Towards roll-to-roll solution processing of OLED devices on an industrial scale

Towards roll-to-roll solution processing of OLED devices on an industrial scale

Pit Teunissen, Eric Rubingh, Ike de Vries, Guy Bex, Pim Groen, Jeroen van den Brand

© Holst Centre

Vision on lighting

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8,000 €/m2

Rigid glass

Vacuum/litho processes

40-60 % material loss

Glass encapsulation

Rare materials

100 €/m2

Flexible substrates

Direct printing processes

<5% material loss

Thin-film encapsulation

Widely abundant materials

2018 Now

© Holst Centre

Large area flexible electronics

One of the key challenges: How to manufacture these products?

Large quantities and large sizes…

• Roll-to-roll (R2R) manufacturing preferred

Easier to make large quantities at low costs

• To be built on low cost flex foils

Not on polyimide-foil: ~ 50 euro/m2

But on PET-foil: ~ 3 euro/m2

Printing preferred over lithographic patterning

• Easier for roll-to-roll processing

• Fine features without complicated masks

innoLAE 2015 - Pit Teunissen

< 4

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Schematic of R2R solution processed OLED (ITO free)

1. Printing and sintering of silver grids (anode)

3. Shunting cathode OLEDs by IJP

2. Large area coating

4. R2R Barrier


< 5

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• Printing silver: Screen printing - Ink jet

• Baseline Process: Thermal Sintering in furnace at high

temperatures (30 min./<150 oC )

Limited to Tg of polymer foils

Slow and inefficient process

In R2R line with 6 m/min a furnace of 60 m needed

• Photonic Flash Sintering


1. Printing & Sintering of Silver grids

< 6

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Reflector geometry

Fast sintering (50 ms) of

development paste

3 flashes of 10 ms

Ref: Abbel et al., MRS Commun., 2012, 2, 145.


• Principle of photonic drying/sintering

Light is absorbed in the printed structures, not substrate

Elliptical reflectors focus the light in narrow lines

High frequency flashing > no stitching effect

Top and bottom illumination

“Off the shelf” lamps and electronics > inexpensive

< 7

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• Photonic sinter equipment

A good understanding of the sinter behavior of materials is essential

Measuring real-time in-line resistance and temperature necessary

Stage 1: Research tool

Single lamp system

Sintering of lines

In-line measurements

Resistance

Temperature

Inert atmosphere capable

Stage 2: S2S tool

Holst S2S setup & Novacentrix 1300

In-line measurements

Resistance

Temperature

Functionalities beyond photonic sintering only

Stage 3: R2R tool

Up to 6 flash lamps

2 X NIR pre-drying

1 meter footprint



Ref.:Transl. Mater. Res. 2014, 1, 015002

< 8

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• Smooth surface is critical for OLED/OPV processing

Conventional pastes have a rough surface

Large risk of direct shorts between anode and cathode

Experimental paste with smooth surface topology developed

Material properties Resistivity: 3-4x bulk Ag @ 190°C, 4-5x bulk Ag @ 160°C

Good adhesion to several types of substrates

Withstands tape test, ethanol wiping and automated cleaning

Conventional paste

DuPont experimental paste Ra = 0.1 µm

Rp = 0.5 µm

Ra = 1.0 µm

Rp = 3.1 µm Cannot be used: Rough surface, short circuit

Smooth surface


< 9

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• Functional OLED devices made with S2S printing

Smooth topology of printed structures

Minimum line widths achievable: 50-70 µm

Low leakage current

Devices show similar IVL curves as devices with evaporated bus bars



3D profile plot of screen printed anode OLED with screen printed anode

< 10

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Movie: 3 layers aligned R2R screen printing Movie available on you-tube

R2R screenprint 3 layers aligned.mp4

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4. R2R Barrier


Schematic of R2R solution processed OLED (ITO free)

< 12

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2. Large area coating (using solution processing)


• Holst Centre’s Approaches:

Spin coating: simple, no patterning

Ink-jet printing: non-contact, freedom

of design

Homogeneity over large areas needs to be

investigated

Slot-die coating: non-contact, large area blanket coating

R2R slot-die coating line S2S slot-die coater in glove-box

< 13

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Intermittent coating stripe coating

• Coating results:

Slot-die coated layers of 100 - 30 nm with

thickness variation of only ± 2 nm

Sequential coating of up to 3 organic layers

on plastic and metal foil proven

• Patterning with slot-die

Post / pre treatment

Laser ablation

Selective wetting/de-wetting

Direct patterning

Intermittent coating

Stripe coating

R2R slot-die coating line

< 14

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Roll-to-roll multilayer solution coated OLEDs on flexible metal foil

8 cm x 8 cm devices with performance not far from smaller sheet-to-sheet processed OLEDs

Homogeneity 60% @ 1000 cd/m2 mostly limited by transparent electrode conductivity


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• Holst Centre multi-coat (2 x slot-die coating) pilot production line

Unique concept where web is never touched on topside essential for Oled production.

Concept makes very efficient use of cleanroom space.

Slot die coating in controlled atmosphere (all coating and drying in

Nitrogen environment if needed).

Closed furnace (class 10 + < 10 ppm O2/H2O)

Possibilities for intermittent slot die (patterning with unique high speed moving slot die).

Class 1000

Class 10 <10 ppm O2

Local Class 100



< 16

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Summary: Schematic of R2R solution processed OLED (ITO free)




4. R2R Barrier


< 17

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8X8cm OLED with transparent cathode

• OLED Cathode

Conductivity of transparent cathode is limited

Intensity drop of 60% in an 8X8cm OLED

Conductivity can be increased by inkjet printing shunt lines

Intensity drop of 60% Intensity plot

< 18

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• Inkjet printed shunt lines

Necessary due to limited conductivity of transparent cathode

In the example below an Ag np ink was used with ~7% Bulk Ag conductivity at 130°C

Further improvements ongoing using different design

DuPont development ink shows promising results

Ink compatible with device stack

Conductivity of ~20% Bulk Ag at 130°C

8X8cm OLED with transparent cathode and

IJP shunt lines

Intensity drop of 30% Intensity plot

< 19

© Holst Centre

• Movie: R2R Inkjet printing and sintering

Printer: SPG inkjet printer

Print head: Xaar 1001

Print speed: 10 m/min

Sintering module

NIR dryer: 60% power

Photonic sintering:

2 lamps used; 10Hz, 60% intensity


Movie: R2R Inkjet printing and sintering


Tool recently upgraded to web-wide

< 20

SPG R2R IJP on PET 10m_min.MOV

© Holst Centre

Summary: Schematic of R2R solution processed OLED (ITO free)




4. R2R Barrier


< 21

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4 R2R barrier

• Holst Centre barrier production line

WVTR of the single SiN sampled over 350m length at 60oC and 90%RH for 20 days : Overall WVTR = (5±1)·10-5 g/m2day

In two weeks 2500 m barrier produced

Full barrier stack R2R processed (OCP-SiN-OCP-SiN)


R2R Barrier production on Holst Centre production line

< 22

© Holst Centre

Conclusion 1. Proven functionality screen printed anode 2. R2R slot die coating used for working OLED devices further work on upscaling and

patterning 3. IJP shunt lines on transparent cathode 4. Holst Centre barrier production line

The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no 281027


< 23

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Industrial partners from across the value chain


< 24

http://www.nxp.com/

http://www.storkprints.com/

Visit us at

www.holstcentre.com

Towards roll-to-roll solution processing of OLED devices on an industrial scale

Documents

holst centre innolae

large area coating

spin coating

holst centre vision

coating lines2s slot

pit teunissen smooth

nm sequential coating

solution processing