Post on 10-Jan-2016
description
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
Ischia, 21-23 giugno 2006Riunione Annuale GE 2006
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
Ischia, 21-23 giugno 2006Riunione Annuale GE 2006
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
Università degli Studi di Salerno Effect of ITO treatment on OLEDs Effect of ITO treatment on OLEDs performanceperformance
Ischia, 21-23 giugno 2006Riunione Annuale GE 2006
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
Università degli Studi di Salerno Effect of ITO treatment on OLEDs Effect of ITO treatment on OLEDs performanceperformance
Ischia, 21-23 giugno 2006Riunione Annuale GE 2006
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
Università degli Studi di Salerno Effect of ITO treatment on OLEDs Effect of ITO treatment on OLEDs performanceperformance
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
Ischia, 21-23 giugno 2006Riunione Annuale GE 2006
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
Università degli Studi di Salerno Effect of ITO treatment on OLEDs Effect of ITO treatment on OLEDs performanceperformance
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
Ischia, 21-23 giugno 2006Riunione Annuale GE 2006
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.
Ischia, 21-23 giugno 2006Riunione Annuale GE 2006
Electric Bistability (I)Electric Bistability (I)
Università degli Studi di Salerno Polymeric MemoriesPolymeric Memories
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
Ischia, 21-23 giugno 2006Riunione Annuale GE 2006
-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]
Università degli Studi di Salerno Polymeric MemoriesPolymeric Memories
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