CN103579521B - A kind of top radiation organic EL part and manufacture method thereof - Google Patents

Abstract

The invention discloses a top emission organic electroluminescence device, the cathode layer of the top emission organic electroluminescence device is plated with a covering layer, wherein the covering layer has a refractive index greater than 1.8, an organic material with an energy gap Eg greater than 3.0eV. The invention also discloses a preparation method of the top emission organic electroluminescence device. The top-emitting organic electroluminescent device of the invention can ensure the light transmittance of the cathode, and at the same time prevent the display screen from changing with the viewing angle.

Description

A top-emitting organic electroluminescent device and its manufacturing method

technical field

The invention belongs to the field of organic electroluminescent devices, and relates to a top-emitting organic electroluminescent device and a manufacturing method thereof.

Background technique

Organic light-emitting diodes, also known as organic electroluminescent devices (OLEDs), are divided into bottom-emitting organic electroluminescent devices and top-emitting organic electroluminescent devices according to the light emitting method. Bottom-emitting organic electroluminescent device (BEOLED), its transparent anode indium tin oxide ITO (or indium zinc oxide IZO) is grown on a glass substrate by sputtering, and the light emitted inside the device passes through the ITO (or IZO) successively. ), glass substrate injection. The display screen fabricated in this way has a relatively reduced area of the display area and a lower aperture ratio of the display screen due to the fact that the driving circuit and the display area are fabricated on the glass at the same time. Compared with ordinary bottom-emitting devices, top-emitting organic electroluminescent devices (TEOLEDs) can emit light from the top electrode due to their own structural characteristics. In active-driven OLEDs, pixel drive circuits, buses, etc. can be fabricated on the display The lower part of the area avoids the competition between the driving circuit and the display area, and greatly improves the aperture ratio of the device. Top-emitting organic electroluminescent devices can also be fabricated on silicon-based substrates, thereby making microdisplays on silicon. Since the display screen made of top-emitting devices also has the advantages of high resolution and high information content, top-emitting organic electroluminescent devices have attracted more and more attention in the past two years and have become a research hotspot.

In top-emitting organic electroluminescent devices, transparent ITO (or IZO) or translucent metals are generally used as the top cathode. Since the production of ITO (or IZO) requires the use of sputtering, high-energy ITO (or IZO) particles are very destructive to the underlying organic layer, so a better alternative is to use translucent metals to replace ITO (or IZO) ) as the top cathode. The advantage is that it is easy to grow and less destructive; the disadvantage is that the light transmission of metal is relatively poor, which is not conducive to the coupling output of light, and the microcavity effect is more obvious. In the application of displays, the change of luminous intensity and color with viewing angle is the largest shortcoming. Therefore, we need to prepare a cover layer on the translucent metal layer to reduce the reflection of light energy on the surface of the optical element and increase the luminous flux of the transmitted light. Similarly, the introduction of a cover layer on the metal cathode surface of top-emitting organic electroluminescent devices can change the distribution of light reflection and transmission energy. The conventionally used covering layer is a high-temperature inorganic material, which is usually prepared by sputtering or chemical vapor deposition. But these methods will cause damage to the organic film layer.

In Samsung patent 101944570, triamine derivatives, arylenediamine derivatives, CBP, and Alq ₃ are used as organic covering layers to increase the efficiency of outgoing light, and the thickness of the organic layer is limited to 30nm-90nm. Although this scheme obtains the maximum outgoing light intensity, it does not consider the change of viewing angle due to the microcavity effect.

Contents of the invention

In order to solve the above technical problems, the present invention provides a top emission organic electroluminescence device, the cathode layer of the top emission organic electroluminescence device is coated with a cover layer,

Wherein, the covering layer is an organic material with a refractive index greater than 1.8 and an energy gap Eg greater than 3.0 eV within a wavelength range of 450 nm to 650 nm.

Preferably, the covering layer is an organic material having a structure of formula 1 or an organic material having a structure of formula 2,

Formula 1

In formula 1, R ₁ -R ₄ , R ₅ -R ₈ , R _5' -R ₈ ' are independently selected from hydrogen elements, halogen elements, CN, NO ₂ , amino, fused ring aryl, condensed Heterocyclic aryl, alkyl or alcohol; A and B are independently selected from phenyl, naphthyl or anilino; R ₉ , R ₁₀ , R ₉ ' and R ₁₀ ' are independently selected from aryl;

Formula 2

In Formula 2, A and B are independently selected from phenyl, naphthyl or anilino, and R ₁ and R ₂ , R ₁ ' and R ₂ ' are independently selected from aryl.

