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© 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
© Fraunhofer 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
© Fraunhofer FEP
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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
© Fraunhofer FEP
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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
© Fraunhofer FEP
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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
© Fraunhofer FEP
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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
© Fraunhofer FEP
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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
© Fraunhofer FEP
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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
© Fraunhofer FEP
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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
© Fraunhofer FEP
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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
© Fraunhofer FEP
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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)
© Fraunhofer FEP
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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.
© Fraunhofer FEP
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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
© Fraunhofer FEP
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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
© Fraunhofer FEP
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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.)
© Fraunhofer FEP
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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)
© Fraunhofer FEP
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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
© Fraunhofer FEP
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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
© Fraunhofer FEP
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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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ctro
de 1
BF 1
with
ele
ctro
de 1
and
…BF
1 w
ith e
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2BF
2BF
2BF
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1BF
2 w
ith e
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1 a
nd…
BF 2
with
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BF 3
BF 3
PEN
PET
thin
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lass
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spot counting, defect density [cm-²]
© Fraunhofer FEP
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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
© Fraunhofer FEP
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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
© Fraunhofer FEP
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Electrical contacts on flexible OLED substrates
Testing different kind of conductive bonding adhesives using ACA/ACF bonding technology.
© Fraunhofer FEP
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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
© Fraunhofer FEP
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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).
© Fraunhofer FEP
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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
© Fraunhofer FEP
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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!
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