INSTITUTE FOR POLYMER RESEARCHCELEBRATING 27 YEARS OF OFFICIAL INSTITUTE STATUS

THIRTY‐THIRD ANNUAL SYMPOSIUMON POLYMER SCIENCE/ENGINEERING

High‐Performance Semiconducting Polymer Materials for

ON POLYMER SCIENCE/ENGINEERING10 May, 2011

High‐Performance Semiconducting Polymer Materials for Printed Organic Electronics

Yuning Li

Department of Chemical Engineering and Waterloo Institute for Nanotechnology (WIN)University of WaterlooUniversity of Waterloo

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Outline- Overview

Motivations for research on organic electronics

Polymer semiconductors

- Design of high-performance polymer g g p p ysemiconductorsFused ring p-type polymers

Donor-acceptor p-type polymers

Ambipolar polymer semiconductors for CMOS-like logic i itcircuits

- Summary and future work

2

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Why printed organic electronics?Silicon Organic

Capital $billions $millions (Low investment)

FAB conditions Ultra clean-room / High Temp Ambient / Low temp (Mild)FAB conditions Ultra clean room / High Temp. Ambient / Low temp (Mild)

Process Multi-step photolithography Continuous direct printing (Simple)

Substrate Rigid glass or metal Flexible plastics (Robust)

Device size << 1m2 10 ft x roll to roll (Large area)

Cost $100’s / ft2 <$10 / ft2 (Low cost)

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Applications of printed organic electronics

RFID tags and smart labels OLED lighting (GE) Organic solar cells

E‐paper (Plastic Logic) Consumer electronics  Flexible displays (LG)

Market forecasts to 2027 ‐ a $330 billion market (Source: IDTechEx)4

p p ( g )(Nokia 888 concept cell phone)

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O i / l TFT C d ti i k

(a)(a)

Organic/polymer TFTsSmall molecule OPV Conductive inks

20 nm20 nm

J. Mater. Chem. 2011, in press.J. Am. Chem. Soc. 2011, 133, 2198.Adv. Mater. 2010, 22, 5409.Adv. Mater. 2010, 22, 4862.

J. Am. Chem. Soc. 2007, 129, 1862.J. Am. Chem. Soc. 2006, 128, 4202.J. Am. Chem. Soc. 2005,127, 3266.

Printed inorganic TFTs

Appl. Phys. Lett. 2010, 97, 133304Polymer BHJ PV

Dye‐sensitized solar cellsZnO

200 nm200 nm

J. Am. Chem. Soc. 2007, 129, 2750.

Energy Env. Sci. 2011, in press.Sol. Ener. Mat. Sol. Cells 2010, 94, 1618.

Thin Solid Films (2011, accepted)

J. Am. Chem. Soc. 2007, 129, 2750.J. Appl. Phys. 2007, 102, 076101.J. Phys. D: Appl. Phys. 2008, 41, 125102.

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‐Conjugated polymersπ electron delocalization in π‐conjugated polymersπ‐electron delocalization in 

benzeneπ conjugated polymers

ChE241‐Prof. Y.Li

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Channel length (L)

Organic thin film transistors (OTFT)

d <1μm

Channel width (W)

Organic SemiconductorSource Drain

gate

source

drainDielectric

Organic Semiconductor

Substrate

Gate

drain

Current

Doping

De‐doping

Source-GateV lt

-7.00E-056 00E 05

Field-effect Mobility ()Transfer Characteristic Output Characteristic

1.00E-04Source-Gate

V lt

-7.00E-056 00E 05

Field-effect Mobility ()Transfer Characteristic Output Characteristic

1.00E-04

Insulating (off) Conductive (on)De doping

Voltage-6.00E-05-5.00E-05-4.00E-05

-3.00E-05-2.00E-05

Linear Regime (Vd < Vg):

Id = Vd Ci µ (Vg-VT) W/L

Saturation Regime: (Vd > Vg):

urce

-Dra

in C

urre

nt

ourc

e-D

rain

Cur

rent

1.00E-09

1.00E-08

1.00E-07

1.00E-06

1.00E-05 Voltage-6.00E-05-5.00E-05-4.00E-05

-3.00E-05-2.00E-05

Linear Regime (Vd < Vg):

Id = Vd Ci µ (Vg-VT) W/L

Saturation Regime: (Vd > Vg):

urce

-Dra

in C

urre

nt

ourc

e-D

rain

Cur

rent

1.00E-09

1.00E-08

1.00E-07

1.00E-06

1.00E-05 IOn

I

7

-1.00E-050.00E+00

0 -10 -20 -30 -40

Id = Ci µ (Vg-VT)2 W/2L

Current on/off ratio (Ion / Ioff)

Sou So

Gate Voltage (V) Source-Drain Voltage (V)

1.00E-11

1.00E-10

-80 -60 -40 -20 0

-1.00E-050.00E+00

0 -10 -20 -30 -40

Id = Ci µ (Vg-VT)2 W/2L

Current on/off ratio (Ion / Ioff)

Sou So

Gate Voltage (V) Source-Drain Voltage (V)

1.00E-11

1.00E-10

-80 -60 -40 -20 0

IOff

7

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Mobility of p‐type polymer semiconductors

1.0E+02

1.0E+03Si wafers PC 

processors 

A‐Si1.0E+00

1.0E+01Low‐cost ICs

Smart cards, RFID, di l

cm2 V

‐1s‐1

Poly‐Si

1 0E 03

1.0E‐02

1.0E‐01displays

E‐paper

P‐type polymers

Mob

ility, 

1.0E‐05

1.0E‐04

1.0E‐03 P type polymers

1980 1985 1990 1995 2000 2005 2010

Year

8

Is 1 cm2/V.s an upper limit?

