Electrode and organic electroluminescent device using same

Abstract

An electrode and an organic electroluminescent device using the same are provided. The electrode comprises a first conductive layer (1), a second conductive layer (2) and a third conductive layer (3) that are arranged in a stacked manner The second conductive layer (2) has a single-layer structure or multi-layer composite structure formed by at least one of alkali earth metal, alkali earth metal alloy and alkali earth metal compound, and the third layer (3) has a work function of less than 3 eV. The respective conductive layers of the electrode can compensate with respect to the defects in one another, thereby making the performance of the electrode more stable. In the meantime, because the work function of the third conductive layer (3) is less than 3 eV, the barrier of organics-metal interface can be effectively reduced for guiding the electron injection, thereby increasing the light-emitting efficiency of device. Also, because the electrode has relatively good transmittance, it can be used as a transparent electrode.

Claims

1. An electrode, comprising a first conductive layer, a second conductive layer and a third conductive layer that are arranged in sequence in a stacked manner, the second conductive layer has a single-layer structure or multi-layer composite structure formed by at least one of alkali earth metal, alkali earth metal alloy and alkali earth metal compound, and the third conductive layer has a work function of less than 3 eV and has a single-layer structure or multi-layer composite structure formed by a rare-earth metal compound, wherein the third conductive layer is a Yb.sub.2O.sub.3 layer or a YbN layer.

2. The electrode according to claim 1, wherein the second conductive layer is a Mg layer, or a MgCO.sub.3 layer, or an alloy layer of Mg and Ag.

3. The electrode according to claim 1, wherein the first conductive layer is a silver layer.

4. The electrode according to claim 1, wherein the first conductive layer has a thickness of 5 nm-20 nm.

5. The electrode according to claim 4, wherein the second conductive layer has a thickness of 0.5 nm-10 nm.

6. The electrode according to claim 5, wherein the second conductive layer has a thickness of 0.5 nm-2 nm.

7. The electrode according to claim 6, wherein the third conductive layer has a thickness of 0.5 nm-10 nm.

8. An organic electroluminescent device, comprising a first electrode, an organic light-emitting layer and a second electrode that are arranged in sequence in a stacked manner, the second electrode is an electrode that comprises a first conductive layer, a second conductive layer and a third conductive layer that are arranged in a stacked manner, the second conductive layer has a single-layer structure or multi-layer composite structure formed by at least one of alkali earth metal, alkali earth metal alloy and alkali earth metal compound, the third conductive layer has a work function less than 3 eV and has a single-layer structure or multi-layer composite structure formed by a rare-earth metal compound, wherein the third conductive layer is a Yb.sub.2O.sub.3 layer or a YbN layer, and the third conductive layer is disposed next to the organic light-emitting layer.

9. The organic electroluminescent device according to claim 8, wherein the second conductive layer is a Mg layer, or a MgCO.sub.3 layer, or an alloy layer of Mg and Ag.

10. The organic electroluminescent device to claim 8, wherein the first conductive layer is a silver layer.

11. The organic electroluminescent device according to claim 8, wherein the first conductive layer has a thickness of 5 nm-20 nm.

12. The organic electroluminescent device according to claim 11, wherein the second conductive layer has a thickness of 0.5 nm-10 nm.

13. The organic electroluminescent device according to claim 12, wherein the second conductive layer has a thickness of 0.5 nm-2 nm.

14. The organic electroluminescent device according to claim 12, wherein the third conductive layer has a thickness of 0.5 nm-10 nm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In order to make the content of the present disclosure easier to be understood clearly, hereinafter, the present disclosure is further described in detail according to specific embodiments of the present disclosure with reference to the accompanying drawings, wherein,

(2) FIG. 1 is a structural schematic diagram of the electrode of Embodiment 1 of the present disclosure;

(3) FIG. 2 is a transmittance comparison diagram of Embodiment 1, Embodiment 3 of the present disclosure as compared to Comparison example 2; and

(4) FIG. 3 is a reflectance comparison diagram of Embodiment 1, Embodiment 3 of the present disclosure as compared to Comparison example 2.

