Introduction to BAYTRON®

PEDOT Inherently Conductive Polymers forClear Conductivity…

History of PEDOTPEDOT ChemistryPEDOT-based CoatingsSome Application ExamplesHigh conductivity PEDOT types

Fall AIMCAL Technical ConferenceOctober 16-19, 2005, Myrtle Beach, SC

N N NN

SSSSSS

S

OORR

S

OORR

S

OORR

S

OORR

S

OORR

S

OORR

S

S

S

S

S

S

OO OO OO

O O O O O O

Polymeric Organic Conductors

PolyacetyleneH. Shirakawa & MacDiarmid

Polyaniline (H+ doped!)A. Heeger

Polythiophene

Poly(3,4-dialkoxythiophene)Hoechst AG

Poly(3,4-ethylenedioxythiophene)PEDOTBayer AG, HC Starck

Conductivity Range of ICPs

Metal

Semiconductor

Insulator

106 S/cm

102 S/cm

10-9 S/cm

10-20 S/cm

CopperIronGraphiteBismuth

Indium

Gallium/ArsenicGermanium

Silicon

Glass

DiamondSulfurPolyethylenePolystyrene PVCTeflonQuartz

Elec

tric

al c

ondu

ctiv

ity

Conductivity of PEDOT :

10-5 to 103 S/cm

Inherently conductive or coated antistatic plastics for:photographic films and packaging materialsthe electronics industry (e.g. batteries and capacitors)

Early conductive polymers were assumed to be:InsolubleNot meltableNot easily processable

Development of PEDOT

Interest in Conducting Polymers in the 1980s

BAYTRON® M Monomer (EDOT, 3,4-ethylenedioxythiophene)

BAYTRON® C “Catalyst” (Oxidant), Iron(III) toluenesulfonatein various alcohols

BAYTRON® P* Aqueous dispersions of PEDOT:PSS Polymer(various grades)

PEDOT Products

OO

S

No branching in 3- or 4- position possibleLinear polymer structureStabilization of the positive charge in the polymer chain by electron-donating substituentsHigh transmission compared to polypyrrole and polyanilineHigh stability of conductivityProcessable aqueous dispersions accessibleSafe-handling

Chemistry of PEDOT/PSS Dispersions

SO3H SO3H SO3H SO3HSO3-SO3

-

( )m

( )n

O OO OO O

SS

SS

SS

O O O O O O

2 +

Polymer-complex PEDOT/PSS

Aqueous template polymerization of EDOT in the presence of PSSA produces PEDOT/PSS:

Dark blue dispersionSolids content about 1.3% [or higher]5-mer to 15-mer PEDOT segmentsHole doped, approx 1 hole per 3 monomer units

S

O O5n+2

Fe2(SO4)3

Na2S2O8Polystyrene-sulfonic acid

0.02 0.04 0.06 0.08 0.100

1

2

3

4Analytical Ultracentrifugation

Particle Diameter (µm)

Parti

cles

(%)

PEDOT:PSS Is a Dispersion of Polymer Particles

Polystyrene Sulfonic AcidPEDOT

Secondary- and tertiary structures:

gel-particle95 % water5 % polymer

PSS-chain with PEDOT-oligomers

Gel Particle Interactions in PEDOT/PSS:From Dispersion to Dried Film

gel-particle

95 % water5 % polymer

STM image (31 x 31 nm2) of a spin coated PEDOT/PSS thin film*.

Syn. Met. 135-136 (2003) 53-54, Touwslager et al. of Philips Research Laboratories, Eindhoven, The Netherlands. Images from RIM, Univ. of Nijmegen, The Netherlands, Prof. H. van Kempen.