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Charge Carrier Transport in Polymer Semiconductors

• Polymer semiconductors always comprise disordered amorphous regions

• Weak ver der Waals bonds between polymer chains: Large intermolecular distance (π: ~3‐4 Å) Large intermolecular distance (π:  3‐4 Å) Charge transport through hopping of charges between localized states Upper limit: ~1 cm2/V.s (G. Horowitz, Adv. Mater. 1998, 10, 365)

Three modes of charge carrier transport at different levels

Intramolecular: Can be very fast (~103 cm2/V.s); determined by coplanarity

Intermolecular (interchain): Slow (up to ~10 cm2/V.s); determined by overlapping area and 

Three modes of charge carrier transport  at different levels

9

( ) ( p / ); y pp gdistance 

Intergranular (interdomian): Very slow (can be ~10‐5 cm2/V.s or lower); determined by crystallinity/morphology

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1 Crystallinity and crystal size

Molecular organization

1. Crystallinity and crystal size

2. Molecular packing motif

•Higher crystallinity and larger crystal domains yield high mobility

e‐ e‐

e‐S D

Dielectric

Edge‐down (face‐on) Edge‐on Larger π‐overlap

•Smaller ‐ distance, edge‐on orientation, and larger ‐ overlap lead to higher mobility10

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Improving  Intermolecular and Intergranularcharge carrier transportscharge carrier transports

Strategy 1: Use of fused aromatic rings • Stronger π‐π stacking force• Large π‐π overlap• Increased crystallinityIncreased crystallinity

11

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Thiophene-based polymers with fused ring structures

PQTThi h PQT

Ong, B. S., et al, J. Am. Chem. Soc.  2004, 126, 3378.

Thiophene

Thieno[3,2‐b]thiophene PBTT(TT)

Li, Y., et al, Adv. Mater. 2006, 18, 3029.

Benzo[1,2‐b:4,5‐b’]dithiophene

(BDT)

PBBDT

2011/6/112

Pan, H., et al, J. Am. Chem. Soc. 2007, 129, 4112.IP

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Synthesis of PBTT

2011/6/1 13

Li, Y.; Wu, Y.; Liu, P.; Birau, M.; Pan, H.; Ong, B. S. Adv. Mater. 2006, 18, 3029.

13

10 steps; total yield: 18%IP

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3x103

Molecular ordering of PBTT revealed by XRD

1x103

2x103

nten

sity

(cou

nts)

As‐cast film

2 0x104

5 10 15 20 25 300

In

2-Theta (degree)

20.53 Å

3.93Å

3

1.0x104

1.5x104

2.0x10

nten

sity

(cou

nts)

Annealed film(150 °C/10min)

(100)

(200)

(300)

2 0x104

5 10 15 20 25 300.0

5.0x103In

2-Theta (degree)

(300)(400)

(500)

1.0x104

1.5x104

2.0x10

nten

sity

(cou

nts)

Annealed powder(150 °C/10min)

π‐stacking d = 3.93 Å

(010)

2011/6/1 14

5 10 15 20 25 300.0

5.0x103In

2-Theta (degree) 14

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10 ‐3  0.01610 ‐3  0.01610 ‐3  0.016606060

OTFT performance of PBTT

A)

10 ‐5 

2(A

1/2 )

0.012

(b)

A)

10 ‐5 

2(A

1/2 )

0.012

A)

10 ‐5 

2(A

1/2 )

0.012

(b)VG=‐40 V

40

30(A)

50

(a) VG=‐40 V

40

30(A)

50

VG=‐40 V

40

30(A)

50

(a)

L = 90 m; W = 5000 m

‐ IDS(A

10 ‐9

10 ‐7

(‐I DS)1

/2

0.004

0.008

‐ IDS(A

10 ‐9

10 ‐7

(‐I DS)1

/2

0.004

0.008

‐ IDS(A

10 ‐9

10 ‐7

(‐I DS)1

/2

0.004

0.008‐30 V

‐20 V

10 V

10

20

30

‐ IDS(

‐30 V

‐20 V

10 V

10

20

30

‐ IDS(

‐30 V

‐20 V

10 V

10

20

30

‐ IDS(

L = 90 m; W = 5000 m

Transfer characteristics (V 60 V)

Annealed at 150 °C10 ‐11

VG (V)10 ‐10 ‐50‐30

010 ‐11

VG (V)10 ‐10 ‐50‐30

010 ‐11

VG (V)10 ‐10 ‐50‐30

0

Output curves

‐10 V0,10 V0

0 ‐10 ‐30‐20 ‐40VDS (V)

‐10 V0,10 V0

0 ‐10 ‐30‐20 ‐40VDS (V)

‐10 V0,10 V0

0 ‐10 ‐30‐20 ‐40VDS (V)

