1. OFET’s in rollable displays
Fred Touwslager
Technology R&D manager
confidential
Outline
ƒ Introduction:
ƒ Organic Field Effect Transistor
ƒ Active matrix display
ƒ Why rollable displays?
ƒ Main technology choices
ƒ Summary
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2. Field Effect Transistor (a.k.a. TFT)
A 3-terminal device in which the current between 2 of the
terminals is determined by the voltage on the third.
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Field effect transistor: basic physics
Transfer characteristics
Drain voltage = -1V
*
- Drain current (A)
Accumulation Variable
Subthreshold
Vt Depletion
*
Vt = onset of accumulation
Gate voltage (V)
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3. Field effect transistors: layouts
bottom contact top contact
bottom gate
top gate
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Organic Field Effect Transistor
Rollable display
TFTs on ultra-thin
plastic
Room temperature
deposition
Organic materials
Integrated in a rollable
display
Resulting in an
extremely thin and
flexible backplane
Enable simple, room
temperature processing
Organics are highly
flexible
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4. (Rollable) Active Matrix display
Active matrix display is a grid of pixels, with a switch connected
to each pixel:
Switch = TFT
CEink
S
Data line
D
G pixel
Gate line
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(Rollable) Active Matrix display
data line
pixel
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5. (Rollable) Active Matrix display
Data
Selection
pulse
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Why displays on flexible carriers
Proposition Target market
Rollable/Foldable Mobile phones, E-readers, UMPCs, …
Flexible Smartcards, advertisement, point of
sale, wearable, …
Robust and lightweight E-readers, point of sale,
advertisement, …
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6. Mobile market: More powerful smaller devices
Device Size decreasing
Storage increasing
Content volume increasing
1G More data 3G+
Mobile display size
Av. Display Av. Display
Size 1.65”
No relative improvement Size 2”
Limited by glass based display technology
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The need for rollable displays
Device size no longer coupled to display size
Display larger
than the
device itself.
Ease of
mobility Display size
ratio:
Smart phone:
<0.3
iPhone: 0.56
Rollable: >1
Display size
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7. Main technology choices
Typical dimensions:
ƒ Pixel: 150μm x 150μm
ƒ Smallest dimensions: 5μm
ƒ Overlay accuracy: < 5 μm
ƒ Layer thicknesses: < 2μm
ƒ Total display thickness for a
rollable display: <100μm
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Main technology choices
Technology Technologies currently under development
block
Substrate Plastic Steel
Substrate Bond-debond Free standing Transfer
handling
Matrix stack Organic a-Si Poly-Si oxides
Patterning Lithography Printing Other
methods
Frontplane Electrophoretic OLED Ch-LC LCD
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8. Substrate
• Chemical stability
• Thermal stability
• Surface quality
• Stiffness
For PEN:
E = 6 GPa
t = 25 μm D = 0.11 Nm
Q =0.33
Et 3
D
12(1 Q ) For steel:
E = 190 GPa
Q = 0.27 – 0.30 t = 8μm
D = 0.11 Nm
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Substrate
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9. Substrate
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Substrate handling
ƒ Free standing (roll to roll or sheet to sheet). Keep in mind the desired
substrate thickness.
ƒ Transfer
ƒ Bond-debond
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10. Matrix stack
Semi-conductor:
ƒ poly-Si: vacuum deposition at T 600°C
ƒ amorphous Si: vacuum deposition / PECVD at T 100°C
ƒ organic: vacuum deposition or spin coating, low temperature
ƒ (mixed) oxides: low T vacuum deposition (ZnO, Ga2O3, ZnMgO, …)
Dielectrics:
ƒ inorganic: vacuum deposition
ƒ organic: spin coating
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Patterning: printing
the vision of kilometers display produced per minute
using roll-to-roll printing methods
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11. Benchmarking different printing technologies
Printing Feature Layer thickness Registration Throughput
Technique size (μm) (μm) (μm) (m²/s)
Inkjet 20-50 0.5 5 - 20 0.01 – 0.5
Flexography 80 0.8 - 2.5 200 3 - 30
Gravure 75 0.1 – 8.0 20 3 - 60
Screen 20 - 200 0.015 - 100 25 2-3
Offset 10 - 50 0.5 – 2.0 10 5 - 30
Pad 20 1 -2 10 0.1
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Patterning
Chosen for lithographic patterning:
- Subtractive technique
- Sacrificial layer
+ Proven manufacturing technology
+ Huge installed base
+ Compatible with standard AMLCD manufacturing
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12. Frontplane
Electrophoretic display (EPD) effect:
Black and white particles with opposite charge in a clear liquid.
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Polymer Vision technology
Technology Technologies currently under development
block
Substrate Plastic Steel
Substrate Bond-debond Free standing Transfer
handling
Matrix stack Organic a-Si Poly-Si oxides
Patterning Lithography Printing Other
methods
Frontplane Electrophoretic OLED C-LC LCD
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13. AM backplane layout
Pixel electrode
Field insulator
Semiconductor
Column Pixel electrode
Row Insulator
Plastic substrate
Rigid support
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carrier
Display construction
Display construction
Laminate electrophoretic frontplane laminate
Laminate electrophoretic frontplane laminate
Field insulator
Semiconductor Field insulator
Semiconductor
Column Pixel electrode
Column Pixel electrode
Row Insulator
Row Insulator
Plastic substrate
Plastic substrate
Rigid support
Rigid support
carrier
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carrier

14. Thinnest, most flexible display in the World
Plastic substrate
30Pm
E Ink display effect
40Pm
0.1mm
Organic electronics
backplane
5Pm
Plastic substrate
25Pm
• Ultra-thin is rollable: roll radius § 50 x thickness
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Unbreakable display
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15. Brief history – Philips Research highlights
1995 First logic gates
1998 All-polymer ICs, first transponders (Si diode)
2000 150mm wafer process, scaleable and industrial
2000 World’s 1st OE glass-based display
2003 shift registers (~ 2000 TFTs)
2004 Ferroelectric memory transistors
Time (s)
2006 13.56MHz RFID tag
2000 2001 2002 2003 2004
rigid Grey scale flexible Size QVGA rollable
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About Polymer Vision
20xx “A rollable display in every mobile device!”
:
:
2010 MA local AMLCD facility
2009 Assets acquired by
2008 Qualified rollable display and device
2007 Production line transfer yield
2006 Spin-out of Polymer Vision Ltd.
2005 Concept device development
:
2000 Development of rollable display
:
1991 Research on organic electronics
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16. Summary
Polymer Vision offers a robust, flexible and
even rollable display solution.
Polymer Vision uses proven manufacturing
technologies to introduce a new display
technology.
The technology and process have successfully
been introduced into a G2.5 AM-LCD line.
The technology has further matured by the
introduction of a full VGA display and touch.
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Food for thought
ƒ Can cost be the driving force for introduction of disruptive
alternative technologies (e.g. LCD versus CRT)?
ƒ Why is batch processing so popular in LCD and IC manufacturing?
ƒ Why is printing of e.g. value paper still done sheet to sheet?
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