CN108807712B

CN108807712B - O L ED top light-emitting device and display device

Info

Publication number: CN108807712B
Application number: CN201810875426.XA
Authority: CN
Inventors: 陈文勇
Original assignee: Shanghai Yaoyi Electronic Technology Co ltd
Current assignee: Shanghai Yaoyi Electronic Technology Co ltd
Priority date: 2018-08-03
Filing date: 2018-08-03
Publication date: 2020-08-04
Anticipated expiration: 2038-08-03
Also published as: CN108807712A

Abstract

the invention discloses an O L ED top light-emitting device and a display device, which consists of a substrate, an anode, a cathode and an organic layer sandwiched between the anode and the cathode, wherein the organic layer comprises at least one hole transport layer contacted with the anode, at least one light-emitting layer and at least one electron transport layer contacted with the cathode, the electron transport layer contains a compound with an O ═ X structure, X is selected from carbon atoms, silicon atoms, sulfur atoms or phosphorus atoms, the cathode comprises silver and/or silver alloy with the mass content of not less than 95 percent, the compound with the O ═ X structure is used as the electron transport layer, the interaction between the compound and metallic silver is good, metal atoms are uniformly and stably formed on the electron transport layer, the film layer is thin, the resistance is low, and good light transmittance and conductivity are obtained.

Description

O L ED top light-emitting device and display device

Technical Field

the invention belongs to the technical field of display, and relates to an O L ED top light-emitting device and a display device.

Background

in the prior art, an organic electroluminescent device (abbreviated as O L EDs) comprises a substrate, an anode, a cathode and an organic layer sandwiched between the anode and the cathode, wherein a top-emitting device refers to a device in which light is emitted from the side far from the substrate, the anode can be far from the substrate, the cathode can be far from the substrate, the most commonly used cathode is far from the substrate, and the light is emitted from the cathode, and the light transmittance and the conductivity of the cathode are required to be good.

however, since the cathode of O L EDs is formed by vacuum heating silver deposition, and the metallic silver is subjected to atomic aggregation during the deposition process, thereby forming many silver "islands", resulting in poor conductivity, and another one or more metallic elements such as Mg or Ga are usually doped with the metallic silver, but the metallic element is poor in conductivity, and can inhibit silver aggregation, but light absorption is severe, and light transmittance is affected, and it is generally required that the silver weight ratio in the silver alloy is less than 99%, and more preferably less than 95%, but as the silver alloy ratio becomes smaller, conductivity is correspondingly poor, and thus, cathode conductivity and light transmittance are very problematic.

Disclosure of Invention

in order to overcome the above-mentioned drawbacks of the prior art, an object of the present invention is to provide an O L ED device and a display device, in which an organic layer in contact with a light-emitting side electrode (normally a cathode, and an anode in an inverted structure) of top emission contains a compound having an O ═ X structure, where X includes a carbon atom, a silicon atom, a sulfur atom, or a phosphorus atom, and the light-emitting side electrode uses metallic silver or an alloy thereof having a silver weight ratio of more than 95%, thereby obtaining good conductivity and light transmittance.

The above object of the present invention is achieved by the following technical solutions:

in a first aspect, an oeld top emission device comprises a substrate, an anode, a cathode, and an organic layer sandwiched between the anode and the cathode,

The substrate is arranged on one side of the anode;

The organic layer includes: at least one hole transport layer in contact with the anode, at least one light emitting layer, and at least one electron transport layer in contact with the cathode, and the electron transport layer contains a compound of the structure O ═ X, where X is selected from one of a carbon atom, a silicon atom, a sulfur atom, or a phosphorus atom;

The cathode is selected from metals and/or alloys thereof.

Further, the cathode is selected from silver and/or silver alloy with the mass content of not less than 95%.

Further, the substrate comprises a glass plate or a plastic plate.