(Vds = ‐60 V)

Mobility,cm2/V.s (μ)

Current on/off ratio

(Ion/Ioff)

6Without annealing ~0.10 106

Annealed at 150 °C

~0.25 107

Li Y ; Wu Y ; Liu P ; Birau M ; Pan H ; Ong B S Adv Mater 2006 18 3029

2011/6/1 15

• High crystallinity, favored molecular organization and large π‐overlap are contributable to the high mobility

• Similar mobility to that of PQT and P3HT even without thermal annealing 15

Li, Y.; Wu, Y.; Liu, P.; Birau, M.; Pan, H.; Ong, B. S. Adv. Mater. 2006, 18, 3029.IP

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Benzo[1,2‐b:4,5‐b’]dithiophene (BDT) building block

R

SSS

S

R

PBT PBBDT

R

PQTµh= ~0.12 cm2/V.s µh= ~0.12 cm2/V.s µh= ?

• More extended fused ring (larger π‐overlap)• Stronger backbone interaction

16

• Additional side chains for better solubilityIP

R 2011

Synthesis of PBBDT

ClMgO

R

S

S

OMgCl

R

SnCl2

10% HCl/60 oC

S

R

Br BrS S

R'

R

S SR'

R

S

R

Br BrSS

R'

R

SSR'

R

n

PBBDT‐6 (R=C4;R’=C6)PBBDT 10 (R C8;R’ C10)

17

PBBDT‐10 (R=C8;R’=C10)PBBDT‐12 (R=C10; R’=C12)

GPC: Mn = 16 ‐274 kD

Pan, H.; Li, Y.; Wu, Y.; Liu, P.; Ong, B. S.; Zhu, S.; Xu, G. J. Am. Chem. Soc. 2007, 129, 4112.

9 steps; total yield: 11%

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11

Molecular organizationX-Ray

Normal

a b( d )

X-Ray

Normal

a b( d )

X-Ray

Normal

a b X-Ray

Normal

a b( d )

6x10 3

(100)

ec d (010)(010)

Thin film on Si wafer

2-D detector

X-RayStack of films

2-D detector

2-D detector

X-Ray

Normal

Parallel

( d )

( e )

ec d (010)(010)

Thin film on Si wafer

2-D detector

X-RayStack of films

2-D detector

2-D detector

X-Ray

Normal

Parallel

( d )

( e )

ec d (010)(010)

Thin film on Si wafer

2-D detector

X-RayStack of films

2-D detector

2-D detector

X-Ray

Normal

Parallel

ec d (010)d (010)(010)

Thin film on Si wafer

2-D detector

X-RayStack of films

2-D detector

2-D detector

X-Ray

Normal

Parallel

( d )

( e )

As-cast film

PBBDT-10

3x10 3

4x10 3

5x10 3

nten

sity

(100)

(300)

(100)(200)(100)

(100)

f g h

(300)

(100)(200)(100)

(100) (300)

(100)(200)(100)

(100) (300)

(100)(200)(100)

(100)(100)

f g h

0

1x10 3

2x10 3

In

(200)(300) (400)

XRD

5 10 15 20 252 ( 0 )

5 10 15 20 252 ( 0 )

5 10 15 20 252 ( 0 )

5 10 15 20 252 ( 0 )

5 10 15 20 252 ( 0 )

5 10 15 20 252 ( 0 )

5 10 15 20 252 ( 0 )

5 10 15 20 252 ( 0 )

5 10 15 20 252 ( 0 )

5 10 15 20 252 ( 0 )

5 10 15 20 252 ( 0 )

5 10 15 20 252 ( 0 )

a ba b

2‐D XRD

0 5 10 15 20 25 300

2 theta, drgree

21 2 Å

~19 Å

3.90 Å

a ba b

21.2 Å

Large crystal domains (~μm’s)

AFM

1 μm 1 μm1 μm 1 μm1 μm 1 μm1 μm1 μm 1 μm1 μm

• Highly crystalline and edge‐on orientation w/o annealing• Exceptionally large crystalline domains

Large crystal domains ( μm s)

18

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11

Vg=

TFT performance

1E-5

1E-4

(A)

0.012

0.016

A1/2 )

-6.0x10-5

-8.0x10-5

-1.0x10-4

A)

g

-40V

-30V

I-V characteristics of an illustrative as-prepared TFT device using PBBDTsemiconductor (channel length = 90 μm; channel width = 1000 μm): (a)transfer curve in saturated regime at a

a b

1E 8

1E-7

1E-6I sd

0 000

0.004

0.008

I sd1/

2 (A0 0

-2.0x10-5

-4.0x10-5 I sd (A

-20V

-10V

0 10V

(a)transfer curve in saturated regime at a constant source-drain voltage of -60 V and square root of absolute value of drain current as a function of gate voltage; and (b)output curves at different gate voltages.

20 0 -20 -40 -601E-8

Vg (V)

0.0000 -10 -20 -30 -40 -50 -60

0.0

Vd (V)

0, 10V

Without annealing:2.42.4

Hot solution (~50 °C)

Overnight at room temp.

