polymer compositeoled

Organic Photonic Materials
• Nonlinear Optics Materials
• Organic Light Emitting Diode (OLED)
Nonlinear optics
The interaction of electromagnetic fields with
various media to produce new
electromagnetic fields altered in
• phase,
• frequency,
• amplitude
from the incident fields
• Second harmonic generation (SHG),
the conversion of coherent light of
frequency ω into light of frequency 2ω
• The electro-optic effect
allows one to change the refractive index
of a material by simply applying a DC
electric field to the material; thus, one can
utilize the modulation of an electrical
signal to activate an optical switch.
• The polarization P induced in a molecule
by a local electric field E
P= αE + βE
2
+γE
3
+ …
α linear polarizability (the origin of refractive
index)
β second order hyperpolarizability (the
origin of the second order nonlinear

polarization response)
Push-Pull in a Donor-Acceptor
βValues of Some Organic Chromophores
(10
-30
esu, 1064 nm)
Charge Transfer Resonance
Structures
•First, the greater the charge separation in the charge
transfer state (Dm), the larger the β
•Second, the closer the frequency of the incident light is
to the resonant frequency of the charge transfer, the
larger the β
Organic Electro-Optic Materials
A Historical Perspective
Statistical mechanical calculations suggested a new paradigm optimization of electro-
optic activity: Control chromophore shape!
N
O
NC
CN
NC
N
S
O
CN
NC
NC
N
O

NC
CN
NC
R' R'
R
R
R
R
R
R
CLD-1
CLD-2
CLD-3
R = OTBDMS
R=H
FTC-1
R = OAc, R' = H
FTC-2
R = OAc
R' = CH
2
CH
2
CH
2
CH
3
R = H
0
20

40
60
80
100
120
140
0 20 40 60
No. Density (10^19/cc)
CLD-2
CLD-3
Disperse Red (1995)→
For Bulk Materials
P = χ
(1)
E + χ
(2)
E
2
+ χ
(3)
E
3
+
Fabrication of organic second order
NLO materials
• organic crystal growth,
• inclusion complexes,
• mono- and multilayered assemblies
(e.g. Langmuir-Blodgett films),
• poled polymers

Polymer poling
• The polymer is heated above the glass
transition temperature and placed in a
strong external electric field; this process
is termed poling.
• The field serves to orient the chromophore
with its dipole moment parallel to the
applied field.
Progress of LED, OLED, and PLED
Ω External Quantum Efficiency (%)
= (Photon# / Electron#) • 100%
Ω Luminance Efficiency (cd/A)
(Photometric Efficiency)
Ω Power Efficiency (lm/W)
Luminance (L) : cd/m
2
Current density (J) : mA/cm
2
Units of OLED Efficiency
Luminous flux Luminous Intensity
Lumen
Name:
Unit:
Candela
Luminance
Candela/m
2
(nit)
Scale of Light Intensity
30,000,000 -

300,000,0000 -
3,000,000 -
300,000 -
30,000 -
3,000 -
300 -
3 -
0.3 -
0.03 -
0.003 -
0.0003 -
0.00003 -
0.0000003 -
cd/m
2
There are two main directions in OLED: Small
Molecules and Polymers.
•The first technology was developed by Eastman-Kodak and is
usually referred to as "small-molecule" OLED. The production of
Small-molecule displays requires vacuum deposition which makes the
production process expensive and not so flexible.
•A second technology, developed by Cambridge Display Technologies or
CDT, is called LEP or Light-Emitting Polymer, though these devices are better
known as Polymer Light Emitting Devices (PLEDs). No vacuum is required,
and the emissive materials can be applied on the substrate by a technique
derived from commercial ink-jet printing.
•Recently a third hybrid light emitting layer has been developed that uses
nonconductive polymers doped with light-emitting, conductive molecules. The
polymer is used for its production and mechanical advantages without
worrying about optical properties. The small molecules then emit the light and

