TWI886031B - Organic electroluminescent devices and material thereof - Google Patents

Abstract

A material of the organic electroluminescent devices is provided. The material comprises a structure represented by following Formula (I): (I); wherein R ₁、R ₂、R ₃、R ₄、R ₅and R ₆are individually selected from H, C _5-10alkyl group, , or

Description

Organic electroluminescent device and its materials

The present invention relates to an organic electroluminescent device and a material thereof, and in particular to a novel material that can be used for an electron transport layer of an organic electroluminescent device.

Organic light-emitting diodes (OLEDs) are light-emitting devices manufactured using the principle of organic electroluminescence (OEL). The principle of luminescence is that under a certain electric field, electrons and holes pass through the hole transport layer (HTL) and the electron transport layer (ETL) respectively, and then enter an organic substance with luminescent properties (organic luminescent layer). When electrons and holes recombine in this luminescent layer, an "exciton" is first formed, and then the energy is released and returns to the ground state. Part of the released energy is released in the form of light of different colors, making the OLED glow.

As the name suggests, the main function of the hole transport layer HTL is to promote the movement of electrons and holes to reduce voltage and improve device efficiency. Currently, the hole transport layer materials commonly used in OLED devices include α-NPD, TPD, m-MTDATA, NPB and other materials mainly formed by the combination of tertiary amines and phenyl groups.

When the ITO electrode surface is treated with UV-ozone, the work function of the ITO surface can be increased to about 5.0 eV, but this value is still about 0.4 eV different from the HOMO energy level of most hole transport materials. Therefore, if a material with a suitable HOMO energy level can be added between ITO and the hole transport layer, it will help increase the hole transfer between the interfaces. This structure is the hole injection layer.

However, when the refractive index of adjacent layers of a light-emitting element is different, total reflection is likely to occur, making it difficult for light to pass through the element, resulting in a decrease in element efficiency. Currently, the commonly used hole injection material in OLED elements is 2-TNATA, which has a glass transition temperature Tg of about 130°C and a refractive index of about 1.9, which is relatively high. Therefore, the development of better light-emitting materials has always been the goal of all related manufacturers.

The present invention provides a material for an organic electroluminescent device, the compound structure and product characteristics of which are different from those of the prior art, and is a novel invention.

According to one embodiment of the present invention, a material for an organic electroluminescent device is provided, which has a structure shown in the following chemical formula (I): (I).

In formula (I), R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are each independently selected from H , C _5-10 alkyl, , or .

In one embodiment, the material of formula (I) is a compound represented by any one of the following chemical formulas: , , , HIL1 HIL2 HIL3 , , , HIL4 HIL5 HIL6 , , , HIL7 HIL8 HIL9 , and . HIL10 HIL11 HIL12

In one embodiment, the above material is used as a hole injection layer of an organic electroluminescent device.

In one embodiment, the material has a glass transition temperature higher than 170° C. and a refractive index lower than 1.85.

According to another embodiment of the present invention, an organic electroluminescent device is provided, which includes a layered structure arranged in the following order: a transparent substrate, an anode layer, a hole injection layer, a hole transport layer, a luminescent layer, an electron transport layer, and a cathode layer. The organic electroluminescent device is characterized in that the hole injection layer includes the above-mentioned materials.

In one embodiment, the organic electroluminescent device further includes an electron injection layer between the electron transport layer and the cathode layer.

In one embodiment, the anode layer and the cathode layer of the organic electroluminescent device are respectively in contact with an external power source to form an electrical path.

In one embodiment, the organic electroluminescent device is a blue light, green light or orange light OLED.

In one embodiment, the refractive index of the hole injection layer of the organic electroluminescent device is lower than 1.85.

Specifically, the novel structural material of the present invention is easier to prepare and purify than conventional hole injection materials, and has better glass transition temperature, refractive index and other properties. When this material is used as an electron transport layer, the organic electroluminescent device produced has higher current efficiency and external quantum efficiency than the organic electroluminescent device using conventional materials, which can improve the efficiency of the light-emitting element.

The present invention provides a material for an organic electroluminescent device having a structure shown in the following chemical formula (I): (I).

In formula (I), R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are each independently selected from H , C _5-10 alkyl, , or .