(5) The reference signs in the accompanying drawings represent: 1-first conductive layer, 2-second conductive layer, 3-third conductive layer.

DETAILED DESCRIPTION OF EMBODIMENTS

(6) In order to make the objectives, technical solutions and advantages of the present disclosure clearer, detailed description of embodiments of the present disclosure is further given below, with reference to the accompanying drawings.

(7) The present disclosure can be implemented in many different forms and should not be interpreted to be limited to the embodiments described herein. On the contrary, by providing these embodiments, the present disclosure is made complete and thorough, and the concept of the present disclosure is sufficiently conveyed to those skilled in the art. The present disclosure will be only defined by the claims. In the accompanying drawings, for the sake of clarity, dimensions and relative sizes of layers and areas might be exaggerated.

Embodiment 1

(8) This embodiment provides an electrode, as shown in FIG. 1, the electrode comprises a first conductive layer 1 and a second conductive layer 2 that are arranged in a stacked manner. The first conductive layer 1 is Ag layer with a thickness of 16 nm, the second conductive layer 2 is Mg layer with a thickness of 1 nm, and a third conductive layer 3 is Yb layer with a thickness of 1 nm.

(9) This embodiment also provides an organic electroluminescent device, Ag/ITO(20 nm)/HATCN(20 nm)/NPB(40 nm)/mCBP:3 wt % Ir(piq).sub.3(30 nm)/TPBi(50 nm)/Yb (1 nm)/Mg(1 nm)/Ag(16 nm)/ITO(20 nm).

(10) Wherein, the stacked Ag and ITO layer is the first electrode.

(11) The HATCN (2,3,6,7,10,11-hexacyanyl-1,4,5,8,9,12-hexaazatriphenylene) layer is a hole injection layer.

(12) The NPB (N,N-di-(1-naphthyl)-N,N-diphenyl-1,1-biphenyl-4,4-diamine) layer is a hole transport layer.

(13) The layer of CBP (N-di-carbazolyl-biphenyl) doped with Ir(piq).sub.3 (Tri-(1-phenylisoquinolinato-C2,N]-Iridium(III)) is a light-emitting layer.

(14) The TPBi (1,3,5-tri-(1-phenyl-1H-benzimidazole-2-yl)-benzene) layer is a hole blocking layer.

(15) The above-mentioned electrode is a second electrode.

(16) The ITO (Indium Tin Oxide) layer is an optical coupling layer.

(17) As an alternative embodiment of the present disclosure, the structure of the organic electroluminescent device is not limited to this, as long as it applies the electrode of the present disclosure and can thereby realize the purpose of the present disclosure, thus belonging to the protection scope of the present disclosure.

Embodiment 2

(18) This embodiment provides an electrode with a structure similar to that of Embodiment 1, but the difference is that the third conductive layer is Yb.sub.2O.sub.3 layer with a thickness of 1 nm.

(19) This embodiment also provides an organic electroluminescent device with a structure similar to that of Embodiment 1, but the difference is that the second electrode is the electrode according to this embodiment:

(20) Ag/ITO (20 nm)/HATCN(20 nm)/NPB (40 nm)/mCBP:3 wt % Ir(piq).sub.3(30 nm)/TPBi(50 nm)/Yb.sub.2O.sub.3(1 nm)/Mg(1 nm)/Ag(16 nm)/ITO (20 nm).

Embodiment 3

(21) This embodiment provides an electrode with a structure similar to that of Embodiment 1, but the difference is that the second conductive layer is an alloy layer of Mg and Ag with a thickness of 2 nm, and the first conductive layer has a thickness of 5 nm.

(22) This embodiment also provides an organic electroluminescent device with a structure similar to that of Embodiment 1, but the difference is that the second electrode is the electrode according to this embodiment.

