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그림차례 - vii -
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5). - 2 -
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유기발광다이오드 ( 고분자또는저분자 ) 무기발광다이오드 (p-n junction LED) - + cathode ETL EML HTL HIL anode 발광 두께 : 100 ~ 200 nm 양극 ( 투명전극, ITO 유리, 등 ) + 정공 정공수송층 (HTL) 발광층 (EML) + - Exciton 전자수송층 (ETL) 전자 - 음극 ( 낮은일함수금속, Ca, Al:Li, Mg:Ag, 등 ) - 4 -
. α A - 5 -
O O O O O O S S S S n S O O O O n n SO 3 SO 3 H PEDOT:PSS N N N O Al O N N O α NPD Alq 3-6 -
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정공의이동도측정 (a) Light (hν) L Oscilloscope V ITO or Semi-Transparent Electrode R Metal Electrode 전자의이동도측정 (b) Light (hν) L Oscilloscope V ITO or Semi-Transparent Electrode R Metal Electrode - 8 -
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Electron energy Conduction band edge at F=0 E PF Tunnelling Conduction band edge at F - 10 -
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- Al - 정공의이동거리 d 1 전자의이동거리 d 2 소멸영역+ + ITO
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Log J J SCL V 0 J OHM J INJ Log V - 14 -
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mm 2-16 -
KEITHLEY 2400 source/measure unit을이용하여 - 17 -
Light (hν) d Transit time τ Bias t = t r i ph t i ph Log i ph Slope = -(1-α) t = t r Slope = -(1+α) t Log t - 18 -
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Electric Pulse d Light (hν) PMT 2 Light (arb. units) 1 delay time 0 0 10x10-6 Time (s) - 20 -
전류-전압-발광특성은유기발광소자의 ITO와알루미늄전극에각각양극과음극을연결하고 KEITHLEY 236 source/measure unit으로전류- 전압특성을측정하고, 동시에 Si-Photodiode를이용하여광전류 (photocurrent) 를 (KEITHLEY 2000 multimeter 이용 ) 측정하였다. - 21 -
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8 Photocurrent (x10-2 arb. units) 6 4 transit time 0.0 0.2 0.4 Time (x10 0.6 0.8 1.0-5 s) Linear scale 가우시안이동 Carrier Density Distance - 24 -
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no buffer : ITO/ α-npd (100nm)/ Al 전자주입층 : ITO/ α-npd (100nm)/ LiF/ Al 정공주입층 : ITO/ PEDOT:PSS/ α-npd (100nm)/ Al 전자, 정공주입층 : ITO/ PEDOT:PSS/ α-npd (100nm)/ LiF/ Al - 26 -
LUMO - ϕ e Cathode (-) Anode (+) ϕ h + HOMO - 27 -
2.6 ev - 4.0 ev - - 4.0 ev (a) ITO Al (b) ITO Buffer (LiF) Al 4.7 ev + 5.7 ev 4.7 ev + ITO/α-NPD/Al ITO/α-NPD/LiF/Al - - - 4.0 ev 4.0 ev (c) ITO Buffer Al (d) ITO Buffer Buffer (LiF) Al 4.7 ev + (PEDOT) + 4.7 ev + (PEDOT) + ITO/PEDOT/α-NPD/Al ITO/PEDOT/α-NPD/ LiF/ Al - 28 -
4 3 단일층전자주입층정공주입층전자, 정공주입층 Current (x10-3 A) 2 1 0 0 2 4 6 Voltage (V) 8 10-29 -
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Carrier Injection Efficiency 10-3 10-4 10-5 10-6 10-7 단일층전자주입층정공주입층전자, 정공주입층 10-8 1 10 Voltage (V) - 31 -
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Carrier Density Distance Dispersive transport Photocurrent (arb. units) 0.20 0.15 0.10 0.05 0.00 0 Alq 3 전자 20 40 60 Time (µs) 80-33 -
