CN104505463A - White light OLED (organic light emitting diode) device with double-layer light emitting layer structure - Google Patents

Abstract

The invention discloses a white light OLED device with a double-layer light-emitting layer structure. The device includes a layer of hole transport and blue light emitting layer, an electron transport and yellow-green light emitting layer, and also includes a substrate, an anode, and a hole injection layer. layer, electron injection layer and reflective metal cathode. Compared with OLED devices in which the double light-emitting layers of the traditional structure are mixed to realize white light emission, the present invention does not need to use an additional hole transport layer and electron transport layer, thereby simplifying the device structure and preparation process, and achieving double light emission of the traditional structure The effect of layer white OLED device.

Description

A white-light OLED device with double-layer light-emitting layer structure

technical field

The invention relates to the technical field of semiconductor light-emitting devices, in particular to a white light OLED device with a double-layer light-emitting layer structure.

Background technique

Organic electroluminescent devices (OLEDs) have broad applications in the fields of next-generation high-resolution new displays, special light sources for sensors, and solid-state lighting due to their excellent properties such as high luminous efficiency, rich colors, mechanical flexibility, and ultra-thin portability. prospect.

For white light OLEDs, white light is usually synthesized by three light-emitting layers (red light + green light + blue light), or double light-emitting layers (blue light + yellow-green light, blue light + yellow light, or blue light + orange light), or each light-emitting layer The guest doping forms a single white light-emitting layer in the same main light-emitting material. Generally speaking, the white light synthesized by three light-emitting layers has good color saturation and high color rendering index, but the corresponding OLED device structure and preparation process are relatively complicated. A white light device composed of a single light-emitting layer is not conducive to popularization and application due to low interaction efficiency between dopants and poor controllability of doping concentration. In contrast, the white light OLED with double-layer structure has the advantages of both.

Due to the limitation of the light-emitting characteristics of OLEDs, a certain distance (generally above 10nm) is required between the light-emitting region of the device and the electrode; on the other hand, the highest occupied orbital (HOMO) and the lowest unoccupied orbital (HOMO) of organic light-emitting materials ( LUMO) and the electrode (ITO, commonly used metal electrodes) are not ideally matched, so it is necessary to introduce a carrier transport layer (including a hole transport layer and an electron transport layer) between the electrode and the light-emitting layer. These Factors have led to the need for a white OLED device to adopt a multi-layer stacked structure. The typical structure of a white OLED device is: ITO anode/hole injection layer/hole transport layer/light emitting layer (usually 1-3 layers)/electron transport layer / Electron injection layer / Cathode. The structure of the device is very complicated, and the process control is difficult, which is not conducive to the reduction of cost and the promotion of industrialization.

Contents of the invention

The invention provides a white light OLED device with a double-layer light-emitting layer structure. The device is a double-layer structure white OLED device that integrates carrier transport and light emission, that is, the first layer adopts a blue light emission and has both Organic materials with hole transport properties to achieve effective transport of holes in organic materials and blue light emission, the second layer uses organic materials with yellow-green light emission and electron transport properties to achieve effective electron transport in organic materials Transmission and emission of yellow-green light, the blue light emitted by the first light-emitting layer and the yellow-green light emitted by the second light-emitting layer are mixed to achieve white light emission. Compared with OLED devices in which the double light-emitting layers of the traditional structure are mixed to realize white light emission, the present invention does not need to use an additional hole transport layer and electron transport layer, thereby simplifying the device structure and preparation process, and achieving double light emission of the traditional structure The effect of layer white OLED device.

The technical scheme of the present invention is as follows.

A white light OLED device with a double-layer light-emitting layer structure, the device includes a layer of hole transport and blue light emission layer and an electron transport and yellow-green light emission layer.

The device also includes a substrate, an anode, a hole injection layer, an electron injection layer, and a reflective metal cathode.

The hole transport and blue light emitting layer is used as the first light emitting layer of the device and is connected to the hole injection layer, and the electron transport and yellow-green light emitting layer is used as the second light emitting layer of the device and is connected to the electron injection layer.

Description of drawings

FIG. 1 is a schematic structural diagram of a white light OLED device with a double-layer light-emitting layer structure.

Fig. 2 is a luminescence spectrum diagram of a non-doped double-layer structure white light OLED device in an embodiment of the present invention, and the CIE color coordinates corresponding to the spectrum are (0.25, 0.34).

Fig. 3 describes the luminous efficiency of the non-doped double-layer structure white OLED device driven by different current densities in the embodiment of the present invention.

Fig. 4 describes the luminance of the non-doped double-layer structure white OLED device driven by different voltages in the embodiment of the present invention.

Fig. 5 is a luminescence spectrum diagram of a doped double-layer structure white OLED device in an embodiment of the present invention, and the CIE color coordinates corresponding to the spectrum are (0.34, 0.40).

FIG. 6 describes the luminance of the doped double-layer structure white OLED device driven by different voltages in the embodiment of the present invention.

In Figure 1: 1. Substrate; 2. Anode; 3. Hole injection layer; 4. Hole transport and blue light emitting layer; 5. Electron transport and yellow-green light emitting layer; 6. Electron injection layer; 7. Reflective metal cathode .

