Printed Device Performance of Polymer-OLED Materials...N2 or Air Ink viscosity vs conc. - Low dependency High dependency Layer formation/ aggregation + +++ ++ Our focus on Polymer

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OLED World Summit Sumitomo Chemical

September 21, 2017

Sumitomo Chemical Co., Ltd. JAPAN

Printed Device Performance of Polymer-OLED Materials

OLED World Summit 2017

T. Yamada, N. Akino, Y. Tsubata, D. Fukushima

S. Amamiya, J. Sekihachi

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Contents

1. Proprietary material design 2. Latest OLED performance 3. Printing basics

4. Ink-jet Printing

5. Printed device performance

6. Challenges for commercialization 7. Summary

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Sumitomo’s OLED material portfolio

Anode

HIL

HTL (IL)

LEP

Cathode

Cathode • Selected from various kind of materials • NaF/Al would be preferred as model

Blue LEP • Proprietary fluorescent polymer system of high efficiency and deep blue.

Green LEP • Proprietary phosphorescent system • Emitter embedded in high T1 polymer

Red LEP • Proprietary phosphorescent system • Emitter embedded in polymer

Polymer HTL (interlayer)

• Proprietary X-linking polymer system with high hole mobility, high T1 and stable layer formation

HIL Selected from various kind of 3rd party’s HIL

Printed ETL • Proprietary soluble-ETL system specially for lighting White devices (for all-phos material)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

350 450 550 650 750wavelength(nm)

Nor

mal

ized

inte

nsity

RedGreenBlueIL

PL spectrum

9 9 9 9

9

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• Sumitomo’s OLED material is a proprietary conjugated polymer system. • Integrated function in polymer-chain via copolymerization instead of multi-layered stacks.

Hole affinitive

Electron affinitive

Emissive

Other functions

Single-stack Integrated in polymer

SM-evap

Multi-stack Functional layers

Ea

Ha

EM

Proprietary OLED design

P-OLED

Integrated in conjugation system

Ea Ea

Ha Ea

EM Ea

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Backbone ETU HTU Emitter Other functions

Fluorenes

Phenylenes

Hetero-atom Aromatic system

Amines Amines

Dendrimers

Other condensed-rings

Hydrocarbon Condensed-ring emitter

Cross-linkers

Other functional units

Advantages of Soluble Polymer System

- Very soluble and ink-stable materials - Uniform film formation without significant phase-separation or aggregation of materials - Distinctive layer formation by thermally cross-linked polymeric-HTL layer

Every monomer has its function and integrated into one polymer chain with keeping conjugation

: show composition of RGBIL polymers respectively

Proprietary polymer design

Other HTU

Ea Ha EM

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1981 Start conductive-polymer study 1990 Find emission from PPV 2000 Start RGB full-color material study 2005 Purchase Dow’s p-OLED activity 2007 Acquire CDT as subsidiary

z RGB T50 have reached to commercially-viable level already in 2012. z Now focusing on T95 (image-sticking LT), and significant improvement obtained recently.

Blue T95

Green T95 Red T95

T50 20khrs established in 2012



BE, Spin device No electrical aging applied before test

History of polymer-OLED development

(hrs

) (h

rs)

(hrs

)

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Spin/BE device ITO/HIL/IL/LEP/NaF/Al Xylene ink

July/2017 Achieved

2017 Our Target

R Efficiency cd/A 24 28 CIE-x,y 0.66, 0.34 0.66, 0.34 T95 hrs @1000nt 5800 6000

G Efficiency cd/A 85 76 90 CIE-x,y 0.32, 0.63 0.32, 0.63 0.32, 0.63 T95 hrs @1000nt 15000 25000 16000

B Efficiency cd/A 8.0 9.2 10 CIE-x,y 0.14, 0.11 0.14, 0.12 0.14,0.12 T95 hrs @1000nt 400 750 750

Current performance

Device structure ITO (45nm)/ Soluble HIL (35-65nm)/ Interlayer (20nm)/ LEP (60-90nm) / low-WF cathode

9 RGB common and simple layer-stack structure. 9 Organics are fully solution-processed.

*Lifetime estimated from luminance acceleration test. *No electrical-ageing applied before lifetime test.

