16. Semiconductor Photon Sources
Electroluminescence devices
Light-emitting diode
Semiconductor Laser diode (LED) Semiconductor
optical amplifier (SOA)
(LD)
Evolution of Lighting to LEDs
LUX (lx)?, LUMEN (lm)?, CANDELA (cd)?
Table 19-1
Radiometry and Photometry
radiometry photometry
watt (W) W/
2lumen (lm) l (l )
Radiant flux : I di
: Luminous flux W/m
2W/sr W/(sr
.m
2)
lux (lx)
candela (cd) Cd/m
2Irradiance : Radiant intensity : Radiance :
: illuminance
: luminous intensity
: luminance
CIE (International Commission on Illumination) Luminous Efficiency curve
555 nm Radiant flux
of 1 Watt at 555 nm is the luminous flux
Luminous Efficiency curve
the luminous flux of 685 lm (lumen)
Radiant flux
of 1 Watt at 610 nm is
th l i fl
610 nm Luminous efficiency V(λ)
the luminous flux of 342.5 lm (lumen)
610 nm
Photometric unit
685 x V(λ) x radiometric unit = 685 x V(λ) x radiometric unit
Ex) 100 lm/W means, )
At Green ~ 100/680 ~ 15 % At Blue/Red ~ 100/340 ~ 30%
(If QE ~ 100%)
Semiconductor Light for Visualization
Osram SID 2004
Semiconductor Light for Illumination
Osram SID 2004
LED Roadmap for Automotive
Osram SID 2004
LED characteristics
+ -
Forward voltage for LEDs
증명 !
Exercise 17 1-3
Exercise 17.1-3
LED characteristics
Internal efficiency Internal efficiency
Extraction efficiency
External efficiency
Power-conversion efficiency (or, wall-plug efficiency)
[ ]
power ext ext
P h
for h eV
IV eV
η = = η ν ≈ η ν ≈
Luminous efficiency (lm/W)
{ } { }
/
685 ( ) 685 ( )
lm W ext
P h
V V
IV eV
η = × λ = η ν × λ
Luminous efficiency (lm/W)
Extraction efficiency
( i )
c
d
θ
φ φ
∫
0( )
2
2 sin 2 (1 cos )
c
c
A r rd
r
π φ φ
π θ
=
= −
∫
4
21
extract
A η r
= π
2
1 (1 cos ) 2
1 (1 1 1/ )
c
n θ
= −
= − −
2
(1 1 1/ ) 2
1 4
n
n
= − −
≈
1.9 % for 3.6 (GaAs)
extract
n
η ≈ =
4n
4 % for 2.5 (GaN)
extract
≈ n =
Extraction efficiency
Spatial pattern of emitted light
Extraction efficiency
Photonic Crystal-LEDs
Baba
Limited by surface recombination
Good scheme!!!
Limited by surface recombination
Good scheme!!!
Lumiled
100 um device size achievable.
Several layer of PC for extraction.
Good internal quantum efficiency N d d ( 90%)
100 um device size achievable.
Several layer of PC for extraction.
Good internal quantum efficiency N d d ( 90%)
Needed (>90%).
Multiple pass limits device size (~10um).
Small volume needed.
Not so good for lighting Needed (>90%).
Multiple pass limits device size (~10um).
Small volume needed.
Not so good for lighting Not so good for lighting.
Surface recombination limited
Surface recombination limited.
Not so good for lighting.
Surface recombination limited
Surface recombination limited.
Noda
OLED (Organic Light Emitting Diode)
OLED는 유기물(단분자/저분자 또는 고분자) 박막에 양극과 음극을 통하여 주입된 전자와 정공이 재결합하 여 여기자를 형성하고, 형성된 여기자로 부터의 에너지에 의해 특정한 파장의 빛이 발생하는 현상을 이용한 자체 발광형 디스플레이 소자.
• 자체 발광형. (어두운 곳이나 외부의 빛이 들어 올 때도 시인성이 좋은 특성을 갖음.)
• 넓은 시야각 (일반 브라운관 같이 바로 옆에서 보아도 화질이 변하지 않음 )
• 넓은 시야각. (일반 브라운관 같이 바로 옆에서 보아도 화질이 변하지 않음.)
• 빠른 응답속도. 텔레비전 화면 수준의 동화상 재생에도 자연스러운 영상을 표현. (LCD의 약 1,000배 )
• 초박, 저전력. 백라이트라 필요 없기 때문에 저소비전력(약 LCD의 ½ )과 초박형(약 LCD의 1/3 )이 가능.
OLED Structure
• 100 – 500 nanometers thick
Organic LEDs (OLEDs)
Discovered by Ching Tang and Van Slyke at Eastman Kodak in 1987.
OLED 제품
But, OLEDs are …
• Life time – blue organics have shorter life time compared to red and green
• Manufacturing - expensive g p
• Moisture can damage OLED
Resonant-cavity LEDs (RC-LEDs)
RCLED spectrum
Semiconductor optical amplifiers (SOA)
forward-biased heavily doped
p-n junction