Detailed ways

In order to better understand the present invention, the present invention will be further described in detail below with the help of examples.

The white light OLED device with a double-layer light emitting layer structure in the embodiment of the present invention includes a substrate, an anode, a hole injection layer, a hole transport and blue light emitting layer, an electron transport and yellow-green light emitting layer, an electron injection layer and a reflective metal cathode.

Preparation and testing method of white OLED device: After cleaning the substrate and anode, the hole injection layer, the hole transport layer and the blue light emitting layer are sequentially deposited by thermal evaporation under the condition of high vacuum (better than 5×10 ^-4 Pa) , Electron transport and yellow-green light-emitting layer, electron injection layer, reflective metal cathode. The thickness of each thin film layer is monitored by a film thickness monitoring instrument, and the doping is realized by dual-source co-deposition technology. When a voltage is applied through an external circuit after the device is fabricated, a white emitting luminescent line will be observed from the anode side. The driving voltage and current of the device were measured with a voltage and current source meter, and the luminance, spectrum and CIE color coordinates of the device were measured with a spectrophotometer.

Example 1: Non-doped double-layer structure white light OLED device

The substrate is made of glass; the anode is made of ITO (indium tin oxide) film with a square resistance of 10-20Ω/□. The hole injection layer is selected from MoO ₃ , with a thickness of 2nm-10nm. The hole transport and blue light emitting layer is made of MADN material with hole transport properties and blue light emission, MADN means 2-methyl-9,10-bis(naphthalene-2-yl)anthracene, and the thickness is 40nm-90nm. The electron transport and yellow-green light-emitting layer is selected from Alq ₃ material with electron transport properties and yellow-green light emission, Alq ₃ represents 8-hydroxyquinoline aluminum, and the thickness is 15nm-60nm. The electron injection layer is made of LiF (thickness 0.5nm-1nm) or Cs ₂ CO ₃ (thickness 1nm-3nm) material. Al is used for the reflective metal cathode, and the thickness is greater than 100nm. The driving power of the external circuit can be selected from DC 3V-20V. Applying a DC voltage to the device will observe a white emitting luminous line from the anode side.

Example 2: A doped double-layer structure white light OLED device using a host-guest doping system for yellow-green light

The substrate is made of glass; the anode is made of ITO (indium tin oxide) film with a square resistance of 10-20Ω/□. The hole injection layer is selected from MoO ₃ , with a thickness of 2nm-10nm. The hole transport and blue light emitting layer is made of MADN material with hole transport properties and blue light emission, and the thickness is 40nm-90nm. The electron transport and yellow-green light-emitting layer is selected from the Alq ₃ main light-emitting material with electron transport characteristics and yellow-green light emission doped with yellow light-emitting guest material rubrene (rubrene represents 5,6,11,12-tetraphenyltetrabenzo), marked It is [Alq ₃ :rubrene], and the doping concentration is 0.3-2Wt%. [Alq ₃ :rubrene] host-guest luminescence system in the host-guest luminescent system, Alq _3, the host luminescent material, transfers part of the energy to rubrene through incomplete energy transfer, which together constitute yellow-green light emission. The thickness of [Alq ₃ :rubrene] is 6nm-30nm. The electron injection layer is made of LiF (thickness 0.5nm-1nm) or Cs ₂ CO ₃ (thickness 1nm-3nm) material. Al is used for the reflective metal cathode, and the thickness is greater than 100nm. The driving power of the external circuit can be selected from DC 3V-20V. Applying a DC voltage to the device will observe a white emitting luminescent line from the anode side.

Claims (9)

1. A white light OLED device with a double-layer light-emitting layer structure, said device comprising a layer of hole transport and a blue-light emitting layer and a layer of electron transport and a yellow-green light-emitting layer. 2. The device of claim 1, further comprising a substrate, an anode, a hole injection layer, an electron injection layer, and a reflective metal cathode. 3. The device according to claim 2, the first layer of the light-emitting layer of the hole transport and blue light emitting layer as the device is connected with the hole injection layer, and the yellow-green light emitting layer of the electron transport is used as the second layer of the device. The light emitting layer is connected with the electron injection layer. 4. The device according to claim 1 or 2, the hole transport and blue light emitting layer is made of 2-methyl-9,10-bis(naphthalene-2-yl)anthracene. 5. The device according to claim 1 or 2, the electron transport and yellow-green light-emitting layer is made of 8-hydroxyquinoline aluminum. 6. The device according to claim 1 or 2, the electron transport and yellow-green light-emitting layer are made of 8-hydroxyquinoline aluminum doped with 5,6,11,12-tetraphenyltetrabenzo, and the doping concentration is 0.3-2Wt%. 7. The device according to claim 4, the thickness of the hole transport and blue light emitting layer is 40nm-90nm. 8. The device according to claim 5, the thickness of the electron transport and yellow-green light-emitting layer is 15nm-60nm. 9. The device according to claim 6, wherein the electron transport and yellow-green light-emitting layer has a thickness of 6nm-30nm.