© Fraunhofer FEP© Fraunhofer FEP

Present status of Roll-to-Roll Fabrication for OLED lighting

AIMCAL, Web Coating and Handling ConferenceJune 2nd, Dresden, Germany

Michael Stanel, Tomasz Wański, Stefan MogckFraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP

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Outline

Fraunhofer Gesellschaft and Fraunhofer FEP

R2R process line for OLED lighting

Challenge of flexible OLED encapsulation Particle Residual water Damage by winding

Summary and Outlook

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Fraunhofer-Gesellschaft

Europe’s largest application-oriented research organization

was set up in 1949 67 institutes and independent

research units with 23,000 employees all over Germany

headquarter is located in Munich

each institute has its own core competences

the individual institutes act as profit centers on the market

Headquartersin Munich

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Fraunhofer FEP: FACTS and FIGURES

Fraunhofer COMEDD merged within Fraunhofer FEP July 1st, 2014:Fraunhofer Institute for Organic Electronics, Electron Beam, Plasma Technology (FEP)

Director: Prof. Dr. Volker Kirchhoff Figures 2014: employees 193, total budget 25.0 M€, industry returns 8.6 M€, public

funding 9.7 M€, investments 1.4 M€

Core competences:

ELECTRON BEAM TECHNOLOGY

SPUTTERING TECHNOLOGY

PLASMA-ACTIVATED HIGH-RATE DEPOSITION

HIGH-RATEPECVD

TECHNOLOGIESFOR ORGANICELECTRONICS

IC AND SYSTEMDESIGN

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Quelle: Marcus Tremonto

Vision of OLED Luminaires

Source: Yang Ze-Siao/Yankodesign

Source: Jonas Samson

Customer specific flexible OLEDs Simple adaption of layoutsApplications: “OLED-wall paper” (ambient lighting) Elongated stripe panels Free forming

Source: 3M Source: Gergo Kassai

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Comparison of flexible Substrates for OLED Devicesmetal ultra-thin glass plastic

bendability o o √

permeation barrier √ √ o

roll-to-rollprocessabilty

√ (√) √

surface roughness o √ √

cost √ o o

advantages good barrierthermal conductivity

good barriersurface quality transparency

transparencyhigh bendability

disadvantages top emissionadditional treatment of reducing surface roughness

brittledevice separation

barrier coatingpin-holesthermal stabilityresidual waterpossible pinholes

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R2R inspection systemR2R printing and lamination unit (N2)

R2R vacuum coater

Substrate Inspection Structuring Substrate

inspectionVacuum coating Encapsulation OLED

characterisation

Typically 300 mm web width

metal strips: thickness up to 500 μm

polymer webs : thickness 50 to 500 μm

flexible glass : thickness 50 and 100 µm

preferably (“pure” or laminated on PET)

100 x 100 mm² devices on barrier film

Overview process flow in R2R R&D line

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Roll-to-Roll vacuum coater RC300MB

8

14 Linear Organic Evaporators

DC Magnetron

Lineare Ion Source

2 Metal Evaporators

Substrate Winder

Interleaf Winder

Port for Inert Substrate Transfer

cathode

EBL

HBL

EMLred EML

green

EMLblue

HTL

ETL

BL

BL

Substrate with Anode layer3-color-white OLED stack

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

high rates at moderate temperatures (reduced degradation)

heated deposition tube with high temperature homogeneity

scalable design

allows inert refill of organic compounds

evaluation of material stabilities over long evaporation time.

Organic co-evaporator in the roll-to-roll coater

Linear evaporation sources for organic deposition

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Triple-evaporation module

module with 2 linear co-evaporators and 1 single linear organic source was reconstructed to triple evaporator

the reconstruction included: rotation of evaporators deposition pipes change of positions of rate control quartzes

including cooling water New module configuration enables: variation of 2 emission layer host materials profiles

in the emission layer (source 1 and 3) maintaining homogenous doping in the emission

layer (source 2)

The aim is to find most beneficial configuration of sources for high efficient OLEDs.

