23.3 Light-Emitting Diodes
647
Fig. 23.4 Spectral
coverage by various
semiconductor materials.
Reprinted with permission
from [574], ©1981 Wiley
• green–blue: SiC, now GaN, (In,Ga)N
• violet: GaN
• ultraviolet: (Al,Ga)N
23.3.3 Efficiencies
External Quantum Efficiency
The external (or total) quantum efficiency η ext is the number of photons emitted from the device per
injected electron–hole pair. It is given by the product of the internal quantum efficiency η int and the
light extraction efficiency χ ex :
η ext = χ ex η int .
(23.5)
In a commercial device another factor, the packaging efficiency may enter which accounts for photon
loss due to packaging the LED dice into its housing.
Wall-Plug Efficiency
The wall-plug efficiency η w is the power conversion ratio of the electrical power and the light output
P out ,
η w =
P out
I V
=
ω
e V
η ext .
(23.6)
647
Fig. 23.4 Spectral
coverage by various
semiconductor materials.
Reprinted with permission
from [574], ©1981 Wiley
• green–blue: SiC, now GaN, (In,Ga)N
• violet: GaN
• ultraviolet: (Al,Ga)N
23.3.3 Efficiencies
External Quantum Efficiency
The external (or total) quantum efficiency η ext is the number of photons emitted from the device per
injected electron–hole pair. It is given by the product of the internal quantum efficiency η int and the
light extraction efficiency χ ex :
η ext = χ ex η int .
(23.5)
In a commercial device another factor, the packaging efficiency may enter which accounts for photon
loss due to packaging the LED dice into its housing.
Wall-Plug Efficiency
The wall-plug efficiency η w is the power conversion ratio of the electrical power and the light output
P out ,
η w =
P out
I V
=
ω
e V
η ext .
(23.6)