Low-Voltage Organic Transistors for Flexible Electronics

Flexible Low-Voltage

Organic Transistors and Circuits

Hagen Klauk

Max-Planck-Institut für Festkörperforschung

Max Planck Institute for Solid State Research

Stuttgart, Germany

Organic Electronics Group at the Max Planck Institute, Stuttgart

Ute Zschieschang Mirsada Sejfić Reinhold Rödel Ulrike Kraft

Frederik Ante Daniel Kälblein

now at:

Hyeyeon Ryu

now at: now at:

Robert Hofmockel

Organic TFTs: Low Process Temperatures Enable Plastic Substrates

semiconductor process temperature choice of substrate

-----------------------------------------------------------------------------------------------------------------------

single-crystalline Si >800 ºC silicon

polycrystalline Si >350 ºC glass

hydrogenated amorphous Si >250 ºC glass

metal oxides (ZnO, IGZO) >150 ºC glass

organic semiconductors 60 .. 120 ºC flexible plastics

Troisi, JPCB 109 1849 (2005) Schiefer, JACS 129 10316 (2007) Sekitani, Science 326 1516 (2009)

Active-Matrix Organic Light-Emitting Diode (AMOLED) Display Layout

~300 µm AMOLED displays require the integration of

organic LEDs with thin-film transistors (TFTs).

Active-Matrix Display Requirements: Dynamic TFT Performance

display # of rows frame row access TFT

resolution (M) rate time cutoff frequency

------------------------------------------------------------------------------------------------------

VGA 480 100 Hz 20 µsec >100 kHz

HD 1080 400 Hz 2 µsec >1 MHz

row

access

time

frame

time

row

= access x # of rows

time

1 2 3

1

N

2

M

Low-Voltage Organic LEDs

2.5 V (1000 cd/m2)

(Ephot ~ 2.0 eV)

2.7 V (1000 cd/m2)

(Ephot ~ 2.3 eV)

3.0 V (1000 cd/m2)

(Ephot ~ 2.7 eV)

http://www.novaled.com

Literature Review: Flexible Organic Ring Oscillators

Drury, Appl. Phys. Lett. 73 108 (1998)

Kane, Electr. Dev. Lett. 21 534 (2000)

de Leeuw, IEEE Int’l Electr. Dev. Meeting (2002)

Fix, Appl. Phys. Lett. 81 1735 (2002)

Ficker, J. Appl. Phys. 94 2638 (2003)

Klauk, Appl. Phys. Lett. 82 4175 (2003)

Zschieschang, Adv. Mater. 15 1147 (2003)

Eder, Appl. Phys. Lett. 84 2673 (2004)

Knobloch, J. Appl. Phys. 96 2286 (2004)

Krumm, IEEE Electr. Dev. Lett. 25 399 (2004)

Klauk, IEEE Trans. Electr. Dev. 52 618 (2005)

Nilsson, Adv. Mater., vol. 17, p. 353 (2005)

Zielke, Appl. Phys. Lett. 87 123508 (2005)

Anthopoulos, Adv. Mater. 18 1900 (2006)

Bartzsch, Org. Electronics 8 431 (2007)

Hübler, Org. Electronics 8 480 (2007)

Takamiya, IEEE J. Solid-State Circ. 42 93 (2007)

Gundlach, Nature Mater. 7 216 (2008)

Park, IEEE Electr. Dev. Lett. 29 1004 (2008)

Heremans, IEEE Int’l. Electr. Dev. Meeting (2009)

Myny, Solid-State Electronics 53 1220 (2009)

Hambsch, Mater. Sci. Eng. B 160 93 (2010)

Myny, Org. Electronics 11 1176 (2010)

Verilhac, Org. Electronics 11 456 (2010)

Guetin, IEEE Trans. Electr. Dev. 58 3587 (2011)


Kempa, IEEE Trans. Electr. Dev. 58 2765 (2011)

Myny, IEEE J. Solid-State Circ. 46 1223 (2011)