Embodiment 4

(23) This embodiment provides an electrode with a structure similar to that of Embodiment 1, but the difference is that the third conductive layer is an alloy layer of Sm and Ca with a thickness of 0.5 nm, wherein the mass content of Sm is 50%.

(24) This embodiment also provides an organic electroluminescent device with a structure similar to that of Embodiment 1, but the difference is that the second electrode is the electrode according to this embodiment.

Embodiment 5

(25) This embodiment provides an electrode with a structure similar to that of Embodiment 1, but the difference is that the third conductive layer is YbN layer, and the second conductive layer is MgCO.sub.3 layer with a thickness of 1 nm.

(26) This embodiment also provides an organic electroluminescent device with a structure similar to that of Embodiment 1, but the difference is that the second electrode is the electrode according to this embodiment.

Embodiment 6

(27) This embodiment provides an electrode with a structure similar to that of Embodiment 1, but the difference is that the first conductive layer has a thickness of 20 nm, and the second conductive layer has a thickness of 0.5 nm.

(28) This embodiment also provides an organic electroluminescent device with a structure similar to that of Embodiment 1, but the difference is that the second electrode is the electrode according to this embodiment.

Embodiment 7

(29) This embodiment provides an electrode with a structure similar to that of Embodiment 1, but the difference is that the second conductive layer has a thickness of 10 nm, and the third conductive layer has a thickness of 10 nm.

(30) This embodiment also provides an organic electroluminescent device with a structure similar to that of Embodiment 1, but the difference is that the second electrode is the electrode according to this embodiment.

Comparison Example 1

(31) This comparison example provides an electrode with a structure similar to that of Embodiment 1, but the difference is that there is no second conductive layer contained therein.

(32) This comparison example also provides an organic electroluminescent device with a structure similar to that of Embodiment 1, but the difference is that the second electrode is the electrode according to this comparison example.

Comparison Example 2

(33) This comparison example provides an electrode with a structure similar to that of Embodiment 1, but the difference is that there is no third conductive layer contained therein, and the second conductive layer is an alloy layer of Mg and Ag with a thickness of 2 nm.

(34) This comparison example also provides an organic electroluminescent device with a structure similar to that of Embodiment 1, but the difference is that the second electrode is the electrode according to this comparison example.

Comparison Example 3

(35) This comparison example provides an electrode with a structure similar to that of Embodiment 1, but the difference is that the third conductive layer is Ag layer.

(36) This comparison example also provides an organic electroluminescent device with a structure similar to that of Embodiment 1, but the difference is that the second electrode is the electrode according to this comparison example.

Comparison Example 4

(37) This comparison example provides an electrode with a structure similar to that of Embodiment 1, but the difference is that the second conductive layer has a thickness of 20 nm.

(38) This comparison example also provides an organic electroluminescent device with a structure similar to that of Embodiment 1, but the difference is that the second electrode is the electrode according to this comparison example.

Test Example 1

(39) Transmittance test and reflectance test are performed on the electrodes provided by the above-mentioned Embodiments and Comparison examples. As shown in FIG. 2, in the range of visible light, the electrodes provided by Embodiment 1 and Embodiment 3 have a transmittance of 30% or more, and even up to 60%, whereas the electrode provided by Comparison example 2 has a transmittance of less than 30%. As shown in FIG. 2 and FIG. 3, by comparing the transmittance values and reflectance values of different cathode structures in Embodiment 1, Embodiment 3 and Comparison example 2, the transmittance values of light in Embodiment 1 and Embodiment 3 exceed 40%, which are 25% higher than that in Comparison example 2, therefore the light out-coupling characteristic of the OLED device can be effectively increased. The reflectance values of light in Embodiment 1 and Embodiment 3 are 42% higher than that of Comparison example 2. The increase of the transmittance values and the reflectance values can effectively improve the light out-coupling efficiency and thus improve the light-emitting efficiency of device.