0.02 0.04 0.06 0.08 0.100

1

2

3

4Analytical Ultracentrifugation

A B C

Particle Diameter (µm)

Par

ticle

s (%

)

PEDOT:PSS 1:6 Solution Particle

Median [nm] Resistivity

[kΩcm] A 58 1.96 B 32 6.52 C 25 12.6

Particle Size Impacts Level of Conductivity

0.0

4.0x103

8.0x103

1.2x104

1.6x104

2.0x104

PEDT:PSS 1:6

Res

istiv

ity [O

hmcm

]

Shear Stress

A

B C

Shear stress reduces the particle size and increases the resistively

Energy Barrier-Controlled Transport in Films

Conductivity (S/cm) Grade + 5%

DMSO+ 5%

NMP + 5% EG

A ~1 80 98 99 B ~0.3 65 32 53 C ~5-10 400 454 492

Reducing resistance between particles:

Range of Conductivity

In situPEDOT

10-6 S/cm 102 S/cm10-2 S/cm

PEDOT/PSS Formulations

PEDOT/PSS (neat)

PEDOT/PSS PLED Grades

• In most applications, surface conductivity can be achieved using very thin films (< 1 µm) of PEDOT-based conductive polymers

• The PEDT layer is usually preferentially applied by using the aqueous polymer dispersion PEDOT/PSS

• Careful control of coating formulation, application method, drying conditions, etc. are required to adjust final film properties

Increase Resistivity

Decrease Viscosity

Decraease Surface Tension

Increase Solid ContentC

ondu

ctiv

ity

Vis

cosi

ty

Sur

face

Ten

sion

Solid

Con

tentWill impact

Increased Shearing

Dilution

Concentration

Addition of Ethanol

Decrease ViscosityIncreased Shearing

Sta

bilit

y

pH Addition of Base?

To By

Formulation Guideline Matrix

0

2

4

6

8

10

12

14

16

18

20

20 30 40 50 60 70 80 90 100

% Baytron P

Surf

ace

resi

stan

ce in

MO

hm/S

quar

e

Adjusting Conductivity by Adjusting Composition With Non-Conductive Binders

Surface Resistivity of Baytron /Polyurethane-Dispersion

Increasing PU dispersion

Increasing PEDOT/PSS

1E+2

1E+3

1E+4

1E+5

1E+6

1E+7

1E+8

1E+9

0.00 0.25 0.50 0.75 1.00 1.25 1.50

Dry film thickness [µm]

R [O

hms/

sq] CPP 103D (high binder content)

CPP 105D (low binder content)

Adjusting Conductivity by Adjusting Thickness

Transparency of PEDOT-Coatings – Varies With Amount of PEDOT/PSS in Dry Film

Transmission Spectra of PEDT/PSS(Data for 200 nm measured directly, all other curves are calculated)

0102030405060708090

100

200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400 2500

Wavelength [nm]

Tran

smis

sion

[%]

50 nm100 nm200 nm500 nm1000 nm

Layer Thickness :

Coatings on PET filmsReference: air

50

60

70

80

90

10030

0

350

400

450

500

550

600

650

700

750

800

Wavelength ( nm )

Tran

smis

sion

(%)

PET Film 175 µm

CPP 103 D 2x10E5 ohm/sq 18 µm

CPP 105 D 1x10E4 ohm/sq 18 µm

CPP 103 D 3x10E4 ohm/sq 36 µm

CPP 105 D 3x10E3 ohm/sq 36µm

Transparency of Formulations – Two Examples

PEDOT/PSS contains acidic groups of sulfonic acids:

Metal ions and amines may react with acidic groupsadjust the pHmay crosslink sulfonic acid groups

PEDOT/PSS contains watercan be diluted with water indefinitelycan be diluted to some extent withwater-miscible solventscannot be diluted with non water-miscible solvents

Compounds sensitive to acidic hydrolysismay be hydrolyzedmay react further

PEDOT/PSS can be RedOx activereduction with strong reducing agents (e.g. hydrazine)overoxidation with strong oxidizing agents (e.g. hydrogen peroxide or hypochlorite)

General Guidelines For Formulating PEDOT/PSS Dispersions

AlcoholsMethanolGlycolEthanolIsopropanolButanol

KetonesAcetoneMethylethylketone

lesspolar

More polar alcohols are more miscible with PEDOT/PSS dispersionsEthanol is compatible at ~ 1:1Excessive addition of alcohols leads to agglomeration