Sun, Adv. Mater. 23 3128 (2011)

Zhao, Adv. Mater. 23 2448 (2011)

Huang, J. Am. Chem. Soc., vol. 134, 10966 (2012)

Koskela, Org. Electronics, vol. 13, p. 84 (2012)


Smaal, Org. Electronics, vol. 13, p. 1686 (1012)

Literature summary:Organic ring oscillators

(signal delay vs. supply voltage)flexible

Supply voltage (V)

0.5 2 5 20 50 2001 10 100

Sig

na

l d

ela

y (

se

c)

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

Literaturesince 1998

Gate Dielectrics: Permittivity, Thickness, Capacitance, Voltage Range

Q V C

(e/cm2) (V) (nF/cm2)

-------------------------------------------

1x1013 20 100

1x1013 3 700

materials ε t C

choice (nm) (nF/cm2)

--------------------------------------------------------------

high-e oxides 16 20 700

thin polymers 3 4 700

Q = V C ε ε0

t C =

Semiconductor

Gate electrode

Gate dielectric

Source Drain

VDS ID

VGS

t

Q ... carrier density in the channel

(target: ~1013 cm-2)

V ... overdrive voltage (VGS-Vth)

C ... gate dielectric capacitance

ε ... gate dielectric permittivity

t ... gate dielectric thickness

Low-Temperature Gate Dielectrics: Materials Choices

Yoon, JACS 127 10388 (2005)

Kim, APL 89 183516 (2006)

Yang, APL 88 173507 (2006)

Kim, JACS 130 6867 (2008)

Roberts, PNAS 105 12134 (2008)

Roberts, Chem. Mater. 20 7332 (2008)

Roberts, Chem. Mater. 21 2292 (2009)

Walser, APL 95 233301 (2009)

Khan, Adv. Mater. 22 4452 (2011)

Khan, Chem. Mater. 23 1946 (2011)

examples ε -------------------------

Al2O3 9

HfO2 11

ZrO2 24

Majewski, J. Phys. D 37 3367 (2004)

Koo, APL 89 033511 (2006)

Tardy, Microelectr. Rel. 47 372 (2007)

Chang, IEEE EDL 29 215 (2008)

Cho, APL 92 213302 (2008)

Tan, APL 93 183503 (2008)

Lin, Org. Electronics 12 955 (2011)

Thin (<10 nm) polymers

OH

n

polyvinyl-

phenol

poly-

styrene

OH

n

examples:

polyimide, CytopTM, ...

High-e metal oxides Polyelectrolytes & ion gels

Panzer, APL 86 103503 (2005)

Dhoot, PNAS 103 11834 (2006)

Lee, JACS 129 4532 (2007)

Cho, Nature Mater. 7 900 (2008)

Herlogsson, Adv. Mater. 20 4708 (2008)

Said, Adv. Funct. Mater. 18 3529 (2008)

Lee, J. Phys. Chem. C 113 8972 (2009)

Braga, APL 97 193311 (2010)

Herlogsson, Adv. Mater. 22 72 (2010)

Xia, Adv. Funct. Mater. 20 587 (2010)

Malti, APL 99 063305 (2011)

examples:

•PEO + LiClO4

•PSS:H, P(VPA-AA)

•PS-PEO-PS + [BMIM][PF6]

Aluminum Oxide / Self-Assembled Monolayer (SAM) Gate Dielectrics

phosphonic acid

anchor group

aliphatic unit

(6~18 C-atoms)

PO OH

OH

Substrates 22, 28, 31

A = 0.0001 cm2 or 0.0003 cm

2

10 devices each

Bias (V)

-3 -2 -1 0 1 2 3

Cu

rre

nt

de

ns

ity (

A/c

m2)

10-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

10-3

AlOx + SAM

AlOx only

(4.6 x 1014 molecules / cm2)

Substrate

Source Drain

Al gate

Organic semiconductor

AlOx (3~4 nm)

SAM (1~2 nm)