Above: schematic drawing presenting evaporation module reconstruction idea and below picture of module after reconstruction

adjustable shieldings

OV07

OV08

OV09

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Test structure: square OLEDs: 1cm², spherical OLEDS: 0.785cm² -> OLED characterization

R2R OLED layout

Substrate structuring by printing process of transparent non conductive layer

Any kind of printable active OLED lighting areas are possible: stripes, text, rounded shapes…

Additional metallization printing possible

25 cm 10 cm

10 cm

Gravure printing concept (up) and substrate after structuring (down)

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Lamination unit

1. Unwinding of the self-adhesive barrier film, removing of the release liner

2. Pressing of barrier film on OLED substrate

3. Curing of barrier adhesive by UV light

FEATURES Lamination with self-adhesive barrier film Encased in an inertbox to process under

inert atmosphere Substrate lamination with edge (cartridge)

and area (hot-melt) encapsulation UV curing and thermal drying All materials can be kept under N2

condition.

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R2R OLEDs on flexible substrates - results

Stacks implemented in R2R machine 3 color white hybrid stack monochromatic phosphorescent green and blue stacks

(no internal or external out-coupling methods used)

white green blue redS2R PE @ 1000 cd/m² [lm/W] 45 55 22 -

PE @ 1000 cd/m² [lm/W] 15 55 15 -CIEx 0.40 0.31 0.20 -CIEy 0.40 0.65 0.40 -

LT50 @ 1000 cd/m² [h] > 5000 > 5000 - -

colour

R2R

process value

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Challenges in R2R OLED processing

to maintain high substrate quality throughout the complete R2R process to achieve high OLED efficacy and long lifetime flexible ultra high barrier against humidity can be damaged due to: any coating process e.g. high conductive transparent electrodes for homogeneous large area OLEDs

required defects, particles on the surface residual stress from the deposition of layers onto a flexible substrate + external

stress from the bending water free barrier

high barrier adhesive for OLED encapsulation lamination of barrier stable electrical contacts for bendable devices low production costs vs S2S OLED fabrication

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Damage from temperature and strain during processing

Strain in processing of coated polymer webs: web-tension in roll-coaters 200 N on 400 mm wide Melinex 400 CW (75 µm): at 20 °C: 0.16 % strain at 120°C: 0.64 % strain

bending on rollers 3.75 cm bending radius on 125 µm PET (centred neutral axis)

= 0.17 % strain on outside mismatch in thermal expansion coefficients PET: α = 7·10-5 K-1: 20°C … 120°C -> 0.7 % strain shrinkage of polymer webs PET Melinex 400 CW at 150 °C: 1 %

300 µm

200 nm Al2O3 on PET after 100 h damp heat test (85°C / 85% r. h.)

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Process development for roll-to-roll drying of barrier films

Barrier film not dried before OLED process.

Barrier film dried for 10 min. at 100 °C under N2 condition before OLED process

The amount of residual water that can affect the OLEDs is monitored (coulometric measurements)

residual water on the surface and in the barrier and electrode films -> direct influence on OLED

residual water in the PET film -> indirect influence of OLEDs due to diffusion to OLEDs having contact to the backside of the roll or through pinholes in barrier

R2R drying process for several substrates developed: significant improvement of OLED LT observed but this process cost time…

proper storage/transport of rolls required getter flayers implemented in the barrier

stack could help

Quality of barrier films is typically qualified by: Optical imaging Calcium degradation test Electrical Calcium degradation test Coulometric measurements (e.g. Brugger,

Mocon) (~10e-3 g/m²d)

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Without drying (35 days) Drying at 80°C, 48 h (35 days)

Without drying (35 + 26 days) Drying at 80°C, 48 h (35 + 26 days)

Ca-test after 35 days storage under protective N2 atmosphere (GB)

Ca-test after 35 days GB and 26 days under ambient conditions

Different degradation velocities → defects have different influences on the OLED degradation

Ca-test for PET barrier films with coated ITO layer

Trapped water inside the device just after encapsulation

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Roll-to-Roll inspection system

Winding unit with inspection system CCD camera- and light bank Modular, moveable optical microscope

Contactless winding of the substrate under clean room class ISO6

100% inspection by means of line scan cameras (pixel resolution 14 μm, defect resolution ≈ 40 µm)

Attached moveable optical microscope (point resolution 1 μm)

Rewind mode for defect analysis detected by the line scan cameras

Automatic statistical analysis of recorded optical images by spot counting

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Defect Density Measured by the Optical Microscope (5x Objective)

High variation of the defect density on barrier films (BF) and thin glass Defect generation by winding and coating reliable correlation with WVTR value? Development of specification together with barrier film supplier necessary.