Preferably, in formula 1, the fused ring aryl group is a fused ring aryl group with 6 to 30 carbon atoms, and the fused heterocyclic aryl group is a fused hetero ring group with 6 to 30 carbon atoms Aryl group, the alkyl group is an alkyl group with 6 to 20 carbon atoms, the alcohol group is an alcohol group with 6 to 30 carbon atoms, and R ₉ , R ₁₀ , R ₉ ′ and R ₁₀ ′ are independently selected from aryl groups having 6 to 30 carbon atoms. In Formula 2, R ₁ and R ₂ , and R ₁ ′ and R ₂ ′ are independently selected from aryl groups with 6 to 30 carbon atoms.

Preferably, the organic material having the structure of formula 1 is the following compound:

Formula 1-1

Formula 1-2

Formula 1-3

Formula 1-4

Formula 1-5

Preferably, the organic material having the structure of formula 2 is the following compound:

Formula 2-1

Formula 2-2

Formula 2-3

Formula 2-4

Formula 2-5

Preferably, the above-mentioned top emission organic electroluminescent device comprises: a substrate, and a reflective layer, an anode layer, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron Injection layer, cathode layer and said cover layer.

Preferably, the cathode layer is silver or silver alloy, with a thickness of 15-25 nm; the covering layer, with a thickness of 30-70 nm.

More preferably, the cathode layer is silver or silver alloy, with a thickness of 15-18nm; the covering layer, with a thickness of 30-70nm.

More preferably, the cathode layer is silver or silver alloy, with a thickness of 18-25nm; the covering layer, with a thickness of 30-50nm.

Wherein, the silver alloy is a silver-magnesium alloy with a weight ratio of 1:10-10:1 or a silver-lithium alloy with a weight ratio of 1:10-10:1.

The present invention provides the method for manufacturing the above-mentioned top-emitting organic electroluminescent device. A reflective layer and an anode layer are prepared on a substrate by a physical vapor deposition method or a chemical vapor deposition method, and then a hole injection layer, a hole injection layer, and a hole injection layer are sequentially deposited by thermal evaporation. Transport layer, light emitting layer, electron transport layer, electron injection layer, cathode layer and cover layer.

The top-emitting organic electroluminescent device of the invention can ensure the light transmittance of the cathode, and at the same time prevent the display screen from changing with the viewing angle.

Description of drawings

FIG. 1 is a schematic structural diagram of a top-emitting organic electroluminescent device of the present invention.

Fig. 2 is a schematic diagram of the variation of the refractive index of the organic material of the covering layer of the present invention with wavelength.

Explanation of reference signs:

Substrate 1; reflective layer 2; anode layer 3; hole injection layer 4; hole transport layer 5; light emitting layer 6; electron transport layer 7; electron injection layer 8; cathode layer 9; cover layer 10.

detailed description

The present invention will be further described below in conjunction with specific examples, so that those skilled in the art can better understand the present invention and implement it, but the given examples are not intended to limit the present invention.

The invention provides a top-emitting organic electroluminescent device, which can improve the viewing angle of the top-emitting organic electroluminescent device.

As shown in Figure 1, the top-emitting organic electroluminescent device structure includes: a substrate 1, and a reflective layer 2, an anode layer 3, a hole injection layer (HIL) 4, and a hole transport layer formed by sequential plating on the substrate 1 (HTL) 5, light emitting layer (EML) 6, electron transport layer (ETL) 7, electron injection layer (EIL) 8, cathode layer 9 and cover layer 10.

Wherein, the substrate 1 is glass or polymer (plastic or polyimide, etc.).

The reflective layer 2 can be metallic silver or silver alloy, metallic aluminum or aluminum alloy.

The anode layer 3 can be ITO (indium tin oxide), IZO (indium zinc oxide).

The hole injection layer 4 is 4,4',4"-tris(N-3-methylphenyl-N-phenylamino)triphenylamine (MTDATA) and 2,3,5,6-tetrafluorotetracyano A mixture of quinodimethane (F4TCNQ), the mass ratio of the two is 25:1, the molecular structure formula of MTDATA and F4TCNQ is as follows:

The hole transport layer 5 is N,N'-di-(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB), which Molecular structure is

The light emitting layer 6 can be red, green or blue. in,

The main body RH of red light is Bebq ₂ (bis(10-hydroxybenzo[h]quinoline) beryllium), the dye RD is Ir(piq) ₂ (acac), and the molecular structural formulas are:

