science and technology on inorganic electroluminescence
TRANSCRIPT
Science and Technology on Inorganic Electroluminescence
- past, present, future -
Hiroshi KobayashiProfessor Emeritus,Tottori University
The 2009 Seminar (45 min.)Date: May 8Place: Hong Kong
Outlines
1. Introduction2. Basic Understanding of Thin Film EL
--- Voltage Dependence--- Electron Injection --- Excitation mechanism of luminescent centers
3. Color EL Materials4. Trial for Electroluminescent Display Panel5. Concluding Remarks
1950 1960 1970 1980 1990 2000 2010
1974
SHARP 二重絶縁構造
19741974
SHARP .
1968BellLab.
RE-dopedZnS thin flmRGB
1999 2004
1st Gen.PowderEL
2nd Gen.,ThinFilm EL(ZnS,IIa-Vb)
3rd. Gen.
4th Gen.
1989 SID Int.Symposium
1987
2005
History of Inorganic ELedited by Dr. Miura (Meiji Univ.)
FPD TAIWAN 2004 Business & Technology Forum on June 9 ~ 12
History of OLED products
passive 1999
active 2003
2000 2001
monochrome(for cellular phone)
Tohoku pioneer
Area color(for in-car products)
Tohoku pioneerTDK
Full color(for cellular phone)
SNMD
Full color(for DSC)
SK Display
ed. by K.Yoneda
IntroductionHistory of EL at Tottori University
1. The preparation of TFEL ; host material, EL centers insulating film, electrode. (1969~ )
2. The Understanding of fundamental physics of TFEL, doped with rare-earth luminescence centers. (1970 ~ 1974)
3. The trial of application of thin film electroluminescence to flat panel displays. (1975 ~ )
4. Multicolor thin film electroluminescence. (1975 ~)
5. Multicolor flat panel electroluminescence. (1980 ~ )
6. Thick dielectric film electroluminescence. (1999 ~ )
7. The organic TFEL (1995 ~ )
Sharp (~1974)
Outline1. Introduction2. Basic Understanding of Thin Film EL
1968---1975 Thesis Work Kobayashi1 Voltage Dependence2 Electron Injection 3 Excitation mechanism of luminescent centers
3. Color EL Materials4. Trial for Electroluminescent Display Panel5. New Development of Color EL 6. Concluding Remarks
These results are summarizedin Kobayashi’Thesis Work
(1974,July in Japanese)
Basic Research on Electroluminescence in Rare Earth Doped ZnS Thin Film
Kobayashi Hiroshi
Voltage Dependence
Previous data
Voltage Dependence of Luminance
Our result:L(E,ΔQ)
Previous result:L(ΔQ)
Electron Injection Mechanism 1
Electron Injection Mechanism 2
Excitation of Luminescent Centers
(a) (b) (c)
Excitation Mechanism of EL 1
Donor-AcceptorPairs Cu-Cl
Nd ion
Donor-Acceptor+
Nd ions
Luminescent Centers in ZnS
Direct Impact Excitation of Er3+ 2
Electron Energy Distribution
E low
E high
Outline
1. Introduction2. Basic Understanding of Thin Film EL3. Color EL Materials4. Trial for Electroluminescent Display
Panel5. New Development of EL6. Concluding Remarks
The Spectra of Mn2+
Emission Spectra Re3+,R,G,B
The Spectra of Ce3+
RGB EL Materials
Eu2+ and Ce3+ in CaS,SrS Host Materials
Outlines
1. Introduction2. Basic Understanding of Thin Film EL3. Color EL Materials4. Trial for Electroluminescent Display
Panel5. New Development of EL6. Concluding Remarks
Powder EL Panel ,R,G,B
Strong Cross Talks
Thin Film EL Panel R,G,B
No Cross Talks
The Full Color EL Panel (1989)
white
Filtered RGB
Blue OrangeWhite
Trials for increasing pixels
Thin Film EL Panel ZnS:Mn
LCD LED
Our New TFELTV picture (4-level gray scale)
Scanning lines (~50),taken out from TV 525 lines
Planar (1)
ZnS:Mn monochrome yellow
Planar (2)
iFire Technology (1)
iFire Technology (2)42 inch
Outline
1. Introduction2. Basic Understanding of Thin Film EL3. Color EL Materials4. Trial for Electroluminescent Display
Panel5. Research on Color EL (1990’s ~ )6. Concluding Remarks
Primary Color (RGB)
R G B
Red Phosphor
ZnS:SmCaS:Eu
Ba2ZnS3:Mn(Ca,Sr)Y2S4:Eu
ZnGa2O4:EuZnS:Mn + FilterZnS:Mn + CCM
Green Phosphor
ZnS:Tb
SrGa2S4:EuCaAl2S4:Eu
Blue Phosphor
ZnS:TmSrS:Ce + Filter
CaGa2S4:CeSrGa2S4:CeSrS:Ag,Cu
CaS:PbBaAl2S4:EuBa2SiS4:Ce
Research on Color EL (1990’s ~ )
After Miura, Meiji University
SrCaYSrCaY22SS44:Eu:Eu
CaAlCaAl22SS44:Eu:Eu
BaAlBaAl22SS44:Eu:Eu
Green
Blue
Red
over 150 cd/m2
over 250 cd/m2
over 50 cd/m2
material Luminance@50 Hz
color
Possibility of RGB emission by Eu2+ ion doped IIa-III2-S4 phosphors for full color inorganic EL displays.(Miura et al., Meiji University)
400 450 500 550 600 650 700 750
EL Inte
nsi
ty (
a.u.)
Wavelength (nm)
BlueGreen Red
NTSC
EBU
BaAl2S4:Eu
CaAl2S4:Eu
SrCaY2S4:Eu
MEIJI University
Possibility of RGB (Miura)
iFire Display TM StructureColor By Blue (CBBTM)
ITOdielectric
thick film dielectric
Glass substrate
gold electrode
BaAl2S4:Eu
(0.134,0.080) (0.32, 0.67) (0.660, 0.340)
Lead magnesium niobate based material combined with aPZT
Color filter CCM 4.1 CCM 1.6
2003i-Fire Display Structure
High Luminance DC Inorganic EL device(Chatani & Kuraray co., LTD, 2005 Oct.)
・Luminance: 650,000 cd/m2 (2,000,000 cd/m2 @8 V)
・Applied Voltage: DC 5.5 V(Threshold Voltage: 3V)
・Luminous Efficiency: 10~14 lm/W・Emission Area: 2 mm X 2 mm・Life: 25,000 h (@350,000 cd/m2)
(2.8 Year)
・Current: 97~137 mA・Resistance: ~40 Ω
ZnS Phosphor based Material
e
Eg: 3.6eV
Chatani
EL Spectra of various materials
5 Concluding Remarks
• Blue Inorganic EL of BaAl2S4:Eu • Color change by blue EL panel• A new 600,000 cd/m2 bright inorganic EL
of dc driven at lower than 10 V.
we summarized the present main topics.
These three findings will stimulate again the researches on inorganic EL
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