Organic electroluminescence device
View Patent ↗An organic electroluminescence device comprises a light transmissive substrate, a light scattering region which is disposed on the light transmissive substrate, and a light emissive layer having a luminescent point. The luminescent point is spaced from the light reflective electrode by a distance of d which satisfies the following equation: nd = a × λ 4 ( 2 + ϕ π ) wherein ϕ = tan - 1 { 2 ( n 1 k 2 - n 2 k 1 ) n 1 2 - n 2 2 + k 1 2 - k 2 2 } . λ is a wavelength of a specific light emitted from said light emissive layer. n is a refractive index of a layer disposed between the luminescent point of the light emissive layer and the light reflective electrode, with respect to the wavelength of λ. n 1 and k 1 are respectively a refractive index and an attenuation coefficient of the layer disposed between the luminescent point of the light emissive layer and the light reflective electrode, and is in contact with said light reflective electrode, with respect to the wavelength of λ. n 2 and k 2 are respectively a refractive index and an attenuation coefficient of the light reflective electrode, with respect to the wavelength of λ. a is a value that satisfies a relation of “1.28<a≦−5.56×n org /n EML +7.74” n org is a refractive index of the layer disposed which is located between the luminescent point of the light emissive layer and the light reflective electrode and which is in contact with the light emissive layer, with respect to the wavelength of λ. n EML is a refractive index of the light emissive layer with respect to the wavelength of λ.
1. An organic electroluminescence device comprising:
a light transmissive electrode,
a light reflective electrode,
an organic luminescent layer disposed between said light transmissive electrode and said light reflective electrode, said organic luminescent layer including at least one light emissive layer that contains a light emitting material,
a light transmissive substrate disposed on said light transmissive electrode away from said organic luminescent layer; and
a light scattering region disposed on an outer surface of said light transmissive substrate,
wherein at least one said light emissive layer of said organic luminescent layer has a luminescent point which is spaced from said light reflective electrode by a distance (d) defined by the following equation:
nd
=
a
×
λ
4
(
2
+
ϕ
π
)
wherein
ϕ
=
tan
-
1
{
2
(
n
1
k
2
-
n
2
k
1
)
n
1
2
-
n
2
2
+
k
1
2
-
k
2
2
}
and wherein
λ is a wavelength of a specific light emitted from said light emissive layer,
n is a refractive index of a layer disposed between the luminescent point of the light emissive layer and the light reflective electrode, with respect to the wavelength of λ,
n 1 and k 1 are respectively a refractive index and an attenuation coefficient of the layer disposed between the luminescent point of the light emissive layer and the light reflective electrode, and is in contact with said light reflective electrode, with respect to the wavelength of λ,
n 2 and k 2 are respectively a refractive index and an attenuation coefficient of the light reflective electrode, with respect to the wavelength of λ,
a is a value that satisfies a relation of “1.28<a≦−5.56×n org /n EML +7.74”,
wherein
n org is a refractive index of the layer disposed which is located between the luminescent point of the light emissive layer and the light reflective electrode and which is in contact with the light emissive layer, with respect to the wavelength of λ, and
n EML is a refractive index of the light emissive layer with respect to the wavelength of λ.
2. An organic electroluminescence device as set forth in claim 1 , wherein
said wavelength of λ is selected to be one that maximizes a product of a spectral radiant flux of photoluminescence spectrum with regard to the light emitted from the light emissive layer and the CIE's standard spectral luminous efficiency.
3. An organic electroluminescence device as set forth in claim 1 , wherein
said wavelength of λ is selected to be one that maximizes a quotient of a spectral radiant flux of photoluminescence spectrum with regard to the light emitted from the light emissive layer divided by a photon energy at the wavelength of λ.
4. An organic electroluminescence device as set forth in claim 1 , wherein
two said organic luminescent layers are disposed between said light transmissive electrode and said light reflective electrode, said light transmissive substrate being disposed on said light transmissive electrode away from said organic luminescent layer; and said light scattering region being disposed on an outer surface of said light transmissive substrate.
5. An organic electroluminescence device as set forth in claim 2 , wherein
two said organic luminescent layers are disposed between said light transmissive electrode and said light reflective electrode, said light transmissive substrate being disposed on said light transmissive electrode away from said organic luminescent layer; and said light scattering region being disposed on an outer surface of said light transmissive substrate.
6. An organic electroluminescence device as set forth in claim 3 , wherein
two said organic luminescent layers are disposed between said light transmissive electrode and said light reflective electrode, said light transmissive substrate being disposed on said light transmissive electrode away from said organic luminescent layer; and said light scattering region being disposed on an outer surface of said light transmissive substrate.