Further, the anode is composed of at least one reflective metal layer and a conductive metal layer; the reflecting metal layer comprises Ag or Ag alloy, and the thickness of a single layer is 50-150 nm; the conductive metal layer comprises Indium Tin Oxide (ITO) or Indium Gallium Zinc Oxide (IGZO), and the thickness of the conductive metal layer is 5-30 nm; in some preferred embodiments, the anode is selected from Ag/ITO, Ag alloy/ITO, or Ag/IGZO.

further, the hole transport layer comprises an amine or carbazole-containing compound, the thickness is 30-250 nm, preferably 100-250 nm, in some preferred embodiments, due to the difference in light thickness of different colors, in order to increase the hole injection capability and improve the device effect, a single-layer or multi-layer material is adopted, a hole injection layer with the thickness of 0.5-30 nm is firstly prepared on the anode, then a hole transport layer with the thickness of 5-200 nm, preferably 50-200 nm, is prepared on the hole injection layer, and then an electron blocking layer with the thickness of 5-100 nm is prepared on the hole transport layer, the hole injection layer can adopt a single P-type material such as HATCN, F4-TCNQ or NOVA L ED company, and can also adopt the P-type material to be mixed with the amine or carbazole-containing compound, wherein the mass ratio of the P-type material is not more than 50%, preferably not more than 10%, and the hole transport layer comprises the amine or carbazole-containing compound, preferably comprises one or more than two of the following chemical structures:

Further, the electron blocking layer includes a compound containing a carbazole group or an aniline group.

Further, the color of the light-emitting layer at least comprises one of red light, green light, blue light, white light and yellow light. The light-emitting layer is composed of a host material and an object light-emitting material, the object light-emitting material is selected from one of a fluorescent material, a phosphorescent material or a thermal retardation fluorescent material, and the thickness of the object light-emitting material is 10-50 nm, preferably 20-40 nm.

Further, when the guest luminescent material is selected from a fluorescent material, the host material is selected from a group consisting of anthracene, perylene, and other condensed ring compounds, preferably a compound including one or two or more of the following chemical structures:

The fluorescent material is selected from aromatic amine or aromatic alkene compounds, preferably compounds containing one or more than two of the following chemical structures:

And the mass ratio of the guest to the fluorescent material to the host material is 1-5: 50.

Further, when the guest light emitting material is selected from phosphorescent light emitting materials, the host material is selected from one or more mixtures containing at least a carbazole unit or an azaaromatic ring unit, and preferably a compound containing one or more of the following chemical structures:

The phosphorescent luminescent material is selected from compounds comprising one or more than two of the following chemical structures:

And the mass ratio of the phosphorescent material to the main material is 2-15: 100.

Further, when the guest luminescent material is selected from a thermal retardation fluorescent material, the host material is selected from aromatic amine and carbazole, the thermal retardation fluorescent material is selected from a compound containing a carbazole unit or a nitrogen-containing aromatic ring unit, and the mass ratio of the thermal retardation fluorescent material to the host material is 1-6: 20.

Further, a hole blocking layer with the thickness of 5-20 nm is included between the light emitting layer and the electron transport layer, and is selected from substituted or unsubstituted pyrimidine, substituted or unsubstituted pyrazine, substituted or unsubstituted pyridazine or substituted or unsubstituted triazine pyrimidine, and preferably a compound containing one or more than two of the following chemical structures:

further, the electron transport layer further comprises one of an alkali metal, an alkaline earth metal or a rare earth metal, and the mass percentage is not higher than 50%, preferably not higher than 25% and not higher than 15%, and more preferably one of L i, Ca, Yb or Mg, and the interaction between the cathode and the electron transport layer is small due to the low metal content, so that a high-quality cathode metal film layer can be obtained.

Furthermore, the electron transport layer further comprises one of an alkali metal compound, an alkaline earth metal compound and a rare earth metal compound, and the mass percentage of the electron transport layer is 20-80%.

Further, the electron transport layer comprises one or more compounds selected from the group consisting of the following structures:

Still further, the electron transport layer comprises one or two or more of the following compounds:

Further, the cathode is selected from one of alkali metal, alkaline earth metal or rare earth metal; more preferably silver and/or a silver alloy having a silver content of not less than 95% by mass.