• μ = ~0.40 cm2V‐1s‐1

• Ion/Ioff = 105

Annealing (up to 200 C): 0.8

1.6Abs

0.8

1.6Abs

10 min at room temp.

g ( p )• No improvements

400 500 600 700

0.0

Wavelength (nm)400 500 600 700

0.0

Wavelength (nm)

19

UV-vis spectra of PBBDT.• Poor solubility at room temperature• Must be processed using hot solutions

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Exemplary Fused‐ring‐containing polymers

S

SSS

R

n

Osaka, I. et al. JACS. 2010.

McCulloch, I. et al. Nat. Mater. 2006.

s S

R

0.5

0.60.3‐0.6 cm2/V.s

0.20‐0.54 cm2/V.sPan, H. et al. JACS. 2007.

ty, cm

2 /V.s

0 3

0.4

0.5

0 25 2/V

0.25‐0.40 cm2/V.sLi ,Y. et al. Adv. Mater. 2006.

Mob

ilit

0.2

0.3 0.25 cm2/V.s

0.3 cm2/V.s0.33 cm2/V.s

Li J et al Chem Mater 2008Fang, H. et al. JACS. 2008.

O B S t l JACS 2004

Bao, Z. et al. APL. 1996.

0.10.08‐0.12 cm2/V.s

Li , J. et al. Chem. Mater. 2008.Ong, B. S. et al. JACS. 2004.

Ring size

20

• Improvements in mobility by using fused rings are limited.• Solubility decreases as ring size increases

Ring sizeIP

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Improving  Intermolecular and Intergranularh icharge carrier transports

Strategy 2: Intermolecular donor‐acceptor interactions

Donor Accepter

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Improving  Intermolecular and Intergranularh icharge carrier transports

Strategy 2: Intermolecular donor‐acceptor interactions

Donor Accepter

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Diketopyrrolopyrrole (DPP)‐based D‐A polymers‐Fused ring + D‐A interactions

•An electron‐accepting moiety

•Very stable in air• Fused ring analog to TT

•Very stable in air

‐A‐D‐

Pigment red 254 or 'Ferrari Red'

Y. Li, U. S. Patent Application 2009/65766 A1 (Xerox)Y. Li, U. S. Patent Application 2009/65878 A1 (Xerox),Y. LI, U. S. Patent  7910684 (Xerox)Y. Li, U. S. Patent  7932344 (Xerox) 23

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PBTDPP

S CN

OO

O

O

NS

S

H

O

OONa

NS

S

R

O

O

R-Br

NH

OONa NR

O

NS

R

OBr2 or NBS Br Method A: Ni(COD)2 NR

O*

l l bili i ld /

N

S

S

R

O

2 Br

Br

( )2

N

S

S

R

O

O

*

*

n

Method B: (CH3)3Sn-Sn(CH3)3

PBTT

R Polymnmethod

Solubility Yield, % Mw/Mn

1‐Dodecyl (C12) A,B Insoluble  Trace ‐

1‐Hexadecyl (C16) A Very poor Trace  ‐

B Hot CB 62% 2590 (HT‐GPC)

1‐Octadecyl (C18) A Insoluble Trace ‐

B Hot CB 63% 2820 (HT‐GPC)

2‐Hexyldecyl (C16) A Good  24% 67,070/28,100

2‐Octyldodecyl (C20) A Very good  99% 392,770/146,290

Y. Li, et al., unpublished results (2006‐2009)

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OTFT Performance

1E-5

• Typical ambipolar transport characteristics

1E-6

I DS (A

mp)

Au Au

Polymer Annealing

temperature, ◦C

Hole mobility,

cm2/V.s

Electron

mobility, cm2/V.s

-75 -60 -45 -30 -15 0 15 30 45 60 751E-7

Electron enhancement mode

VGS (Volts)

Hole enhancement mode

n+-Si

PBTDPP‐HDAu Au

SiO2

(a) (b)

PBTDPP-HD r. t. 0.024 0.056

100 0 017 0 057

2

3

4

S (

A)

0V VGS

-10V VGS

-20V VGS

-30V VGS

-40V VGS

-50V VGS

-60V VGS

-70V VGS-10

-12

-14

-16

-18

-20

S (

A)

0V VGS

-10V VGS

-20V VGS

-30V VGS

-40V VGS

-50V VGS

-60V VGS

70V V

( ) ( )100 0.017 0.057

140 0.013 0.036

PBTDPP-OD 0 006 0 025

0 20 40 600

1

I DS

VDS (Volts)

GS

0 -10 -20 -30 -40 -50 -60 -700

-2

-4

-6

-8I DS

VDS (Volts)

-70V VGS

( ) (d)

PBTDPP-OD r. t. 0.006 0.025

100 0.013 0.010

140 0 013 0 007(c) (d) 140 0.013 0.007IP

R 2011

Cyclic VoltammetryCyclic Voltammetry

C10H21

N

N O

O S

S

n

C8H17

C H

PBTDPP‐OD

urre

nt (m

A)nC8H17

C10H21

Cu

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0Potenetial (V, vs Ag/Ag+)

• Reversible oxidative and reductive processes• Might be good for both hole and electron transports

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P‐Type DPP‐based Polymers

NR

R2

R1

N

NS

S

O

O ArN

N O

O S

S

R2

R n

Ar: An electron donor

nR2

R1

S S

S

SS

S

S

S

etc.

