CN101931054B - White organic light emitting device - Google Patents

Abstract

A white light organic light emitting element comprises: an anode, a hole transport layer, a first light emitting layer, a second light emitting layer, a third light emitting layer, an electron transport layer and a cathode, wherein the second light emitting layer is formed between the first and third light emitting layers, and its light emitting wavelength is longer than that of the first and third light emitting layers, and the main light emitting materials of the first and third light emitting layers are different materials. The white light organic light emitting element of the present invention can effectively improve the light emitting efficiency, reduce the operating voltage, and provide color stability.

Description

White OLED

【Technical field】

The present invention relates to an organic light-emitting element, in particular to a white light organic light-emitting element that can effectively improve luminous efficiency, reduce operating voltage, and provide color stability.

【Background technique】

The light-emitting layer of the phosphorescent organic light-emitting element is generally mixed with a light-emitting host material (host) with a high-efficiency light-emitting guest material (guest), so as to achieve the purpose of improving the light-emitting efficiency of the element and adjusting light color. Typically, phosphorescent guest materials consist of organic complexes with transition metals.

In phosphorescent organic light-emitting devices, the energy level of the triplet state of the light-emitting host material must be greater than that of the light-emitting guest material (refer to Ref. Molecularly, the efficiency of the device is reduced. Especially in the blue phosphorescent organic light-emitting element, since the blue-emitting phosphorescent luminescent guest material has a triplet energy level of about 2.7eV, it is necessary to select an organic material with a triplet energy level greater than 2.7eV as the light-emitting host material. However, when the required triplet energy level of an organic molecule is larger, its singlet energy level (or called a bandgap) is larger. Therefore, generally speaking, the light-emitting host materials used in blue phosphorescent organic light-emitting devices have a band gap larger than 3.0 eV. The light-emitting layer made of organic materials with such a large band gap as the light-emitting host material will create barriers to charge transport with the adjacent hole transport layer or electron transport layer, or between the two. As a result, blue phosphorescent organic light-emitting devices have problems of high operating voltage and low luminous efficiency.

The preparation of white light organic light-emitting elements can pass through a single light-emitting host material, doped with two or more different light-emitting light-emitting guest materials (such as blue/yellow, blue/red, or blue/green/red), by adjusting each different concentrations to produce white light. However, the disadvantage of this method is that it is difficult to control the concentration of each light-emitting guest material, which is not conducive to the manufacturing process.

Therefore, the industry usually utilizes two or more layers of light emitting layers of different light colors to form a white light organic light emitting device, wherein the blue light emitting layer is indispensable for the composition. However, for the element structure of multi-layer light-emitting layers, when different operating voltages are applied to the organic light-emitting element, the carrier recombination area will be changed to produce a color change, and the white light will have a color shift. Therefore, Taiwan Patent No. I279165 and U.S. Patent No. US 2007/0035240 disclosed that a blue light emitting layer is sandwiched between two red light emitting layers, and the two red light emitting layers contain light emitting host materials, light emitting Both the guest material and the layer thickness are the same, thereby improving the color shift. Japanese Patent No. JP2007/335214 discloses an organic light-emitting element in which a long-wavelength light-emitting layer is sandwiched between two short-wavelength light-emitting layers. The long-wavelength light-emitting layer produces yellow, red, or orange light, while the short-wavelength light-emitting layer The light emitting layer produces blue light or green light, and the composition of the two blue light emitting layers is the same. Japanese Patent No. JP2007/189002 discloses an organic light-emitting device in which a yellow/red light-emitting layer is sandwiched between two blue-light emitting layers, and the light-emitting guest materials contained in the two blue-light emitting layers are different from each other, respectively defined as Materials with emission wavelengths of 430-465nm and 465-485nm.

However, in a white light organic light-emitting device with multiple light-emitting layers, where the light-emitting layers are all composed of the same light-emitting host material, there will be problems as described above between the adjacent hole transport layer or electron transport layer, or Between the two, there is an obstacle to the charge transfer, which leads to the disadvantages of high operating voltage and low luminous efficiency of the organic light-emitting device.