The main body of green light GH is CBP (4,4'-Bis(9H-carbazol-9-yl)biphenyl), the dye GD is Ir(ppy) ₃ , and the molecular structural formulas are:

The blue light main body BH is AND (9,10-Di(naphtha-2-yl)anthracene), the dye BD is DPAVB (4-(di-p-tolylamino)-4'-[(di-p-tolylamino)styryl]stilbene ), the molecular structural formulas are:

Electron transport layer 7 is Bphen, and its molecular structural formula is:

In the specific implementation process, the following formula (1) can be used to make the thickness of each layer in the organic layer (including HIL layer, HTL layer, light emitting layer and ETL layer) and the anode layer satisfy:

$\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}\underset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&Phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&Phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Among them, λ is the peak value of the luminescent spectrum, Φ1 is the phase angle of the reflective layer, Φ2 is the phase angle of the cathode, and _dm is the thickness of each layer in the organic layer and the ITO layer (that is, each layer between the reflective layer and the transparent cathode) ( The total thickness _d =Σd _m ), nm is the corresponding refractive index of each layer, θ ₀ is the corresponding exit light angle of each layer, and k is a constant.

The electron injection layer 8 can be an alkali metal, an inorganic alkali metal compound or an organic alkali metal complex. Preferably, the alkali metal is lithium metal and potassium metal, the inorganic alkali metal compound is LiF, and the organic alkali metal complex is lithium octahydroxyquinolate.

The cathode layer 9 can be Ag, silver-magnesium alloy (Mg:Ag weight ratio=1:10~10:1), silver-lithium alloy (Li:Ag weight ratio=1:10~10:1), and the thickness of the cathode layer is 15nm -25nm.

The covering layer 10 is an organic material with a refractive index greater than 1.8 and an energy gap Eg greater than 3.0eV within the wavelength range of 450nm to 650nm.

For top-emitting organic electroluminescent devices, in order to obtain both high efficiency and good viewing angle, the cover layer material must first have an appropriate refractive index and an appropriate energy gap, and its refractive index is required to be within the visible wavelength range (450nm-650nm ) is greater than 1.8 to increase the light transmittance of the cathode; the energy gap Eg>3.0eV to ensure that there will be no light absorption even if dark blue light passes through the covering layer. In the light band from 450nm to 650nm, especially the red light band with a wavelength greater than 600nm, the refractive index of organic materials is only about 1.7. However, some organic materials with a higher refractive index have a larger conjugated system, so their energy band width is less than 3.0eV, which may absorb the blue light emitted by the OLED.

It has been determined that the refractive index of the organic material with the structure of formula 1 and the organic material with the structure of formula 2 is greater than 1.8 in the range of 450nm-650nm, as shown in Figure 2, the refractive index of the compound of formula 1-1 and the compound of formula 2-1 varies with wavelength schematic diagram. The energy levels of the organic material with the structure of formula 1 and the organic material with the structure of formula 2 are measured by cyclic voltammetry, and are 3.0eV-3.3eV and 3.15eV-3.45eV, respectively.

Covering layer 10 can be selected to have the organic material of formula 1 molecular structure for use:

Formula 1

In Formula 1, R ₁ -R ₄ , R ₅ -R ₈ , and R _5' -R ₈ ' are independently selected from hydrogen elements, halogen elements, -CN, -NO ₂ , amino, fused-ring aryl groups, A condensed heterocyclic aryl group, an alkyl group and an alcohol group, the condensed ring aryl group is preferably a condensed ring aryl group with 6 to 30 carbon atoms, and the condensed heterocyclic aryl group is preferably a carbon atom number of A condensed heterocyclic aryl group of 6 to 30, the alkyl group is preferably an alkyl group with 6 to 20 carbon atoms, and the alcohol group is preferably an alcohol group with 6 to 30 carbon atoms. A and B are respectively selected from phenyl, naphthyl and anilino. R ₉ , R ₁₀ , R ₉ ′ and R ₁₀ ′ are independently selected from aryl groups, preferably aryl groups with 6 to 30 carbon atoms. Organic materials having the structure of Formula 1 can be:

Formula 1-1

Formula 1-2

Formula 1-3

Formula 1-4

Formula 1-5

Compounds of formula 1-1 to formula 1-5 can be prepared according to the methods disclosed in US6586120.

The cover layer can also be an organic material with the structure of formula 2:

Formula 2

Wherein, A and B are independently selected from phenyl, naphthyl and anilino. R ₁ and R ₂ , R ₁ ' and R ₂ ' are independently selected from aryl groups, preferably aryl groups with 6 to 30 carbon atoms.

