# US 2014/0191226 A1 · Organic electroluminescent element

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- Number: US 2014/0191226 A1
- Document ID: US20140191226A1
- Status: Published application
- Kind: A1
- Application number: 14/238,368
- Filed: 2012-08-09
- Published: 2014-07-10
- Earliest claimed: 2011-08-12
- Assignees: Panasonic Corporation
- Inventors: Kazuyuki Yamae
- Web page: https://patentgrep.com/patent/US20140191226A1

## CPC

- H10K 50/131: {with spacer layers between the electroluminescent layers}
- H10K 50/125: specially adapted for multicolour light emission, e.g. for emitting white light
- H10K 50/19: Tandem OLEDs
- H10K 50/852: comprising a resonant cavity structure, e.g. Bragg reflector pair
- H10K 2102/351: {Thickness}
- H10K: ORGANIC ELECTRIC SOLID-STATE DEVICES

## Abstract

An organic electroluminescent element having a structure in which a plurality of light-emitting layers stacked between a first electrode with light reflectivity and a second electrode with optical transparency while one or more interlayers with a light transmissive property are interposed between the plurality of light-emitting layers. A first interlayer is formed as the interlayer closest to the first electrode. A first light-emitting unit is formed between the first electrode and the first interlayer to include a first light-emitting layer which has a first light-emitting source, and a second light-emitting unit is formed on a side of the first interlayer close to the second electrode to include a second light-emitting layer which has a second light-emitting source. The first interlayer is a semi-transmissive layer which has both of optical transparency and light reflectivity and has a total light absorption ratio of 10% or less.

## Claims

### Claim at position 1

1-9. (canceled)

### Claim 10

An organic electroluminescent element with a structure in which a plurality of light-emitting layers are stacked between a first electrode with light reflectivity and a second electrode with optical transparency while one or more interlayers with a light transmissive property are interposed between the plurality of light-emitting layers,
wherein:
the one or more interlayers includes a first interlayer closest to the first electrode;
a first light-emitting unit is formed between the first electrode and the first interlayer to include a first light-emitting layer which is one of the plurality of light-emitting layers and has a first light-emitting source;
a second light-emitting unit is formed on a side of the first interlayer close to the second electrode to include a second light-emitting layer which is one of the plurality of light-emitting layers and has a second light-emitting source; and
the first interlayer is a semi-transmissive layer which has both of optical transparency and light reflectivity and has a total light absorption ratio of 10% or less,
wherein
the organic electroluminescent element has a characteristic which satisfies relations of:
0.9*X≦D1(λ1)≦1.1*X;
0.1*Y≦D3(λ2)≦2.0*Y; and
0.8*Z≦D1(λ1)+D2(λ1)≦1.2*Z,
wherein:
λ1 represents a weighted-averaged emission wavelength of the first light-emitting source;
λ2 represents a weighted-averaged emission wavelength of the second light-emitting source;
D1(λ1) represents an optical path length defined as a product of a refractive index at the wavelength λ1 and a thickness with regard to a medium situated between the first light-emitting source and the first electrode;
D2(λ1) represents an optical path length defined as a product of a refractive index at the wavelength λ1 and a thickness with regard to a medium situated between the first light-emitting source and the semi-transmissive layer;
D3(λ2) represents an optical path length defined as a product of a refractive index at the wavelength λ2 and a thickness with regard to a medium situated between the second light-emitting source and the semi-transmissive layer; and
X, Y, and Z satisfy equations of X=φ1(λ1)*(λ1/4π)+λ1*l/2, Y=(φ2(λ2)*(λ2/4π)+λ2*m/2, and Z=φ1(λ1)+φ2(λ1)*(λ1/4π)+λ1*n/2, respectively,
wherein:
l, m, and n are integers of 0 or more, respectively;
φ1 represents a phase shift expressed by a following formula (I) which occurs at the first electrode;
φ2 represents a phase shift expressed by the following formula (I) which occurs at the semi-transmissive layer;
φ1(λ1) represents a phase shift of light emitted from the first light-emitting source which arises from reflection at the first electrode;
φ2(λ1) represents a phase shift of light emitted from the first light-emitting source which arises from reflection at the semi-transmissive layer;
φ2(λ2) represents a phase shift of light emitted from the second light-emitting source which arises from reflection at the semi-transmissive layer; and
the formula (1) is:
ϕ
=
tan
-
1

{
2

(
n
1

k
2
-
n
2

k
1
)
n
1
2
-
n
2
2
+
k
1
2
-
k
2
2
}
,
(
1
)
wherein:
n1 and k1 representing a refractive index and an extinction coefficient of a layer in contact with a reflection layer, respectively;
n2 and k2 representing a refractive index and an extinction coefficient of the reflection layer, respectively; and
n1, n2, k1, and k2 are functions of λ.

### Claim 11 (depends on 10)

The organic electroluminescent element as set forth in claim 10, wherein the semi-transmissive layer has a total light reflectance of 10% or more but less than 50%.

### Claim 12 (depends on 10)

The organic electroluminescent element as set forth in claim 10, wherein the semi-transmissive layer contains Ag or an alloy of Ag as a main component.

### Claim 13 (depends on 10)

The organic electroluminescent element as set forth in claim 10, wherein l is not less than 1 in the equation for X.

### Claim 14 (depends on 10)

The organic electroluminescent element as set forth in claim 10, wherein l, m, and n are not less than 1, respectively in the equations for X, Y, and Z.

### Claim 15 (depends on 10)

The organic electroluminescent element as set forth in any one of claim 10, further comprising a light diffusion layer on an outcoupling face of the second electrode.

### Claim 16 (depends on 15)

The organic electroluminescent element as set forth in claim 15, wherein an optical path length Dd(λ1) between a face of the light diffusion layer close to an outcoupling side and the semi-transmissive layer at the wavelength λ1 is ten times or more as long as an emission wavelength λ1 of the first light-emitting unit.

### Claim 17 (depends on 15)

The organic electroluminescent element as set forth in claim 15, further comprising a substrate with optical transparency on the outcoupling face of the second electrode,
wherein
the substrate has a refractive index of 1.55 or more.