CN100554366C - Dendritic green-emitting iridium complex, its preparation method and organic electroluminescent device of the complex - Google Patents

Abstract

The invention belongs to the technical field of organic electroluminescence, and relates to a dendritic green-emitting iridium complex, a preparation method thereof and an organic electroluminescence device of the complex. The compound has the following structure: The compound is prepared by a two-step method. First, the ligand and IrCl ₃ ·3H ₂ O react to form the precursor of the chlorine bridge, and then the chlorine bridge precursor is transformed into the final product at high temperature. The non-doped electroluminescent device prepared by this compound has a luminous efficiency of 53.2cd/A, a maximum power efficiency of 42.4lm/W, a maximum external quantum efficiency of 15.8%, and a maximum brightness of 17600cd/m ² .

Description

Dendritic green-emitting iridium complex, its preparation method and organic electroluminescent device of the complex

technical field

The invention belongs to the technical field of organic electroluminescence, and relates to a dendritic green-emitting iridium complex, a preparation method thereof and an organic electroluminescence device of the complex.

technical background

Organic electroluminescence materials and devices are the international frontier research field. At present, many organic electroluminescent materials have been commercialized, and some organic display devices have also been applied in mobile phones, car audio and so on.

According to different luminescent principles, organic electroluminescent materials can be divided into two categories: fluorescent materials and phosphorescent materials. For phosphorescent materials, since all energy forms including singlet and triplet states can be fully utilized, the efficiency of the device can be greatly improved, and the internal quantum efficiency of the device can theoretically reach 100%. Therefore, the use of transition metal complexes as light-emitting materials has become a good means to improve device efficiency.

However, in order to obtain good efficiency, such phosphorescent materials are generally doped in a certain proportion in the host material for use. This has led to how to select a suitable host material has become a major problem in the fabrication process of the device. For example, the phase separation between the host material and the phosphorescent material, the matching between triplet energy levels, the carrier transport of the host material, etc. need to be considered. At the same time, how to precisely control the doping concentration has become a major difficulty in the device fabrication process. Therefore, developing solution-processable and highly efficient phosphorescent materials for the construction of non-doped organic electroluminescent devices has become a major challenge in academia and industry.

Contents of the invention

In order to solve the above-mentioned technical problems, the present invention is based on the characteristics of dendrimers, and uses carbazole units with hole transport capability as dendrons to develop dendritic iridium complexes that emit green light and are used to construct non-doped organic electrical compounds. Luminescent devices with device efficiencies comparable to those of doped devices.

The object of the present invention is to provide dendritic green-emitting iridium complexes.

Another object of the present invention is to provide a method for preparing dendritic green-emitting iridium complexes.

The third object of the present invention is to provide the use of the dendritic green-emitting iridium complex: use the complex to make organic electroluminescent devices.

The dendritic green-emitting iridium complex provided by the present invention has a chemical formula as shown in (1):

Describe the preparation method of the iridium complex of dendritic green light below, and its steps and conditions are as follows:

1. Ligand LG reacts with IrCl ₃ 3H ₂ O to form a chlorine bridge precursor: the molar ratio of ligand LG to complex IrCl ₃ 3H ₂ O is 2 to 5, preferably 2 to 2.5; the reaction temperature is 100°C to 140°C, the reaction time is 24-72 hours; the reaction solvent is a mixed solvent of ethylene glycol monoethyl ether and water, and the volume ratio of the two is 3:1; in order to improve the solubility of the system, 0-50% tetrahydrofuran can be added ; The chemical formula of the ligand LG is shown in (2);

2. The dendritic green-emitting iridium complex obtained by reacting the chlorine bridge precursor obtained in the above step 1 with the ligand LG: the molar ratio of the ligand LG to the chlorine bridge precursor is 2 to 5, preferably 2 to 2.5; The catalyst uses basic compounds, such as K ₂ CO ₃ , Na ₂ CO ₃ , Cs ₂ CO3 or CF ₃ SO ₃ Ag, preferably K ₂ CO ₃ ; the reaction temperature is 200°C-250°C, and the reaction time is 48-96 hours; The reaction solvent uses alcohol derivatives with high boiling points, such as 1,2-propanediol or glycerol, preferably glycerol; in order to improve the solubility of the system, 10-50% of diethylene glycol and triethylene glycol can be added Or tetraethylene glycol derivatives, preferably tetraethylene glycol.

In order to achieve the third object of the present invention, an organic electroluminescence device using the above-mentioned dendritic iridium complex emitting green light is provided.