【Content of invention】

In order to solve the foregoing and other shortcomings, the present invention provides a white light organic light-emitting element, comprising: an anode; a hole transport layer formed on the anode; a first light-emitting layer formed on the hole transport layer, comprising a first light-emitting a host material, a first transition metal organic complex, and a carrier transport material; a second light emitting layer formed on the first light emitting layer, so that the first light emitting layer is sandwiched between the hole transport layer and the second light emitting layer Between layers, the second light-emitting layer includes a second transition metal organic complex; a third light-emitting layer formed on the second light-emitting layer, so that the second light-emitting layer is sandwiched between the first light-emitting layer and the third light-emitting layer Between the light-emitting layers, the third light-emitting layer includes a third light-emitting host material, a first transition metal organic complex, and a carrier transport material; an electron transport layer is formed on the third light-emitting layer, so that the third light-emitting layer Sandwiched between the second light-emitting layer and the electron transport layer; and the cathode, formed on the outer surface of the electron transport layer; wherein, the light-emitting wavelength of the second light-emitting layer is lower than that of the first light-emitting layer and the third light-emitting layer The wavelength is longer, and the first luminescent host material and the third luminescent host material are different materials (the first luminescent layer is sometimes referred to as the B1 layer, the second luminescent layer is referred to as the Y1 layer, and the third luminescent layer is referred to as the B2 layer).

In the white light organic light-emitting element of the present invention, if only in terms of the light color or wavelength emitted by each layer, the material of the transition metal organic complex can be selected to make the Y1 layer emit yellow, red or orange light, and can also The B1 layer and the B2 layer emit blue or green light through the selection of the transition metal organic complex. In one embodiment, the emission wavelength of the Y1 layer is 520-640 nm, and the wavelength of the B1 layer and/or the B2 layer is 400-480 nm.

In the present invention, the luminescent host materials contained in the B1 layer and the B2 layer are different from each other, while the luminescent guest materials (ie, the first transition metal organic complex) are the same. The Y1 layer is disposed between the B1 layer and the B2 layer, and the Y1 layer may further include a second light-emitting host material, and the included second light-emitting host material is the same as one of the light-emitting host materials of the B1 layer or the B2 layer.

In one embodiment, the second light emitting layer may also include a carrier transport material.

In one embodiment, the white light organic light-emitting element of the present invention further includes a fourth light-emitting layer formed between the first light-emitting layer and the third light-emitting layer, and the fourth light-emitting layer includes a fourth light-emitting host material and a second transition layer. Metal-organic complex (hereinafter sometimes referred to as the fourth light-emitting layer Y2 layer). Wherein, the light emitting wavelength of the Y2 layer is longer than that of the B1 layer and the B2 layer, and the Y2 layer can emit yellow light, red light or orange light. In one embodiment, the emission wavelength of the Y2 layer is 520 to 640 nm.

In one embodiment, the fourth light emitting layer may also include a carrier transport material.

In the fourth light-emitting layer, the fourth light-emitting host material is the same material as one of the first light-emitting host material or the third main light-emitting material, and is different from the second main light-emitting material. For example but not limitation, for example, when the light-emitting layer of the white light organic light-emitting element of the present invention is set as B1-Y1-Y2-B2, then the B1 layer and the Y1 layer can contain the same light-emitting host material, and the B2 layer and the Y2 layer can contain the same The luminescent host materials of B1 and B2 are different from each other.

In one embodiment, the white light organic light emitting element of the present invention further comprises an electron blocking layer disposed between the hole transport layer and the first light emitting layer.

In one embodiment, the white light organic light emitting element of the present invention further comprises a hole blocking layer disposed between the electron transport layer and the third light emitting layer.

In the present invention, the triplet energy levels of the carrier transport material and the first and third light-emitting host materials are all greater than the triplet energy levels of the first transition metal organic complex. Both the triplet energy levels of the carrier transport material and the second light-emitting host material are larger than the triplet energy levels of the second transition metal organic complex.

The white light organic light-emitting device of the present invention can provide white light with color stability, reduce the operating voltage of the device and significantly improve the performance of the device. In addition, the device composition of the present invention can improve the convenience in the manufacturing process.

In addition, the white light organic light-emitting device of the present invention has the characteristics of a flat light source, no mercury-containing metal, no ultraviolet light, and high color rendering (color rendering), so it can be applied to lighting equipment (such as indoor lighting, etc.), and can also be used in Decorative light source.

