TWI306000B - Organic electroluminescence device and electron transporting layer - Google Patents

Description

I306(mwfdoc/g IX. Description of the invention: [Technical field to which the invention belongs] A list of illuminating elements, a luminescent element, .. „ , Q u 1 thousand (luminescenc 丨6, another related to an organic electro An organic electroluminescence device and its electron transport layer. [Prior Art] —

. The display is a communication interface between people and information. Currently, the display is mainly based on flat display. Where 'organic electroluminescence shows crying

EleCtr〇luminescence Display, 〇ELD) has great application potential due to its self-illumination, no viewing angle dependence, power saving, simple process, low cost, low temperature operating range, high response speed and full color. The mainstream of flat panel displays. The organic electroluminescent display mainly uses the spontaneous characteristics of the organic electroluminescent element to achieve the display effect. Among them, the organic electroluminescence element is mainly composed of a pair of electrodes and a layer of an organic functional material. When the current = between the anode and the cathode, the electron and the hole are combined in the organic functional material & layer to generate an exciton, the organic functional material layer can be made to emit light of different colors according to the characteristics of the material. Mechanism, and then achieve the effect of ^ light display. x Figure 1 is a schematic view showing the structure of a conventional organic electroluminescent device. Referring to FIG. 1, a conventional organic electroluminescent device 100 is composed of a substrate, an anode 12, a hole transport layer, a light-emitting layer 14, an electron transport layer 150, and a cathode 160. composition. When a bias voltage is applied across the anode 120 and the cathode 160, electrons are injected from the cathode 16 电子 into the electron transport layer 150' and transmitted to the light-emitting layer 13'. On the other hand, the hole is injected into the hole transport layer 13A by the anode 120 and transmitted to the light-emitting layer 14A. At this time, electrons and holes will recombine (Re_binati〇n) phenomenon in the light-emitting layer (10), and then excitons are generated to achieve the effect of light emission. In the prior art, the common electron transfer layer 15 is made of Alq3 'however, the electron mobility of Alq3 tends to be lower than that of the hole transport layer, so that the conventional organic electroluminescent element is in the middle. There is a problem that the carrier transport is unbalanced, thus affecting the luminous efficacy of the organic electroluminescent element 1 [Abstract]

In view of the above, an object of the present invention is to provide an organic electroluminescent device which has a high luminous efficiency. X Another object of the present invention is to provide an electron transport layer for improving the luminous efficiency of an electroluminescent device. Based on the above and other objects, the present invention provides an organic electroluminescent device which includes a substrate, a first electrode layer, a hole transport layer, a light-emitting layer, an electron transport layer, and a second electrode layer. The first electrode layer is disposed on the substrate, and the hole transport layer is disposed on the first electrode layer. The light emitting layer is disposed on the hole transport layer, and the electron transport layer is disposed on the light emitting layer, and the second electrode layer is disposed on the electron transport layer. Further, the electron transport layer includes n+1 layers of the first sub-transport layer and the n-layer second sub-wheel layer, where n is a positive integer. The first sub-transport layer is stacked on the light-emitting layer, and each of the second sub-transport layers is disposed between two adjacent first sub-transport layers, and the energy gap and the second sub-transmission of the first sub-transport layer The energy gap of the layers is different. D060l - /g The above organic electroluminescent device further includes, for example, a hole injection layer disposed between the first electrode layer and the hole transport layer. The above organic electroluminescent device further includes, for example, an electron injecting layer disposed between the second electrode layer and the electron transporting layer. The present invention further provides an electron transport layer comprising n+1 layers of a first sub-transport layer and an n-layer second sub-transport layer, wherein n is a positive integer. The first sub-transport layers are stacked on each other, and each of the second sub-transport layers is disposed between two adjacent first sub-transport layers, and the energy gap of the first sub-transport layer and the energy gap of the second sub-transport layer different. In the above organic electroluminescence device and electron transport layer, the energy gap of the first sub-transport layer is, for example, larger than the energy gap of the second sub-transport layer. In the above organic electroluminescence device and electron transport layer, the energy gap of the first sub-transport layer is, for example, smaller than the energy gap of the second sub-transport layer. In the above organic electroluminescence device and electron transport layer, the thickness of each of the first sub-transport layer and each of the second sub-transport layers is, for example, 10 to 200 Å. In the above organic electroluminescence device and electron transport layer, the thickness of each of the first sub-transport layer and each of the second sub-transport layers is, for example, 20 to 100 Å. In the above organic electroluminescence device and electron transport layer, the thickness of each of the first sub-transport layer and each of the second sub-transport layers is, for example, 10 to 20 Å. In the above organic electroluminescence device and electron transport layer, the materials of the first sub-transport layer and the second sub-transport layer are, for example, one selected from the group consisting of the following four chemical formulas: I3〇6〇〇65〇 Twfdoc/g chemical formula (1):