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PDBT‐co‐TT polymer

Yield = 95.4%Mw/Mn (GPC) = 211,300/89,700

Y. Li, S. P. Singh, P. Sonar, Adv. Mater. 2010, 2010, 22, 4862.

Elctron donor

Elctron acceptor

28•π‐π distance is expected to be reduced due to DA interactions

Strong interchain interactions

IPR 20

11

Molecular organization of PDBT‐co‐TT

20.4 Å

3.71 Å

( ) (b)

0.10

0.15

0.20

0.25

ty (a

.u.)

140 °C

200 °C

0.6

0.8

1.0

1.24.34° (d = 20.4 Å)

sity

(a. u

.)0.2

0.3

0.4

0.5

24° (d = 3.71 Å)

sity

(a. u

.)

(a) (b)

0 5 10 15 20 25 30 35 40

0.00

0.05Inte

nsi

2(degree)

r. t.

100 °C

0 5 10 15 20 25 30 35 40

0.0

0.2

0.4In

tens

2(°)0 5 10 15 20 25 30 35 40

0.0

0.1

0

Inte

ns

2(°)

(d)(c) ( )( )

2‐D XRD of a stack of thin filmsXRD of spin‐coated thin films

• Small π π distance of 3 71 Å: Good for interchain charge transport

29

• Small π‐π distance of 3.71 Å: Good for interchain charge transport• High crystallinity of as‐cast films: Strong self‐assembly ability• Crystallinity is not very sensitive to annealing temperature

IPR 20

11

Cyclic Voltammetry

6.0x10-4

8.0x10-4PDBT‐co‐TT

2.0x10-4

4.0x10-4

ent (

A)

4 0 10-4

-2.0x10-4

0.0

C

urre

-1.6 -1.2 -0.8 -0.4 0.0 0.4 0.8 1.2-6.0x10-4

-4.0x10 4

E (V vs Ag/Ag+)E (V, vs Ag/Ag+)

HOMO: 5.25 eV LUMO: 3.40 eV (4.02 eV from UV‐vis)

IPR 20

11

OTFT performance of PDBT‐co‐TTWithout annealing

-50

-60

-70 0 V -10 V -20 V -30 V -40 V -50 V

60 V

VG

10-6

10-5

10-4

8.0x10-3

1.2x10-2Output (left, VG = 0 V to ‐70V) and transfer (right, VDS = ‐70 V) characteristics of an OTFT device with a PDBT‐co‐TT thin film without annealing (L = 100 µm; W = 1 mm). 

-10

-20

-30

-40

I DS (

A) -60 V

-70 V

10-9

10-8

10-7

10

I DS (A

)4.0x10-3

(I DS)1/

2

µh= ~0.72 cm2/V.s Ion/Ioff = ~105‐6

VT = ‐22 V0 -15 -30 -45 -60 -75

0

VDS (V)

0 -15 -30 -45 -60 -75

VG (V)

0.0VT   22 V

-100 0 V

VG10-4

1.5x10-2

Annealed at 200 °C

-40

-60

-80

I DS

(A

)

-10 V -20 V -30 V -40 V -50 V -60 V -70 V

10-7

10-6

10-5

I DS (A

)

5 0 10-3

1.0x10-2

(I DS)1/

2Output (left: VG = 0 V to ‐70 V) and transfer (right: VDS = ‐70 V) characteristics of an OTFT device with PDBT‐co‐TT thin film annealed at 200 °C for 15 min. Device dimensions: 

Annealed at 200 °C

0 -15 -30 -45 -60 -750

-20

VDS (V)0 -15 -30 -45 -60 -75

10-10

10-9

10-8

VG (V)

0.0

5.0x10 3

channel length (L) = 100 µm; channel width (W) = 1 mm.

µh= ~0.94 cm2/V.s I /I ~105 6

31

DSIon/Ioff = ~105‐6

VT = ‐9 V Y. Li, S. P. Singh, P. Sonar, Adv. Mater. 2010, 22, 4862.

IPR 20

11

PDQTR

N

NS

S

R

R

O

O SS

n

PDQTPDBT‐co‐TT

0.3

0.4

200 oC

100 oC

2= 4.4o 0.20

0.25 RT 100C 140C 200C

.)

4.16

0.1

0.2

RT

13.5o

8.9o

Inte

nsity

(a.u

.)

0.05

0.10

0.15

Inte

sity

(A.U

.

8.3212.72

3 71 Å 3 75 Å

5 10 15 20 250.0

2

Thin film XRD data of DPP‐LT thin films5 10 15 20 25 30

0.00

2

20.4 Å

3.71 Å

19.9 Å

3.75 Å

32

• Improved crystallinity by annealing • Larger π‐π distance and band gap

Li, Y.; Sonar, P.; Singh, S. P.; Soh, M. S.; van Meurs, M.; Tan, J. J. Am. Chem. Soc. 2011, 133, 2198.