Substrate 16

A = 0.126 ... 1.131 cm2

Frequency (Hz)

100 101 102 103 104

Cap

acit

an

ce (

µF

/cm

2)

0.0

0.2

0.4

0.6

0.8

1.0

0.28 cm2

0.50 cm2

0.78 cm2

1.13 cm2

Sekitani et al., Nature Mater. 9 1015 (2010)

Manufacturing Process: Organic TFTs with AlOx/SAM Gate Dielectric

vacuum deposition

of Al gates, Au S/D,

org. semiconductor

plasma oxidation

of Al gate electrodes,

producing 3~4 nm AlOx

Substrate

Source Drain

Al gate electrode

Substrate

Al gate electrode

Substrate

Al gate electrode


SAM

AlOx

Substrate

Al gate electrode

Substrate

Al gate electrode

maximum process temperature: 80 °C

Manufacturing Process: Patterning Using Shadow or Stencil Masks

Source

Drain

1 µm

polyimide

shadow masks

• inexpensive

• easy to use

• poor resolution

silicon

stencil masks

• high resolution

• expensive

• fragile

Source

Drain

Gate

30 µm

30 µm

30 µm

Flexible Pentacene TFTs: Current-Voltage Characteristics

Substrate MPI-32

W = 100 m, L = 50 m

Gate-source voltage (V)

-3 -2 -1 0

Ga

te c

urr

en

t (A

)

10-12

10-11

10-10

10-9

10-8

10-7

10-6

Dra

in c

urr

en

t (A

)

10-12

10-11

10-10

10-9

10-8

10-7

10-6

Drain-source voltage = -1.5 V

Substrate MPI-32

W = 100 m, L = 50 m


-2 -1 0

Ho

le m

ob

ilit

y (

cm

2/V

s)

0.0

0.1

0.2

0.3

0.4Drain-source voltage = -1.5 V

carrier mobility = 0.3 cm2/Vs

on/off current ratio = 105

subthreshold slope = 140 mV/dec

L = 50 µm

W = 100 µm

pentacene

pentacene

Flexible polymeric substrate

Source Drain

Al gate electrode

AlOx/SAM gate dielectric Organic semiconductor

Substrate MPI-32

W = 100 m, L = 50 m

Drain-source voltage (V)

-3 -2 -1 0

Dra

in c

urr

en

t (

A)

-0.4

-0.3

-0.2

-0.1

0.0

Gate-source voltage = -3.0 V

-1.8 V

-2.1 V

-2.4 V

-2.7 V

G

D

S

Pentacene: Rapid Air-Induced Oxidation and Loss of Conjugation

de Angelis, Chem. Phys. Lett. 468 193 (2009)

pentacene

O

O

air

Substrates MPI-122, MPI-144, MPI-285 (pentacene)

Exposure to air (days)

0 30 60 90 120

Ho

le m

ob

ilit

y (

cm

2/V

s)

0.0

0.1

0.2

0.3

0.4

0.5stored andtested in air

pentacene

Qiu, Appl. Phys. Lett. 83 1644 (2003)

Lee, Synth. Metals 143 21 (2004)

Kim, J. Vac. Sci. Technol. B 23 2357 (2005)

Han, Appl. Phys. Lett. 88 073519 (2006)

Sekitani, Jpn. J. Appl. Phys. 46 4300 (2007)

Ashimine, Jpn. J. Appl. Phys. 47 1760 (2008)

Jeon, Appl. Phys. Lett. 93 163304 (2008)

Jung, Appl. Phys. Lett. 92 163504 (2008)

Yang, J. Phys. Chem. C 112 16161 (2008)

after 240 days

in air

DNTT: Built-In Oxidation Resistance and Improved Air Stability

DNTT mass spectrogram(after 240 days in air)

mass (z)

330 340 350 360 370 380

Re

lati

ve

in

ten

sit

y

0.0

0.2

0.4

0.6

0.8

1.0

S

S

dinaphto-thieno-thiophene

(DNTT) Yamamoto, JACS

129 2224 (2007)