"Each independently" means that each substituent can be the same or different. For example, R ₁ , R ₂ , R ₃ can be the same as R ₄ , R ₅ , R ₆ (i.e., the substituents on the four benzene rings correspond), or different from R ₄ , R ₅ , R ₆ (i.e., there are two groups of benzene rings with different substituents in formula (I)). Alternatively, R ₁ , R ₂ , R ₃ can also be exactly the same (i.e., the substituents on the benzene rings are exactly the same), or can be three different substituents.

_C5-10 alkyl represents an alkyl group containing 5, 6, 7, 8, 9 or 10 carbons.

Substituents (Second butyl), (tert-butyl) and The wavy line ﹏ on (adamantane) represents the position where the substituent is attached to the benzene ring in formula (I).

The material of formula (I) can be obtained, for example, by the following synthesis method:

Step 1 : Suzuki coupling ​ ​ (Intermediate A)

This method yields the symmetrical intermediate A. Or (Intermediate B)

This method obtains an asymmetric intermediate B in which R ₁ , R ₂ , R ₃ are different from R ₄ , R ₅ , R _{6 .}

Step 2 : Buchwald - Hartwig coupling (Intermediate) (Starting material) (HOL material)

The above synthesis method has only two steps, using Suzuki coupling reaction and Buchwald-Hartwig coupling reaction respectively, both of which are common organic synthesis reactions in industrial applications. The above reaction is used for synthesis, the reaction time is short and the preparation is easy, and the by-products are less and the purification difficulty is lower. In addition, the starting materials for preparing the intermediates and the starting materials of step 2 can be obtained through simple synthesis or purchased on the commercial market.

The following uses several application examples to illustrate the various steps of the above reaction. However, it should be noted that the proportions and types of the components added in the examples are only for demonstration purposes and are not intended to limit the present invention. Example 1

Synthesis of Intermediate A1 (A1)

In a 500 ml three-neck flask under nitrogen, place 11.5 g of di(4-bromophenyl)amine, 13.1 g of 4-tert-butylphenylboric acid, and 240 ml of toluene and mix. Weigh 14.5 g of potassium carbonate into a beaker, add 80 ml of water to dissolve, and add to the three-neck flask. Add 4.1 g of tetrakis(triphenylphosphine)palladium and heat to reflux. After reacting for 6 hours, cool down and pour the reaction into a beaker containing 300 ml of methanol. After stirring for 30 minutes, filter and collect the solid. Place the solid in a 500 ml three-neck flask, add 150 ml of ethyl acetate, heat to reflux and stir. After cooling to room temperature, filter and collect the solid, and dry the solid to prepare 11.4 g of intermediate A1 with a yield of 75%. Example 2

Synthesis of Intermediate A2 (A2)

Following the synthesis steps of compound A1 (Example 1), 13.1 g of 4-tert-butylphenylboronic acid was replaced with 17.2 g of 3,5-di-tert-butylphenylboronic acid, and other reagents were adjusted according to the same molar ratio to prepare 16.1 g of intermediate A2 with a yield of 84%. Example 3

Synthesis of Intermediate A3 (A3)

Following the synthesis steps of compound A1 (Example 1), 13.1 g of 4-tert-butylphenylboronic acid was replaced with 18.8 g of (4-(adamantan-1-yl)phenyl)boronic acid, and other reagents were adjusted in the same molar ratio to prepare 13.4 g of intermediate A3 with a yield of 65%. Example 4

Synthesis of Intermediate B1 (B1)

In a 500 ml three-neck flask under nitrogen, place 11.4 g of N-(4-bromophenyl)-biphenyl-4-amine, 6.5 g of 4-tert-butylphenylboric acid, and 240 ml of toluene and mix. Weigh 9.7 g of potassium carbonate into a beaker, add 80 ml of water to dissolve, and add to the three-neck flask. After adding 2.0 g of tetrakis(triphenylphosphine)palladium, heat the reaction until reflux. After reacting for 4 hours, cool down and pour the reaction into a beaker containing 300 ml of methanol. After stirring for 30 minutes, filter and collect the solid. Place the solid in a 500 ml three-neck flask, add 150 ml of ethyl acetate, heat to reflux and stir. After cooling to room temperature, filter and collect the solid, and dry the solid to prepare 10.4 g of intermediate B1 with a yield of 79%. Example 5

Synthesis of Intermediate B2 (B2)

