 2x2 mm² (Q1) and 5x5 mm² (Q2), resp.

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GREEN PIN OLED ON METAL SUBSTRATE

1021024

10-2

10-1

100

101

10

103

104

e J

[mA

/cm

2 ]

te [c

d/m

2 ]

10-2

10-1

100

101

10

103

104

e J

[mA

/cm

2 ]

te [c

d/m

2 ]

10-6

10-5

10-4

10-3

10

101

102

LB000115Q2 LB00019Q2LB000110Q2

Stro

mdi

chte

Leuc

htdi

cht

10-6

10-5

10-4

10-3

10

101

102

Stro

mdi

chte

LB000115Q1 LB00019Q1 LB000110Q1LB000114Q1

Leuc

htdi

cht

-5 -4 -3 -2 -1 0 1 2 3 4 510-8

10-7

100

LB000110Q2 LB000114Q2

Spannung U [V]-5 -4 -3 -2 -1 0 1 2 3 4 5

10-8

10-7

100

Spannung U [V]

LB000114Q1

Layer nmAnode 200HTL 195EBL 10

Thick hole transport layer usedReduced reverse leackage currentVery good reproducibility

EL-G 10HBL 10

Cathode 154 different deposition runsdiode size 2x2 mm² (Q1) and 5x5 mm² (Q2), resp.

13

p

GREEN OLED ON 200X200 MM² processed in VES400

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ROLL-TO-ROLL COATER FOR METAL STRIP

Batch type Roll-to-Roll CoaterSubstrate width 300 mm, thickness 0.2 … 0.5 mmPretreatment by ion beam and heatingPretreatment by ion beam and heating

Coating Stations:up to 9 novel linear evaporators for organic materials in total (5 double, 4 single)2 evaporators for metals1 DC/RF magnetron

organic materialEvaporationsources

ion beampretreatment

OLED-specific substrate handlingstrip guidance w/o front side roller contactun/rewinding with plastic liner

substrate and linerunwinding

transfer of coated substrate under inert atmosphere

metal evaporation sources

substrateand linerrewinding

magnetron

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IMAGES ROLL TO ROLL VACUUM COATER

winding unit

deposition cylinder

attachement possibilityfor an inert shuttle

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LINEAR ION SOURCE AND COOLING TRAP

Plasma treatment

Cooling trap below -100 °C

17

DEPOSITION CYLINDER

Tape guiding

Holes for insitu reflectometry

Deposition cylinder can be heated p yfor moisture reduction on the foil surface

Cylinder deposition speeds b t 0 01 1 / i t ibetween 0,01 – 1 m/minute is possible

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NEW LINEAR EVAPORATION SOURCES FOR ORGANICS

horizontal orientation with rotatablehorizontal orientation with rotatable (360°) deposition tube enables deposition in top-down and bottom-up geometry

Organic evaporatorin the roll-to-rollcoater

new primary evaporator with distributed surface*

High rates at moderate t t ( d ddeposition tube (rotatable) temperatures (reduced degradation)

directly heated deposition tube with high temperature

deposition tube (rotatable)

shielding with high temperature homogeneity

scalable design

ll i t fill f iprimaryevaporator allows inert refill of organic

compounds

substrate

evaporator

shutter*Patent pending

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p g

STATIC RATES OF ORGANIC LINEAR EVAPORATOR

20

Thickness homogenity of R2R organic evaporation of Alq3

95

100

105

110

3%

80

85

90

95

ckne

ss [n

m]

65

70

75

80

thi

60-20 -15 -10 -5 0 5 10 15 20

Lateral position across the web (cm)

Organic linear evaporator in ROLLEX 300 system by VON ARDENNEEvaporator to substrate distance 150 mmThickness measurement determined on Alq3 evaporated plastic foil using the Lambda 900 spectrometer

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900 spectrometer

Thickness homogenity of R2R silver evaporation

15.60

15.20

15.40

15.60

14.80

15.00

ckne

ss (n

m)

thickness variation 3.7%

14.40

14.60

thic

14.200 1 2 3 4 5 6 7 8

lateral position across the web

Metal evaporator in ROLLEX 300 system by VON ARDENNEThickness measurement determined on silver evaporated plastic foil using the Optical thin film monitor GSM210 (Balzers)

p

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THIN FILM ENCAPSULATION

Encapsulation against water and oxygen diffusion is needed to avoid degradationEncapsulation against water and oxygen diffusion is needed to avoid degradation of flexible electronic devices.Highest permeation barrier requirements: OLED water: < 10-5 g/(m²d) oxygen: < 10-5 cm³/(m²d bar)“Be flexible” – only with thin film encapsulation techniquesCommon understanding: Permeation only through defects in barrier layerBarrier improvement by minimizing effect, size and number of defectsMultilayer concept for direct encapsulationMultilayer concept for direct encapsulation

defect decoupling: tortuous path formoisture and oxygen permeation

increased lag time of permeationg p

reduce mechanical stress in the layer stack interlayerbarrier layer

Substrate(OLED)

barrier layer

(OLED)

More details, see the presentation from Nicolas Schiller (FhG-FEP) “Transparent

Barrier Coatings on Polymer Films“ in the Vaccum Materials Session.

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SUMMARY AND OUTLOOKTo fabricate large area lighting devices existing OLED display fabrication technologies have to be adapted in several aspectsadapted in several aspects

High efficient bottom emitting OLED on glass was shown

Highly efficient manufacturing

Low cost materialsLow cost materials

Metal strips and R2R deposition have potential for low cost production of lighting devices - First results promising

High efficient and stable top emitting OLED on metals substrates are possibleHigh efficient and stable top emitting OLED on metals substrates are possible

Unique approach for an OLED R2R coater using new evaporator concept

Promising results of thin film encapsulation

OutlookDevelopment of white OLED stack in R2R deposition process

Further developments in R2R thin film encapsulation

Roll-to-Roll process integration: cleaning, patterning, lamination

Implementation of R2R defect monitoring

Processes also to be used for Organic Solar Cells24

Processes also to be used for Organic Solar Cells

ACKNOWLEDGEMENT

All project members, especiallyM. Ammann, C. Rothe, Novaled

C. Deus, Von Ardenne

K. Leo, IAPP, TU Dresden

N. Schiller, J. Fahlteich, Fraunhofer FEP

J Drechsel CreaPhysJ. Drechsel, CreaPhys

This work is supported by the German Federal Ministry of Education and Research

Further Information: www.rollex-projekt.de

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