Substrate MPI-479 (DNTT, W = 100 m, L = 50 m)Substrates MPI-122, MPI-144, MPI-285 (pentacene)

Exposure to air (days)

0 60 120 180 240

Ho

le m

ob

ilit

y (

cm

2/V

s)

0.1

1

10stored andtested in air

pentacene

DNTT

S

S

(isotopes)

after 240 days

in air

• no encapsulation

• continuous air exposure

• relative humidity: 40 .. 60%

Zschieschang, Org. Electronics 12 1370 (2011)

Flexible DNTT TFTs: Current-Voltage Characteristics


Source Drain

Al gate electrode


G

D

S

Substrate MPI-479

W = 100 m, L = 30 m


-2 -1 0

Ho

le m

ob

ilit

y (

cm

2/V

s)

0

1

2

3Drain-source voltage = -1.5 V

L = 30 µm

W = 100 µm

Substrate MPI-479

W = 100 m, L = 30 m


-3 -2 -1 0

Dra

in c

urr

en

t (

A)

-10

-8

-6

-4

-2

0


-1.8 V

-2.1 V

-2.4 V

-2.7 V

Substrate MPI-479

W = 100 m, L = 30 m


-3 -2 -1 0

Ga

te c

urr

en

t (A

)

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

Dra

in c

urr

en

t (A

)

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

Drain-sourcevoltage = -1.5 V

S

S

DNTT




Zschieschang, Org. Electronics 12 1370 (2011)

Low-Voltage Organic TFTs: Controlling Large-Area Organic LEDs

VGS = -3.5 V

ILED = 67 µA

VGS = -2.5 V

ILED = 25 µA

VGS = -2.0 V

ILED = 10 µA

-5 V

IOLED

Substrate MPI-654

W = 200 m, L = 10 m


-3 -2 -1 0

OL

ED

dri

ve

cu

rre

nt

(A)

10-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

0 V

-3.5 V

L = 10 µm

W = 200 µm

2.6 mm

2.6

mm

Zschieschang, Org. Electronics

12 1370 (2011)

VGS = -3.0 V

ILED = 46 µA

S

S

Low-Voltage Organic TFTs and Circuits on Banknotes


Substrate MPI-307 (5-Euro bill)DNTT TFTs

W = 100 m, L = 30 m


-3 -2 -1 0

Gate

cu

rren

t (A

)

10-12

10-11

10-10

10-9

10-8

10-7

10-6

Dra

in c

urr

en

t (A

)

10-12

10-11

10-10

10-9

10-8

10-7

10-6

92 TFTs

L = 30 m

W = 100 m

Substrate MPI-253 (5-Euro bill)

W = 100 m, L = 15 m


-3 -2 -1 0

Dra

in c

urr

en

t (

A)

-1.2

-0.9

-0.6

-0.3

0.0


-1.8 V

-2.1 V

-2.4 V

-2.7 V

Relationship Between Intermolecular Distance and Carrier Mobility

Troisi,

J. Phys. Chem. B

109 1849 (2005)

SS

SS

SS

SS

distance

Bredas,

Proc. Nat’l. Acad. Sci.

99 5804 (2002)

d ~ 0.7 nm

Kang,

Adv. Mater.

23 1222 (2011)

increased van-der-Waals interactions

smaller intermolecular distance

improved orbital overlap

larger carrier mobility

dialkyl-DNTT DNTT

Yamamoto,

J. Am. Chem. Soc.

129 2224 (2007)

orbital

overlap

Flexible C10-DNTT TFTs: Current-Voltage Characteristics



subthreshold slope = 68 mV/dec L = 30 µm

W = 100 µm

Substrate MPI-1120

W = 100 m, L = 30 m


-3 -2 -1 0

Dra

in c

urr

en

t (

A)

-15

-12

-9

-6

-3

0


-1.2 V

-1.4 V

-1.6 V

-1.8 V

Substrate MPI-1120

W = 100 m, L = 30 m


-2 -1 0

Gate

cu

rren

t (A

)