The organic material having the structure of formula 2 can be:

Formula 2-1

Formula 2-2

Formula 2-3

Formula 2-4

Formula 2-5

The preparation method of formula 2-1～2-5 compound is as follows:

Under nitrogen protection, 7.4 grams of bis(o-bromophenyl)dimethylsilane (see J.Organomet.Chem.1984,271,319-326 for the synthesis method) (20mmol) was added to a 500ml three-necked flask, and 150ml of anhydrous ether was added dissolve. Cool the reaction system to -80°C, slowly add 1.5M tert-butyllithium (59ml, 88mmol) dropwise, keep the reaction mixture at -80°C during the dropwise addition, continue to stir at this temperature for 1 hour after the dropwise addition is complete . Then add 3.65g benzophenone (20mmol), stir at low temperature for 30 minutes, then remove the cold bath, let the reaction system warm up to room temperature naturally, and continue to stir at room temperature for 3 hours. The reaction was quenched by adding saturated ammonium chloride solution, the product was extracted with ethyl acetate, and the organic phase was dried over anhydrous magnesium sulfate. The product was separated by column chromatography to obtain 4.67 g of white solid II, with a yield of 67%.

Dissolve 4.67g of white solid (12.4mmol) obtained in the previous step in 10ml of dry dichloromethane, cool the reaction system to 0-5°C with an ice-water bath, slowly add liquid bromine (4.4g, 27mmol) dropwise, after the addition is complete Warm up to room temperature and continue to stir for 5 hours. TLC monitors disappearance of starting material. Aqueous sodium bisulfite was added to quench the reaction and remove excess bromine. After post-processing and separation by silica gel column chromatography, 4.92 g of white solid III was obtained, with a yield of 83%.

Add the above 4.92g dibromo compound (10.3mmol) into a 250ml three-necked flask under nitrogen protection, add 100ml of a 1:1 mixture of anhydrous ether and THF, cool the system to -80°C with a cold bath, and slowly add 1.5 M tert-butyllithium (30ml, 45mmol), keep the temperature constant during the dropwise addition, after the dropwise addition is complete, continue to stir at this temperature for 1 hour. Then 3.4 g of bis(4-bromophenyl)methanone (10 mmol) was added and kept at this temperature for 30 minutes, then the cooling bath was removed, the reaction system was naturally warmed to room temperature, and continued to stir at room temperature for 4 hours. The reaction was quenched by adding saturated ammonium chloride solution, the product was extracted with ethyl acetate, and the organic phase was dried over anhydrous magnesium sulfate. The product was separated by column chromatography to obtain 3.6 g of white solid IV, with a yield of 56%.

Under the protection of _N2 , 150ml of toluene, 6.4g of 9,9-bis(p-bromophenyl)-10,10-diphenyldihydroanthracene IV (10mmol), 6.1 g phenyl-(4-biphenyl)amine (25mmol), under stirring, add 2.9g sodium tert-butoxide (30mmol), can not be completely dissolved, then add 86mgPd(dba) ₂ (0.15mmol), the color becomes dark , then add 0.6g of 10% tri-tert-butylphosphine-n-hexane solution (0.3mmol), heat to reflux, the reaction solution turns yellow-green, after reflux for 5 hours, there is almost no raw material, and when the temperature drops below 45°C, add 5ml concentrated A mixed solution of hydrochloric acid and 100ml of water, separated, the aqueous phase was extracted with 150ml of toluene, combined and spin-dried to obtain a crude product, which was separated by petroleum ether/ethyl acetate (volume ratio 5:1) system column chromatography to obtain a white solid 7.1 g, is the compound of formula 2-1, and the yield is 73%.

Product MS (m/e): 970, elemental analysis (C ₇₄ H ₅₄ N ₂ ): theoretical value C: 91.51%, H: 5.60%, N: 2.88%; found value C: 91.38%, H: 5.55%, N: 2.72%.

Under the protection of _N2 , 150ml of toluene, 6.4g of 9,9-bis(p-bromophenyl)-10,10-diphenyldihydroanthracene IV (10mmol), 8.0 g di(4-biphenyl)amine (25mmol), under stirring, add 2.9g sodium tert-butoxide (30mmol), can not dissolve completely, then add 86mgPd(dba) ₂ (0.15mmol), the color becomes darker, and then Add 0.6g of 10% tri-tert-butylphosphine-n-hexane solution (0.3mmol), heat to reflux, and the reaction solution turns green. After reflux for 5 hours, spot the plate, and there is basically no raw material. When the temperature drops below 45°C, add 5ml of concentrated hydrochloric acid and 100ml of A mixed solution of water, separated, the water phase was extracted with 150ml of toluene, combined and spin-dried to obtain a crude product, which was separated by petroleum ether/ethyl acetate (volume ratio 6:1) system column chromatography to obtain 7.75g of a white solid, namely It is the compound of formula 2-2, and the yield is 69%.