Substrateaverage

defect density[1/cm2]

Melinex 400 CWcoating side 1840 ± 410

Teonex Q65 FA 6.6 ± 2,8

After winding of TEONEX Q65FA in labFlex® 200 635 ± 75

After coating of ZTO, 100 nm on TEONEX-Film 141 ± 57

PECVD-Coating of [(CH3)2-Si-O]n-Plasmapolymer 4950 ± 41

0

1000

2000

3000

4000

5000

6000

BF 1

BF 1

with

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spot counting, defect density [cm-²]

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OLED devices on barrier film (sheets without winding in)

OLED devices on metal foil (13 m web fully winded in).

OLED devices on barrier film (20 m web fully winded in).

Leakage current at -5V

Examples Leakage Current Distribution within an R2R OLED Process

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Lifetime measurement from R2R OLEDs on barrier foils

#7B dark spots: 0.18%#7B dark spots: 0.08% #20A dark spots: 0.02% #20A dark spots: 0.03%

Part 2: with out-gassing in vacuum (OLED 1 cm² and 10 cm²)Part 1: no out-gassing in vacuum

OLEDs from not out-gassed part show higher level of degradation (shadings) -> water residues cause a significant reduction of the OLED lifetime (1x1 cm²).

“Large” OLED areas is at present hard to get dark spot free after 1000h with typical WVTR in the range of 10-3 -10-4 g/m²*d on rolls (the same OLED run).

Picture after 1500h

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Electrical contacts on flexible OLED substrates

Testing different kind of conductive bonding adhesives using ACA/ACF bonding technology.

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R2R OLEDs on flexible glass encapsulated with barrier foil

Flexible glass (G-LeafTM from NEG)50 µm thick laminated on the PET foil

Complete R2R processing -> no cracking of flexible glass during OLED deposition

Reliable electrical contact with low contact resistance for large area illumination

Encapsulation by lamination with barrier film…

solution: encapsulation also with flexible glass…

after 1500h

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R2R OLEDs on flexible glass encapsulated with flexible glass Flexible glass (G-LeafTM from NEG) 50

µm thick laminated on the PET foil used as the substrate but also as the encapsulant

Complete performed in roll-to-roll All coating process including electrode

coating, structuring, OLED deposition, OLED encapsulation are performed at F-FEP

Almonst no dark spot nucleations

Demonstrator samples of OLEDs fabricated on flexible glass and encapsulated with flexible glass in S2S (on the left, 175 mm long) and complete R2R process (on the right, 250 mm long).

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The roll-to-roll OLED process can be reproducible and stable performed on metal-, plastic-and ultra-thin glass web. Still high variation of dark spots and leakage current

OLED lifetime at 1000 cd/m² > 5000 h and power efficacy of > 25 lm/W could be possible with 2-unit OLED stacks.

Challenges to remove residual water in barrier films in roll-to-roll with understanding of drying kinetics low WVTR values makes customer not happy only!

Improvement of web handling in the equipment is necessary, but solvable (just a matter of investment)

Roll-to-roll OLED manufacturing with low priced substrate and for mass production has a high potential for low cost (manufacturing on sheets needs a bonding, de-bonding process on a carrier).

Optimization of the R2R cleaning process to bring particle level down to minimize dark spots (particle size > adhesive thickness) Control dark spot forecast and density Forecast with the yield for a certain substrate surface quality

Cost model analysis and concept studies for roll-to-roll OLED pilot line manufacturing have been started.

Summary and Outlook

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ACKNOWLEDGEMENT The research is funded within the framework for technology promotion by

means of the European Fund for Regional Development (EFRE) as well as by means of the Free State of Saxony.

Parts of this work were supported by the German Federal Ministry of Education and Research within the projects R2Flex (FKZ 13N11058) and R2D2 (FKZ: 13N12948).

Special thanks to my colleagues, especially: Christian May, Tomasz Wański, Michael Stanel, Michael Törker, Jacqueline Hauptmann, Jan Hesse; Claudia Keibler, David Wynands, Claus Luber, John Fahlteich

Thank you for your attention!