The structure of an organic EL device using the above-mentioned dendritic green-emitting iridium complex is shown in FIG. 1 .

An organic electroluminescent device prepared from the dendritic green-emitting iridium complex, a first electrode (102) connected to a substrate (101) and a second electrode (108) have a layer or The multi-layer organic layer is characterized in that at least one of the organic layers is an emission layer (104), and the emission layer (104) is the dendritic green-emitting iridium complex.

An organic electroluminescent device prepared from the dendritic green-emitting iridium complex, characterized in that the first electrode (102) and the second electrode (108) connected to the substrate (101) ) between the multi-layer organic layers are: hole injection layer (103), emission layer (104), hole blocking layer (105), electron transport layer (106), electron injection layer (107), which are connected in turn, The substrate (102) is connected with the hole injection layer (103), and the electron injection layer (107) is connected with the second electrode (108).

An organic electroluminescent device prepared from the dendritic green-emitting iridium complex, its substrate 101, the material used as the substrate is transparent, easy to handle and waterproof, and has a uniform surface glass substrate or transparent A flexible plastic substrate; a patterned first electrode 102 is formed on the surface of the substrate 101, the first electrode 102 is made of a conductive metal or a conductive metal oxide that is easy to inject holes, and is suitable for the material of the first electrode 102 Indium tin oxide (ITO), indium zinc oxide (IZO), nickel (Ni), platinum (Pt) or gold (Au); selectively form a hole injection layer (HIL) 103 on the first electrode 102 , the material of HIL103 comprises water-soluble PEDOT (poly (3,4-ethylenedioxythiophene)) or PSS (polystyrene sulfonate); Form EML layer 104 on HIL layer 103, EML layer 104 is made of alone The dendritic green-emitting iridium complex of the above chemical formula (1) is made; on the EML layer 104, a hole blocking layer (HBL) 105 is formed by vacuum deposition, and materials suitable for HBL105 include phenanthroline derivatives compounds (which are preferably 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)), triazole derivatives, oxadiazole derivatives or aluminum complexes; The material of transport layer 106 is oxazole, oxadiazole, isoxazole, triazole, thiadiazole, imidazole or aluminum complex; Form electron injection layer (EIL) 107 on ETL106, the material for EIL107 comprises LiF , NaCl, NaOH, CsF, Cs ₂ CO ₃ or Ca(acac) ₃ ; the second electrode 108 is deposited on the EIL 107, and the material suitable for the second electrode 108 is generally a low work function metal, such as Ca, Ba, Al, Mg or Ag.

The structure of the organic EL device of the present invention as shown in Figure 1, wherein HIL103, HBL105, ETL106 or EIL107 can be optionally used or not used.

Next, a method of manufacturing an organic EL device will be described in detail.

Referring to FIG. 1 , firstly, a patterned first electrode 102 is formed on the surface of a substrate 101 . Materials generally used as substrates are transparent, easy-to-handle and waterproof, and have a uniform surface glass substrate or transparent, flexible plastic substrate. The substrate 101 preferably has a thickness of 0.3 to 0.7 mm.

The first electrode 102 is made of a conductive metal or a conductive metal oxide that is easy to inject holes. Materials suitable for the first electrode 102 include indium tin oxide (ITO), indium zinc oxide (IZO), nickel (Ni), platinum (Pt), or gold (Au).

The substrate 101 with the first electrode 102 is cleaned using an organic solvent such as isopropanol or acetone. After cleaning, the substrate 101 is subjected to ultraviolet/ozone treatment.

Next, a hole injection layer (HIL) 103 is selectively formed on the first electrode 102 of the substrate 101 . The HIL 103 can reduce the contact resistance between the first electrode 102 and the emission layer (EML) 104 and increase the hole injection capability. Preferred materials suitable for HIL 103 are water-soluble PEDOT (poly(3,4-ethylenedioxythiophene)) or PSS (polystyrene sulfonate). When coating the first electrode 102 with this material, it should be heated and dried to form the HIL 103 . Among them, when PEDOT is used for HIL103, it is preferable to dry the coating at a temperature of 100 to 250°C.

Next, EML104 is formed on HIL103. EML104 alone is made from the dendritic green-emitting iridium complex of formula (1) above. The emission layer EML104 is prepared by solution spin coating, and the organic solvent can be chloroform, toluene or chlorobenzene.