IPR 20

11

OTFT performance of PDQT

8

10-7

10-6

10-5

10-4

S (A)

8.0x10-3

1.2x10-2

DS)1/

2

-60

-80

-100

-120

S (

)

0V -10V -20V -30V -40V -50V -60V -70V

VG

60

-80

-100

-120

-140

S (

A)

0V -10V -20V -30V -40V -50V -60V -70V

VG

10-7

10-6

10-5

10-4

S (A

) 8.0x10-3

1.2x10-2

DS)1/

2

20 0 -20 -40 -60

10-10

10-9

10-8

V (V)

I DS

0.0

4.0x10-3

(I D

0 -20 -40 -600

-20

-40

I DS

V (V)0 -20 -40 -60

0

-20

-40

-60I DS

VD (V)20 0 -20 -40 -60

10-10

10-9

10-8

VG (V)

I DS

0.0

4.0x10-3

(I D

VG (V)VD (V)

(a) (b)

Output (VG = 0 V to ‐70V) and transfer (VD = ‐70 V) characteristics of OTFTs with DPP‐LT thin films without annealing (a, b) and annealed at 100 ºC (c, d) (L = 100 µm; W = 1 mm).

D ( ) VG (V)

(c) (d)

As‐span 100 °C

Hole mobilityμh, cm2/V.s

Current on-to-off ION/IOFF

Threshold voltageVT, V

Without annealing 0 89 ~107 -3 0Without annealing 0.89 10 3.0

Annealed at 100 ºC/10min 0.97 2x106 -3.0

33

•Mobility is not very sensitive to annealing temperature (or crystallinity) • Suitable for high‐throughput roll‐to‐roll manufacturing 

IPR 20

11

Furan‐DPP Polymers

NR

N

NO

O

O

O ArnN

Rn

• Furan is more electron‐rich than thiophene• Furan may suppress electron transport behaviour and make the hole transport more pronounced p IP

R 2011

PDBFBTC10H21

N O

OO

O

C8H17

C10H21

S

1.5x10-3

2.0x10-3

2.5x10-3

.u)0.8

1.0

ity

Solution Thin Film

NO

nC8H17

C10H21

S

-1.0x10-3

-5.0x10-4

0.0

5.0x10-4

1.0x10-3

Cur

rent

(a.

0.2

0.4

0.6

Nor

mal

ized

Inte

nsi

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0-2.0x10-3

-1.5x10-3

Potential (V, vs Ag/Ag+)300 400 500 600 700 800 900 1000 1100 1200

0.0

0

Wavelength (nm)

HOMO = 5.32 eVEg = 1.41 eV C10H21g

PDQT

Eg =1.24 eV)N

N O

OS

S

C8H17

C8H17

SS

n

• Incorporation of furan broadens band gap and lowers HOMO level

EHOMO = 5.20 eVC10H21

IPR 20

11

Molecular packing

x Edge‐on

1.0 (a)x

0.6

0.8

zed

inte

nsity

0.2

0.4

Nor

mal

iz

parallel normal

1‐D: Parallel to Spin‐coated film2 D XRD P ll l t fil

Random 5 10 15 20 25 30

0.0

2°)

2‐D XRD: Parallel to films2‐D XRD: Normal to films

A mixture of edge‐on and face‐on orientations

IPR 20

11

OTFT performanceC10H21

N

NO

O

O

O SS

n

C8H17

C

PDBFBT

10-5

10-4

10-3

0 012

0.014

0.016

-1.2x10-4

-1.4x10-4

-1.6x10-4

GateV 0 to -60VStep -10V

n

C10H21

C8H17

10-9

10-8

10-7

10-6

|I DS|1/

2 (A1/

2 )

|I DS| (

A)

0.006

0.008

0.010

0.012

-6.0x10-5

-8.0x10-5

-1.0x10-4

1.2x10

I DS(A

)

10 0 -10 -20 -30 -40 -50 -6010-12

10-11

10-10

10

V (V)

0.000

0.002

0.004

0 -10 -20 -30 -40 -50 -600.0

-2.0x10-5

-4.0x10-5

V (V) VGS (V)VDS(V)

Output and Transfer characteristics of DA  p‐type polymer based OTFT (gold S/D; L = 125 μm; W = 4 mm) on OTS treated n+‐Si/SiO2 substrate (annealed at 200 ºC for 15 min)

Li,Y.; Sonar, P.; S. P. Singh, W. Zeng, M. S. Soh, J. Mater. Chem. under revision.

37

• µh= ~1.54 cm2/V.s (annealed at 200 °C)• Ion/Ioff = ~105‐6

IPR 20

11

Mobility of p‐type polymer semiconductors

1.0E+02

1.0E+03Si wafers PC 

processors 

A‐Si1.0E+00

1.0E+01Low‐cost ICs

Smart cards, RFID, di l

cm2 V

‐1s‐1

Poly‐Si

PDBFBT: 1.54 cm2/V.s

1 0E 03

1.0E‐02

1.0E‐01displays

E‐paper

P‐type polymers

Mob

ility, 

1.0E‐05

1.0E‐04

1.0E‐03 P type polymers

1980 1985 1990 1995 2000 2005 2010

Year

• Mobility of 1 cm2/V.s is not an upper limit for polymer semiconductors

38

• Polymer semiconductors should show higher mobility than small molecules (record mobility: ~20 cm2/V.s for single crystal rubrene)

IPR 20

11

Design of ambipolar polymer semiconductors for g p p yCMOS‐like logic circuits

39

IPR 20

11

CMOS (Complementary Metal Oxide Semiconductor)