Still further, the cathode has a transmittance of greater than 37% at a wavelength of 460nm, preferably greater than 43% at a wavelength of 460 nm; the resistance of the cathode is <20 Ω, preferably <10 Ω.

Further, the cathode surface also includes a cap layer.

in a second aspect of the invention, an O L ED display device comprises the above O L ED top emission device.

The principle of the invention is as follows: ag of the cathode interacts with a compound having an O ═ X structure in the electron transport layer, as shown in the following formula.

Compared with the prior art, the invention has the beneficial effects that: the traditional organic electroluminescent device adopts a vacuum evaporation high-proportion metal silver film layer, and the cathode resistance is high and the conductivity is poor due to silver accumulation; the compound with the structure of O ═ X is adopted as the electron transport layer, the compound and the metal silver have good interaction, so that metal atoms can be uniformly and stably formed on the electron transport layer, the film layer is thin, the resistance is low, and good light transmission and conductivity can be obtained.

Drawings

FIG. 1 is a schematic diagram of a conventional O L ED light emitting device, wherein 1-anode (ITO), 2-hole transport layer (HT L), 3-emitting layer (EM L), 4-electron transport layer (ET L), and 5-cathode;

fig. 2 is a schematic structural diagram of an oeld top emission device in an embodiment of the present invention.

Detailed Description

The technical solutions of the present invention will be described in detail below with reference to the accompanying drawings, but the scope of the present invention is not limited to the following embodiments.

first, cathode transmittance and conductivity test of the oeld top emission device

1. Test method

The cathode transmittance test method comprises the following steps: adopting corrected optical transmittance testing equipment, continuously scanning the wavelength from 400 to 700nm, and measuring the area of a light spot by using the transmittance ²。

Testing method of cathode conductivity: the square resistance was tested by the four-probe method.

2. Device with a metal layer

the structure is glass substrate/ET L (35 nm)/cathode (13 nm).

Example 1

according to the device structure, the cathode is Ag, ET L is

Example 2

according to the device structure, the cathode is Ag, ET L is

Example 3

according to the device structure, the cathode is Ag, ET L is

Example 4

according to the device structure, the cathode is Mg: Ag (mass ratio of 3: 7, 13nm), ET L is

Comparative example 1

according to the device structure, the cathode is Ag, ET L is

Comparative example 2

Table 1: transmittance and resistance data

the cathode transmittance and conductivity test results of the oeld top emission devices prepared in examples 1-4 and comparative example are shown in table 1, and it can be seen that the devices prepared in examples 1-4 have uniform and flat surfaces, the light transmittance at 460nm is improved, and the conductivity is greatly enhanced compared to comparative examples 1 and 2.

second, the comprehensive performance test of the O L ED top light-emitting device

1. Test method

the performance of the oeled top emission devices was tested as follows, respectively, according to the standard:

1) Voltage @10mA/cm ²In units of V;

2) Current efficiency @10mA/cm ²In Cd/A;

3) Lifetime 95% decay time @40mA/cm ²The unit is h.

2. Device with a metal layer

Although the red light, the green light and the white light are different in material structure and thickness, the matching method of the cathode and the electron transport layer is also applicable, the following embodiments all adopt the blue top light emitting device, and the specific materials of the layers are as follows:

(1) Substrate: a glass substrate or a plastic substrate.

(2) Anode (ITO): the reflective metal layer is composed of a reflective metal layer with the thickness of 50-150 nm and a conductive metal layer with the thickness of 5-30 nm, such as AG/ITO, AG alloy/ITO or AG/IGZO, and can be a multilayer reflective layer for increasing the reflection effect of a device.

(3) the hole transport layer (HT L) is made of a single-layer or multi-layer material at least containing amines or carbazole compounds to increase hole injection capability and improve device effect if the functional layer is adopted to adjust the length of a resonant cavity of top light emission and the thicknesses of light of different colors are different, and the hole transport layer (HT L) is made of a single-layer or multi-layer material at least containing amines or carbazole compounds to increase the hole injection effect.