CH3 CH3

O OH OPossible side reaction of ketones:

Condensation reactionFormation of diacetone alcohols from acetoneVery slow reaction

PEDOT:PSS dispersions can be partly diluted with water miscible solvents

Formulation With Water-Miscible Solvents

Amidic solventsNMPDMFDMAC

DMSO

NCH3

CH3O

CH3

HydrolysisOH

O

CH3

NHCH3

CH3

+Possible side reaction:

Formation of dimethylamine and acetic acidReaction is slow (within months)Dimethylamine reacts with PSS

Polar compounds, especially…

Amidic solvents likeN-methylpyrrolidone (NMP)N,N-dimethylformamide (DMF)N,N-dimethylacetamide (DMAC)

Dimethylsulfoxide (DMSO)

And low volatile alcohols likeethylene glycol (EG)glycerinsorbitol

Partly re-dissolve PEDOT-groupsRearrange morphologyDecrease resistance between PEDOT/PSS gel particlesIncrease film conductivity

During drying

Enhancing Conductivity With Additives

Multivalent cations or compounds with multiple basic groups can serve as crosslinkers for PEDOT:PSS :

PEDOT-segment

PSS-chain

Crosslinking by divalent metal ions isfast, with complete reaction in dispersionwill cause coagulation in the dispersionmay be used to enhance resistance towards solvent by subsequent treatment

MSO

O

S

OH

OO

S

OH

OO

SO

OO

*

S OO

O O

SOO

OM

Using Crosslinking Additives to Adjust Coating Properties

Silanes as crosslinking agents and hardening agents

TEOS(Tetraethylorthosilicate) Silicic acid

fast acid-catalyzed hydrolysisslower base-catalyzed condensation/network-formationmakes very hard coatingsespecially useful for coatings on glass

SiO

OO O

Et

Et

Et

EtHydrolysis

SiOH

OHOH OH

CondensationNetwork formation

SiO

OHOH OH

SiOH

OHO OHSi

OO

SiOH

O OH

SiO

OHOH

SiOH

OH

Using Crosslinking Additives to Adjust Coating Properties

Glycidyloxypropyltrimethoxy silaneSilquest® A 187™

hydrolysis like TEOSbut…additional reaction:

hydrolysis of the epoxy-groupreduced effectiveness over time if left in liquid formulation

SiO

OO

Me

Me

Me OO

SiOH

OHOH O

O

SiOH

OHOH O

O OHSOO

R

SiOH

OHOH O

OH OH

SOO

R

OH

H2O

Using Crosslinking Additives to Adjust Coating Properties

drying temperature between 80 to 200 °C.

drying time depends on coating thickness, temperature and air humidity and should be determined by appropriate application tests

minimum drying time is limited to about 30 to 60 s under practical conditions (due to the low evaporation rate of water from the polymer gel)

Drying temperature in °C

80 100 120 140 160 180 200

30

60

90

Dry

ing

ti me

in s

Recommended drying

Drying of PEDOT/PSS-Based Coatings

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

0 500 1000 1500Time in h

Con

duct

ivity

in S

/cm

CPP105D

CPP135D

CPP137D

CPP141D

2000

Stability/Aging of BAYTRON® CoatingsConditions: 52 ºC, 95% RH

Stability of PEDOT/PSS-Based Coatings

COMPONENT % BY WEIGHT BAYTRON® P (1.3% solids PEDOT/PSS dispersion)

57.65

Bayderm® Finish 85UD or Bayhydrol® 140 AQ (aqueous/solvent polyester-polyurethane binder solution)

15.63

N-Methyl-2-pyrrolidinone 3.48 Isopropanol 23.24 Total 100.00

Antistatic coating for thermoforming

Wet film thickness: 4 µm 6 µm 24 µmSurface resistivity: < 105 Ω/ 3.0 x 104 Ω/ 9.0 x 103 Ω/Quantity of BAYTRON® P used in coating: 2.3 g/m² 3.45 g/m² 13.8 g/m²

