PMOLED and AMOLED 2007
전자물리특강 2007. 2학기
Changhee Lee School of Electrical Engineering and Computer Science Seoul National Univ. [email protected]
Organic Semiconductor Lab 0 Changhee Lee, SNU, Korea
전자물리특강 PMOLED and AMOLED 2007. 2학기
김기용박사 (엘리아텍) Organic Semiconductor Lab 1 Changhee Lee, SNU, Korea 전자물리특강 PMOLED vs. AMOLED 2007. 2학기 PMOLED AMOLED 공통전극 (Cathode) Scan Line Data Line
Source Gate Drain 화소전극 (Anode) Passive Matrix Active Matrix Display during frame time 구동법 Display during line time: Duty driving (Row line 선택시 점등) Static driving Row line수 증가에 따라 고휘도 높은 순간 휘도 요구 수명 수에 관계없이 고휘도 실현가능 △ Æ , ◎ Row line , 고정세화 소비전력에 불리 고해상도 가능 Row line수의 한계(현재240)
순간휘도=Row line X 휘도 요구 휘도의 구동전압 구동 저소비 전력 △ ○ 고전압구동 저전압구동
소형화 ○ 구동 IC 외장 ◎ 구동회로 Panel 내부 내장
Simple process 저온 poly Si TFT+유기 EL 소자구조 ◎ Low cost △ 복잡한 Process Cost Low initial investment High Fab. Cost 권장혁박사 (삼성SDI) Organic Semiconductor Lab 2 Changhee Lee, SNU, Korea
전자물리특강 Grey Scale Control: PWM 2007. 2학기
김기용박사 (엘리아텍) Organic Semiconductor Lab 3 Changhee Lee, SNU, Korea 전자물리특강 Grey Scale Control: PAM 2007. 2학기
김기용박사 (엘리아텍) Organic Semiconductor Lab 4 Changhee Lee, SNU, Korea
전자물리특강 PMOLED Driving 2007. 2학기
김기용박사 (엘리아텍) Organic Semiconductor Lab 5 Changhee Lee, SNU, Korea 전자물리특강 AMOLED : Panel Structure 2007. 2학기
•Matrix 전극 사이에 switching TFT →OLED pixel의독립구동가능 •Frame time 동안 emission 가능 → EL 구동주파수 감소 •High resolution, Large size panel 가능 •해결과제: TFT 불균일성 및 전원 line 저항에 의한 voltage drop :
Organic Semiconductor Lab 6 Changhee Lee, SNU, Korea
전자물리특강 AMOLED vs. AMLCD 2007. 2학기
AMOLED AMLCD
김기용박사 (엘리아텍) Organic Semiconductor Lab 7 Changhee Lee, SNU, Korea 전자물리특강 AMOLED: Sony PDA – CLIE PEG-VZ90 2007. 2학기
http://www.sony.net/SonyInfo/News/Press/200409/04-048E/
Organic Semiconductor Lab 8 Changhee Lee, SNU, Korea
전자물리특강 Sony PDA : OLED vs LCD 2007. 2학기
Reference : Sony’s equal level LCD Sony’s OLED display display (transmissive / reflective combined type) Display Size 9.7cm (3.8-inch) (same) Number of Dots 480xRGBx320 (HVGA) (same) Dot Pitch 56µm×168µm (same) Number of colors 262,144 colors (same) Brightness 150cd per square meter 55cd per square meter 94.7mm(horizontal) × 77.2mm(vertical) × 65.0mm(horizontal) × 96.5mm(vertical) × External 2.14mm(thickness) (thickness including 3.49mm(thickness) (thickness includes Dimensions the panel only and not including the the panel + backlight) protruding portions) Response Time ~ 0.01 Mil. sec. ~ 16 Mil. sec. (at 25ºC, ON) Color Gamut Approx. 100% Approx. 40% (NTSC* Ratio) Vertical: Approx. 180 degrees Vertical: Approx. 130degrees Viewing Angle Horizontal:Approx.180degrees Horizontal: Approx. 125 degrees Contrast Ratio Approx. 1000 : 1 Approx. 100 : 1 (in darkness) http://www.sony.net/SonyInfo/News/Press/200409/04-048E/
Organic Semiconductor Lab 9 Changhee Lee, SNU, Korea 전자물리특강 I-V-L characteristics of OLED 2007. 2학기
Organic Semiconductor Lab 10 Changhee Lee, SNU, Korea
전자물리특강 Driving Technologies for AMOLED 2007. 2학기
White Balance • Different data swing range • Different size of driving TFT • Different illumination time of each colors • CCM (Color Changing Media) Different efficiency to luminescence
25 . Eff
20 Red Green 15 Blue
10
5
0 Lum. 0 200 400 600 800 1000
Organic Semiconductor Lab 11 Changhee Lee, SNU, Korea 전자물리특강 TFT Characteristics 2007. 2학기 Transfer Curve Output Curve
PMOS NMOS PMOS NMOS • Linear region Ioff 영역 : Vg=0V WC ox VD I D = μ (VG −VT − )VD Sub threshold 영역: 0V
Organic Semiconductor Lab 12 Changhee Lee, SNU, Korea