Following the synthesis steps of compound B1 (Example 4), 6.5 g of 4-tert-butylphenylboronic acid was replaced with 8.6 g of 3,5-di-tert-butylphenylboronic acid, and other reagents were adjusted according to the same molar ratio to prepare 13.4 g of intermediate B2 with a yield of 88%. Example 6

Synthesis of Intermediate B3 (B3)

Following the synthesis steps of compound B1 (Example 4), 6.5 g of 4-tert-butylphenylboronic acid was replaced with 9.4 g of (4-(adamantan-1-yl)phenyl)boronic acid, and other reagents were adjusted in the same molar ratio to prepare 11.3 g of intermediate B3 with a yield of 71%. Example 7

Synthesis of hole injection layer material HIL1 (HIL1) (Intermediate A1)

In a 250 ml three-necked flask under nitrogen, 4.7 g of 2,2'-dibromo-9,9'-spirobifluorene and 9.0 g of intermediate A1 were placed, 100 ml of toluene (Tol) was stirred and dissolved, 3.3 g of potassium tert-butoxide, 0.22 g of sodium acetate, and 0.52 g of tri-tert-butylphosphine were added, and the mixture was heated to reflux for 2 hours. After cooling and concentration, a solid was precipitated. The solid was recrystallized twice with tetrahydrofuran/methanol (THF/MTA), and filtered to obtain 7.5 g of the finished product HIL1 with a purity of 99% and a yield of 64%. After sublimation and purification, 6.0 g of the product was obtained.

¹ H NMR (400MHz, CDCl ₃ ): δ7.66(d, 2H), δ7.62(d, 2H), δ7.49-7.35(m, 24H), δ7.29(t, 2H), δ7.09-7.01(m, 12H), δ6.75(d, 2H), δ6.72(d, 2H), δ1.32(s, 36H).

MS (m/z): [M ⁺ ] calcd. C89H82N2 for, 1178.7; found, 1178.7 Example 8

Synthesis of HIL4 (Intermediate A2) (HIL4)

Following the synthesis steps of compound HIL1 (Example 7), 9.0 g of intermediate A1 was replaced with 11.4 g of intermediate A2, and other reagents were adjusted according to the same molar ratio to prepare 10 g of HIL4 with a purity of 99% and a yield of 72%. After sublimation and purification, 8.5 g of the product was obtained.

¹ H NMR (400MHz, CDCl ₃ ): δ7.66(d, 2H), δ7.62(d, 2H), δ7.49-7.25(m, 24H), δ7.09-7.01(m, 10H), δ6.76(d, 2H), δ6.71(d, 2H), δ1.33(s, 72H).

MS (m/z): [M ⁺ ] calcd. C105H114N2 for, 1403.9; found, 1404.0 Example 9

Synthesis of HIL6 (Intermediate A3) (HIL6)

Following the synthesis steps of compound HIL1 (Example 7), 9.0 g of intermediate A1 was replaced with 12.3 g of intermediate A3, and other reagents were adjusted according to the same molar ratio to prepare 8.6 g of HIL6 with a purity of 99% and a yield of 58%. After sublimation and purification, 4.6 g of the product was obtained.

¹ H NMR (400MHz, CDCl ₃ ): δ7.64(d, 2H), δ7.62(d, 2H), δ7.51-7.33(m, 24H), δ7.28(t, 2H), δ7.11-7.02(m, 12H), δ6.76(d, 2H), δ6.72(d, 2H), δ2.20-1.67(m, 60H).

MS (m/z): [M ⁺ ] calcd. C113H106N2 for, 1491.8; found, 1491.9 Example 10

Synthesis of HIL7 (Intermediate B1) (HIL7)

Following the synthesis steps of compound HIL1 (Example 7), 9.0 g of intermediate A1 was replaced with 7.9 g of intermediate B1, and other reagents were adjusted according to the same molar ratio to prepare 7.4 g of HIL7 with a purity of 99% and a yield of 70%. After sublimation and purification, 5.8 g of the product was obtained.

¹ H NMR (400MHz, CDCl ₃ ): δ7.65(dd, 4H), δ7.50 (d, 4H), δ7.45-7.25(m, 28H), δ7.15-7.00(m, 10H), δ6.76(d, 2H), δ1.32(s, 18H).

