Scientific and Technological. Progress with Polyaniline and. Poly-ethylenedioxythiophene. Dr. Bernhard Wessling. Ormecon Chemie, FRG. Nanotechnology at ...
Dr. Bernhard Wessling Ormecon Chemie, FRG
Scientific and Technological Progress with Polyaniline and Poly-ethylenedioxythiophene Nanotechnology at its Best
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Need of a HIL Cathode: Ba, Ca, Al
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Light Emitting Polymer (LEP)
anode: ITO carrier: glass
electron
+
h*
light
recombination
hole
injection barrier: difficult hole transport into LEP layer / level of work function; rough topology; impurities higher operating voltage necessary poor lifetime values
Previous attempts to HILs with PAni “solutions”
short shelf life because of gelation and particle aggregation very poor reproducibility even on laboratory scale conductivity too high => cross talk problems expensive and toxic components thin films with high surface roughness not filterable with nanopore filters
New PAni Dispersions for HIL requirements: environment friendly medium => water nanoscale particle size (< 80 nm) low conductivity (< 10-5 S/cm) to avoid cross talk tunable work function to improve HI tunable viscosity (appropriate for each application technique) reproducible properties commercial scale
stable device performance and improved lifetime
Particle Size Distribution AFM / EFM: Laser Doppler Measurement: PAni PA T 010, av = 35 nm 24 PEDT CH8000, av = 20022nm PEDT 4083, av = 400 nm
24 22
parts [% ]
20
20
18
18
16
16
14
14
12
12
10
10
8
8
6
6
4
4
2
2
0 1E-3
0 0,01
0,1
1
10
Particle size [µm]
=> particle size distribution stable > 12 months => surface roughness < 10 nm
OLED with PAni-HIL
on glass, with a performance increase of 5 - 27% vs PEDT
Passive Matrix Displays avoid cross-talk between dots
conductivity < 10-5 S/cm
2-point probe measurements on coated ITO substrates
COVION
EIS
glass
ITO glass
Resistance • coating thickness = specific conductivity
Conductivity measurement on the real HIL layer, as if in OELD
Fourier Transformation Impedance Spectroscopy
Conductivity Measured under Vacuum => accelerate equilibration time for HIL
COVION HIL PAT 010 PEDT 4083 EL PEDT CH 8000
Cond. [S/cm] 2,2*10-6 1.5*10-1 8,8*10-6
HIL PAT 010 PEDT 4083 EL PEDT CH 8000
Cond. [S/cm] 7,0*10-7 1.5*10-1 1.5*10-5
Customer’s requirements for cond. < 10-5 S/cm fulfilled with PAni PAT010
Work Function measurement with the Kelvin Probe
Work function in correlation with device performance optim um range ITO P Ani sam ple < 100 %
P Ani sam ple = 100 % P Ani sam ple > 100%
PE DT CH8000 PED T 4083EL
HOMO: by CV
SuperY ellow
4,2 4,3 4,4 4,5 4,6 4,7 4,8 4,9 5,0 5,1 5,2 5,3 5,4
work function [eV]
optimum for hole injection: wf = - 4.85 - 4.95 eV