The implementation of the present invention is described below through specific examples, and those skilled in the art can understand other advantages and effects of the present invention from the content disclosed in this specification.

【Description of drawings】

FIG. 1 is a schematic cross-sectional structure diagram of a white light organic light-emitting device according to an embodiment of the present invention;

2 is a schematic diagram of the structure of the organic light-emitting layer used in the white light organic light-emitting element of the present invention; and

FIG. 3 is a schematic diagram of the structure of an organic light emitting layer used in a white light organic light emitting device according to the present invention.

[Description of main component symbols]

100 white organic light-emitting elements

102 Substrate

104 anode

106 hole transport layer

108, 208, 308 organic light-emitting layer

110 electron transport layer

112 Cathode

218, 318 The first luminous layer

228, 328 Second light-emitting layer

238, 338 The third luminescent layer

348 fourth luminous layer

【Detailed ways】

The features of the present invention will be further illustrated by specific examples below, but are not intended to limit the scope of the present invention.

FIG. 1 is a schematic cross-sectional structure diagram of a white light organic light-emitting element of the present invention. In this example, the white organic light emitting device 100 sequentially includes a substrate 102 , an anode 104 , a hole transport layer 106 , an organic light emitting layer 108 , an electron transport layer 110 , and a cathode 112 from bottom to top. In a specific example, both the substrate 102 and the anode 104 are made of transparent materials. Examples of the substrate 102 include, but are not limited to, a glass substrate or a plastic substrate, and the organic light-emitting device made of the plastic substrate has the advantage of flexibility. Examples of the anode 104 include, but are not limited to, transparent conductive metal oxide films, such as indium tin oxide (ITO for short).

Materials for the hole transport layer 106 include, for example, N,N'-bis-(1-naphthyl)-N,N'-diphenyl, 1,1'-biphenyl-4,4'-diamine ( N, N'-bis-(1-naphthyl)-N, N'-diphenyl, 1, 1'-biphenyl-4, 4'-diamine, referred to as NPB).

2 is a schematic diagram of an organic light-emitting layer 208 of the present invention, which includes a first light-emitting layer (B1 layer) 218, a second light-emitting layer (Y1 layer) 228 formed on the first light-emitting layer, and a second light-emitting layer (Y1 layer) formed on the second light-emitting layer. The third light emitting layer (B2 layer) 238 on the light emitting layer. Wherein, the first light-emitting layer 218 is in contact with or close to the hole transport layer, and the third light-emitting layer 238 is in contact with or close to the electron transport layer. More specifically, the first light-emitting layer 218 and the third light-emitting layer 238 are short-wavelength light-emitting layers, preferably blue light-emitting layers, and the second light-emitting layer 228 is a long-wavelength light-emitting layer, preferably yellow or red light-emitting layers .

3 is a schematic diagram of another organic light-emitting layer 308 according to the present invention. The organic light-emitting layer includes a first light-emitting layer (B1 layer) 318, a second light-emitting layer (Y1 layer) 328 formed on the first light-emitting layer, and formed on the second light-emitting layer. A fourth light emitting layer (Y2 layer) 348 on the second light emitting layer, and a third light emitting layer (B2 layer) 338 formed on the fourth light emitting layer. Wherein, the first light-emitting layer 318 is in contact with or close to the hole transport layer, and the third light-emitting layer 338 is in contact with or close to the electron transport layer. More specifically, the first light-emitting layer 318 and the third light-emitting layer 338 are short-wavelength light-emitting layers, preferably blue light-emitting layers, and the second light-emitting layer 328 and the fourth light-emitting layer of long-wavelength light-emitting layers are arranged between them. Layer 348 is preferably a yellow or red light emitting layer.

In one embodiment, the first light-emitting layer includes a first light-emitting host material, a first transition metal organic complex, and a carrier transport material, and the second light-emitting layer includes a second light-emitting host material and a second transition metal organic complex. compound, the third light-emitting layer includes a third light-emitting host material, a first transition metal organic complex and a carrier transport material, wherein the triplet of the first light-emitting host material, the third light-emitting host material and the carrier transport material The state energy levels are larger than those of the first transition metal organic complexes. In a specific embodiment, the triplet energy levels of the first light-emitting host material and the third light-emitting host material are greater than 2.7 eV.