On the EML 104, a hole blocking layer (HBL) 105 is formed by vacuum deposition. The HBL 105 can prevent excitons or holes from migrating into the electron transport layer (ETL) 106 . Suitable materials for HBL105 are phenanthroline derivatives, preferably 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, triazole derivatives, oxadiazole derivatives or Aluminum complexes.

On the HBL 105, an electron transport layer (ETL) 106 is formed by vacuum deposition. Suitable materials for ETL 106 are oxazole, oxadiazole, isoxazole, triazole, thiadiazole, imidazole or aluminum complexes.

Next, an electron injection layer (EIL) 107 is formed on the ETL 106. The material used for the EIL 107 is LiF, NaCl, NaOH, CsF, Cs ₂ CO ₃ or Ca(acac) ₃ , and the thickness of the EIL 107 is preferably 1-

Finally, the second electrode 108 is deposited on the EIL 107 to complete the fabrication of the organic EL device. Suitable materials for the second electrode 108 are metals with low work function, such as Ca, Ba, Al, Mg or Ag. Preferably the thickness of the second electrode 108 is 800-

Beneficial effects: the dendritic green-emitting iridium complex of chemical formula (1) designed and synthesized by the present invention is a solution-processable, highly efficient non-doped phosphorescent material, has high film luminous efficiency, and can be used without the use of host materials At the same time, it has good film-forming properties and solution processability, and can be used to prepare organic electroluminescent devices by solution-based processes such as solution spin coating, inkjet printing, and screen printing. The non-doped electroluminescent device prepared by the compound has a luminous efficiency of up to 53.2cd/A, a maximum power efficiency of 42.4lm/W, a maximum external quantum efficiency of 15.8%, and a maximum brightness of 17600cd/m ² .

Description of drawings

Fig. 1 is a schematic structural diagram of an organic electroluminescence device of a dendritic green-emitting iridium complex.

Fig. 2 provides the current density-voltage-brightness characteristic curve of the organic EL device that embodiment 1 makes;

Fig. 3 provides the variation curve of the luminous efficiency of the organic EL device that embodiment 1 makes with current density;

Fig. 4 provides the variation curve of the power efficiency of the organic EL device that embodiment 1 makes with current density;

Fig. 5 provides the variation curve of the external quantum efficiency of the organic EL device that embodiment 1 makes with current density;

FIG. 6 shows the EL spectrum of the organic EL device fabricated in Example 1. FIG.

Detailed ways

Preparation Example 1: Synthesis of Compounds of Chemical Formula (1)

Reaction 1:

1), the synthesis of chlorine bridge precursor

Ligand LG (908mg, 1.10mmol) and IrCl ₃ 3H ₂ O (176mg, 0.50mmol) were dissolved in 15mL ethylene glycol monoethyl ether, 5mL distilled water, repeated ventilation 3 times, stirred and heated under the protection of argon, reflux reaction After 48 hours, it was filtered, and the obtained precipitate was washed with ethanol and distilled water, and dried to obtain an impure chlorine bridge precursor.

2), the synthesis of the compound of chemical formula (1)

The chlorine bridge precursor obtained in step 1), ligand LG (495mg, 0.60mmol), anhydrous potassium carbonate (345mg, 2.50mmol), glycerol 25mL and tetraethylene glycol 5mL were added to a 50ml round bottom flask, Under the protection of argon, the temperature was raised to 210° C., and the reaction was carried out for 72 hours. Cool to room temperature, add distilled water, extract with dichloromethane, wash repeatedly, anhydrous _Na2SO4Dry , filter, rotary evaporate the solvent, column separation and _purification , to obtain the dendritic green-emitting iridium complex of chemical formula (1) 133 mg (11% yield).

3), the structural analysis of the compound of chemical formula (1)

The structure of the dendritic complex was determined by NMR, MALDI-TOF and elemental analysis.

¹ H NMR (300MHz, CDCl ₃ )[ppm]: δ8.15(s, 15H), 7.79(s, 6H), 7.45-7.60(m, 24H), 7.28(d, J=8.2Hz, 3H), 7.15(d, J=7.4Hz, 3H), 7.03-7.05(m, 6H), 6.85(t, J=7.1Hz, 3H), 6.67-6.72(m, 6H), 6.61(d, J=8.0Hz , 3H), 1.47(s, 108H).

MALDI-TOF (m/z): 2663.6[M ⁺ +H].

Anal. Calcd for C ₁₇₇ H ₁₇₇ N ₁₂ Ir: C, 79.78; H, 6.70; N, 6.31. Found: C, 79.51; H, 6.75; N, 6.28.