have the same longevity that they have in the Small-Molecule OLEDs.
Organic Light-Emitting Diodes (OLEDs)
• Flexibility (vs. inorganic LEDs)
• Simple and easy thin film fabrication and micronscale patterning
(vs. wire-bonded epitaxial AlGaAs or group III nitride discrete
semiconductor LEDs)
OLEDs will have most impact on markets for small, high
information content display required low to medium
brightness (mobile phone, PDA, lap-top computer).
• Flat-panel-display (vs. liquid crystal display, LCD)
Wide viewing angle
Very bright and highly contrast
No back-lighting needed (low energy consumption)
Fast switching times (video-rate display)
Multicolor emission (RGB)
Thin and light weight
Foldable, very thin screen possible
比一比看誰炫
比一比看誰炫
( )
( )
Configuration of LCD and OLED
LCD
OLED
吸收光譜與螢光光譜— 螢光發光原理
Stokes shiftPhotoexcitation and Relaxation
S
1
S
2

T
1
S
0
vc
ISC
vc
vc
vc
ISC
IC
vc
vc
hν
a
hν
a
hν
f
hν
p
IC
vc : vibrational cascade
hν
a
: absorption energy
hν
f
: fluorescence energy
hν

p
: phosporescence energy
IC: internal conversion
ISC : intersystem crossing
I
l
l
u
s
t
r
a
t
i
n
g

p
o
s
s
i
b
l
e

electronic
process following
absorption of
a photon with energy hν

a
J
a
b
l
o
n
s
k
i

D
i
a
g
r
a
m
S
0
: singlet ground state
S
2
: second lowest singlet excited state
S
1
: lowest singlet excited state
T
1
: lowest triplet excited state

Competition Among Flat Panel Displays (FPDs)
Thin-film transistor (TFT)
From Wikipedia, the free encyclopedia.
•A thin film transistor (TFT) is special kind of field effect
transistor made by depositing thin films for the metallic
contacts, semiconductor active layer, and dielectric layer.
•Most TFTs are not transparent themselves, but their
electrodes and interconnects can be. The first transparent
TFTs, based on zinc oxide were reported in 2003.
•The best known application of thin-film transistors is in
TFT LCDs. Transistors are embedded within the panel
itself, reducing crosstalk between pixels and improving
image stability. As of 2004, all but the cheapest color LCD
screens use this technology.
CIE 1931 (x, y) – Chromaticity Diagram
International Commission on Illumination
The human eye has receptors
for short (S), middle (M), and
long (L) wavelengths, also
known as blue, green, and red
receptors. That means that one,
in principle, needs three
parameters to describe a color
sensation. In the CIE diagram,
those parameters are not the M,
S, and L stimuli, but rather a
more abstract x and y parameter,
and an implicit luminosity
(brightness) parameter, that is
not shown

Adv. Mater. 2000, 12, 1737
Comparison of OLEDs with the Other FPDs
* US Billion; source from StandfordResource, 2000, 8
Item LCD PDP VFD FED Inorg. EL OLED
View Angle Improving Excellent Excellent Excellent Excellent Excellent
Efficiency
(lm/W)
2 - 3 1 0.8 - 14 7 2 – 4 5 - 10
Full color Excellent good Limited Limited Limited Improving
Size (in.) < 21 > 40 Small 5 - 20 2 - 20 2 - 20
Voltage
TFT: 2 – 5
BL: 1000
AC
90 - 150
DC
10 - 40
DC
1000
AC
200
DC
<10
Response
(µs)
20 60 ms 2 - 20 10 1 50 1
Issues
View angle
Large area
Efficiency; Cost;

Voltage; Power
Resolution;
Weight
Full-color
resolution;
Wieght; Voltage
Blue podsphor
Voltage;
Contrast
Blue
phosphor
Power
Reliability
Full color
Market
1999*
Active: 13
Passive: 4.5
0.8
−−−−−−−−−−−−−−−1.4−−−−−−−−−−−−−−
0.003
Market
2005*
Active:31.3
Passive:5.8
5.8
−−−−−−−−−−−−−−−1.3−−−−−−−−−−−−−−
0.7