In a preferred embodiment, the first light emitting layer is located between the anode and the second light emitting layer, and the third light emitting layer is located between the second light emitting layer and the cathode.

In the specific implementation of the present invention, the first luminescent host material and the third luminescent host material are different materials, and the second luminescent host material is the same material as either the first luminescent host material or the third luminescent host material .

In a specific embodiment, the first light-emitting host material is selected from carbazole-based compounds or aromatic compounds containing tertiary amines. Preferably, one or more main luminescent materials can be selected, specifically, the first luminescent host material is selected from 9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl) -9H-carbazole (CzSi), 2,2'-bis(4-carbazolylphenyl)-1,1'-biphenyl (4CzPBP), 4,4'-bis(9-carbazolyl)- 2,2'-Dimethyl-biphenyl (CDBP), N,N'-dicarbazolyl-2,5-benzene (mCP), 3,5-bis(9-carbazolyl)tetraphenylsilane (SimCP), tris[4-(9-phenylfluoren-9-yl)phenyl]amine (TFTPA), 4,4',4'-tris(N-carbazolyl)triphenylamine (TCTA) , bis[4-(p,p'-dimethyldianilino)-phenyl]diphenylsilane (DTASi), 1,1-bis[4-[N,N-bis(p-tolyl) Amino]phenyl]cyclohexane (TAPC) or combinations thereof.

In a specific embodiment of the present invention, the third luminescent host material may be selected from phosphineoxide-based, triazine-based compounds or imidazole-based compounds. Preferably, one or more third light-emitting host materials can also be selected in the third light-emitting layer, specifically, the third light-emitting host material is selected from phosphine oxide 2,8-bis(diphenylphosphino ) dibenzofuran (DPDBF), 2,8-bis(diphenylphosphino)dibenzothiophene (PPT), 2,4,6-carbazolo-1,3,5-triazine (TRZ) , 1,3,5-tris(phenylbenzimidazol-2-yl)benzene (TPBI), or combinations thereof.

In the organic light-emitting device of the present invention, the first transition metal organic complex contained in the first light-emitting layer and the third light-emitting layer is the same transition metal organic complex.

In a specific embodiment, the first transition metal organic complex is one that can generate blue light, and is independently selected from bis(4,6-difluorophenyl)-pyridine-N,C ² ') iridium(III) picolinate (FIrpic), bis(4',6'-difluorophenylpyridine) tetra(1-pyrazolyl)iridium(III) borate (FIr6), bis(4,6-difluorophenylpyridine)(3- (Trifluoromethyl)-5-(pyridin-2-yl)-1,2,4-triazine ester iridium (III) (FIrtaz), or bis(4,6-difluorophenylpyridine) (5- (Pyridin-2-yl)-1H-tetrazine ester iridium (III) (FIrN4) and the like.

In the organic light-emitting device of the present invention, the second transition metal organic complex contained in the second light-emitting layer and the optional fourth light-emitting layer is one that can generate red light or yellow light. In a specific embodiment, the second transition metal organic complex can be selected from bis(2-phenylquinolyl-N, C2) (acetylacetonate) iridium (III) (PQIr) or PO-01 with the following structure wait.

In a specific embodiment, the carrier transport material can be an aromatic compound containing a tertiary amine, selected from the following structural formula (I) or (II):

Among them, Ar1, Ar2 and Ar3 are independently selected from C ₆ -X ₁₀ aryl groups or C ₆ -C ₁₀ aryl groups substituted by 1 to 3 substituents, wherein the substituents are selected from C ₁ -C ₆ alkyl groups, C ₁ -C ₆ alkoxy, C ₁ -C ₆ alkylamino, N-carbazolyl or 9-phenylfluoren-9-yl; and L is independently selected from a single covalent bond, C ₃ -C ₁₀ Cycloalkyl, silicon, mono- or di-phenylsilyl.

Preferably, the carrier transport material can be selected from tris[4-(9-phenylfluoren-9-yl)phenyl]amine (TFTPA), 4,4',4'-tris(N-carbazolyl ) triphenylamine (TCTA), bis[4-(p,p'-dimethyldianilino)-phenyl]diphenylsilane (DTASi), 1,1-bis[4-[N,N - bis(p-tolyl)amino]phenyl]cyclohexane (TAPC) or combinations thereof.