전자물리특강 AMOLED Driving 2007. 2학기 VDD • Active-matrix 방식에서 각 화소마다 OLED 전류 공급원이 필요. • 2 TFT + 1 Cap이 가장 단순한 구조
Driving Vcontrol 1 W 2 TR I = μC (V −V ) • Voltage-based OLED ox Data th I 2 L • Current-based OLED OLED RGB Light 20 OLED VGS=20V
Light ∝ IOLED × Efficiency 15
1000 40000 A
Current Density μ 15 Luminance , ΔVth
) 800 10 2
30000 DS Luminance (cd/m Luminance OLED I 600 20000 5 10 400 2 ) 10000
Current Density (mA/cm 5 200 0 0 0 0 2 4 6 8 10 0 5 10 15 20 Voltage (V) VDS, V
Organic Semiconductor Lab 13 Changhee Lee, SNU, Korea 전자물리특강 Brightness Nonuniformity 2007. 2학기 Standard Two Transistor OLED Pixel Four Transistor OLED Pixel
Organic Semiconductor Lab Sarnoff 14 Changhee Lee, SNU, Korea
전자물리특강 AMOLED Pixel Circuit 2007. 2학기
• Equivalent OLED Current (IOLED) by the same Vdata regardless of TFT
• 전압구동방식: 인가된 Vdata 에의해IOLED가결정됨
• 전류구동방식: 인가된 Idata 에의해IOLED가결정됨(인가된 Idata 에의해적절한Vgate 값이 정해짐)
Organic Semiconductor Lab 15 Changhee Lee, SNU, Korea 전자물리특강 AMOLED : Programming Technologies 2007. 2학기
Organic Semiconductor Lab 16 Changhee Lee, SNU, Korea
전자물리특강 Backplanes for OLEDs 2007. 2학기 COLUMN DRIVERS (DATA VOLTAGE)
Poly-Si TFT a-Si TFT OTFT Type CMOS NMOS PMOS Performance :
ROW DRIVERS Mobility Very good OK for PHOLED OK?
(PIXEL SELECT SIGNAL) SELECT (PIXEL Leakage OK Very good OK Stability Good OK Issue Uniformity Issue Issue
Data Line Power Line Manufacturability Maturing Excellent N/A VDATA VDD Scan Line # of Interconnercs Data? scan +data scan +data Cost >Medium Medium Low C Driving Plastic Under Good Excellent Switching TR TR compatibility development OLED RGB Light M. Hack, IMID’03
Organic Semiconductor Lab 17 Changhee Lee, SNU, Korea 전자물리특강 LTPS vs a-Si TFTs 2007. 2학기 LTPS –TFT (ELA) a-Si –TFT – Expensive process (~2 x a-Si TFT) – Low mobility (< 1 cm2/Vs) – Poor Uniformity – Operational instability (V shift) – Max out at 4th Gen Tools th 1.E-02 1.E-03 1.E-04 1.E-04 1.E-05 1.E-05 ] 1.E-06 1.E-06 1.E-07 1.E-07 1.E-08 1.E-08 1.E-09 1.E-09 1.E-10 1.E-10 Drain Current [A Current Drain 1.E-11 1.E-11 1.E-12 1.E-12 1.E-13 1.E-13 1.E-14 1.E-14 -20 -15 -10 -5 0 5 10 15 20 -20 -15 -10 -5 0 5 10 15 20 Gate Voltage [V] LTPS TFT a-Si TFT Source Drain Passivation Interlayer Source Drain Insulator
Gate a-Si:H Gate Insulator n+ poly-Si n+ poly-Si Gate Insulator Blocking Layer Gate
LDD: n- poly-Si Glass Glass
Organic Semiconductor Lab 18 Changhee Lee, SNU, Korea
전자물리특강 LTPS non-uniformity 2007. 2학기
Non-uniformity problem of ELA (Excimer Laser Annealed) Poly-Si TFT •XeXl (λ=308 nm) ELA: 가장 일반적인 Si 박막 결정화 방법 • Laser energy fluctuation Æ non-uniform crystallization
Æ non-uniform VTH and μ of poly-Si TFTs Æ non-uniform brightness
Organic Semiconductor Lab 19 Changhee Lee, SNU, Korea 전자물리특강 Possibility of a-Si TFT 2007. 2학기
• Required Compensation of Vth Shifting • Small Size High Resolution is very difficult (Low Mobility) • Temp. Stability ?
Organic Semiconductor Lab 20 Changhee Lee, SNU, Korea
전자물리특강 Threshold voltage shift of a-Si TFT 2007. 2학기
• Long term bias stress leads to threshold voltage shift (ΔVth). μ W I = eff Cα −1 (V −V )α OLED α i L GS T 1 ⎛ ⎞α 7 ⎜ ⎟ β I DS ⎛ t ⎞ ΔVT = ⎜ ⎟ ⎜ ⎟ 6 ⎜ W ⎟ τ ⎜ μC ⎟ ⎝ ⎠ 5 ⎝ i 2L ⎠ Power Law Model 4
-Shift (V) 3 T Vth V 2 Stretched Expo. Model ⎡ ⎛ β ⎞⎤ 1 ⎜ ⎛ t ⎞ ⎟ ΔVT =(VG −VT0)⎢1−exp −⎜ ⎟ ⎥ ⎢ ⎜ ⎝τ ⎠ ⎟⎥ 0 ⎣ ⎝ ⎠⎦ 0 102030405060 Stress Time (Hours) Source Drain a-Si:H layer
a-SiNx:H layers metallization Gate n+μc-Si:H layers A. Nathan, IMID’05 substrate Organic Semiconductor Lab 21 Changhee Lee, SNU, Korea