Product MS (m/e): 1122, elemental analysis (C ₈₆ H ₆₂ N ₂ ): theoretical value C: 91.94%, H: 5.56%, N: 2.49%; found value C: 91.79%, H: 5.63%, N: 2.31%.

Under the protection of _N2 , 150ml of toluene, 6.4g of 9,9-bis(p-bromophenyl)-10,10-diphenyldihydroanthracene IV (10mmol), 4.3 g diphenylamine (25mmol), under stirring, add 2.9g sodium tert-butoxide (30mmol), can not be completely dissolved, then add 86mgPd(dba) ₂ (0.15mmol), the color becomes darker, then add 0.6g10% three tert-butylphosphine-n-hexane solution (0.3mmol), heated to reflux, the reaction solution turned green, and after 5 hours of reflux, the plate was almost free of raw materials. When the temperature was lowered to below 45°C, a mixed solution of 5ml of concentrated hydrochloric acid and 100ml of water was added. Separate the liquid, extract the water phase with 150ml of toluene, combine and spin dry to obtain the crude product, which is separated by petroleum ether/ethyl acetate (volume ratio 6:1) system column chromatography to obtain 6.6g of white solid, which is formula 2-3 Compound, yield 81%.

Product MS (m/e): 818, elemental analysis (C ₆₂ H ₄₆ N ₂ ): theoretical value C: 90.92%, H: 5.66%, N: 3.42%; found value C: 90.84%, H: 5.60%, N: 3.51%.

Under the protection of _N2 , 150ml of toluene, 6.4g of 9,9-bis(p-bromophenyl)-10,10-diphenyldihydroanthracene IV (10mmol), 5.5 g phenyl-(2-naphthyl) amine (25mmol), under stirring, add 2.9g sodium tert-butoxide (30mmol), can not dissolve completely, then add 86mgPd(dba) ₂ (0.15mmol), the color becomes darker, Then add 0.6g of 10% tri-tert-butylphosphine-n-hexane solution (0.3mmol), heat to reflux, the reaction solution turns green, and after reflux for 5 hours, there is basically no raw material. When the temperature drops below 45°C, add 5ml of concentrated hydrochloric acid and A mixed solution of 100ml of water was separated, and the aqueous phase was extracted with 150ml of toluene, combined and spin-dried to obtain a crude product, which was separated by petroleum ether/ethyl acetate (volume ratio 6:1) system column chromatography to obtain 7.2g of a white solid, It is the compound of formula 2-4, and the yield is 78%.

Product MS (m/e): 918, elemental analysis (C ₇₀ H ₅₀ N ₂ ): theoretical value C: 91.47%, H: 5.48%, N: 3.05%; found value C: 91.55%, H: 5.39%, N: 3.11%.

Under the protection of _N2 , 150ml of toluene, 6.4g of 9,9-bis(p-bromophenyl)-10,10-diphenyldihydroanthracene IV (10mmol), 5.5 g phenyl-(1-naphthyl)amine (25mmol), under stirring, add 2.9g sodium tert-butoxide (30mmol), can not dissolve completely, then add 86mgPd(dba) ₂ (0.15mmol), the color becomes darker, Then add 0.6g of 10% tri-tert-butylphosphine-n-hexane solution (0.3mmol), heat to reflux, the reaction solution turns green, and after reflux for 5 hours, there is basically no raw material. When the temperature drops below 45°C, add 5ml of concentrated hydrochloric acid and A mixed solution of 100ml of water was separated, and the aqueous phase was extracted with 150ml of toluene, combined and spin-dried to obtain a crude product, which was separated by petroleum ether/ethyl acetate (volume ratio 6:1) system column chromatography to obtain 5.1g of a white solid, It is the compound of formula 2-5, and the yield is 56%.

Product MS (m/e): 918, elemental analysis (C ₇₀ H ₅₀ N ₂ ): theoretical value C: 91.47%, H: 5.48%, N: 3.05%; found value C: 91.41%, H: 5.52%, N: 3.16%.