The following chemical formula and Table 1 illustrate the main luminescent material, carrier transport material and phosphorescent material used in the embodiment of the present invention.

The luminescent host material of the B1 layer The luminescent host material of the B2 layer

                                                                         

Phosphorescent material of Y1 layer and Y2 layer Phosphorescent material of Y1 layer and Y2 layer

Table 1

compound HOMO(eV) LUMO(eV) triplet energy level 4CzPBP 6.1 2.6 2.8 PPT 6.6 2.9 3.1 DTASi 5.6 2.3 3.0 Bphen 6.4 3.0 2.5 FIrpic 5.8 2.9 2.7 TCTA 5.9 2.7 2.9

Therefore, referring to FIG. 1, when an external voltage is applied to the white light organic light-emitting element of the present invention, electrons and holes will be transported to the organic light-emitting layer 108 through the electron transport layer 110 and the hole transport layer 106, and then the electrons and holes It will be combined in the organic light-emitting layer 108 to emit light. At this time, since the triplet energy level of the light-emitting host material and the triplet energy level of the carrier transport material are respectively greater than the triplet energy level of the transition metal organic complex, the required element operating voltage is low and can simultaneously Improve the luminous efficiency of components.

The following is a description of various embodiments of the white light organic light-emitting device of the present invention, but the materials, thicknesses and concentrations used in each layer are not intended to limit the scope of the present invention.

Example 1

In Example 1, the ingredients contained in B1, B2, Y1, and Y2 are as follows:

B1: the main luminescent material 4CzPBP, the first transition metal organic complex FIrpic and the carrier transport material TCTA, the weight ratio of each component is 75:15:10.

Y1: the main luminescent material 4CzPBP, the second transition metal organic complex PO-01 and the carrier transport material TCTA, the weight ratio of each component is 85:5:10.

Y2: the main luminescent material PPT, the second transition metal organic complex PO-01 and the carrier transport material TCTA, the weight ratio of each component is 85:5:10.

B2: the main luminescent material PPT, the first transition metal organic complex FIrpic and the carrier transport material TCTA, the weight ratio of each component is 75:15:10.

And prepare the white light organic light-emitting element of the present invention according to the following process.

Form 150 nanometers (nm) indium tin oxide (ITO) as an anode on a glass substrate with a thickness of 0.7 millimeters (mm), and then plate NPB with a thickness of 10 nm on the anode as a hole transport layer by thermal evaporation. Next, DTASi with a thickness of 20 nm was plated on the hole transport layer by thermal evaporation as an electron blocking layer. 4CzPBP, FIrpic and TCTA were co-evaporated on the electron blocking layer to form the first light-emitting layer (layer B1) with a thickness of 8 nm. Next, 4CzPBP, PO-01 and TCTA were co-evaporated on the first light-emitting layer to form a second light-emitting layer (Y1 layer) with a thickness of 0.2 nm. Next, PPT, PO-01 and TCTA were co-evaporated on the second light-emitting layer to form a fourth light-emitting layer (Y2 layer) with a thickness of 0.2 nm. Next, PPT, FIrpic and TCTA were co-evaporated on the fourth light-emitting layer to form a third light-emitting layer (layer B2) with a thickness of 0.2 nm.

Afterwards, on the third light-emitting layer, 4,7-diphenyl-1,10-phenanthroline (4,7-diphenyl-1,10-phenanthroline, hereinafter referred to as Bphen) as the electron transport layer. Next, cesium carbonate (Cs ₂ CO ₃ ) and Bphen with a weight ratio of 20:80 were co-evaporated on the electron transport layer to form an electron injection layer with a thickness of 20 nm. Finally, an aluminum cathode with a thickness of 100 nm is formed by thermal evaporation.

In this embodiment, the light-emitting layer B1-Y1-Y2-B2 is composed of four layers of blue-yellow-yellow-blue, and each layer includes a carrier transport material. Table 2 shows the test results of the current efficiency and operating voltage when the component brightness is 1000cd/m ² , and the component white light chromaticity coordinates.

Example 2

In Example 2, the ingredients included in B1, B2, Y1, and Y2 are as follows:

B1: the main luminescent material 4CzPBP, the first transition metal organic complex FIrpic and the carrier transport material TCTA, the weight ratio of each component is 75:15:10.