(4) and a light-emitting layer (EM L) which is made on the hole transport layer or the electron blocking layer, has a thickness of 10-50 nm, preferably 20-40 nm, is selected from a single-layer light-emitting layer or a combination of multiple light-emitting layers of red light, green light, blue light, white light and yellow light, and consists of a host material and an object light-emitting material selected from a fluorescent material, a phosphorescent material or a thermal delay fluorescent material, wherein the mass ratio of the fluorescent material to the host material is 2-10%, the mass ratio of the phosphorescent material to the host material is 2-15%, and the mass ratio of the thermal delay fluorescent material to the host material is 5-30%.

(5) the electron transport layer (ET L) is an electron transport layer made of materials from the light emitting layer to the cathode and has the thickness of 30-70 nm, in order to improve the effect of the device, a hole blocking layer with the thickness of 5-20 nm is made on the light emitting layer, an electron transport layer made of one or a mixture of multiple materials is made on the hole blocking layer, and the electron transport layer is mixed with alkali metal, alkaline earth metal or rare earth metal when being mixed, the weight ratio of the metal added is less than 50%, preferably less than 25%, more preferably less than 15%, or the alkali metal compound, the alkaline earth metal compound and the rare earth metal compound are mixed, the weight ratio of the metal compound is 20-80%, electrons can be well injected when the mixed material is contacted with a high ratio of metal silver, mixed metal L i, Ca, Yb or Mg is adopted in a preferred embodiment, because the metal content is very low, the interaction effect on the silver and the electron transport material is very small, and the cathode.

(6) Cathode: silver and/or silver alloy with the mass content of not less than 95 percent.

(7) Capping layer (Capping layer): materials with refractive index larger than 1.8 such as amine compounds and aromatic fused ring compounds are adopted.

The structures, as particularly illustrated in the examples below, are:

Anode/HIL (10nm)/HT L (80nm)/EB L (30nm)/EM L-B L UE (30nm)/HB L (10nm)/ET L/cathode/CP L (70 nm).

Example 5

the Blue top-emitting device is manufactured according to the materials, wherein the materials of HIL, HT L, EB L, EM L-Blue, HB L and CP L have the chemical structures shown in table 2, the cathode is Ag and the thickness is 13nm, the thickness of the ET L layer is 35nm, a mixture of an organic material and metal Yb is adopted, the mass ratio of the Yb is 5%, and the organic material has the following structure:

Example 6

the Blue top luminescent device and the material are prepared, wherein the materials of HIL, HT L, EB L, EM L-Blue, HB L and CP L adopt the materials the chemical structure of the cathode is shown in Table 2, the cathode is Ag and the thickness is 13nm, the thickness of ET L layer is 35nm, the mixture of organic material and metal Yb is adopted, the mass ratio of Yb is 5%, and the organic material structure is as follows:

Example 7

Example 8

the Blue top light-emitting device is manufactured according to the materials, wherein the materials of HIL, HT L, EB L, EM L-Blue, HB L and CP L have the chemical structures shown in table 2, the cathode is a mixture of Mg and Ag, the weight ratio of Ag is 70%, the thickness is 13nm, the thickness of ET L layer is 35nm, the mixture of an organic material and metal Yb is adopted, the mass ratio of Yb is 5%, and the organic material has the following structures:

Comparative example 3

Comparative example 4

the Blue top luminescent device and the material are manufactured according to the above, wherein the HIL, HT L, EB L, EM L-Blue, HB L and CP L layer materials adopt chemical structures As shown in table 2; the cathode is a mixture of Mg and Ag, the weight ratio of Ag is 70%, and the thickness is 13 nm; the method adopts a mixture of an organic material and metal Yb, wherein the mass ratio of the Yb is 5 percent, and the structure of the organic material is as follows:

Table 2: functional layer material

Table 3: device performance test results

the performance test results of the oeled top-emitting blue light devices prepared in examples 5 to 8 and comparative examples 3 and 4 are shown in table 3, and it can be seen that the device voltage is low, the lifetime is long at 95% decay time, and the service life of the device can be greatly prolonged.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention, and the present invention should not be limited by the disclosure of the preferred embodiments. Therefore, it is intended that all equivalents and modifications which do not depart from the spirit of the invention disclosed herein are deemed to be within the scope of the invention.

