Towards a flexible OLED display with an organic active matrix backplane

P. Heremans1, J. Genoe1, S. Steudel1, K. Myny1, S. Smout1, P. Vicca1, L. Ruppel3, C. Grillberger3, O. R. Hild3, F. Furthner2, B. van der Putten2, A. K. Tripathi2, G. H. Gelinck2

1 2 3 4

Acknowledgement

FP7 STREP project #216546

start Jan 2008

Flexible Organic Active Matrix OLED displays forNomadic Applications

FLAME

http://www.imec.be/FLAME

Paul Heremans, SID-ME 2010, Dresden 2

Paul Heremans, SID-ME 2010, Dresden 3

Introduction

• Goal: – Technology for flexible and rollable OLED display

• Implementation:– Plastic foil substrate (with moisture barrier)

– Organic transistor backplane

– Small molecule top-emitting OLED stack

– Topstrate barrier foil

State of the art

• 48X48 bottom-emitting monochrome OLEDs on flexible substrateT. Jackson: Pentacene TFT driven AM OLED displays, Electron device letters 26, 640 (2005)T. Jackson: All-organic active matrix flexible display, Appl. Phys. Lett. 88, 083502 (2006)

• 12X12 (2mm pixel size), Ta2O5 gate dielectric, aperture ratio 37% M. Mizukami et al.: Flexible AM OLED panel driven by bottom-contact OTFTs, IEEE El. Dev. Lett. 26, 9 (2006)

• SONYSID07-1753QQVGA full color

• T. Someya and T. Sekitani: many other backplane appliations!Examples: pressure sensors, image scanner, actuators, …

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Outline

• Backplane

• OLED

• Integration

• Moisture Barrier

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Pixel

< 1pAIOFF

Requirement

Mobility 0.5 ± 0.03 cm2/Vs

L 5 µm

Cox > 20 nF/cm2

∆VT 0.2 V

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Technology

• Laminate foil on carrier– Freedom of foil type

– Flexibility in process

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Technology

• Laminate foil on carrier– Freedom of foil type

– Flexibility in process

• Use of conventional process technology– Transferable to flat panel line

– CD ≥ 2 µm

cfr. DowCorning

cfr. Yokogawa

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Technology

• Laminate foil on carrier– Freedom of foil type

– Flexibility in process

• Use of conventional process technology– Transferable to flat panel line

– CD ≥ 2 µm

• Organic thin-film transistors– Pentacene (and soluble derivatives) semiconductor (p-type only)

– Bottom-gate bottom-contact geometry

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Carrier

glue

PEN Teonex™

Planarization

Au (30nm)

resist

Al2O3 (100-150 nm)

Carrier

glue

PEN Teonex™

Planarization

Au (30nm)

resist

Al2O3 (100-150 nm)

Drop-on-demand Ink jet

Au (30nm) Au (30nm)

Organic Vapor Phase Deposition

C. Rolin et al., Appl. Phys. Expr. 2, 086503 (2009) C. Kjellander et al., MRS Fall (2009)

J. Anthony,

JACS123, 9482, (2001)

T. Jackson,

AdvMat15,2009 (2003)

Backplane process

Performance evaporated pentacene

7

6

5

4

3

2

1

0

Number

1.00.80.60.40.20.0

µ [cm2 / Vs]

µ (AVG) = 0.472 cm2 / Vs

µ (StDev) = 0.0174 cm2 / Vs

3.0

2.5

2.0

1.5

1.0

0.5

0.0

Number

-10 -5 0 5 10VT [V]

VT (AVG) = 0.906096 V

VT (StDev) = 0.496683 V

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Inkjet printed TIPS pentacene formulation

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Performance

< 1pA< 1pAIOFF

Requirement Pentacene/Al2O3

Mobility 0.5 ± 0.03 cm2/Vs 0.5 ± 0.05 cm2/Vs

L 5 µm 5 µm

Cox > 20 nF/cm2 50-70 nF/cm2

∆VT 0.2 V 0.4 V

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Array

• Generation 1:– 32 x 32

– Pixels 1 mm2

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OLED on foil

• Top emitting (transparent cathode)

• Silver anode

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target

Transparent cathode

OLED layer stack

interlayer dielectric

Integration of OLED on backplane

Carrier

glue

PEN Teonex™

Planarization

Au (30nm)

resist

Al2O3 (100-150 nm)

Au (30nm)pentacene

Via hole

Ag anode

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Example green OLED

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Example orange OLED

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Aperture ratio

Top-emitting OLED

Aperture ratio : 79.7%

off

on

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Brightness

D65 white color point

100

80

60

40

20

0

Cox [nF/cm2]

2 3 4 5 6

0.12 3 4 5 6

12 3 4

Carrier Mobility [cm2/Vs]

2000 Cd/m2

500 Cd/m2

200 Cd/m2

800 Cd/m2

Al2O3

Polymer gate dielectrics

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Brightness

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Moisture barrier

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5 X 5 µmRMS 1.1 nmRmax 10 nm

Barrier foil

• Integration of barrier with OLED on foil

Radius 0.8 cm

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OLED stack

Summary

• Status :– Pentacene/Al2O3 backplane with green and orange OLEDs integrated

on foil in 32x32 test vehicles

– Moisture barrier with OLEDs integrated on foil and tested for rollability

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• Near future :– Integrate row and column drivers

– Develop top-emitting blue OLED pixels on foil

– Apply 3 colors on backplane

– Scale pixel size

– Integrate all in demonstrator

Thank you

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