15. OLED——全彩方式
方式 RGB 3色排列 白光+彩色滤光片(CF) 蓝光+色变换层(CCF)
图示
R G B R G B R G B
原理 RGB三色发光材料独立 以白光为背光,再加彩 以蓝光为光源,经色变
发光 色滤光片 换层将光转为RGB三
色
发光效率 *** * **
开发重点 ?RGB精确定位 ?白光的光色纯度 ?色变换材料的光色纯
?高纯度长寿命红光材料 ?提高光线使用率 度与效率
的开发 (CF会遮挡光线) ?提高红光转换效率
50. Characteristics Variation of TFT
Vdd
W
Ioled = μ ? COX ? ? (VGS ?Vth )
Scanline 1 2
2 L
TFT1
TFT2 Variation of μ or Vth between pix
can result in non-uniform brightn
in AM-OLED.
Cs OLED
Dataline
51. Digital Driving Scheme: Area Period
One pixel with 3 bit gray level
Vdd
Scanline
Level 0 Level 1
TFT1
TFT2
Cs OLED Level 2 Level 3
Level 4
52. Digital Driving Scheme: Time Period
One pixel with 5 bit gray level
Voltage One pixel turn-on period
16 8 4 2 1
5V
Time
53. Comparison of Driving Scheme
Principle Advantag Disadvantag Applicatio
e
Digital 1.Area period Precise 1.Complex data Smallnsize
e
gray level color driver with low
Drivin
g 2.Time period reproductio 2.Complex resolution
n
gray level process
Sche
Analo Divided
me Reduced Non-uniformity Small to
g voltage data driver of gray level medium
gray level due to threshold size with
Drivin voltage change high
g resolution
Sche
me
54. 2 Transistors (2-T) Pixel Circuit
Vdd
Scanline
TFT1
TFT2
Cs OLED
Dataline
Display
Area
? Variations of threshold voltage(Vth) and
mobility(μ) can affect the output current
of TFT2.
Variation of gray-scale
58. Variation of Drain Current
Modified 4-transistor pixel 12.3%
12
Conventional 2-transistor pixel
Drain Current Variation (%)
10
8.4%
8
6 5.9%
4 3.5% 3.17%
2
0.9% 0.68%
0.59% 0.2%
0.02%
0
0.5 0.7 0.9 1.1 1.3
Threshold Voltage (V)
59. Comparison of Analog Driving Scheme
Advantage Disadvantage
Voltag 1.Simple architecture of 1. Non-uniformity of gray
e driver. level due to threshold
2.Compatible with LCD voltage change.
Drivin driver.
g 3.Simple pixel circuit.
Schem 4.High aperture ratio.
e
Curren 1.Control the brightness 1. Complex driver circuit.
of 2. Complex pixel circuit.
t
OLED directly. 3. Low aperture ration
Drivin 2.Great tolerance of
g variations of Vth and
Schem mobility.
e