Claims

1. an O L ED top-emitting device, which consists of a substrate, an anode, a cathode and an organic layer sandwiched between the anode and the cathode,

The substrate is arranged on one side of the anode, and the cathode comprises silver with the mass content not lower than 95% formed by an evaporation process;

The organic layer includes: at least one hole transport layer in contact with the anode, at least one light emitting layer, and at least one electron transport layer in contact with the cathode; wherein the content of the first and second substances,

The electron transport layer comprises one or more compounds with the structure shown in the formula (II):

2. the O L ED top emission device of claim 1, wherein the electron transport layer further comprises a metal or metal compound,

The metal is selected from one of alkali metal, alkaline earth metal or rare earth metal, and the mass percentage is not higher than 50%;

The metal compound is selected from one of alkali metal compounds, alkaline earth metal compounds and rare earth metal compounds, and the mass percentage of the metal compound is 20-80%.

3. the O L ED top emission device of claim 2, wherein the metal is selected from one of L i, Ca, Yb or Mg and is not greater than 25% by mass.

4. the oeld top emission device of claim 1 wherein said anode is comprised of at least one reflective metal layer and at least one conductive metal layer,

The reflecting metal layer is Ag or Ag alloy, and the thickness of a single layer is 50-150 nm;

The conductive metal layer comprises Indium Tin Oxide (ITO) or Indium Gallium Zinc Oxide (IGZO), and the thickness of the conductive metal layer is 5-30 nm;

The hole transport layer contains amine or carbazole-containing compounds, and the thickness of the hole transport layer is 30-250 nm.

5. the O L ED top emission device of claim 4,

The anode is selected from one of Ag/ITO, Ag alloy/ITO or Ag/IGZO;

The hole transport layer contains amines or carbazole-containing compounds, and the thickness of the hole transport layer is 100-250 nm.

6. the oeld top emission device according to claim 4 or 5, wherein said hole transport layer is selected from one or two or more compounds represented by the following formula (iii):

7. the O L ED top emission device of claim 1,

The color of the luminescent layer is selected from one of red light, green light, blue light, white light and yellow light;

The light-emitting layer is composed of a host material and an object light-emitting material, and the thickness of the light-emitting layer is 10-50 nm; wherein the content of the first and second substances,

The guest luminescent material is selected from one of a fluorescent material, a phosphorescent material or a thermal retardation fluorescent material, and the mass ratio of the fluorescent material to the host material is (1-5): 50, or

The mass ratio of the phosphorescent material to the main material is 2-15: 100, or

The mass ratio of the thermal delay fluorescent material to the main material is 1-6: 20.

8. the O L ED top emission device of claim 1,

A hole injection layer with the thickness of 0.5-30 nm is arranged between the anode and the hole transport layer, and the hole injection layer is selected from a P-type material or a mixture of no more than 50 wt.% of the P-type material and an amine or carbazole compound;

An electron blocking layer with the thickness of 5-100 nm is arranged between the hole transport layer and the light emitting layer, and the electron blocking layer is selected from compounds containing carbazole groups or aniline groups;

The hole blocking layer is arranged between the light emitting layer and the electron transport layer and has a thickness of 5-20 nm, and the hole blocking layer is selected from one of substituted or unsubstituted pyrimidine, substituted or unsubstituted pyrazine, substituted or unsubstituted pyridazine or substituted or unsubstituted triazine pyrimidine.

9. the oeled top emission device according to claim 8, wherein said hole blocking layer is one or more selected from the group consisting of compounds represented by the following formula (iv):

10. the O L ED top emission device of claim 1,

The substrate comprises a glass or plastic plate and the cathode surface comprises a capping layer.

11. an oeld display device comprising an oeld top emission device according to any one of claims 1 to 10.