Chemical formula (2):

Alq3

JBEM 9 I3060Q5Q9twfdoc/g Chemical Formula (3):

Chemical formula (4):

DPVBi

TPBi ίο I3〇6〇Q5Q9tw, doc/g

Pi Μ In the electron transport layer of the present invention, a superlattice junction formed by stacking a salivary energy gap and a second sub-transport layer, "electron mobility of the sub-transport layer to improve conventional organic electricity The problem of unbalanced carrier wheel of the Stg towel is improved, and the luminous efficiency of the organic electroluminescent element is improved. The above and other objects, features and advantages of the present invention are made more apparent. Actual (4), and with the amount of the formula, a detailed description is as follows.

[Embodiment] _ Figure 2 edge: The structure of the organic electroluminescent element of the present invention-embodiment is not shown in Fig. 2. The organic electroluminescent element 2 of the present embodiment includes - substrate 210, - - The electrode layer 22, the hole transport layer 23, the light-emitting layer 240, the electron transport layer 25A, and the second electrode layer 26A. The 'first electrode layer 220' is disposed on the substrate 21A, and the hole transport layer 23 is disposed on the first electrode layer no. The light-emitting layer is disposed on the hole transport layer 23G, and the electron transport layer 25() is disposed on the light-emitting layer 24A, and the second electrode layer 260 is disposed on the electron transport layer 25A. Further, the electron transport layer 250 includes n+1 layers of the first sub-transport layer 252 and n-layer second sub-transport layer 254' where n is a positive integer. In the present embodiment, η = ι is used as the ', that is, the electron transport layer 25 〇 includes two layers of the first sub-transport layer - the second sub-transport layer 254. In addition, the first sub-transport layer 252 is stacked on the light-emitting layer 240, and each of the second sub-transport layers 254 is disposed between the adjacent two-layer first-sub-transport layer 252, and the first sub-transport layer 252 is The energy gap of the second sub-transport layer 254 is different. ', 13060 chaos. /g In the above organic electroluminescent element 200, the first electrode layer 22 is, for example, an anode, and the second electrode layer 260 is, for example, a cathode. When a bias voltage is applied across the first electrode layer 220 and the second electrode layer 260, electrons are injected into the electron transport layer 250 from the second electrode layer 260, and the light is transmitted to the light 9f 24 〇. On the other hand, the hole is injected into the hole transmission layer 23 by the first electrode layer 220 and transmitted to the light-emitting layer 240. At this time, electrons and holes are recombined in the light-emitting layer 240, and excitons are generated to achieve the effect of light emission. In the present embodiment, the electron transport layer 250 is the first sub-transmission different from the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). A superlattice structure composed of a layer 252 and a second sub-transport layer 254. Wherein, a two-dimensional quantum well is formed at the contact surface of the first sub-transport layer 252 and the second sub-transport layer 254, and free electrons that can swim on the contact surface are generated in the two-dimensional quantum well. Such free electrons generated by the superlattice structure are called two-dimensional free electrons. Since two-dimensional free electrons have little chance of collision with each other, the two-dimensional free electrons are faster to move than ordinary electrons. Therefore, the electron transport layer 250 of such a superlattice structure can increase the electron mobility such that the electron mobility of the electron transport layer 250 is close to or equal to the hole mobility of the hole transport layer 230. As a result, the problem of unbalanced carrier transport in the prior art can be improved, and the luminous efficiency of the organic electroluminescent element 200 can be improved. In addition, since the superlattice structure has a low resistance characteristic 'there is better contact between the second electrode 260 and the electron transport layer 250, the luminous efficiency of the organic electroluminescent element 200 can be increased 12 I3060fi4wfd〇〇/ g and lower its operating voltage. In a preferred embodiment of the present invention, the material of the first sub-transport layer 252 and the second sub-transport layer 254 is an organic material, which is, for example, one of the compounds represented by the following four chemical formulas: • Chemical formula (1) ):