10-14

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

Dra

in c

urr

en

t (A

)

10-14

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5Drain-sourcevoltage = -2.0 V

C10-DNTT

S

S C10H21

H21C10


Source Drain

Al gate electrode


Substrate MPI-1120

W = 100 m, L = 30 m


-2 -1 0

Ho

le m

ob

ilit

y (

cm

2/V

s)

0

1

2

3

4

5Drain-source voltage = -2.0 V

Zschieschang, J. Mater. Chem. 22 4273 (2012)

G

D

S

S

S C10H21

H21C10

Dynamic TFT Performance: Theoretical Prediction

fT ~ µ VDS

2π L (L + 2L)

µ ~ 4 cm2/Vs

VDS ~ 2 V

Source

Drain

Gate

polyimide shadow masks:

L ~ 30 µm

L ~ 30 µm

fT ~ 50 kHz

(2fT)-1 ~ 10 µsec

30 µm

30 µm

30 µm

display # of rows frame row access TFT

resolution (M) rate time cutoff frequency

------------------------------------------------------------------------------------------------------

VGA 480 100 Hz 20 µsec >100 kHz

HD 1080 400 Hz 2 µsec >1 MHz

High-Resolution Silicon Stencil Masks

organic TFTs patterned using silicon stencil mask

Butschke, Microelectronic Eng. 46, 473 (1999)

Letzkus, Microelectronic Eng. 53, 609 (2000) Ante, Small 8 73 (2012)

S

D

1 µm

Substrate

Source Drain

Al gate electrode

L L L

High-Resolution Silicon Stencil Masks: Static TFT Characteristics

L = 1 µm

W = 10 µm

Source

Drain

1 µm




Ante, Small 8 73 (2012)

Substrate MPI-1294C10-DNTT/DNTT TFT on PEN

W = 10 m, L = 1 m


-2 -1 0 1

Gate

cu

rren

t (A

)

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

Dra

in c

urr

en

t (A

)

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5Drain-sourcevoltage = -2.0 V


W = 10 m, L = 1 m


-3 -2 -1 0

Dra

in c

urr

en

t (

A)

-15

-12

-9

-6

-3

0


-1.2 V

-1.4 V

-1.6 V

-1.8 V

C10-DNTT

S

S C10H21

H21C10


Source Drain

Al gate electrode



W = 10 m, L = 1 m


-2 -1 0 1

Tra

nsc

on

du

cta

nc

e (

S/m

)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4Drain-source voltage = -2.0 V

High-Resolution Silicon Stencil Masks: TFT Parameter Uniformity




Ante, Small 8 73 (2012)

Substrate MPI-1294

W = 10 m, L = 1 m16 C10-DNTT TFTs on PEN, fresh

Transconductance (S/m)

0.0 0.5 1.0 1.5 2.0

Co

un

ts

0

1

2

3

4

5

6

7

8

9mean = 1.2 S/m

= 0.078 S/m (6%)

L = 1 µm

W = 10 µm

C10-DNTT

S

S C10H21

H21C10

Substrate MPI-1294

W = 10 m, L = 1 m16 C10-DNTT TFTs on PEN, fresh


-2 -1 0

Dra

in c

urr

en

t (A

)

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5Drain-source voltage = -2.0 V

16 TFTs

L = 1 m

W = 10 m

S

S C10H21

H21C10

Dynamic TFT Performance: Theoretical Prediction

fT ~ µ VDS

2π L (L + 2L)

µ ~ 4 cm2/Vs

VDS ~ 2 V

Source

Drain

Gate


L ~ 30 µm

L ~ 30 µm

fT ~ 50 kHz

(2fT)-1 ~ 10 µsec

30 µm

30 µm

30 µm

silicon stencil masks:

L ~ 1 µm

L ~ 5 µm

fT ~ 5 MHz

(2fT)-1 ~ 100 nsec Source

Drain

1 µm

Dynamic TFT Performance: Experimental Ring Oscillator Delay

fT ~ µ VDS

2π L (L + 2L)