In the present invention, the top-emitting organic electroluminescent device needs to obtain good efficiency and viewing angle characteristics, requiring the cathode to have a specific light transmittance or a light extraction rate of a specific wavelength, so the thickness of the cathode Ag and the thickness of the covering layer preferably have a certain relationship. Correspondence. When the thickness of Ag is 15-18nm, the thickness of the covering layer is 30nm-70nm; when the thickness of Ag is 18-25nm, the thickness of the covering layer is 30-50nm. For example, when Ag is selected as the cathode layer to be 15nm, it is plated with covering layers of different thicknesses (organic materials in formula 1-1). Table 1 shows the light transmittance of the cathode layer coated with the covering layer at the wavelength.

Table 1

It can be seen from Table 1 that the covering layer has the effect of increasing the light transmittance, and the cathode structure plated with the covering layer improves the light transmittance compared with that without the covering layer.

When Ag is selected as the cathode layer to be 20nm, it is covered with covering layers of different thicknesses (organic material in formula 2-1). The light transmittance of the cathode layer of the covering layer is shown in Table 2.

Table 2

The cathode structure plated with the covering layer improves the light transmittance compared with that without the covering layer.

Enumerate specific embodiment below to further illustrate the present invention

Example 1

Sputter-deposit Ag on the glass substrate as a reflective layer with a thickness of 150 nm, sputter 10 nm of ITO as the anode of the device, and etch out the desired pattern, and treat it with _O2 plasma for 3 minutes. The resulting substrate was placed in a vacuum, and a mixture of MTDATA and F4TCNQ was deposited by co-evaporation as a hole-injection layer (HIL) at 130 nm, where the weight of F4TCNQ was 4% of the weight of MTDATA. Next, 10 nm of NPB was deposited as a hole transport layer (HTL). A 30nm mixture of ADN and DPAVB was co-evaporated and deposited as the light-emitting layer, wherein the weight of DPAVB was 5% of the weight of AND. Then 20nm of Bphen was deposited as electron transport layer (ETL). Keep the vacuum degree constant, evaporate 1nm Li as the electron injection layer (EIL) by decomposing Li ₃ N during the evaporation process (temperature 600°C), deposit 20nm Ag as the cathode, and deposit 40nm with formula 1-1 The organic material of the structure serves as the covering layer.

The emitted light of the device prepared in this example is blue light, and the peak value of the luminescence spectrum changes with the viewing angle as shown in Table 3

table 3

It can be seen from Table 3 that the variation range of the peak emission spectrum of the top-emitting organic electroluminescent device of this embodiment is very small, which avoids the display screen from changing with the viewing angle.

Example 2

Sputter-deposit Ag on the glass substrate as a reflective layer with a thickness of 150 nm, sputter 10 nm of ITO as the anode of the device, and etch out the desired pattern, and treat it with _O2 plasma for 3 minutes. The resulting substrate was placed in a vacuum, and a mixture of MTDATA and F4TCNQ was deposited by co-evaporation as a hole-injection layer (HIL) at 170 nm, where the weight of F4TCNQ was 4% of the weight of MTDATA. Next, 10 nm of NPB was deposited as a hole transport layer (HTL). A 30nm mixture of CBP and Ir(ppy)3 was co-evaporated and deposited as an emitting layer, where the weight of Ir(ppy) ₃ was 5% of the weight of CBP. Then 20nm of Bphen was deposited as electron transport layer (ETL). Keeping the vacuum constant, vapor-deposit 1nm of K as the electron injection layer (EIL) by decomposing KBH ₄ during the evaporation process (temperature 400°C), deposit 20nm of Ag as the cathode, and deposit 40nm with the structure of formula 1-3 organic material as the covering layer.

The device prepared in this example is green light, and the peak value of the luminescence spectrum changes with the viewing angle as shown in Table 4

Table 4

It can be seen from Table 4 that the variation range of the peak emission spectrum of the top-emitting organic electroluminescent device of this embodiment is very small, which avoids the display screen from changing with the viewing angle.

Example 3

Sputter-deposit Ag on the glass substrate as a reflective layer with a thickness of 150 nm, sputter 10 nm of ITO as the anode of the device, and etch out the desired pattern, and treat it with _O2 plasma for 3 minutes. The resulting substrate was placed in a vacuum, and a 60 nm mixture of MTDATA and F4TCNQ was deposited by co-evaporation as a hole-injection layer (HIL), where the weight of F4TCNQ was 4% of the weight of MTDATA. Next, 10 nm of NPB was deposited as a hole transport layer (HTL). A 30nm mixture of BeBq ₂ and Ir(piq) ₂ (acac) was co-evaporated and deposited as an emitting layer, wherein the weight of Ir(piq) ₂ (acac) was 5% of the weight of BeBq ₂ . Then 20nm of Bphen was deposited as electron transport layer (ETL). Keeping the vacuum constant, vapor-deposit 1nm of K as the electron injection layer (EIL) by decomposing KBH ₄ during the evaporation process (temperature 400°C), deposit 25nm of Ag as the cathode, and deposit 30nm to have the structure of formula 1-5 organic material as the covering layer.