Chemical formula (2):

JBEM Chemical Formula (3): 13 1306000 16599twf.doc/g

DPVBi chemical formula (4):

For example, the first sub-transport layer 252 and the second sub-transport layer 254 are 14 I3060Q0 lo599twf.doc/g materials such as Alq3 with smaller energy gap and jbem with larger energy gap, or JBEM and Alq3. In other words, the energy gap of the first sub-transport layer 252 in this embodiment may be larger than the energy gap of the second sub-transport layer 254 or smaller than the energy gap of the second sub-transport layer 254. In this embodiment, the thickness of the first sub-transport layer 252 and the second sub-transport layer 254 may be the same or different, and the thickness of each of the first sub-transport layer 252 and each of the second sub-transport layers 254 may also be required. Same or different. The thickness of the first sub-transport layer 252 and the second sub-transport layer 254 is approximately 10 to 200 angstroms or 20 to 100 angstroms, and more preferably 10 to 2 angstroms. Fig. 3 is a view showing the structure of an organic electroluminescence device according to another embodiment of the present invention. Referring to FIG. 3, which is similar to FIG. 2, the difference is that the organic electroluminescent device 200 illustrated in FIG. 3 further includes an electron injection layer 270 and a hole injection layer 280. The electron injection layer 270 is disposed between the second electrode layer 260 and the electron transport layer 250, and the hole injection layer 28 is disposed between the first electrode layer 220 and the hole transport layer 230 to enhance the organic electrolysis. The luminous efficiency of the light-emitting element 200. It is to be noted that the electron injection layer 270 and the hole injection layer 280 described above may alternatively be disposed in the organic electroluminescent element 2''. In addition, the above-mentioned electron transport layer 250 is exemplified by two layers of the first sub-transport layer 252 and one layer of the second sub-transport layer 254, but it is not intended to limit the present invention. In fact, the number of layers of the first sub-transport layer 252 and the second sub-transport layer 254 is increased as needed in the present embodiment. In summary, the organic electroluminescent device of the present invention has at least the following excellent 15 1306000 16599 twf.doc/g!:=^(4) The nano-form formed by the transmission layer of the 1G~200 angstrom-proton The film, and the energy gap of the first sub-transport layer partially overlap, so that there is a problem of unbalanced transmission, thereby improving the emission of the organic electroluminescent element.

2. Since the electron transport layer of the present invention has a low resistance characteristic, the 7 electrode and the electricity are selected? The oscillating layer has a well-recorded ohm, so that the luminous efficiency of the organic electroluminescent element can be improved and the operating voltage can be lowered. Although the present invention has been implemented as described above, the financial system is not used in the present invention, and the present invention can be used without departing from the present invention. It shall be subject to the definition of the application for the special fiber enclosure. [Simple description of the map]