ITO

HIL

IL

LEP

Low-WF cathode

Better color (0.68,0.32) Higher efficiency

Better color (0.30,0.64) Higher efficiency

Better spectrum for TE Longer T95

Future Direction

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HIL: Effective and stable hole injection into deeper HOMO IL

New IL: -Higher S1/T1 -Higher exciton stability -Good hole mobility -Deeper HOMO

EML: -Best RZ location -Exciton confinement on emitter (energy transfer engineering) -Best material stability (intrinsic, extrinsic)

Cathode: Effective and stable electron injection via selected EIL/cathode system

IL HIL

EML

Best optical design to maximize out-coupling efficiency (layer thickness, n/k…)

A winning strategy leading to best performance

Emitting dipole alignment

Interface : Engineering to avoid energy migration

Best fabrication condition commonly applied to mass-production (IJP)

Effective TTA system in Blue

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Best practice


July/2017 Achieved

R Efficiency cd/A 24 CIE-x,y 0.66, 0.34 T95 hrs @1000nt 5800

G Efficiency cd/A 76 CIE-x,y 0.32, 0.63 T95 hrs @1000nt 25000

B Efficiency cd/A 8.0 CIE-x,y 0.14, 0.11 T95 hrs @1000nt 400

Best practice Now

28 0.66, 0.34

6000 92

0.33, 0.62 17000

9.3 0.14, 0.11

400

Winning strategy

Our winning strategy leads to impressively high polymer-OLED performance now.

Green best practice

>25% EQE >90cd/A T95 >17000hrs@1knt

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Best practice : Latest Blue Our winning strategy leads to impressively high polymer-OLED performance now

For Blue!

EL at 1000cd/m2

Peak 460nm

FWHM 40nm

EQE 6.9%

Efficiency 7.8cd/A

Voltage 4.5V

CIE-x,y 0.14, 0.13

LT95* 1400hrs *1) From luminance accelerated test

Device structure : ITO (45nm)/ Soluble HIL (35nm)/ Interlayer (20nm)/ LEP (60nm) / low-WF cathode

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Challenges for next-gen. materials


Best practice

Now

R

Efficiency cd/A 28

CIE-x,y 0.66, 0.34

T95 hrs @1000nt 6000

G

Efficiency cd/A 92

CIE-x,y 0.33, 0.62

T95 hrs @1000nt 17000

B

Efficiency cd/A 7.8

CIE-x,y 0.14, 0.13

T95 hrs @1000nt 1400

Aligned phosphorescent

emitter

(Emitter in polymer already aligned)

New Flu/Phos emitter

TADF emitter -Polymer TADF -TADF emitter in chain

Lifetime Efficiency

Management of triplet exciton through TTA

(for Blue)

Ultimate reduction of impurities/

chemical defects

Color

112cd/A 0.33, 0.62 LT on-going

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1.E-04

1.E-03

0 2000 4000 6000

ΔO

D

ps

Host上Tripletの減衰

0.6

0.7

0.8

0.9

1.0

0 5 10 15 20 25

Nor

m. L

umin

ance

Exposure time [hr]

UV stability

0

50

100

150

200

250

300

350

400

450

0 10 20 30 40

EL T

95 (h

ours

)@1k

knit

UV stability (hours @T70)

Host Polymer

S1

T1

TCP S1

T1

Prompt& Delayed

1 2

1. Efficient energy transfer by controlling polymer morphology.

2. Efficient T-T annihilation by optimized sequencing of TTA unit in TCP.

Shorter Triplet lifetime on host shows efficient energy transfer

Efficient energy transfer gives better photo-stability

Better photo-stability gives better device LT

LT : Management of triplet exciton

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Polymer impurities : (1) Insertion of P (2) OH generation at end-point (3) Residue of non-reactive Br and Cl (4) Others

Device structure : Glass/ITO/HIL/IL/LEP/NaF/Al

- Device performance is dependent on the quantity of impurities. - We can successfully control the level impurities below detection limit.

LT : Impact from impurities

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Efficiency : Aligned emitter in polymer

Expected gain X1.21

Combination of : Best emitting dipole alignment - Anisotropic emitter - Attached linearly in - Aligned polymer Optimized charge-balance/RZ Use of high S1/T1 IL

Now >100cd/A (EQE~24%) with CIE-x,y=0.31,0.64 achieved

Measured gain X1.15

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Polymer TADF in literatures

Category

Main-chain D-A

Main-chain D-A

Side-chain TADF Macromolecules 2016, 49, 5452−5460

Adv. Mater. 2015, 27, 7236–7240

Adv. Mater. 2016,

J. of Polymer Science, A, Polymer Chemistry, 2017, 55, 575–584

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Emitter classes

Code #

CIE- By

Peak nm

FWHM nm

Existing class

Em-1 0.08 440 60 Em-2 0.10 448 62 Em-3 0.12 463 50

New class Nem-1 0.06 455 28

New class emitter -Moderate peak position -Very narrow FWHM ->Suitable for TE ->Accessible to BT.2020

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EL at 1000cd/m2

Peak 455nm

FWHM 30nm

EQE 8.3%

Efficiency 5.5cd/A

CIE-x,y 0.14,0.068

New class emitter in polymer

Polymer Emitter

S1

T1

S1

T1

Polymer Emitter

S1

T1 S1

T1

Current : Good color Low efficiency

Future : Good color High efficiency

New class emitter in polymer shows -Very deep Blue -High efficiency in EL.