µ ~ 4 cm2/Vs

VDS ~ 2 V

Zschieschang, J. Mater. Chem. 22 4273 (2012)

Ante, Small 8 73 (2012)

S

S C10H21

H21C10


L ~ 30 µm

L ~ 30 µm

fT ~ 50 kHz

(2fT)-1 ~ 10 µsec

silicon stencil masks:

L ~ 1 µm

L ~ 5 µm

fT ~ 5 MHz

(2fT)-1 ~ 100 nsec

MPI-1120 (C10-DNTT, flexible PEN, L = 30 µm)MPI-1150 (C10-DNTT, flexible PEN, L = 1 µm)

Supply voltage (V)

1 2 3 4

Sig

nal d

ela

y p

er

sta

ge (

sec)

10-7

10-6

10-5

10-4

L = 1 m, L = 5 m(420 ns @ 3 V)

L = L = 30 m

(25 s @ 3 V)

Literature Comparison: Flexible Organic Ring Oscillators

Drury, Appl. Phys. Lett. 73 108 (1998)

Kane, Electr. Dev. Lett. 21 534 (2000)

de Leeuw, IEEE Int’l Electr. Dev. Meeting (2002)

Fix, Appl. Phys. Lett. 81 1735 (2002)

Ficker, J. Appl. Phys. 94 2638 (2003)

Klauk, Appl. Phys. Lett. 82 4175 (2003)


Eder, Appl. Phys. Lett. 84 2673 (2004)

Knobloch, J. Appl. Phys. 96 2286 (2004)

Krumm, IEEE Electr. Dev. Lett. 25 399 (2004)

Klauk, IEEE Trans. Electr. Dev. 52 618 (2005)

Nilsson, Adv. Mater., vol. 17, p. 353 (2005)

Zielke, Appl. Phys. Lett. 87 123508 (2005)

Anthopoulos, Adv. Mater. 18 1900 (2006)

Bartzsch, Org. Electronics 8 431 (2007)


Takamiya, IEEE J. Solid-State Circ. 42 93 (2007)

Gundlach, Nature Mater. 7 216 (2008)

Park, IEEE Electr. Dev. Lett. 29 1004 (2008)

Heremans, IEEE Int’l. Electr. Dev. Meeting (2009)

Myny, Solid-State Electronics 53 1220 (2009)

Hambsch, Mater. Sci. Eng. B 160 93 (2010)

Myny, Org. Electronics 11 1176 (2010)

Verilhac, Org. Electronics 11 456 (2010)

Guetin, IEEE Trans. Electr. Dev. 58 3587 (2011)


Kempa, IEEE Trans. Electr. Dev. 58 2765 (2011)


Sun, Adv. Mater. 23 3128 (2011)

Zhao, Adv. Mater. 23 2448 (2011)

Huang, J. Am. Chem. Soc., vol. 134, 10966 (2012)

Koskela, Org. Electronics, vol. 13, p. 84 (2012)


Smaal, Org. Electronics, vol. 13, p. 1686 (1012)

Literature summary:Organic ring oscillators

(signal delay vs. supply voltage)flexible

Supply voltage (V)

0.5 2 5 20 50 2001 10 100

Sig

na

l d

ela

y (

se

c)

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

Literaturesince 1998

L = 1 m

L = 10 m

Active-Matrix Displays: External Row and Column Drivers

Ro

w S

hif

t R

eg

iste

r

Digital/Analog Converter

Latch

Column Shift Register

data

clock

clock

Rollable Active-Matrix Displays with Integrated Row Drivers

http://www.sony.net/SonyInfo/News/Press/201005/10-070E/index.html

Integrated Circuits: Digital-to-Analog Converters in a Unipolar Design

6-bit current-steering DAC

15 organic TFTs

(129 in the layout)

circuit area:

2.6 x 4.6 mm2

Transfer function

Zaki, IEEE J. Solid-State Circuits 47 292 (2012)

100 kS/sec

Comparison: Unipolar vs. Complementary Logic

complementary

p-channel TFT

VDD

input

output

n-channel TFT

VDD

input

output

p-channel TFT

p-channel TFT

unipolar

Substrate MPI-248Inverter with saturated load

Wdrive

= 100 µm, Ldrive

= 10 µm, Wload

= 50 µm, Lload

= 100 µm

Ou

tpu

t vo

ltag

e (

V)

-3

-2

-1

0

Cu

rren

t (A

)

10-10

10-9

10-8

10-7

10-6

10-5

10-4

10-3

10-2

Input voltage (V)

-3 -2 -1 0

Gain

0

1

2

VDD

= -3 V

Substrate MPI-28850% C18H37-PA, 50% C18H22F15-PA

Complementary inverterW

p = 100 µm, L

p = 30 µm, W

n = 1000 µm, L

n = 30 µm

Ou

tpu

t vo

ltag

e (

V)

0

1

2

Cu

rren

t (A

)

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

10-3

Input voltage (V)

0 1 2

Gain

0

200

400

VDD

= 2 V

Semiconductors for n-Channel TFTs: Orbital Energy Considerations

Au

p-channel TFT

(air-stable)

HOMO ~ 5 eV

Au

n-channel TFT

(air-stable)

LUMO ~ 4.5 eV

NN

N

N

Cu

NN

N N

F F

FF

F

F

F

F

F

FF

F

F

F

F

F

F16CuPc

S

S C10H21

H21C10

S

S

HOMO ~ 6.3 eV

LUMO ~ 2 eV

F16CuPc n-Channel TFTs: Current-Voltage Characteristics

Substrate MPI-411

W = 1000 m, L = 20 m


0 1 2 3

Dra

in c

urr

en

t (

A)

0.0

0.5

1.0

1.5

2.0

Gate-source voltage = 3.0 V

2.1 V

1.5 V

2.4 V

1.8 V

2.7 V

Substrate MPI-411

W = 1000 m, L = 20 m


0 1 2 3

Dra

in c

urr

en

t (A

)

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

Ga

te c

urr

en

t (A

)

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

Drain-source voltage = 1.5 V

N

N N N

N

NNN

Cu

F

F

F

F

F

F F

F

F

F

F

F

F

F

F

F

F16CuPc

Glass substrate

Source Drain

Al gate electrode


L = 20 µm

W = 1000 µm




Zschieschang, Langmuir 24 1665 (2008)

Kraft, J. Mater. Chem. 20 6416 (2010)


Organic Complementary Inverters: Static Performance

p-channel TFT

VDD

input

output

n-channel TFT

Substrate MPI-28850% C18H37-PA, 50% C18H22F15-PA

Complementary inverterW

p = 100 µm, L

p = 30 µm, W

n = 1000 µm, L

n = 30 µm

Ou

tpu

t v

olt

ag

e (

V)

0

1

2

Cu

rre

nt

(A)

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

10-3

Input voltage (V)

0 1 2

Ga

in

0

200

400

VDD

= 2 V

N

N N N

N

NNN

Cu

F

F

F

F

F

F F

F

F

F

F

F

F

F

F

F

pentacene

F16CuPc

• large output swing (= VDD)

• small static currents (<10 pA)

• large gain (>200)

Substrate

Gate (Al) Gate (Al)

S D D S

Semiconductor for p-channel TFT

Semiconductor for n-channel TFT

AlOx/SAM gate dielectric


Organic Complementary Ring Oscillators: Dynamic Performance

VDD

silicon stencil masks (L = 1 µm)

polyimide shadow masks (L = 20 µm)


Ante, Int’l Electron Devices Meeting (2010)

MPI-288 (complementary, 20 µm, mixed C18-PA SAM)Stencil-9 (complementary, 20 µm, 5 µm, 1 µm)

Supply voltage (V)