• High robustness• Lower power dissipationHi h i i it• Higher noise immunity

• CMOS is dominating the integrated digital logic circuits

40

IPR 20

11

Printing CMOS-like circuit with discrete p- and n-channel OTFT

p-type

•Complex fabrication process

n-typep-type

Complex fabrication process•Difficulty in printing closely located p‐type and n‐type transistors

41

IPR 20

11

Ambipolar polymer OTFT

P‐type mode N‐type mode

S D S D

Vd

V

Vd

Dielectric

GSubstrate

Dielectric

GSubstrate

VgVg

Substrate Substrate

|Vg| >|Vd| , Vg < 0 |Vg| >|Vd| , Vg > 0

Meijer et al Nat Mater 2003 2 678 (Philips)

An ambipolar polymer can work as either a p‐type semiconductor or an n‐type 

Meijer, et al, Nat. Mater. 2003, 2, 678 (Philips)Bürgi, et al, Adv. Mater. 2008, 20, 2217 (Ciba)

42

p p y p yp ypsemiconductor

IPR 20

11

Printing CMOS‐like circuits with ambipolar OTFT

Conductive ink Dielectric Conductive inkAmbipolar polymer

Ambipolar Ambipolar

CMOS

(p or n)p

(n or p)

• Simplified printing process• Improved device yield• Reduced cost

43

IPR 20

11

Ambipolar polymer design

Poor air stabilityHOMO < 5 eV is required to achieve good oxidative stability

LUMO

4.0 eVPoor air stability Desired 

LUMO

HOMO

5.0 eV

4.5 eV

ll b dDesired HOMO

5.5 eV

Too small band gap (large off current)

Desired HOMO

Poor hole injection/contact resistance 

Electron conduction

LUMO < 4 eV is required to achieve stability towards H O OH etc

44Hole conduction

H2O, ‐OH, etc.IP

R 2011

PDPP‐TBT ambipolar polymer

BB

NS

NOO

NS

C8H17

C10H21

Br O+

Pd(PPh3)4

l /

Acceptor

N

S

SNS

N

C8H17

C10H21

O

BBOO

NS

C8H17

C10H21

BrO

+Toluene/2MK2CO3

Aliquat 336

Sonar, P; Singh, S. P.; Li, Y.; Soh, M. S.; Dodabalapur, A. Adv. Mater. 2010, 22, 5409.

NS

C8H17

C10H21

O n

0.0004

0.0005

, ; g , ; , ; , ; p , , ,

LUMO = –4.0 eV N‐channeloperation

0 0000

0.0001

0.0002

0.0003

C

urre

nt (a

.u) operation

Egapopt

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

-0.0002

-0.0001

0.0000

E (V s Ag/Ag+)

HOMO = –5.2 eV

P‐channeloperation

45

E (V, vs Ag/Ag+)

• Favored HOMO and LUMO levels for stable hole and electron transport

IPR 20

11

Molecular organization

0.20

0.25

200°C

0 00

0.05

0.10

0.15

Inte

nsity

(a.u

.)

r. t.

200°C

100 °C

140 °C

0 5 10 15 20 25 30 35 40

0.00

2(°)

XRD data obtained from spin-coated PDPP-TBT thin films (~35 nm) on OTS modified SiO2/Si substrates annealed at different temperatures.

2-D XRD data for PDPP-TBT film stacks: (a) and (b) are, respectively, 2-D transmission XRD images obtained with the incident X-ray parallel and normal to the film stacks; (c) and (d) are, respectively, XRD diffractograms of pattern intensities of (a) and (b) obtained by

46

g p ( ) ( ) yintegration of Chi (0-360°) with GADDS software.

Randomly orientated?

IPR 20

11

Thin film morphology

(a) (b)R. T. 120 C

200nm 200nm

(c) (d)180 C 200 C

200nm 200nm

50nm

200nm 200nm

AFM phase images of PDPP-TBT thin films at: (a) room temperature, (b) annealed at 120°C, (c) annealed at 180°C, (d) annealed at 200°C on OTS treated p+-Si/SiO2 substrates. An inset zoom-in image in (c) shows clearly that each nanofiber is comprised of stacked nanorods

47

each nanofiber is comprised of stacked nanorods.

• Crystalline fibrils grow as annealing temperature increases• Intertwined networks facilitate interdomain charge transport 

IPR 20

11

OTFT performance of PDPP‐TBT ambipolar polymer

SiO2

S (Au) D (Au)

Semiconductor

-70

-80 0V VGS

-10V VGS

-20V VGS

-30V VGS 50

60

70 0V VGS

10V VGS

20V VGS

30V VGS

P+‐Si

-30

-40

-50

-60

I DS (

)

GS

-40V VGS

-50V VGS

-60V VGS

-70V VGS

20

30

40

50

I DS (

A)

GS

40V VGS

50V VGS

60V VGS

70V VGS

0 -10 -20 -30 -40 -50 -60 -700

-10

-20

VDS (Volts)

0 10 20 30 40 50 60 700

10

VDS (Volts)

Output characteristics (VDS vs IDS) of IMRE 1st Gen Ambipolar polymer based OTFT device annealed at 200 °C on OTS treated p+‐Si/SiO2 substrate.