The device prepared in this example is red light, and the peak value of the luminescence spectrum changes with the viewing angle as shown in Table 5:

table 5

It can be seen from Table 5 that the variation range of the peak emission spectrum of the top-emitting organic electroluminescent device of this embodiment is very small, which avoids the display screen from changing with the viewing angle.

Example 4

Sputter-deposit Ag on the glass substrate as a reflective layer with a thickness of 150 nm, sputter 10 nm of ITO as the anode of the device, and etch out the desired pattern, and treat it with _O2 plasma for 3 minutes. The resulting substrate was placed in a vacuum, and a mixture of MTDATA and F4TCNQ was deposited by co-evaporation at 130 nm as a hole injection layer (HIL), where the weight of F4TCNQ was 4% of the weight of MTDATA. Next, 10 nm of NPB was deposited as a hole transport layer (HTL). A 30nm mixture of ADN and DPAVB was co-evaporated and deposited as the light-emitting layer, wherein the weight of DPAVB was 5% of the weight of ADN. Then 20nm of Bphen was deposited as electron transport layer (ETL). Keeping the vacuum degree constant, 1nm Li is deposited as the electron injection layer (EIL) by Li ₃ N decomposing during the evaporation process (temperature 600°C), 15nm Ag is deposited as the cathode, and 70nm deposited has formula 2-1 The organic material of the structure serves as the covering layer.

The device prepared in this example is a blue light device, and the peak value of the luminescence spectrum changes with the viewing angle as shown in Table 6

Table 6

It can be seen from Table 6 that the variation range of the peak emission spectrum of the top-emitting organic electroluminescent device of this embodiment is very small, which avoids the display screen from changing with the viewing angle.

Example 5

Sputter-deposit Ag on the glass substrate as a reflective layer with a thickness of 150 nm, sputter 10 nm of ITO as the anode of the device, and etch out the desired pattern, and treat it with _O2 plasma for 3 minutes. The resulting substrate was placed in vacuum, and a mixture of MTDATA and F4TCNQ was deposited by co-evaporation as a hole-injection layer (HIL) at 170 nm, where the weight of F4TCNQ was 4% of the weight of MTDATA. Next, 10 nm of NPB was deposited as a hole transport layer (HTL). A 30 nm mixture of CBP and Ir(ppy) ₃ was co-evaporated and deposited as an emitting layer, where the weight of Ir(ppy) ₃ was 5% of the weight of CBP. Then 20nm of Bphen was deposited as electron transport layer (ETL). Keeping the vacuum constant, 1nm of K is evaporated as the electron injection layer (EIL) through the decomposition of KBH ₄ during the evaporation process (temperature about 400°C), and 25nm of Ag is deposited as the cathode, and the deposition of 50nm has formula 2-2 The organic material of the structure serves as the covering layer.

The device prepared in this example is a green light device, and the peak value of the luminescence spectrum changes with the viewing angle as shown in Table 7

Table 7

It can be seen from Table 7 that the variation range of the peak emission spectrum of the top-emitting organic electroluminescent device of this embodiment is very small, which avoids the display screen from changing with the viewing angle.

Example 6

Sputter-deposit Ag on the glass substrate as a reflective layer with a thickness of 150 nm, sputter 10 nm of ITO as the anode of the device, and etch out the desired pattern, and treat it with _O2 plasma for 3 minutes. The resulting substrate was placed in a vacuum, and a 60 nm mixture of MTDATA and F4TCNQ was deposited by co-evaporation as a hole-injection layer (HIL), where the weight of F4TCNQ was 4% of the weight of MTDATA. Next, 10 nm of NPB was deposited as a hole transport layer (HTL). A 30nm mixture of BeBq ₂ and Ir(piq) ₂ (acac) was co-evaporated and deposited as a light-emitting layer, wherein the weight of Ir(piq) ₂ (acac) was 5% of the weight of BeBq ₂ . Then 20nm of Bphen was deposited as electron transport layer (ETL). Keeping the vacuum constant, vapor-deposit 1nm of K as the electron injection layer (EIL) by decomposing KBH ₄ during the evaporation process (temperature about 400°C), deposit 22nm of Ag as the cathode, and deposit 45nm with formula 2-4 The organic material of the structure serves as the covering layer.