Coating Guide Formulation: Example CPP 4531II

outer graphite layer

PEDOTCOATING

deflection yoke

COMPONENT % BY WEIGHT BAYTRON® P (1.3% solids PEDOT/PSS dispersion) 32

Isopropanol 39 Ethylene glycol 16 Tetraethylorthosilicate 12 Acetic Acid 1 Total 100

Antistatic scratch-resistant coating for CRTs (glass)

Spray-applicationSurface resistivity: < 106 Ω/Pencil Hardness: 9HQuantity of BAYTRON® P used in coating: ~ 2 g/m²

Coating Guide Formulation: Example CPG 130.6

CPP141DCPP141D

Cond

uctiv

ity

CPP103DCPP103D

CPP105DCPP105D

CPP 116.6DCPP

116.6D

CPP 134.18DCPP

134.18D

CPP135DCPP135D

CPP4532ICPP4532I

S V2S V2

CPG 130.6CPG 130.6

CPUD2CPUD2

Polymer Coating – Antistatic or ESD

Glass coating

Polymer Coating - Thermoformable

Electrostatic coating

Polymer Coating – Conductive

Screen-printable coating paste

CPP4532E3D

CPP4532E3D

F HCF HC

F CPP105DMF CPP105DM

F PVAF PVA

100 Ω/sq

100 MΩ/sq

Hardness/Adhesion

PEDOT/PSS “Guide” Formulations – A Comparison

Flow Coating

Coater with NozzlesPipe with Formulation

AFTER

Coated Plastic Sheet

BEFORE

Uncoated Plastic Sheet

Tank with Coating Mixture

Roller Coating

Sheet to be coated

Transport Roll

Transport Belt

Supply Roll

Variable distance to control coating thickness

Common Coating Methods

film extrusionlongitudinal stretching

coating with ICPtransverse stretching

winding up

Conductive coating is applied in this step

Roll-to-Roll Coatings

PEDOT/PSS in Antistatic Coatings

LCD-Module Trays

Carrier TapesCover TapesPackaging films

Cathode Ray Tubes

LCD-Backlights

LCD-Polarizers

PEDOT/PSS in Conductive Applications

EL-Lamps1)

Touch-Screens

ITO-Replacement in LCD

1) Publication Bayer Material Science / Lumitec

PEDOT/PSS As an Electrode in Thick Film Electroluminescent Devices

Advantages of Using PEDOT/PSS:Replacement of ITOLower price compared to ITOElectrode patterned by screen printingSurface resistance ~ 500 to 5000 Ω /SimpleInexpensiveNo etching or patterningMoldable films possible

Operation Conditions:

U = 100 – 300 Volts AC

F = 100 – 400 Hz

Lumitec, Switzerland

0

1

10

100

1.000

10.000

1994 1997 1999 2002 2005 2008 2010Year

Con

duct

ivity

[S/c

m]

Baytron P

early versions PEDT:PSS

Baytron Pimproved versions

Baytron P high conductive versions

Indium Tin Oxide ?

Increasing the Conductivity of PEDOT:PSS

Challenge:

Transmission Spectra: ITO vs. PEDOT/PSS

400 600 800 1000 1200 1400 1600 1800 2000 22000

10

20

30

40

50

60

70

80

90

100

Transmission_ITO_AI4071.opj

ITO (d=120nm)

Baytron® P HC (d=255nm)in

tern

al T

rans

mis

sion

T/T

0

W avelength [nm]

Inte

rnal

Tra

nsm

issi

on (T

/T0)

x 1

00

10-2 10-1 100 101 102 103 104 105 1060

20

40

60

80

100

Transmission_ITO_Baytron P.opj

ITO σ = 5600 S/cm K = 2700 cm-1 (@550nm)

Baytron® P HC σ = 450 S/cm K = 10400 cm-1 (@550nm)

In-Situ_PEDT σ = 600 S/cm K = 21000 cm-1 (@550nm)

inte

rnal

Tra

nsm

issi

on T

/T0 [

%]