To develop TADF system by controlling polymer energy level is next challenge.

Device structure : ITO (45nm)/ Soluble HIL (35nm)/ Interlayer (20nm)/ LEP (60nm) / low-WF cathode

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Well-established and well-understood

system

Much-attention paid to understand the difference from

Evaporative Material

Need to clarify differences from

Evaporative SM and Soluble SM

Evaporative Small-molecule

Soluble Small-molecule Polymer

Comparison of various OLED systems

Konika-Minolta, 2013 LOPE-C Dupont, 2013 SPIE EMD, 2013 Printed Electronics USA

FMM evap

IJP

Nozzle

Flexography

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Area Focus Evaporative Small-molecule

Soluble Small-molecule Polymer

Material Charge injection / transport +

(Much attention paid here recently)

TBD

S1:T1 ratio including TTA + TBD

Molecular Orientation + +++ Film Density + +++ Morphology / crystallization + + Material impurity + ++

Structure Intermixing between layers + +++ +++ Use of ETL + + +

Process Residual solvent - +++ +++ Solvent impurity - +++ +++

Deposition condition + Vac

+++ N2 or Air

+++ N2 or Air

Ink viscosity vs conc. - Low dependency High dependency

Layer formation/ aggregation + +++ ++

Our focus on Polymer system

+++ Big difference (beneficial or problematic) ++ Small difference + Standard

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IL/LEP interface detected by TEM/TOF-SIMS

TOF-SIMS

Very clear interface between IL/LEP established - No significant intermixing - No significant penetration of LEP into IL

This originated from ; - Polymeric HTL (=IL) with reasonable Mw - Efficient thermal X-linking system

From UPS, TOF-SIMS and TEM measurement : TEM

EML IL HIL : polymer on IL : SM-evap on IL Sulfur detected (polymer and SM-evap contain S) (IL contains no S)

At interface, there is no significant difference of S-profile between SM-evap and polymer.

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Engineering of interface between layers

Engineering of IL/EML interface should be a key to “ideal stack”

Penetration Inter-mixing Dissolution Observed phenomena

EML material penetrates into IL while EML ink deposited on IL

EML material mixed with IL polymer at interface

Non X-linked IL polymer dissolves into EML

Issues Exciton migration into IL > low EQE, short LT

No distinctive layer formation results in possibility of lower EQE

Our strategy

EML should be polymer. Emitter should be embedded into polymer chain. High S1/T1 IL to confine exciton on emitter.

Highly X-linked IL polymer used Parameters : -Activity of X-linker -Polymer formulation -Mw -Tg

= Ensemble to evaporated device stack

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Key Technologies (1) Bank (2) Ink formulation (3) Drying process (4) Printing tech.

■ Capable for flexible panel design ■ Effective material (ink) utilization (no waste)

Inkjet Printing

Encapsulation

Bank Formation Inkjet Printing (IJP) Substrate Drying - baking

Cathode Deposition Organic Layers

Printed

HIL → IL → LEP layers

■ Cost effective process

Ink-jet printed device fabrication

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Symbol Name Size(μm)

A Pixel (x) 90

B Pixel (y) 270

C Bank Aperture (x) 50

D Bank Aperture (y) 198

E Bank Width (x) 40

F Bank Width (y) 72

※Thickness of bank：1μm ※Aperture ratio：38.5%

A

B

F

C D

E

Bank

ITO

Structure of electrodes

Cr/ITO (Light emitting region：ITO only)

Bank Single bank Thickness：1μm

Light-emitting region

90μm×270μm Aperture ratio：38.5%

8×30pixels Light-emitting

area 2.25mm2

Test cell design for IJP evaluation (with bank)

Ink-jet device evaluation detail

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IJ Printer： Litrex 142P ・Head: Dimatix SX-3 (128 nozzles) ・Droplet size: 6 -15pL /pulse ・Operation conditions of printing IJ-TEG - Scan speed： 15mm/sec - Jetting frequency： 1000Hz - Swath：Print 1 column by 1 swath, and print ① to ④ columns in order