MS (m/z): [M ⁺ ] calcd. C81H66N2 for, 1066.5; found, 1066.6 Example 11

Synthesis of HIL10 (Intermediate B2) (HIL10)

Following the synthesis steps of compound HIL1 (Example 7), 9.0 g of intermediate A1 was replaced with 9.0 g of intermediate B2, and other reagents were adjusted according to the same molar ratio to prepare 9.0 g of HIL10 with a purity of 99% and a yield of 77%. After sublimation and purification, 7.2 g of the product was obtained.

¹ H NMR (400MHz, CDCl ₃ ): δ7.65(dd, 4H), δ7.49 (d, 4H), δ7.45-7.25(m, 24H), δ7.15-7.00(m, 10H), δ6.76(d, 2H), δ6.73(d, 2H), δ1.34(s, 36H).

MS (m/z): [M ⁺ ] calcd. C89H82N2 for, 1178.7; found, 1178.7 Example 12

Synthesis of HIL12 (Intermediate B3) (HIL12)

Following the synthesis steps of compound HIL1 (Example 7), 9.0 g of intermediate A1 was replaced with 9.0 g of intermediate B3, and other reagents were adjusted according to the same molar ratio to prepare 7.5 g of HIL12 with a purity of 99% and a yield of 62%. After sublimation and purification, 5.4 g of the product was obtained.

¹ H NMR (400MHz, CDCl ₃ ): δ7.64(dd, 4H), δ7.49 (d, 4H), δ7.46-7.24(m, 28H), δ7.16-7.00(m, 10H), δ6.75(d, 2H), δ2.20-1.67(m, 30H).

MS (m/z): [M+] calcd. C93H78N2 for, 1223.6; found, 1223.7 Example 13 Synthesis of other HIL compounds

The above Examples 1-12 introduce the synthesis examples of several compounds of formula (I) (HIL1, 4, 6, 7, 10, 12), but are not limited thereto. A person skilled in the art can prepare different intermediates according to the synthesis steps of the above Examples and use different starting materials to obtain different HIL materials. For example, different intermediates A and B can be obtained by using different starting materials for Suzuki coupling reaction according to the preparation method of Example 1, as shown in Table 1 below.

Table 1 Comparison table of starting materials and products (intermediate A and intermediate B) of Suzuki coupling reaction A1 [ Example 1] B1 [ Example 4] A2 [ Example 2] B2 [ Example 5] A3 [ Example 3] B3 [ Example 6] A4 B4 A5 B5 A6 B6

By using different intermediates A and intermediates B shown in Table 1, and 2,2'-dibromo-9,9'-spirobifluorene (67665-47-8), and following the same synthesis method as taught in Example 7, different HIL products as shown in Table 2 below can be prepared.

Table 2 Comparison table of intermediates and HIL products Intermediate Starting material HIL Products A1 67665-47-8 HIL1 [Example 7] A2 HIL4 [Example 8] A3 HIL6 [Example 9] A4 HIL2 A5 HIL3 A6 HIL5 B1 HIL7 [Example 10] B2 HIL10 [Example 11] B3 HIL12 [Example 12] B4 HIL8 B5 HIL9 B6 HIL11

In Table 1 and Table 2, the numbers under the chemical formula are CAS numbers, indicating that the drugs of the structure can be purchased on the commercial market. The bracket [Example X] (X represents the number of the example) indicates that the detailed preparation process of the compound has been described in Example X. According to Table 1 and Table 2, a variety of different HIL materials can be easily synthesized through different intermediates A and intermediates B. The detailed structures of various HIL products that meet formula (I) can be referred to in Table 3 below:

Table 3 HIL product list , , , HIL1 HIL2 HIL3 , , , HIL4 HIL5 HIL6 , , , HIL7 HIL8 HIL9 , and . HIL10 HIL11 HIL12 Example 14 Measurement of glass transition temperature (T _g ) and refractive index

The hole injection layer material synthesized in the above embodiment has a glass transition temperature (T _g ) measured by a differential scanning calorimetry (DSC) and a refractive index (n) at 460 nm measured by an ellipsometer. The results are listed in the following Table 4:

Table 4 Comparison of glass transition temperature (T _g ) and refractive index (n) _Tg (℃) n (@460nm) HIL 1 203 1.773 HIL 4 185 1.656 HIL 6 277 1.785 HIL 7 181 1.846 HIL 10 171 1.846 HIL 12 220 1.833 2-TNATA (Comparison Example 1) 110 1.901 Spiro-D Spiro-DBP (Comparative Example 2) 159 1.877

As shown in Table 4, the glass transition temperature (T _g ) of the materials of the present invention is higher than 170°C, and can even reach 277°C (HIL6). Compared with the currently commonly used hole injection layer materials (compare Examples 1 and 2), the materials have a higher glass transition temperature and higher thermal stability, and are suitable for application in industrial processes.