Surface Resistance Rsq [Ωsq]

V4

Absorption of PEDOT/PSS vs. ITO

Resistivity:

ρ = 1/σ [Ωcm]

Surface Resistance :ρ = Rsq · d

Item Unit PEDOT/PSS Formulation

ITO (Reference) Specification

Surface Resistivity Ω/sq 900 382 < 1000

Transmission (incl. Substrate)

% 88.2 88.6 > 88

Linearity % 0.6 0.6 -1.5 ~ +1.5

High temp. aging Times (SR rise) 1.8 1.8 < 2.0

High temp. and moisture aging

Times (SR rise) 1.2 0.9 < 2.0

Flex test Times 1.0 30.6 --

Pen-striking test Times 10,000,000 1,000,000 > 1,000,000

Character writing test

Times 200,000 100,000 --

Using PEDOT/PSS (Instead of ITO) in a Touch Panel Application

Comparison of Selected BAYTRON® P Types*

BAYTRON® Typical Applications Solids (%)

PEDOT:PSS ratio

Particle size, mean(nm)

Visc. (mPa-s)

Cond.(S/cm)

1 : 2.5 1

0.3

5 – 10

5 – 10

1

1 x 10-3

1 x 10-5

1 : 2.5

1 : 2.5

PH 500 Conductive coatingsEL-displays, TFTs, Touch screen electrodes

1.2 1 : 2.5 30 25 500

1 : 2.5

Antistatic coatingsESD protection coatings, such as for packaging, carrier tapes, LCD backlights and polarizersElectrochromicsElectrostatic coating primersElectronics packagingTransparent clean-room coatings

1 : 6

1 : 20

80

30

100

80

75

35

Ultra-thin antistatic coatings (CRTs), Optical coatings

80

20

80

>200

8

Conductive coatingsEL-displays, TFTs, Touch screen electrodes

Higher solids raw material for printing pastes

HIL for OLEDs and PLEDs, active matrix devices

15HIL for OLEDs and PLEDs, passive matrix devices

Cond.With 5% added DMSO(S/cm)

P 1.3 80

PH 1.3 65

P HC V4 1.2 400

P HS 4 -

P VP AI 4083

1.5 -

P VP CH 8000

2.8 -

* All values are approximate!

Ready-to-Use BAYTRON® Coating FormulationsProduct Applications Approximate

Surface Resistivity, Ω/(for 18-μm wet film thickness)

Approximate Transmission at ~ 500 nm, %(incl. 100-μm PET substrate)

~ 83%

BAYTRON® F E Conductive coatings ~ 300 ~ 85%

~ 87%

~ 84%

~ 88%

~ 78%

BAYTRON® F HC

Variable, but usually > 89%

~ 500Conductive coatings

Conductive coatings

Thermoformable antistatic coatings

General, all-purpose antistatic coating

BAYTRON® S V2 Screen-printable paste for circuitry in EL-displays and other applications

Approx. 1 kΩ/sq(14.5 g/m2 test print)

Coating formulations customized for specific applications – See Coating Guide for more details.

BAYTRON® F CPP 105DM

~ 2000

BAYTRON® F PVA ~ 3000*(prior to thermoforming)

BAYTRON® CPUD2 1 x 106

OTHERS…CPP 105D, CPP 134.18D, CPP 135D, etc.

Variable

Thank you for your attention !

Klaus Wussow Application Technology - BaytronFriedrich Jonas Application Technology - BaytronAndreas Elschner Development - Organic LEDsUdo Guntermann Coatings developmentUrsula Tracht Kinetic studiesAlexander Karbach X-Ray, AFM, TEM labKnud Reuter SynthesisUdo Merker Development Capacitor TechnologyWilfried Lövenich Application Technology - Baytron/Pilot plantStephan Kirchmeyer Manager of R&DKlaus Lerch Global Sales Manager – EOIIIRon Lubianez NAFTA Sales Manager – EOII & EOIII

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