Y1: the main luminescent material 4CzPBP, and the second transition metal organic complex PO-01, the weight ratio of each component is 95:5.

Y2: the main luminescent material PPT, and the second transition metal organic complex PO-01, the weight ratio of each component is 95:5.

B2: the main luminescent material PPT, the first transition metal organic complex FIrpic and the carrier transport material TCTA, the weight ratio of each component is 75:15:10.

In addition, the white light organic light-emitting element of Example 2 was prepared according to the procedure described in Example 1.

In this embodiment, the light-emitting layer B1-Y1-Y2-B2 is composed of blue-yellow-yellow-blue four layers, and Y1 and Y2 do not contain carrier transport materials. Table 2 shows the test results of current efficiency and operating voltage when the device brightness is 1000cd/m ² , and the white light chromaticity coordinates of the device.

Example 3

In Example 3, the ingredients included in B1, B2, and Y1 are as follows:

B1: the main luminescent material 4CzPBP, the first transition metal organic complex FIrpic and the carrier transport material TCTA, the weight ratio of each component is 75:15:10.

Y1: the second transition metal organic complex PO-01.

B2: the main luminescent material PPT, the first transition metal organic complex FIrpic and the carrier transport material TCTA, the weight ratio of each component is 75:15:10.

In addition, the white light organic light-emitting element of Example 3 was prepared according to the procedure described in Example 1, wherein the thickness of the Y1 layer was 0.1 nm. In this embodiment, the light-emitting layer B1-Y1-B2 is composed of three layers of blue-yellow-blue. Table 2 shows the test results of current efficiency and operating voltage when the device brightness is 1000cd/m ² , and the white light chromaticity coordinate system of the device.

Comparative example 1

The ingredients contained in B1, B2, Y1, and Y2 are as follows:

B1: the main luminescent material 4CzPBP, and the first transition metal organic complex FIrpic, the weight ratio of each component is 85:15.

Y1: the main luminescent material 4CzPBP, and the second transition metal organic complex PO-01, the weight ratio of each component is 95:5.

Y2: the main luminescent material PPT, and the second transition metal organic complex PO-01, the weight ratio of each component is 95:5.

B2: the main luminescent material PPT and the first transition metal organic complex FIrpic, the weight ratio of each component is 85:15.

In addition, the white light organic light-emitting element of Comparative Example 1 was prepared according to the procedure described in Example 1.

In this embodiment, the light-emitting layer B1-Y1-Y2-B2 is composed of four layers of blue-yellow-yellow-blue, and B1, B2, Y1, and Y2 are not added with carrier transport materials. Table 2 shows the test results of current efficiency and operating voltage when the device brightness is 1000cd/m ² , and the white light chromaticity coordinates of the device.

Comparative example 2

The ingredients contained in B1, B2, and Y1 are as follows:

B1: the main luminescent material 4CzPBP, and the first transition metal organic complex FIrpic, the weight ratio of each component is 85:15.

Y1: the main luminescent material 4CzPBP, and the second transition metal organic complex PO-01, the weight ratio of each component is 95:5.

B2: the main luminescent material 4CzPBP, and the first transition metal organic complex FIrpic, the weight ratio of each component is 85:15.

And prepare the white light organic light-emitting element of the present invention according to the following process.

Form 150 nanometers (nm) indium tin oxide (ITO) on a glass substrate with a thickness of 0.7 millimeters (mm) as an anode, and then plate NPB with a thickness of 10 nm on the anode as a hole transport layer by thermal evaporation, and then DTASi with a thickness of 20 nm was plated on the hole transport layer by thermal evaporation as an electron blocking layer. 4CzPBP and FIrpic were co-evaporated on the electron blocking layer to form a first light-emitting layer (layer B1) with a thickness of 8 nm. Next, 4CzPBP and PO-01 were co-evaporated on the first light-emitting layer to form a second light-emitting layer (Y1 layer) with a thickness of 0.2 nm. Next, 4CzPBP and FIrpic were co-evaporated on the second light-emitting layer to form a third light-emitting layer (B2 layer) with a thickness of 8 nm.

Afterwards, on the third light-emitting layer, Bphen with a thickness of 25 nm was deposited as an electron transport layer by thermal evaporation. Next, cesium carbonate and Bphen with a weight ratio of 20:80 were co-evaporated on the electron transport layer to form an electron injection layer with a thickness of 20 nm. Finally, an aluminum cathode with a thickness of 100 nm is formed by thermal evaporation.