In addition, the refractive index (n) of the materials of the present invention is lower than 1.85, and the lowest can reach 1.656 (HIL4). Compared with the hole injection layer materials commonly used at present (compare Examples 1 and 2), it has a lower refractive index, which can effectively reduce the occurrence of total reflection in the device, thereby increasing the light extraction efficiency (LEE: Light Extraction Efficiency) of the device, and ultimately obtaining a higher device efficiency.

When the ratio of tert-butyl or adamantane in R _1-6 substituents in formula (I) is higher, the Tg of the material is higher; and when the ratio of alkyl in R _1-6 substituents is higher (i.e., the less adamantane in R _1-6 substituents), the n of the material is lower.

Please refer to FIG. 1, which shows a schematic diagram of the structure of the organic electroluminescent device 10 used in this embodiment. The organic electroluminescent device 10 of this embodiment is mainly prepared by vacuum evaporation, and includes a glass substrate 1, ITO 2 (anode layer), a hole injection layer 3 (hole injection layer, HIL), a hole transport layer 4 (hole transport layer, HTL), a luminescent layer 5 (host luminescent material and guest luminescent material), an electron transport layer 6 (electron transport layer, ETL) and a cathode layer 7. The anode layer 2 and the cathode layer 7 are respectively in contact with an external power source to form an electrical path. This embodiment uses this device to test the characteristics of the organic electroluminescent device of the present invention.

It is particularly noted that the organic electroluminescent device of the present invention is not limited to the above-mentioned aspects in actual application, and the structure can be adjusted according to the needs. For example, an electron injection layer (EIL) can be designed between the electron transport layer 6 and the cathode layer 7, and a hole blocking layer can be designed between the electron transport layer and the light-emitting layer. The present invention does not limit the structure of the organic electroluminescent device.

The characteristic of the organic electroluminescent device of this embodiment is that its hole injection layer 3 uses the compound HIL of formula (I) of the present invention, and adopts the known hole injection layer materials (2-TNATA, Spiro-D Spiro-DBP) as a comparative example. In addition, the materials used for other layers of the organic electroluminescent device of the embodiment and the comparative example are exactly the same, as shown in Table 5 below:

Table 5 Materials of each layer of the organic electroluminescent device 10 Structure Material Substrate 1 Glass Anode layer 2 Indium Tin Oxide ITO Hole injection layer (HIL)3 Inventive HIL or comparative example (2-TNATA, Spiro-DBP): 3% HAT-CN (60nm) Hole transport layer (HTL)4 HT-1 (20nm) Luminescent layer 5 Blue host: α,β-ADN guest: BD-1 5% (30nm) Green host: α,β-ADN guest: GD1-2 5% (35nm) Orange host: α,β-ADN guest: TBRb 5% (35nm) Electronic Transport Layer (ETL)6 ET-1 : 50% LiQ (20nm) cathode layer 7 LiF 1nm, Al 100nm

Depending on the light-emitting layer material used, the device can be a blue, green or orange OLED. The chemical structures of the materials mentioned in Table 5 are as follows:

The test results of organic electroluminescent devices using various HIL materials of the embodiments of the present invention and traditional materials as hole injection layers are shown in Table 6 below:

Table 6 Characteristics of organic electroluminescent devices of the embodiment and the comparative example Embodiment HIL:3% HAT-CN thickness Voltage* (V) EL max (nm) EQE* CE* (Cd/A) 1 HIL1 60nm 4.70 465 9.4% 14.5 2 HIL4 60nm 5.42 464 10.2% 15.5 3 HIL4 75nm 5.26 464 10.3% 15.5 4 HIL7 75nm 5.59 465 10.1% 15.4 5 HIL10 75nm 5.47 465 10.1% 15.0 6 HIL12 60nm 4.63 465 10.2% 15.0 Comparative example 1 2-TNATA 60nm 5.76 464 7.3% 10.6 Comparative example 2 Spiro-DBP 60nm 5.24 464 8.8% 13.3 G1 HIL4 75nm 4.59 517 10.03% 35.70 Comparative example G Spiro-DBP 60nm 4.88 517 9.48% 33.94 O1 HIL4 75nm 5.44 564 8.51% 24.74 Comparative example O Spiro-DBP 60nm 4.88 564 7.81% 22.56 1.*Measured at a current density of 100 mA/ ^cm2 2. G: Green; O: Orange