IJ print process HIL IJ print

Dry

Bake & cooling

IL IJ print

Dry

Bake & cooling

LEP IJ print

Dry

Bake & cooling

2 in

ch

Printing direction

① ② ④ ③

Procedure of IJP device fabrication

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IJP parameters

Jettability of ink

Film morphology

Solvent Residue

Impurity

Film uniformity

In-pixel

In-panel

IL intractability

Bank interaction

Spin low bp ink

IJP TEG high bp ink

IJP Panel high bp ink

Flood spin high bp ink

Overview of IJP parameters

★

OLED performance

Step-wise performance verification done at Sumitomo/Customers

★

★

★

★

★

★

★

Should be identical each others

Selection of ink solvent is very important for all aspects of IJP parameters

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Ink performance

Ink intrinsic property

Jettability from nozzle

-Solubility -Viscosity -Viscosity increase during drying

-Droplet Verocity Directionality Volume Dependence on frequency and piezo-voltage -Latency (interval) -Nozzle plate wetting -Satellite formation

Layer formation Film formation

Ink jettability

-Solvent drying Diffusion of solute Coffee-ring effect -Film flatness

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Morphology & residual solvent

1

time

Wei

ght (

%)

100

0

2 3

Residual solvent Solute (polymer)

3 modes of drying 1．Pre-heat mode (Isothermal) 2．Constant-rate drying period - Driven by solvent evaporation from surface 3．Reduced-rate drying mode - Driven by internal diffusion

Temperature controls rate and efficiency of reduced-rate drying -Increased mobility of polymer chain (Tg) -Increased mobility of solvent molecule (bp and vapor pressure)

VCD

Bake Constant-rate

Reduced-rate

Confined solvent molecule by surface polymer layer (high Tg)

Cannot eliminate solvent molecule by the bake under Tg ->Becomes residual solvent

Fast drying by high vacuum results in formation of surface polymer layer, and slow removal of solvent molecule from inside of film.

Surface evaporation driven

Diffusion driven

Tg and its relationship with solvent bp is very important to eliminate residual solvent

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Flood-spin is beneficial to check film morphology and impact from high-bp solvent.

Spin low bp

Flood spin high bp

Xylene Ink

High-bp Ink

Bake &

Cathode evap.

VCD

-Quite similar layer formation process to IJP -Quite similar Morphology & Impact from solvent to IJP printed EML

50-100nm film

2-3 μm wet volume

50-100nm film

Flood-spin

Xylene Flood-spin (1) (2) (3)

Improved drying condition results in completely same performance with xylene spin.

This drying condition should be applied to IJP

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Film uniformity in-pixel

Film thickness controlled within 5nm range RGB: 100×280μm 58ppi

Thic

knes

s (n

m)

Position (μm)

Ambient pressure Drying > Convex

Reduced pressure Drying > Concave

Fast Drying Low bp solvent Reduced-pressure

Slow Drying High bp solvent Ambient-pressure

Issue Measure

Result

Combination of Fast and Slow drying

×

Film uniformity in pixel can be controlled by ink formulation & drying process.

Thic

knes

s (n

m)

Thic

knes

s (n

m)

Position (mm) Position (mm)

Film thickness HIL/IL/EML

& Low temp

& High temp

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[slow VCD] A B C [fast VCD]

13℃

25℃

35℃

55℃

70℃

0

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Film uniformity in pixel can be controlled by - Ink bp : low bp ink and high bp ink - Drying VCD speed - Drying temperature

Uniformity 30%

32%

48%

89%

81%

76%

91%

67%

61%

47%

25%

28%

59%

96%

94%

81%

84%

73%

61%

53%

31%

29%

40%

35%

34%

90%

69%

48%

45%

69%

Uniformity

Uniformity

Uniformity

Uniformity

Uniformity

Uniformity

Uniformity

Uniformity

Uniformity

Uniformity

Uniformity

Uniformity

Uniformity

Uniformity

※ Uniformity(%) = Film thickness [Min+10nm] area in the pixel (EML)

Control of film uniformity in-pixel

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Film uniformity across-panel

Issue

Measures

(1) Droplet volume control by DPN to eliminate Nozzle MURA (2) Use of 1-pass printer to eliminate Swathe MURA

Result

Droplet volume control ⇒Variation (CV) < 0.2% ⇒Nozzle MURA invisible 1-pass printer ⇒Swathe MURA invisible

13 inch panel printing

Film uniformity across panel can be controlled by printing methodologies.

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Film uniformity vs performance Film uniformity in pixel is important to secure IJ printed device LT.