0.15 Photocurrent (arb. units) 0.10 0.05 0.00 0 10 20 Time (s) (A) 30 40x10 Linear scale -6 Photocurrent (arb. units) 10-1 10-2 10-3 t 0.55 transit time t 1.57 (B) 10-8 10-7 10-6 10-5 Time (s) Log scale - 34 -
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Light (arb. units) 10 5 4V 5V 6V 7V (a) 0 0 20 Time (s) 40x10-6 10 0~2.0X10-5 s 영역확대 (b) Light (arb. units) 5 delay time t d 0 0 10 Time (s) 20x10-6 - 36 -
10-4 Mobility µ (cm 2 /Vs) 10-5 TOF TEL 10-6 0.5 1.0 E 1/2 (x10 3 (V/cm) 1/2 ) - 37 -
no buffer : ITO/ Alq 3 (100nm)/ Al 전자주입층 : ITO/ Alq 3 (100nm)/ LiF/ Al 정공주입층 : ITO/ PEDOT:PSS/ Alq 3 (100nm)/ Al 전자, 정공주입층 : ITO/ PEDOT:PSS/ Alq 3 (100nm)/ LiF/ Al - 38 -
2.7 ev - 4.0 ev - - 4.0 ev (a) ITO Al (b) ITO Buffer (LiF) Al 4.7 ev + 6.0 ev 4.7 ev + ITO/ Alq 3 /Al ITO/ Alq 3 /LiF/Al - - - 4.0 ev 4.0 ev (c) ITO Buffer Al (d) ITO Buffer Buffer (LiF) Al 4.7 ev + (PEDOT) + 4.7 ev + (PEDOT) + ITO/ PEDOT / Alq 3 /Al ITO/PEDOT/ Alq 3 / LiF/ Al - 39 -
2 단일층전자주입층정공주입층전자, 정공주입층 Current (x10-3 A) 1 0 0 2 4 6 Voltage (V) 8 10-40 -
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Carrier Injection Efficiency 10-1 10-2 10-3 10-4 10-5 단일층전자주입층정공주입층전자, 정공주입층 10-6 1 10 Voltage (V) - 42 -
ITO/ PEDOT:PSS/ α-npd(60nm)/ Alq 3 (70nm)/ LiF(5nm)/ Al/ 양극 + 정공주입층 (HIL) 정공수송층 (α-npd) - +- 발광층및 전자수송층 Exciton (Alq 3 ) 완충증 - 음극 + - 43 -
α NPD/Alq3 α NPD Alq3 Current (x10-3 A) 20 10 0 0 2 4 6 8 10 Voltage (V) 12 14 Lumimance (cd/m 2 ) 10 4 10 3 10 2 10 1 α NPD/Alq3 α NPD Alq3 10 0 10-1 1 2 3 4 5 6 7 8 9 10 Voltage (V) - 44 -
3 2 α NPD/Alq3 α NPD Alq3 양자효율 Q.E. (%) 1 0 10-1 10 0 10 1 10 2 10 3 Current Density (ma/cm2) ITO/ PEDOT:PSS/ α-npd(60nm)/ Alq 3 (50nm)/ LiF(5nm)/ Al/ (70nm) (90nm) (110nm) - 45 -
Current Density(mA/cm 2 ) 10 3 10 2 10 1 10 0 10-1 10-2 10-3 Alq3_50nm Alq3_70nm Alq3_90nm Alq3_110nm 10-4 2 3 4 5 6 1 2 3 4 5 6 10 Voltage (V) 10 4 Alq3_50nm Alq3_70nm Alq3_90nm Alq3_110nm Lumimance (cd/m 2 ) 10 3 10 2 10 1 10 0 2 3 4 5 6 1 Voltage (V) 2 3 4 5 6 10-46 -
4 양자효율 Q.E. (%) 3 2 Alq3_50nm Alq3_70nm Alq3_90nm Alq3_110nm 1 0 10-1 10 0 10 1 10 2 10 3 Current Density (ma/cm2) 0.4 스펙트럼 Light (arb. units) 0.3 0.2 0.1 Alq3_50nm Alq3_70nm Alq3_90nm Alq3_110nm 0.0 400 500 600 Wavelength (nm) 700 800-47 -
I ITO/ PEDOT:PSS/ α-npd(60nm)/ Alq 3 (70nm)/ LiF(5nm)/ Al/ P-I-N ITO/ anpd:fecl 3 / α-npd(60nm)/ Alq 3 (70nm)/ BCP:Cs/ Al/ 양극 + 정공주입층 (P-type) doping 정공수송층 (α-npd) - +- 발광층및 전자수송층 Exciton (Alq 3 ) 전자주입층 (N-type) doping - 음극 + - 48 -
10 3 10 2 I P-I-N Current Density (ma/cm 2 ) 10 1 10 0 10-1 10-2 10-3 10-4 10-5 1 10 Voltage (V) 10 4 I P-I-N Luminance (cd/m 2 ) 10 3 10 2 10 1 10 0 10-1 1 10 Voltage (V) - 49 -
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