Test Example 2

(40) When an organic electroluminescent device has worked for a long time, an organic film thereof may change from an initial amorphous film into a crystalline film, such a change of film would cause the decaying of device.

(41) Therefore, the devices are annealed respectively at different temperatures for 1 hour, and the test results of T.sub.97 (service life for the brightness to decay from 10000 nit to 97%) of the annealed devices as compared to unannealed devices (25 C.) are listed in Table 1.

(42) TABLE-US-00001 TABLE 1 Test results of T.sub.97 of different devices annealing temperature ( C.) 25 80 100 120 140 T.sub.97(h) T.sub.97(h) T.sub.97(h) T.sub.97(h) T.sub.97(h) Embodiment 1 765 749 721 690 573 Embodiment 2 733 705 645 620 527 Embodiment 3 755 726 694 618 564 Embodiment 4 621 605 573 526 473 Embodiment 5 681 629 566 504 441 Embodiment 6 756 732 713 677 545 Embodiment 7 741 725 705 681 531 Comparison example 1 421 378 301 193 56 Comparison example 2 350 295 150 97 33 Comparison example 3 211 156 123 91 29 Comparison example 4 599 456 323 191 79

(43) The data in Table 1 indicates that, when the electrode of the present disclosure is used in an organic electroluminescent device, the service life of device is far longer than that in the Comparison examples, with even better stability of device in high temperature condition.

Test Example 3

(44) Dynamic service-life experiments (50% alternating checkerboard evaluation) are carried out, that is, in a certain work environment, the display screen is lit up in a pattern of alternating checkerboard which changes once every 10 seconds. The service life of device is evaluated by measuring the brightness decay, and the experiment is stopped when the brightness decays to 50% of the initial brightness. The brightness is measured by using a Spectrascan PR655 photometer, and the dynamic service-life experiments can be classified into normal temperature experiments (25 C.) and high temperature experiments (85 C.).

(45) TABLE-US-00002 TABLE 2 Result of dynamic service-life experiments of different devices at normal temperature (25 C.) Bright- Drive ness voltage Efficiency T.sub.97 CIE Groups (cd/m.sup.2) (V) (cd/A) (h) (x, y) Embodiment 1 5000 4.94 55.09 765 (0.66, 0.33) Embodiment 2 5000 4.95 54.94 733 (0.66, 0.33) Embodiment 3 5000 4.99 56.77 755 (0.66, 0.33) Embodiment 4 5000 5.02 54.68 621 (0.66, 0.34) Embodiment 5 5000 5.10 55.66 681 (0.67, 0.33) Embodiment 6 5000 4.95 55.06 756 (0.67, 0.33) Embodiment 7 5000 4.96 55.13 741 (0.67, 0.33) Comparison 5000 5.26 47.13 421 (0.66, 0.33) example 1 Comparison 5000 5.22 49.42 350 (0.65, 0.33) example 2 Comparison 5000 5.46 50.36 211 (0.66, 0.32) example 3 Comparison 5000 5.12 50.86 599 (0.67, 0.34) example 4

(46) It can be known from the data in Table 2 that, when the electrode of the present disclosure is used in an organic electroluminescent device, it can significantly increase the light-emitting efficiency and service life of device as well as lower the driving voltage. In the meantime, it can be seen from the data of color coordinates (CIE) that, as the electrode has relatively low light absorbance, it has no influence on the light-emitting color of device.

(47) Apparently, the aforementioned embodiments are merely examples illustrated for clearly describing the present disclosure, rather than limiting the implementation ways thereof. For a person skilled in the art, various changes and modifications in other different forms can be made on the basis of the aforementioned description. It is unnecessary and impossible to exhaustively list all the implementation ways herein. However, any obvious changes or modifications derived from the aforementioned description are intended to be embraced within the protection scope of the present disclosure.