1 is a schematic structural view of a conventional organic electroluminescent device. FIG. 2 is a view showing the structure of an organic electroluminescent device according to an embodiment of the present invention. FIG. 3 is a view showing an organic electro-electrode according to another embodiment of the present invention. Schematic diagram of the light-emitting element structure. 'σ [Description of main component symbols] 100, 200, 200': organic electroluminescent elements 110, 210: substrate 120 · anode 16 I3060fiatwfdoc / g 130, 230: hole transport layer 140, 240: light-emitting layer 150, 250: Electron transport layer 160: cathode 220: first electrode 252: first sub-transport layer 254: second sub-transport layer 260: second electrode 270: electron injection layer 280: hole injection layer

17

Claims (1)

13 060 通...- 16599twf.doc/g X. Patent Application Range: 1. An organic electroluminescent device comprising: a substrate; a first electrode layer disposed on the substrate; a hole transport layer disposed at The first electrode layer; _ _ a luminescent layer disposed on the hole transport layer; - an electron transport layer comprising: n +1 layer first sub-transport layer stacked on the luminescent layer, wherein a positive integer; n layer second sub-transport layer, each second sub-transport layer is disposed between two adjacent first sub-transport layers, wherein the energy gap of the first sub-transport layer and the second sub-transmission The energy gap of the layers is different; and a second electrode layer is disposed on the electron transport layer. 2. The organic electroluminescent device according to claim 1, wherein an energy gap of the first sub-transport layer is greater than an energy gap of the second sub-transport layer. 3. The organic electroluminescent device according to claim 1, wherein the energy gap of the first sub-transport layer is smaller than the energy gap of the second sub-transport layer. 4. The organic electroluminescent device according to claim 1, wherein each of the first sub-transport layer and each of the second sub-transport layers has a thickness of 10 to 200 angstroms. 5. The organic electroluminescent device according to claim 1, wherein each of the first sub-transport layer and each of the second sub-transport layers has a thickness of 20 to 100 angstroms. 6. The organic electroluminescent device according to claim 1, wherein the first sub-transport layer and each of the second sub-transport layers have a thickness of 10 to 20 angstroms. 18 B 〇 60 〇 9 twfdoc/g. 7. The organic electroluminescent device according to claim 1, wherein the materials of the first sub-transport layer and the second sub-transport layer are respectively selected from one of the following four chemical formulas: _ Chemical formula (1): Chemical formula (2): JBEM 19 I306H. The organic electroluminescent device of claim 1, further comprising a hole injection layer disposed between the first electrode layer and the hole transport layer. 9. The organic electroluminescent device of claim 1, further comprising an electron injecting layer disposed between the second electrode layer and the electron transporting layer. 10. An electron transport layer suitable for use in an organic electroluminescent device, the electron transport layer comprising: n+1 layers of a first sub-transport layer, the first sub-transport layers being stacked on each other, wherein n is a positive integer And an η layer second sub-transport layer, each second sub-transport layer is disposed between two adjacent first sub-transport layers, wherein an energy gap of the first sub-transport layer and the second sub-transport layer The energy gap is different. 11. The electron transport layer of claim 10, wherein the energy gap of the first sub-transport layer is greater than the energy gap of the second sub-transport layer. 12. The electron transport layer of claim 10, wherein the energy gap of the first sub-transport layer is smaller than the energy gap of the second sub-transport layer. 13. The electron transport layer of claim 10, wherein each of the first sub-transport layer and each of the second sub-transport layers has a thickness of 10 to 200 angstroms. 14. The electron transport layer of claim 10, wherein each of the first sub-transport layer and each of the second sub-transport layers has a thickness of 20 to 100 angstroms. 15. The electron transport layer of claim 10, wherein 21 I3060QL each of the first sub-transport layer and each of the second sub-transport layers has a thickness of ί 〜 20 Å. The electron transport layer of claim 10, wherein the materials of the first sub-transport layer and the second sub-transport layers are respectively selected from one of the following four chemical formulas: _ Chemical formula (1): Alq3 chemical formula (2): JBEM 22