1 2 3

Sig

na

l d

ela

y p

er

sta

ge

(s

ec

)

10-5

10-4

10-3

10-2

10-1

100

L = 1 m, L = 2 m

(63 s @ 3 V)

L = L = 20 m(3.3 ms @ 3 V)

F16CuPc n-Channel TFTs: Current-Voltage Characteristics

Substrate MPI-411

W = 1000 m, L = 20 m


0 1 2 3

Dra

in c

urr

en

t (

A)

0.0

0.5

1.0

1.5

2.0

Gate-source voltage = 3.0 V

2.1 V

1.5 V

2.4 V

1.8 V

2.7 V

Substrate MPI-411

W = 1000 m, L = 20 m


0 1 2 3

Dra

in c

urr

en

t (A

)

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

Ga

te c

urr

en

t (A

)

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

Drain-source voltage = 1.5 V

N

N N N

N

NNN

Cu

F

F

F

F

F

F F

F

F

F

F

F

F

F

F

F

F16CuPc

Glass substrate

Source Drain

Al gate electrode


L = 20 µm

W = 1000 µm




Zschieschang, Langmuir 24 1665 (2008)

Kraft, J. Mater. Chem. 20 6416 (2010)


Semiconductors for High-Mobility Air-Stable Organic n-Channel TFTs

N

N

OO

OO

F2C

CF2

F3C

CF2

F2CCF3

0.12 cm2/Vs 1.2 cm2/Vs

N

N

OO

O O

Cl

Cl

F2C

CF2

F3C

CF2

F2CCF3

1.3 cm2/Vs

N

N

OO

OO

CN

NC

F2C

CF2

F3C

CF2

F2CCF3

0.64 cm2/Vs

Katz, J. Am. Chem. Soc.

122 7787 (2000)

N OO

F2C

CF2

F3C

N OO

CF2

F2CCF3

Jones, Angew. Chem. Int. Ed.

43 6363 (2004)

Schmidt, J. Am. Chem. Soc.

131 6215 (2009)

Oh, Adv. Funct. Mater.

20 2148 (2010)

Air-Stable Organic n-Channel TFTs: Current-Voltage Characteristics

N

N

OO

O O

Cl

Cl

F2C

CF2

F3C

CF2

F2CCF3

L = 100 µm

W = 200 µm

ALD AlOx/SAM

Au source Au drain

Gate dielectric (100 nm thermal SiO2)

Heavily doped silicon wafer




subthreshold slope = 1.1 V/dec

Substrate MPI-780

W = 200 m, L = 100 mfresh


0 10 20 30 40

Dra

in c

urr

en

t (

A)

0

5

10

15

20Gate-source voltage = 35 V

25 V

30 V

20 V

Substrate MPI-780

W = 200 m, L = 100 mfresh


-10 0 10 20 30 40

Dra

in c

urr

en

t (A

)

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

Gate

cu

rren

t (A

)

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5Drain-source voltage = 50 V

Air-Stable Organic n-Channel TFTs: Mobility Prospects

Minder, Adv. Mater. 24 503 (2012)

N

N

OO

OO

CN

NC

F2C

CF2

F3C

CF2

F2CCF3

Summary

• Organic thin-film transistors that can be fabricated at

low temperatures (<100 ºC) and can be operated with

low voltages (~3 V) are useful for flexible displays.

• Low-temperature processing and low-voltage operation

are enabled by hybrid gate dielectrics based on

a plasma-grown metal oxide (~4 nm AlOx) and

a molecular self-assembled monolayer (~2 nm).

• Improved air stability is enabled by organic

semiconductors with greater oxidation resistance.

• Low-voltage organic TFTs have cutoff frequencies

between 10 kHz and 4 MHz, depending on the

lateral dimensions (~1 to 20 µm).

• Complementary circuits based on organic TFTs

are useful to integrate the row and column drivers

on the flexible display backplane.

PO OH

OH

S

S

Low-Voltage Organic Transistors for Flexible Electronics

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