Hole enhancement mode Electron enhancement mode

48Characteristic behavior of an ambipolar OTFT 

Sonar, P; Singh, S. P.; Li, Y.; Soh, M. S.; Dodabalapur, A. Adv. Mater. 2010, onlineIP

R 2011

OTFT performance of PDPP‐TBT ambipolar polymer

1E-4electron enhencement modehole enhencement mode

1E-5mp.

)

1E-5

I DS (A

m

-80 -60 -40 -20 0 20 40 60 801E-6

VGS (Volts)

Transfer characteristics (VGS‐IDS ) OTFT device annealed at 200 °C operated i h l (l f ) d l ( i h ) h d

Hole enhancement mode Electron enhancement mode

in hole (left) and electron (right) enhancement mode.

49

IPR 20

11

OTFT performance of PDPP‐TBT ambipolar polymer

Charge carrier mobility  for PDPP‐TBT Ambipolar polymer based OTFT

Serial # Annealing temperature, °C

Charge carrier mobility (cm2/V.s)Electron mobility

(µe)Hole mobility

(µh)1 Room temperature 0.037 0.0642 80 0.16 0.203 120 0.26 0.224 160 0.28 0.225 200 0.40 0.35

Sonar P; Singh S P ; Li Y ; Soh M S ; Dodabalapur A Adv Mater 2010 22 5409

• Very well balanced high electron and hole mobilities

Sonar, P; Singh, S. P.; Li, Y.; Soh, M. S.; Dodabalapur, A. Adv. Mater. 2010, 22, 5409.

• Very well balanced, high electron and hole mobilities• Excellent solubility/processability

50

IPR 20

11

Comparison with other ambipolar polymers

μe = 0.04 cm2 /V.s2 /

μe = 0.09 cm2 /V.s0 1 2 /V

μe = 0.2 cm2 /V.s2 /

Kim, et, al, Adv. Mater. 2010, 22, 478.Bürgi, et al, Adv. Mater. 2008, 20, 2217. 

μh = 0.003 cm2 /V.sμh = 0.1 cm2 /V.sBa contactsSolution processed

Au contactsSolution processed

μh = 0.5 cm2 /V.sAu contactsVacuum deposition

Singh, et al, Adv. Mater. 2005, 17, 2315. 

PDPP TBT ambipolar polymerC10H21

• μe = 0.40 cm2 /V.s; • μh = 0.35 cm2 /V.s • Au contact

PDPP‐TBT ambipolar polymerN

NS

SNS

N

C8H17

C8H17

O

O

n

51

• Solution processedC10H21

IPR 20

11

Summary and Future Work• Fused ring aromatic structures such as thienothiophene (TT) and benzodithiophene(BDT) could improve the charge carrier mobility up to 0.4 cm2/V.s due to increased π‐π overlap and crystallinity.p y y

• DPP‐based polymers having intermolecular D‐A interactions coupled with fused ring structures improved mobility up to 0.89 cm2/V.s and 1.54 cm2/V.s for  g p y p / /respective annealing‐free and annealed polymer thin films. 

• By using appropriate design principles, ambipolar polymers with very balanced, y g pp p g p p , p p y y ,high electron (0.40 cm2/V.s) and hole mobility (0.35 cm2/V.s) were developed, which are useful as one‐component semiconductors for printed CMOS‐like logic circuits.

• Currently working with Prof. Hany Aziz and Prof. William Wang in Electrical Engineering on printing OTFT arrays for OLED display applications.

• Aiming for polymers with high mobilities (~5‐10 cm2/V.s) for wider applications.52

IPR 20

11

Acknowledgements(J l 2010 t) • Dr. Beng S. Ong

• Dr. Yiliang Wu

• Dr. Maria Birau

• Ms. Ping Liu

• Dr Hualong Pan• Bin Sun

(Before August 2008)

(July 2010 ‐ present)

• Dr. Hualong Pan• Michael Pan

• Riley Dahmer

• Prof. Hany Aziz (Electrical Eng) Sponsors and collaborators

(August 2008‐July 2010)

bGroup members

Dr. Prashant Sonar

Dr. Samarendra P. Singh

Dr. Soh Mui Siang

Dr. Yong Kian Soon

Ph. D. studentsMr. Lam Kwan HangMr. He LiningMr. Yao Lin

CollaboratorsDr. Yong Kian Soon

Dr. Zeng Wenjin

Dr. Jiang Changyun

Dr. Hualong Pan

Mr. Kam Zhi Ming

CollaboratorsProf. Rusli (EEE, NTU)Prof. Lam Yeng Ming (Mater Sci & Eng, NTU)Prof. Cheol‐Min Park (Chem, NTU)Dr. Koh Wee Shing (IHPC, A*STAR)Dr. Yuriy Akimov (IHPC, A*STAR)

53

Ms. Leung Man Yin

Ms. Koh Wei Ling

Ms. Joey Ng

Mr. Goh Wei Peng

y ( , )Dr. Sudhakar Sundarraj (BASF)Dr. Patrick Poa Chun Hwa (BoschProf. Jens Pflaum (U. Wuerzburg)

IPR 20

11

Thank you!Thank you!yy

IPR 20

11