As shown in Table 6, the blue organic electroluminescent device using the hole injection layer material of the present invention (Examples 1-6) is compared with the blue organic electroluminescent device using the conventional hole injection layer materials 2-TNATA and Spiro-DBP (Comparison Examples 1 and 2). The compound (I) of the present invention has a lower refractive index (n) than the currently commonly used hole injection layer materials (Comparison Examples 1 and 2), which can effectively reduce the occurrence of total reflection, thereby increasing the light extraction effect (LEE: Light Extraction Efficiency) of the device. Since the external quantum efficiency (EQE) = internal quantum efficiency (IQE) × light extraction efficiency (LEE), the light-emitting device of the present invention has a better device efficiency, including higher external quantum efficiency (EQE) and current efficiency (CE).

Compared with the traditional hole injection layer material 2-TNATA, the device using the hole injection layer material of the present invention has a maximum EQE improvement of 41.1% (7.3→10.3%) and a maximum CE improvement of 25.5% (10.6→13.3 Cd/A).

In addition, the green organic electroluminescent device using the hole injection layer material of the present invention (Example G1) has an EQE improvement of 5.8% (9.48→10.03%) and a CE improvement of 5.2% (35.70→33.94 Cd/A) compared with the green organic electroluminescent device using the conventional hole injection layer material Spiro-DBP (Comparative Example G). The orange organic electroluminescent device using the hole injection layer material of the present invention (Example O1) has an EQE improvement of 9.0% (7.81→8.51%) and a CE improvement of 9.7% (22.56→24.74 Cd/A) compared with the orange organic electroluminescent device using the conventional hole injection layer material Spiro-DBP (Comparative Example O). This indicates that the hole injection layer material of the present invention can improve the efficiency of components in light-emitting devices of different light colors.

In addition, the above materials are simple to prepare, easy to synthesize and purify, have the potential for commercial application, and have industrial application value.

Although the present invention is described above with embodiments, these embodiments are not intended to limit the present invention. A person skilled in the art can implement or modify these embodiments equivalently without departing from the technical spirit of the present invention, so the protection scope of the present invention shall be subject to the scope of the patent application attached hereto.

1: Glass substrate 10: Organic electroluminescent device 2: ITO (anode layer) 3: Hole injection layer 4: Hole transport layer 5: Luminescent layer 6: Electron transport layer 7: Cathode layer

FIG. 1 is a schematic diagram of an organic electroluminescent device according to an embodiment of the present invention.

1: Glass substrate

10: Organic electroluminescent device

2:ITO (anode layer)

3: Hole injection layer

4: Hole transport layer

5: Luminescent layer

6:Electron transmission layer

7:Cathode layer

Claims (9)

A material for an organic electroluminescent device has a structure shown in the following chemical formula (I): (I); wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are each independently selected from H , C _5-10 alkyl, , or , and R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are not H at the same time. The material described in Item 1 of the patent application is a compound represented by any of the following chemical formulas: , , , HIL1 HIL2 HIL3 , , , HIL4 HIL5 HIL6 , , , HIL7 HIL8 HIL9 , and . HIL10 HIL11 HIL12 The material as described in item 1 or 2 of the patent application is used as a hole injection layer of an organic electroluminescent device. The material as described in claim 1 or 2 has a glass transition temperature higher than 170° C. and a refractive index lower than 1.85. An organic electroluminescent device comprises a layered structure arranged in the following order: a transparent substrate, an anode layer, a hole injection layer, a hole transport layer, a luminescent layer, an electron transport layer and a cathode layer; The organic electroluminescent device is characterized in that the hole injection layer comprises the material described in item 1 or 2 of the patent application scope. The device as described in claim 5, wherein an electron injection layer is further included between the electron transport layer and the cathode layer. The device as described in claim 5, wherein the anode layer and the cathode layer are respectively in contact with an external power source to form an electrical path. The device as described in item 5 of the patent application scope is a blue light, green light or orange light OLED. A device as described in claim 5, wherein the refractive index of the hole injection layer is less than 1.85.