Drying condition

EML film profile in pixel IVL LT

Flatness Average nm

Ave±5nm %

Ave±10nm %

Efficiency cd/A

dV V

EQE % CIE-y T95

hrs

A Good 61.9 74 93 9.9 3.9 9.0 0.131 48 B Fair 58.3 13 35 9.6 4.0 8.9 0.128 35 C Poor 59.6 15 32 9.8 4.0 9.0 0.129 30

Spin Uniform - 9.8 3.8 9.2 0.125 52

A Same as spin B Fair C Poor Spin

Luminance distribution in pixel Lifetime with different uniformity

A Good

B Fair

C Poor

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IL intractability & Bank interaction

Ink

• Out-material from bank may be on ITO

• Out material from bank may be on HIL and IL

• Out material from bank may dissolve into ink • Non X-linked IL polymer may dissolve into ink

• Out material from bank may be on EML

• Interaction with Bank and evaporated EIL/cathode

These reduce IJ-printed OLED performance Needs to eliminate these by Bank chemicals AND Highly X-linked IL

To eliminate IL dissolution and interaction with bank is important to secure OLED performance

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IJP-printed device performance

BE STD materials

Efficiency cd/A CIE-x, y T95 hrs

@1000nt

Red Spin 22.1 0.66, 0.34 4300

IJP 20.1 0.66, 0.34 7600

Green Spin 71.3 0.33, 0.63 12000

IJP 72.3 0.33, 0.63 9000

Blue Spin 7.4 0.14, 0.11 400

IJP 7.5 0.14, 0.12 300

Device structure : ITO/HIL/IL/EML/ low-WF cathode Not for the latest material set. Spin : xylene / IJP : high-bp ink

- By controlling IJP parameters, quite similar performance with Spin and IJP achieved. - Now IJP test for state-of-the-art materials on-going.

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Challenges for commercialization

Material Performance

Top-emission Device structure

Ink-jet Printing

Material scale-up QC/QA

• Baseline performance already achieved in BE/Spin • Current focus : Blue LT95, Green/Red efficiency and color.

• Same performance as Spin in IJP device should be secured. • Specific IJP parameters have been identified.

• Efficient micro-cavity structure with simple device stack. • Selection of HIL, EIL, anode/cathode and optimization.

• Several ten kg-scale facility already set-up in Osaka works. • QC/QA system development and specification necessary.

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Top-emission device for polymer-OLED

IVL characteristics @1000cd/m2

eficiency cd/A

voltage V

CIE-x CIE-ｙ

BE R 18.1 4.2 0.645 0.353

G 70.5 4.8 0.322 0.630

B 11.3 3.9 0.140 0.119

Cavity Mode

Eff. [cd/A]

@1kcd/m2

Vol. [V]

@10mA/cm2

CIE_x,y @1kcd/m2

TE R 1st 40.9 5.4 0.655, 0.344 G 1st 101.4 5.0 0.243, 0.699 B 2nd 3.7 4.3 0.134, 0.058

Structure: Anode / HIL / IL / EML / ETL / Cathode Anode : APC / 13nm ITO Cathode : 2nm Mg / 18nm Ag / 80nm Org.(capping layer)

Structure: Anode / HIL / IL / EML / Cathode Anode : ITO 45nm Cathode : 4nm NaF / 80nm Al / 200nm Ag

Introduction of micro-cavity structure (tested on spin-coat device) (same material set used)

- Enhanced efficiency - Wider color-space than sRGB.

Bottom Emission (BE)

Top Emission (TE)

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Scale-up synthesis and QC

Polymerization

End-capping

Precipitation Dried-up

Purification

Process Our technology

Polymerization

- Precise control of Mw and Mw/Mn - Best reaction condition to minimize side- reactions - Best control of monomer sequences

End-capping - Best reaction condition to eliminate halogen residues

Purification - Best Process to eliminate residual reactive materials and various impurities

Polymer

Quality of polymer is controlled by : (1) Reaction condition (2) Purity level by precise purification condition

-> OLED performance is also well-controlled and assured.

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Summary

Development is focused on color, efficiency and lifetime through material AND device stack.

Alignment of phosphorescent emitter Effective exciton confinement by state-of-the art ILs Improvement of material photo-stability Best optimized device stack including HIL/IL and EIL/cathode New class emitter introduced in blue polymer

OLED printing needs precise control of material/process/interfacial engineering. Key IJP parameters identified to secure 100% performance with IJP printing.

Material performance

Printing basics

IJP parameters

We discussed…

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Thank you for your attention.

[email protected]

Documents

Printed Device Performance of Polymer-OLED Materials...N2 or Air Ink viscosity vs conc. - Low dependency High dependency Layer formation/ aggregation + +++ ++ Our focus on Polymer