Transcript 슬라이드 1 - 중앙대학교 화학신소재공학부

( 襲名: 沈壽官, 1928~/ 薩摩燒 )
April, 5, 2011
형광체
유 재 수
LG 이노텍 LED 연구소
중앙대학교 화학신소재 공학부
디스플레이 재료 Lab
순서
형광체 소개
1. 형광체
2. 종류
3. 응용 및 상용 제품
LED 용 형광체
1. 요구조건
- LCD B/L unit
- Lighting
2. State-of-the-art Technology
Nitride/Oxynitride Phosphor
1. Characteristics
2. Structure
3. Processing
Patent
Phosphor (Energy Converter)
Color Purity
Luminance
Stability
Source
electron,
electric field,
photon
cathodoluminescence
electroluminescence
photoluminescence
Wrong because of LED !
Phosphor Application
Y2.93Al5O12:Ce0.07
Principle-Excitation
Activator (+ Sensitizer) Electronic Configuration
Eu2+: 1s 22s 22p6 3s23p6 4s23d104p65s 2 4d105p66s2 4f5 5d
Host(band absorption )~ semiconductor material
http://en.wikipedia.org/wiki/Atomic_orbital
Crystal Field Splitting
(Configuration Coordinate) Model
The deviation from the equilibrium position of the ions:Q
•Stokes' law; i.e., the fact that the energy of
absorption is higher than that of emission in
most cases. The energy difference between the
two is called the Stokes' shift.
•Spectral Properties; the widths of absorption or
emission bands and their temperature
dependence.
•Thermal quenching of luminescence. It must by
remarked, however, that the one-dimensional
model gives only a qualitative explanation of
thermal quenching.
K:Force constant of the chemical bond
By thermal energy
The probability for an excited electron to lose energy by
generating lattice vibration :1012 to 1013s-1
The probability for light emission is at most 109s-1.
At finite temperature, the electron state oscillates around the
equilibrium position along the configurational coordinate curve
up to the thermal energy of kT.
At relatively high temperature, a nonradiative relaxation process
the transition probability per unit time, N :
with the activation energy DU
By letting W by the luminescence probability, the luminescence
efficiency h can by expressed as:
The Franck-Condon principle :
the nucleus of an emitting ion stays approximately at the same
position throughout the optical processes (mass of electron and
nucleus: magnitude of 3~5 difference)
Excitation-The Rare Earth Ions(4f n)
4p65s 2
4d105p66s2
4f ?
5d
• Incompletely filled 4 f shell
• 4 f orbital shielded from
surroundings by the filled 5s2
&5p6 orbital
small influence of the host
lattice to optical transition
Eu3+
Excitation-The Rare Earth Ions(4f n)
• 4f-5d transition
(4 f n – 4 f n-1 5d)
&
• Charge-Transfer
Transition
(4 f n – 4 f n+1 5L-1)
ex) Ce3+
Ce3+
Principle-charge transfer
In inorganic chemistry, most charge-transfer complexes involve electron
transfer between metal atoms and ligands.
LMCT complexes arise from transfer of electrons from MO with ligand like
character to those with metal like character. This type of transfer is
predominant if complexes have ligands with relatively high energy lone
pairs (example S or Se) or if the metal has low lying empty orbitals. Many
such complexes have metals in high oxidation states (even d0). These
conditions imply that the acceptor level is available and low in energy.
Example:
Eu - O
Eu - N
Energy Transfer
• Host, Sensitizer
Activator
phonon (lattice vibration)
charge transfer
Principle-Center Luminescence
Spectral Shape
sharp
broad
Efficiency
Decay time
Donor Acceptor Pair Luminescence
Semiconductor materials : ZnS, ZnSe, GaP
Phosphor -Efficiency
• Energy efficiency = Pout/ Pin
ηtot = (Eem/Eexc) ηt ηact η esc
~ 25 %
CCFL
CCFL (Cold Chathode Fluorescense Lamp)
Intensity (count)
White by CCFL + CF
400
450
500
550
600
650
WL(nm)
W CCFL + R CF
W CCFL + G CF
W CCFL + B CF
CCFL + CF
700
PDP 구조
 면 방전 type
~ Simple cell structure
~ Easy to fabricate
Bus electrode
 반사형
Front panel
~ Transparent conductor (ITO)
~ High luminance
Dielectric
MgO layer
Barrier
ITO electrode
Phosphor
---
+ ++
Discharge
Address
electrode
Rear panel
Efficiency of PDP
•
효율 그림
0.91%
0.24%
100%
18%
8.5%
0.74%
Total
Visible
0.42%
0.18%
ηtot = η dis η vuv η phos η vis
Low efficiency !
3D Technology
Shutter Glasses (PDP)
Polarized Glasses (LCD)
• Vertical Resolution ½ ↓
• Natural 3D Image
Original
Image
Original
Image
Resolution
Left Eye
Right Eye
• Viewing Angle Free
Viewing
Angle
Add. Cost
PDP
Free
Left Eye
Right Eye
• Limitation of Viewing Angle
After Image
LCD
60°
Polarized Film
3D PDP with shutter glasses
Phosphor -Application
Core/Shell Structured Semiconductor Nanocrystals
 Highly Efficient CdS:Mn/ZnS Core/Shell Nanocrystals: Core/Shell Structure
PL emission
application 1
application 2
 Hybrid nanocrystal-conjugated polymer
 Biological tagging agents
EL devices
Tied external carotid artery
EL spectra with applied voltages
Al (cathode)
20V
Injection of Quantum dots
into internal carotid artery
PVK † (120 nm)
EL intensity (a.u.)
CdS:Mn/ZnS NCs
16V
Tied common carotid artery
13V
10V
PEDOTPEDOT- PSS §
300
400
500
600
700
wavelength (nm)
ITO € glass (anode)
800
900
<Fluorescence image>
Other Nanostructured Materials and Their Applications
 Ternary Alloyed Nanodots and Nanorods: ZnCdSe Nanocrystals
(d)
(c)
(b)
(a)
:Evolution of emission spectra of ZnCdSe
<TEM image of ZnCdSe nanodots and nanorods>
nanocrystals by quantum confinement effect
and alloying effect
 ZnO nanorods and Their Application to Plasma Display Panel
-Development of electron emitter
using ZnO nanorods for fabrication
of hybrid PDP
Front glass
sustain electrode
bus electrode
upper dielectric
MgO
ZnO nanorods
coated with MgO
phosphor
barrier rib
lower dielectric
<SEM image of ZnO nanorods>
address electrode
YAG:Ce0.06Sm0.01~0.06 nanophosphors
-Chemically controlled YAG nanocrystalline phosphors
-Fabrication of white LED using nano-sized phosphors
Normalized PL intensity
 Development of Nano-Sized Phosphors
Ce0.06Sm0.06
Ce0.06Sm0.03
Ce0.06Sm0.01
<SEM image of nano-YAG:Ce>
500
550
600
650
Wavelength (nm)
700
750
Solar Cell
force4
Intermatics
System makers control & take All
意志?