The device prepared in this example is a red light device, and the peak value of the luminescence spectrum changes with the viewing angle as shown in Table 8

Table 8

It can be seen from Table 8 that the variation range of the peak emission spectrum of the top-emitting organic electroluminescent device of this embodiment is very small, which avoids the display screen from changing with the viewing angle.

Example 7

The preparation method of the top-emitting organic electroluminescent device in this example is the same as in Example 1, except that 1nm of metal complex LiQ is deposited as the electron injection layer, and 18nm of silver-magnesium alloy (Mg:Ag weight ratio = 1:10) is deposited as the electron injection layer. For the cathode, the covering layer is an organic material with a structure of formula 1-2 with a thickness of 40 nm.

The device prepared in this example is a blue light device, and the peak value of the luminescence spectrum changes with the viewing angle as shown in Table 9

Table 9

Example 8

The preparation method of the top-emitting organic electroluminescent device in this embodiment is the same as that in Embodiment 2, except that the covering layer is an organic material with a thickness of 40 nm and a structure of formula 1-4.

The device prepared in this example is a green light device, and the peak value of the luminescence spectrum changes with the viewing angle as shown in Table 10:

Table 10

Example 9

The preparation method of the top-emitting organic electroluminescent device of this embodiment is the same as that of Embodiment 4, except that the covering layer is an organic material with a structure of formula 2-3 with a thickness of 45 nm.

The device prepared in this example is a blue light device, and the peak value of the luminescence spectrum changes with the viewing angle as shown in Table 11:

Table 11

Example 10

The preparation method of the top-emitting organic electroluminescent device in this embodiment is the same as that in Embodiment 6, except that the covering layer is an organic material with a structure of formula 2-5 with a thickness of 40 nm.

The device prepared in this example is a red light device, and the peak value of the luminescence spectrum changes with the viewing angle as shown in Table 12

Table 12

The above-mentioned embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or transformations made by those skilled in the art on the basis of the present invention are all within the protection scope of the present invention. The protection scope of the present invention shall be determined by the claims.

Claims (9)

1. A top-emitting organic electroluminescent device, characterized in that a cathode layer of the top-emitting organic electroluminescent device is coated with a cover layer,

the covering layer is made of an organic material with the refractive index larger than 1.8 and the energy gap Eg larger than 3.0eV in the wavelength range of 450nm to 650 nm;

wherein the covering layer is an organic material with a structure of formula 2,

formula 2

In the formula 2, A and B are respectively and independently selected from phenyl, naphthyl or anilino, R₁And R₂、R₁' and R₂' are each independently selected from aryl groups.

2. The top-emitting organic electroluminescent device according to claim 1,

in the formula 2, R₁And R₂、R₁' and R₂' are each independently selected from aryl groups having 6 to 30 carbon atoms.

3. The top-emitting organic electroluminescent device according to claim 1, wherein the organic material having the structure of formula 2 is a compound of:

formula 2-1

Formula 2-2

Formula 2-3

Formula 2-4

And (5) formula 2-5.

4. The top-emitting organic electroluminescent device according to claim 1, comprising: the light-emitting diode comprises a substrate, and a reflecting layer, an anode layer, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, a cathode layer and the covering layer which are sequentially plated and formed on the substrate.

5. The top-emitting organic electroluminescent device according to claim 4, wherein the cathode layer is silver or a silver alloy and has a thickness of 15 to 25 nm; the thickness of the covering layer is 30-70 nm.

6. The top-emitting organic electroluminescent device according to claim 4, wherein the cathode layer is silver or silver alloy and has a thickness of 15 to 18 nm; the thickness of the covering layer is 30-70 nm.

7. The top-emitting organic electroluminescent device according to claim 4, wherein the cathode layer is silver or silver alloy and has a thickness of 18 to 25 nm; the thickness of the covering layer is 30-50 nm.

8. The top-emitting organic electroluminescent device according to any one of claims 5 to 7, wherein the silver alloy is a silver magnesium alloy in a weight ratio of 1:10 to 10:1 or a silver lithium alloy in a weight ratio of 1:10 to 10: 1.

9. The method of manufacturing a top-emitting organic electroluminescent device as claimed in any one of claims 1 to 8, wherein the reflective layer and the anode layer are prepared on the substrate by a physical vapor deposition method or a chemical vapor deposition method, and then the hole injection layer, the hole transport layer, the light emitting layer, the electron transport layer, the electron injection layer, the cathode layer and the capping layer are sequentially deposited by thermal evaporation.