# US 10,770,686 B2 · Organic light emitting device which emits white light

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- Number: US 10,770,686 B2
- Document ID: US10770686B2
- Status: Granted
- Kind: B2
- Application number: 15/762,245
- Filed: 2016-08-11
- Published: 2018-10-18
- Granted: 2020-09-08
- Earliest claimed: 2015-09-22
- Assignees: Cambridge Display Technology Limited
- Applicants: Cambridge Display Technology Limited
- Inventors: Philip Benzie; Colin Baker; Adam Strevens; William Young
- Web page: https://patentgrep.com/patent/US10770686B2

## CPC

- H10K 50/13: comprising stacked EL layers within one EL unit
- H10K 50/828: Transparent cathodes, e.g. comprising thin metal layers
- H10K 50/852: comprising a resonant cavity structure, e.g. Bragg reflector pair
- H10K 50/818: Reflective anodes, e.g. ITO combined with thick metallic layers
- H10K 2102/3026: {Top emission}
- H10K: ORGANIC ELECTRIC SOLID-STATE DEVICES

## Abstract

An organic light emitting device which emits white light in use, comprising a reflective anode (3), a first light emitting layer (9) which emits red light located over said anode, a second light emitting layer (11) which emits blue light and green light located over said first light emitting layer, and a cathode structure located over said second light emitting layer comprising a first semi-reflecting layer (15) and a second semi-reflecting layer (21) with a layer (19) of light transmissive material between the first and second semi-reflecting semi-transparent layers, the distance between the reflective anode (3) and the first semi-reflecting semi-transparent layer (17) being selected to form a micro-cavity which enhances blue light emission and red light emission from the device, and the distance between the reflective anode (3) and the second semi-reflecting semi-transparent layer (21) being selected to enhance green light emission from the device.

## Claims

### Claim 1

An organic light emitting device which emits white light, comprising:
a reflective anode,
a first light emitting layer which emits red light located over said reflective anode,
a second light emitting layer which emits blue light and green light located over said first light emitting layer, and
a cathode structure located over said second light emitting layer comprising:
a first semi-reflecting semi-transparent layer; and
a second semi-reflecting semi-transparent layer with a layer of light transmissive material between the first and second semi-reflecting semi-transparent layers,
wherein a first distance between the reflective anode and the first semi-reflecting semi-transparent layer is selected to form a first micro-cavity which enhances blue light emission and red light emission from the organic light emitting device, and
wherein a second distance between the reflective anode and the second semi-reflecting semi-transparent layer is selected to form a second micro-cavity which enhances green light emission from the organic light emitting device.

### Claim 2 (depends on 1)

The organic light emitting device as claimed in claim 1 in which the reflective anode is carried by a substrate, and the white light is emitted out of the organic light emitting device through the cathode structure.

### Claim 3 (depends on 1)

The organic light emitting device as claimed in claim 1 in which the first distance between the reflective anode and the first semi-reflecting semi-transparent layer is in a range 330 to 370 nm.

### Claim 4 (depends on 3)

The organic light emitting device as claimed in claim 3 in which the first distance between the reflective anode and the first semi-reflecting semi-transparent layer is between 345 and 355 nm.

### Claim 5 (depends on 3)

The organic light emitting device as claimed in claim 3 in which a refractive index of the first light emitting layer is in a range 1.55 to 1.67.

### Claim 6 (depends on 5)

The organic light emitting device as claimed in claim 5 in which a refractive index of the second light emitting layer is in a range 1.55 to 1.67.

### Claim 7 (depends on 2)

The organic light emitting device as claimed in claim 2 in which the first distance between the reflective anode and the first semi-reflecting semi-transparent layer is in a range 330 to 370 nm.