Ink Jet Printing and Spin-coating of Electrically Conductive Polymers

Peter C. Wilson, Constantina Lekakou, John F. Watts

Ink Jet Printing and Spin-coating

of Electrically Conductive Polymers

Presentation Outline

• PhD Outline

• Background

• Custom Ink Jet Printing Equipment

• Electro-impedance Model

• Charge Transport Method

• Microscale Comparison

• Mobility & Morphology

• Ongoing & Future Work




PEDOT Useage

Simple organic device structure displaying PEDOT:PSS as a

high work function anode

Figure 8 - Comparative assessment of

PEDOT:PSS films compared to ITO

layers.

Device life-time is omitted ~ 7x ITO




Gas Line

Motors

Control Cards

JetServer

Camera

Reservoir

Heat Pad

Substrate Temp Control

Jetter

Strobe

Control Program

Monitor

Inkjet Printer Setup




InkJet Printer OverviewControllable Parameters

• Drop size

• Ejection wave guide architecture

• Drop velocity

• Drop / substrate Temperature

• Drop placing / overlap

• Print rate

• Print layering

• Ejection angle

• Drop chemistry

Rig Specification

250dpi @ Ts = 50deg C

Position accuracy < 2μm (at 1/8th step)

Position repeatability < 10 μm

Print rate from 0 – 100mm s-1

Print acceleration 0 – 100m s-2Transmission Optical Microscopy Of

Printed PEDOT:PSS Tracks - 100um orifice jetter, 5% drop overlap




PEDOT:PSS Surface Tension As A Function Of DMSO DMSO & Surfynol 2502

Concentration

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0 1 2 3 4 5 6

DMSO %wt

Surf

ace T

ensio

n (

N/m

)

0% Surfynol

1% Surfynol

Linear (0% Surfynol)




Electro-impedance Spectroscopy

Nyquist plot for Inkjet Printed PEDOT:PSS (5%wt DMSO, 0%Surfynol) at 93K





|REL| Bode plot for Inkjet Printed PEDOT:PSS (5%wt DMSO, 0%Surfynol) at 93K





Zplot model fitting for Inkjet Printed PEDOT:PSS (5%wt DMSO, 0%Surfynol) at 93K





Zplot equivalent circuitry for Inkjet Printed PEDOT:PSS (5%wt DMSO, 0%Surfynol) at 93K

Series Resistance

Surface capacitive region

Bulk PEDOT:PSS film




Surface Resistivity For 0-1% Surfynol, 0-5% DMSO InkJet Printed Films

1.00E+02

1.00E+03

1.00E+04

1.00E+05

1.00E+06

1.00E+07

0 1 2 3 4 5

DMSO %wt

Res

isti

vit

y W

/sq

Surface Resistivity (0%wt Surfynol)

Surface Resistivity (1%wt Surfynol)




4-Point Hall Probe demonstrate the effect on carrier mobility in inkjet printed PEDOT:PSS thin films

• 0% DMSO, 1% Surfynol,

•

• 1.164x 105 W sq-1 ~ 11 W cm-1 (0.09 S cm-1)

• Carrier Mobility 1.43 cm-2 v-1s-1

• Carrier Concentration ~ 3.74 x1013 cm-2

• 5% DMSO, 1% Surfynol,

• 633 W sq-1 ~ 6.33 x10-2 W cm-1 (16 S cm-1)

• Carrier Mobility 397 cm-2 v-1s-1

• Carrier Concentration ~ 2.48 x1013 cm-2

Printed samples displayed ohmic contacts and excellent film uniformity




Surface Resistivity For 0-1% Surfynol, 0-5% DMSO Spin Coated Films

1.00E+03

1.00E+04

1.00E+05

1.00E+06

1.00E+07

1.00E+08

0 1 2 3 4 5

DMSO %wt

Re

sist

ivit

y W

/sq

Surface Resistivity (0% Surfynol)

Surface Resistivity (1% Surfynol)




x

e




T

TEXP 0

0

Mott Variable Range Hopping Law,

denote the recipical dimensionality of conduction

the conductivity

o & T0 are material constants




Reproduced from - A. M. Nardes, M. Kemerink, R. A. J. Janssen,

“Anisotropic hopping conduction in spin coated PEDOT:PSS thin films”,

Phys. Rev. B 2007, 76, 085208-1.