In this comparative example, the light-emitting layer B1-Y1-B2 is composed of three layers of blue-yellow-blue light, B1 and B2 have the same main light-emitting material, and each layer does not contain a carrier transport material. Table 2 shows the test results of current efficiency and operating voltage when the device brightness is 1000cd/m ² , and the white light chromaticity coordinates of the device.

Comparative example 3

The ingredients contained in B1 and Y1 are as follows:

B1: the main luminescent material 4CzPBP, the first transition metal organic complex FIrpic and the carrier transport material TCTA, the weight ratio of each component is 75:15:10.

Y1: the main luminescent material 4CzPBP, and the second transition metal organic complex PO-01, the weight ratio of each component is 95:5.

And prepare the white light organic light-emitting element of the present invention according to the following process.

Form 150nm indium tin oxide (ITO) on a glass substrate with a thickness of 0.7mm as an anode, and then coat the anode with 10nm thick NPB as a hole transport layer by thermal evaporation, and then thermally evaporate DTASi with a thickness of 20 nm was plated on the hole transport layer as an electron blocking layer. 4CzPBP and PO-01 were co-evaporated on the electron blocking layer to form a second light emitting layer (Y1 layer) with a thickness of 12 nm. Next, 4CzPBP, FIrpic and TCTA were co-evaporated on the second light-emitting layer to form a first light-emitting layer (layer B1) with a thickness of 8 nm. Afterwards, on the first light-emitting layer, Bphen with a thickness of 25 nm was deposited as an electron transport layer by thermal evaporation. Next, cesium carbonate and Bphen with a weight ratio of 20:80 were co-evaporated on the electron transport layer to form an electron injection layer with a thickness of 20 nm. Finally, an aluminum cathode with a thickness of 100 nm is formed by thermal evaporation.

In this comparative example, the light-emitting layer Y1-B1 is composed of two layers of yellow-blue light. Table 2 shows the test results of current efficiency and operating voltage when the device brightness is 1000cd/m ² , and the white light chromaticity coordinates of the device.

Table 2

For chromaticity coordinates, the chromaticity coordinates (x, y) of the standard white formulated by the International Commission on Illumination (Commission International del'Eclairage, CIE) are (0.33, 0.33), but white light also includes different color temperatures (such as cool white, Daylight white, warm white, etc.), so the CIE chromaticity value of white light has a relatively large range of variation.

According to the results shown in Table 2, compared with Comparative Example 1, the elements of Examples 1 and 2 of the present invention (layers B1 and B2 have carrier transport materials) have carrier transport materials in the blue light-emitting layer. , effectively reduce the operating voltage by 16% and improve the device efficiency by about 36-43%. Compared with Comparative Example 2, the elements of Examples 1 and 2 of the present invention (the B1 layer and the B2 layer have carrier transport materials), when the two blue light-emitting layers are formed of different light-emitting host materials, the operating voltage can be effectively reduced and the element can be improved. efficiency. In addition, in the device of Example 3 of the present invention, when the yellow light-emitting layer is formed of a single transition metal organic complex, the device can still maintain high luminous efficiency and low operating voltage.

To sum up, the white light organic light emitting element of the present invention can simultaneously reduce the operating voltage of the white light organic light emitting element and significantly improve the luminous efficiency of the element, and can provide white light with stable chromaticity.

The above examples are only illustrative to illustrate the composition and preparation method of the present invention, and are not intended to limit the present invention. Any person skilled in the art can modify and change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the appended claims.

Claims (13)

1. organic white-light emitting element comprises:

Anode;

Hole transmission layer, it is formed on this anode;

Be formed at first luminescent layer on this hole transmission layer, it comprises the first luminous material of main part, first metal organic complex and carrier transmission material;

Be formed at second luminescent layer on this first luminescent layer, make this first luminescent layer be folded between this hole transmission layer and second luminescent layer, this second luminescent layer comprises second metal organic complex;

Be formed at the 3rd luminescent layer on this second luminescent layer, make this second luminescent layer be folded between this first luminescent layer and the 3rd luminescent layer, the 3rd luminescent layer comprises the 3rd luminous material of main part, first metal organic complex and carrier transmission material;

