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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
IPR 20
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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
R 2011
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
R 2011
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
R 2011
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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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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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.
IPR 20
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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
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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
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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)
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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.
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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
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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
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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
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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
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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
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)
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Design of ambipolar polymer semiconductors for g p p yCMOS‐like logic circuits
39
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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
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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
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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
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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
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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
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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?
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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
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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
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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
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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
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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
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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)
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Thank you!Thank you!yy
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