Charge transport asymmetry in spin coated

PEDOT:PSS films due to oblate spheroid-type

conducting grain morphology

- 3d variable range hopping in the parallel plane

- Space Charge limited tunnelling in the normal plane




Processing Dynamics

The deposit, spin, spread & evaporate

process for spin coated films

Fluid flow in drying droplets displaying

surface & interface evaporation and

redistributive flow




Parallel plane conductivity displaying Nearest Neighbour Hopping (nn-H)

conduction mode.




R² = 0.9855

0.001

0.01

0.1

0.25 0.26 0.27 0.28 0.29 0.3 0.31

D

C (

S/cm

)

T-0.25 (K-0.25)

(DC) As A Function Of Temperature For InkJet PEDOT:PSS (4%wt DMSO) - Fitting T-0.25

Parallel plane conductivity displaying 3d Variable Range Hopping

behaviour




Drop Observation

303K

323K

353K

SEM Images For Identical Inks At 3 Substrate Temperatures




Drop Profilometry

303K

323K

353K

Single Drop Profilometry For Identical Inks At 3 Substrate Temperatures




Drop Profile As A Function Of Substrate Temperature

-0.05

0.05

0.15

0.25

0.35

0.45

0 20 40 60 80 100 120 140 160 180 200

Displacment (mm)

Hei

gh

t ( m

m)

Ts = 30

Ts = 40

Ts = 50

Ts = 60

Ts = 70

Drop Shape Evolution For Identical InkJet Printed PEDOT:PSS Drops At Varying Substrate Temperatures




Droplet Diameter As A Function Of Substrate To Liquid

Temperature Ratio

0

20

40

60

80

100

120

140

160

180

303 313 323 333 343

Substrate Temperature (K)

Dro

ple

t D

iam

ete

r (u

m)

0.9

0.95

1

1.05

1.1

1.15

1.2

Sub

stra

te T

o L

iqu

id

Te

mp

era

ture

Rat

io

Droplet Diameter

Liquid To Substrate

Temperature Ratio




Peak To Trough Ratio As A Function Of Substrate To Liquid

Temperature Ratio

0

1

2

3

4

5

6

7

8

303 313 323 333 343

Substrate Temperature (K)

Pe

ak T

o T

rou

gh

Rat

io

0.9

0.95

1

1.05

1.1

1.15

1.2

Sub

stra

te T

o L

iqu

id

Te

mp

era

ture

Rat

io

Peak To Trough Ratio

Liquid To Substrate

Temperature Ratio




Electrostatic Force Microscopy

Electrostatic Force Microscopy (EFM) Displaying sub-surface concentric ring charge

concentration in InkJet Printed PEDOT:PSS films

AFM Phase AFM TopographyEFM Phase




5um x 5um topographic

Spin Coated (1% DMSO, 0% Surfynol)


Spin Coated (1% DMSO, 1% Surfynol)





InkJet (1% DMSO, 0%Surfynol)


InkJet (1% DMSO, 1%Surfynol)




Film Roughness

RMS Roughness For 0-1% Surfynol, 0-5% DMSO Spin Coated Films

0

5

10

15

20

25

0 1 2 3 4 5

DMSO %wt

1% S

urf

yn

ol

RM

S R

ou

gh

ne

ss

0

0.5

1

1.5

2

2.5

0% S

urf

yn

ol

RM

S R

ou

gh

ne

ss

1%wt Surfynol Height RMS Roughness





Film Roughness

RMS Roughness For 0-1% Surfynol, 0-5% DMSO InkJet Films

0

5

10

15

20

25

30

35

0 1 2 3 4 5

DMSO %wt

1% S

urf

yn

ol R

MS

Ro

ug

hn

ess

0

0.5

1

1.5

2

2.5

0% S

urf

yn

ol R

MS

Ro

ug

hn

ess






On Going & Future Work

>> Normal direction charge conduction as a function of printing parameters.

Variable electric field measurements for characteristic hopping length.

T0 and 0 comparison.

>> In plane and cryogenically cleaved Electrostatic Force Microscopy to view grain morphology.

>> Scanning Kevlin Probe Force Microscopy to observe work-function changes as a function of chemistry &

processing.

>> Characterisation of the effects of annealing on in-plane and normal direction charge conduction.

>> Validating the role of Electro-Impedance Spectroscopy as an analytical method for characterisation of multiple

thin-film properties.

Ink Jet Printing and Spin-coating of Electrically Conductive Polymers

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Transcript of Ink Jet Printing and Spin-coating of Electrically Conductive Polymers