Electron transfer layer, it is formed on the 3rd luminescent layer, makes the 3rd luminescent layer be folded between this second luminescent layer and the electron transfer layer; And

Negative electrode, it is formed on the lateral surface of electron transfer layer;

Wherein, the emission wavelength of this second luminescent layer is longer than the emission wavelength of first luminescent layer and the 3rd luminescent layer, and this first luminous material of main part and the 3rd luminous material of main part are different materials;

Also comprise the 4th luminescent layer that is formed between first luminescent layer and the 3rd luminescent layer; The 4th luminescent layer comprises the 4th luminous material of main part and second metal organic complex, and the emission wavelength of the 4th luminescent layer is longer than the emission wavelength of first luminescent layer and the 3rd luminescent layer.

2. organic white-light emitting element as claimed in claim 1, wherein, this second luminescent layer also comprises second luminous material of main part and the carrier transmission material.

3. organic white-light emitting element as claimed in claim 2, wherein, this second luminous material of main part is and one of the first luminous material of main part or the 3rd luminous material of main part identical materials.

4. organic white-light emitting element as claimed in claim 1, wherein, the emission wavelength of this first luminescent layer and the 3rd luminescent layer is 400 to 480nm, the emission wavelength of this second luminescent layer is 520 to 640nm.

5. organic white-light emitting element as claimed in claim 1, wherein, the 4th luminescent layer also comprises carrier transmission material.

6. organic white-light emitting element as claimed in claim 2, wherein, the 4th luminous material of main part is and one of the first luminous material of main part or the 3rd luminous material of main part identical materials, and with the second luminous material of main part be material different.

7. organic white-light emitting element as claimed in claim 2; Wherein, the triplet of this carrier transmission material and the first and the 3rd luminous material of main part can rank all can rank greater than the triplet of this first metal organic complex and the triplet of this carrier transmission material and the second luminous material of main part can rank all can rank greater than the triplet of this second metal organic complex.

8. organic white-light emitting element as claimed in claim 1, wherein, this carrier transmission material is selected from following structural (I) or (II):

Wherein, Ar1, Ar2 and Ar3 independently are selected from C ₆-C ₁₀Aryl or 1 to 3 substituted C of substituting group of warp ₆-C ₁₀Aryl, wherein, this substituting group is selected from C ₁-C ₆Alkyl, C ₁-C ₆Alkoxyl, C ₁-C ₆Alkyl amine group, N-carbazyl or 9-phenyl fluorenes-9-base; And

L independently is selected from single covalent bond, C ₃-C ₁₀Cycloalkyl, silicon, list-or two-phenyl silane base.

9. organic white-light emitting element as claimed in claim 8; Wherein, this carrier transmission material is selected from three [4-(9-phenyl fluorenes-9-yl) phenyl] amine, 4,4 '; 4 '-three (N-carbazyl) triphenylamine, two [4-(p; P '-dimethyl hexichol amido)-and phenyl] diphenyl silane, and 1, at least a in two [4-[N, N-two (p-tolyl) amido] phenyl] cyclohexanes of 1-.

10. organic white-light emitting element as claimed in claim 1, wherein, the aromatic series compounds that this first luminous material of main part is selected from carbazole compound or contains tertiary amine.

11. organic white-light emitting element as claimed in claim 1, wherein, the 3rd luminous material of main part is selected from phosphine oxide compounds, compound in triazine class or glyoxaline compound.

12. organic white-light emitting element as claimed in claim 1, wherein, this first metal organic complex independently is selected from two (4, the 6-difluorophenyl)-pyridine-N, C ²') pyridine carboxylic acid iridium (III), two (4 '; 6 '-difluorophenyl pyridine) four (1-pyrazolyl) boric acid iridium (III), two (4; 6-difluorophenyl pyridine) (3-(trifluoromethyl)-5-(pyridine-2-yl)-1; 2,4-triazine ester iridium (III) or two (4,6-difluorophenyl pyridine) (5-(pyridine-2-yl)-1H-tetrazine ester iridium (III).

13. organic white-light emitting element as claimed in claim 1, wherein, this second metal organic complex is selected from two (2-phenylchinoline base-N, C2) (acetylacetone,2,4-pentanedione) iridium (III) or have the PO-01 of following formula

Images