Università degli Studi di Salerno Dip. Ing. Informazione ed Ing. Elettrica

Ischia, 21-23 giugno 2006Riunione Annuale GE 2006

Università degli Studi di SalernoDip. Ing. Informazione ed Ing. Elettrica

• Effect of ITO treatment on OLEDs performance

• Realization and Characterization ofPolymeric Memories

Organic ElectronicsOrganic Electronics

S. Bellone, M. Petrosino, A. Rubino, P. Vacca


Effect of ITO treatment on OLEDs Effect of ITO treatment on OLEDs performanceperformance

Università degli Studi di Salerno Effect of ITO treatment on OLEDs Effect of ITO treatment on OLEDs performanceperformance

Al

ITO

glass

Hole transporter (NPD or PF6)Electron transporter (ALQ3)

70 nm

60 nm

200 nm

200 nm

light

The effect of various chemical–physical ITO surface treatments have been studied.

These treatments remove surface impurity, decrease surface roughness and increase ITO work–function.

Small molecules–ITO (NDP) interface and Polymeric–ITO (PF6) interface have been considered.

The hole-transporter layers depositing technique are been

• thermic evaporation for small molecules

• spin coating for polymeric molecules

This work is done in collaboration with Portici ENEA Research Center


OLEDs Energy diagramsOLEDs Energy diagrams

ITO–NPD–Alq3–Al device

ITO–PF6–Alq3–Al device

An additional hole barrier is in NPD device

A bigger hole anode barrier is in PF5 device



ITO chemical–physical propertiesITO chemical–physical propertiesfor various treatmentsfor various treatments

0,4932,5617,202,4010,55Untreated

0,4433,3124,7012,5012,46HCl (6%)

0,5234,4024,903,0010,00UV ozone

0,4836,3411,902,5010,33Annealing 200°C

0,6538,7211,001,8010,44Oxygen plasma

0,3142,3614,503,1012,31HCl (12%)

0,5146,609,402,6011,13UV ozone–HCl (12%)

0,5863,0810,704,5010,03Piranha solution

Xp(mJ/m2)(nm)(nm)(

PolaritySurface energySpikes

RMS roughness

Sheet resistance

Treatment



PF6–OLED ResultsPF6–OLED Results

• The best result is obtained with HCl–UV treatment with an increase of 60 in luminance

• The device’s improvement is due to a better adhesion between polymer and substrate during spinning gotten by

• increment of the apolar ITO surface energy because the solvent used is apolar

• decrement of ITO surface roughness


12 14 16 18 201E-3

0.01

0.1

1

Voltage (V)

f

eg

dc

a HClb UV-HClc O

2-plasma

d annealinge untreatedf piranhag UV ozone

Lum

inan

ce (

cd/m

^2)

b

a

0.0 4.0 8.0 12.0 16.0 20.01x10-7

1x10-6

1x10-5

1x10-4

1x10-3

gfe

d

c

ba HClb UV-HClc O

2-Plasma

d annealinge untreatedf UV Ozonog Piranha

Cu

rren

t D

ensi

ty (

A /

cm2 )

Voltage (V)

a


NPD–OLED ResultsNPD–OLED Results

• The best result is obtained with HCl treatment with an increase of 100 in luminance

• The device’s improvement is due to a better adhesion between evaporated organic moleculs and substrate during Joule–deposition gotten by

• increment of the apolar ITO surface energy because NPD is an apolar molecule

• increment of ITO surface roughness


0.01 0.1 1 10

1E-7

1E-6

1E-5

1E-4

1E-3

0.01

0.1

a HClb UV-HClc O-Plasmad annealinge untreated

Cu

rren

t d

en

sit

y [A

cm-2

]

Voltage (V)

a

b

cd

e

4 5 6 7 8 9 10 11 12 13 14

10

100

1000

d

b c

a

e

Lu

min

an

ce [c

d/m

2 ]

Voltage [V]

a HCL b UV-HCl c O

2-Plasma

d annealing e untreated


Realization and Characterization of Realization and Characterization of Polymeric MemoriesPolymeric Memories

Università degli Studi di Salerno Polymeric MemoriesPolymeric Memories

Al

Polymeric Active Layer

150 nm

200 nm

Al on glassor

doped–Si

This research work is done in collaboration withDip. Ing. Chimica ed AlimentareUniversità di Salerno

New ad hoc polymers are used to realize organic memory cells.

Organic layer is deposited usingspin–coating technique.

The goal is to realize organic memory using low-cost technologies.

To study transport and dynamic phenomena dummy device have been realized on p-type and n-type Si substrate.


Electric Bistability (I)Electric Bistability (I)


The molecules show two states with different electrical conductivity

This electrical bistability is imputable to conformational bistability

To return from high conductivity state to low conductivity state, conformational switching is forced by high reverse electric field

-8 -6 -4 -2 0 2 4 6

0,0

50,0µ

100,0µ

150,0µ

200,0µ

250,0µ

300,0µ

Cu

rre

nt

(A

)

Voltage (V)

cycles (1) (2) (3) (4)

0 2 4 60,0

0,0

0,0

0,0

0,0

0,0

0,0

0,0

Cu

rren

t

[A]

Voltage [V]

cycles (1) (2) (3) (4)

N-Si / ON-Si / O22-Polymer / Al device-Polymer / Al device


-4 -3 -2 -1 0 1 2 3 41E-13

1E-11

1E-9

1E-7

1E-5

1E-3

cycles (1) (2) (3) (4) (5) (6) (7) (8)

| Cu

rren

t |

[A]

Voltage [V]


One order of difference in current between high conductive state and low conductive one is obtained

Read voltage – 1.5 V

Write voltage – 4 V

Erase voltage + 4 V

0 25 50 75 100 125 150 175 200 225

1E-9

1E-8

1E-7

1E-6

Cu

rren

t [A

]Time [s]

High

Low

-4

-2

0

2

4

Vo

ltag

e [V

]

erase

read

write

Electric Bistability (II)Electric Bistability (II)Al / N-Polymer / Al deviceAl / N-Polymer / Al device

Università degli Studi di Salerno Dip. Ing. Informazione ed Ing. Elettrica

Documents

Transcript of Università degli Studi di Salerno Dip. Ing. Informazione ed Ing. Elettrica