EL device preparation example 1:

The emissive layer is formed using a dendritic green-emitting iridium complex of formula (1). The structure of the device is: ITO/PEDOT (50nm)/dendritic green-emitting iridium complex of chemical formula (1)/TPBI (60nm)/LiF (1nm)/Al (100nm). The assembly process of the device is as follows:

1. Use an indium tin oxide (ITO) substrate with 100 Ω/cm ² as the anode. A water-soluble polythiophene derivative (PEDOT) was spin-coated on the anode at a speed of 3000 rpm, and baked at 120° C. for 30 min to form a 50 nm-thick hole injection layer.

2. The dendritic green-emitting iridium complex of chemical formula (1) was dissolved in chlorobenzene to form a solution of 5 mg/ml, which was spin-coated on PEDOT at a speed of 1200 rpm as an emission layer.

3. Evaporate 60 nm-thick 1,3,5-tris(2-N-phenylbenzimidazolyl)benzene (TPBI) on the light emitting layer as a hole blocking and electron transporting layer.

4. Evaporating 1 nm thick LiF and 100 nm thick Al electrodes on the electron transport layer in sequence to complete the preparation of the organic EL device.

The performance of the obtained EL device is as follows: the maximum luminous efficiency is 53.2cd/A, the maximum power efficiency is 42.4lm/W, the maximum external quantum efficiency is 15.8%, the maximum brightness is 17600cd/m ² , the emission peak is 532nm, and the color coordinate CIE value x=0.39, y=0.58.

Claims (13)

1. the complex of iridium of dendroid green light is characterized in that, its chemical formula is shown in (1):

2. the preparation method of the complex of iridium of a dendroid green light as claimed in claim 1 is characterized in that preparation process and condition are:

1) ligand L G and IrCl ₃3H ₂The O reaction forms chlorine bridge precursor: ligand L G and title complex IrCl ₃3H ₂The mol ratio of O is 2～5, and temperature of reaction is 100 ℃～140 ℃, and the reaction times is 24～72 hours; Reaction solvent uses the mixed solvent of ethylene glycol monomethyl ether and water, and both volume ratios are 3: 1;

2) chlorine bridge precursor that is obtained by above step 1) and ligand L G reaction obtains the complex of iridium of the dendroid green light of chemical formula (1): the mol ratio of ligand L G and chlorine bridge precursor is 2～5, and catalyzer uses basic cpd to be K ₂CO ₃, Na ₂CO ₃, Cs ₂CO3 or CF ₃SO ₃Ag, temperature of reaction is 200 ℃～250 ℃, the reaction times is 48～96 hours; It is 1 that reaction solvent uses high boiling alcohol derivatives, 2-propylene glycol or glycerine;

3. the preparation method of the complex of iridium of a dendroid green light as claimed in claim 2 is characterized in that, described step 1), ligand L G and title complex IrCl ₃3H ₂The mol ratio of O is 2～2.5.

4. the preparation method of the complex of iridium of a dendroid green light as claimed in claim 2 is characterized in that, described step 1) in order to improve the solvability of system, adds 0～50% tetrahydrofuran (THF).

5. the preparation method of the complex of iridium of a dendroid green light as claimed in claim 2 is characterized in that, described step 2), the mol ratio of ligand L G and chlorine bridge precursor is 2～2.5.

6. the preparation method of the complex of iridium of a dendroid green light as claimed in claim 2 is characterized in that, described step 2), catalyzer uses basic cpd to be K ₂CO ₃

7. the preparation method of the complex of iridium of a dendroid green light as claimed in claim 2 is characterized in that, described step 2), reaction solvent uses high boiling alcohol derivatives to be glycerine.

8. the preparation method of the complex of iridium of a dendroid green light as claimed in claim 2, it is characterized in that, described step 2), in order to improve the solvability of system, add 10～50% glycol ether, Triethylene glycol or tetraethylene-glycol derivative.

9. the preparation method of the complex of iridium of a dendroid green light as claimed in claim 8 is characterized in that, described step 2), in order to improve the solvability of system, add tetraethylene-glycol.

10. the organic electroluminescence device of the complex of iridium of a dendroid green light as claimed in claim 1 preparation, has one or more layers organic layer between first electrode (102) that is connected with substrate (101) and second electrode (108), it is characterized in that, wherein having one deck organic layer at least is emission layer (104), and emission layer (104) is the complex of iridium of described dendroid green light.

11. the organic electroluminescence device of the complex of iridium of dendroid green light as claimed in claim 10 preparation, it is characterized in that, having the multilayer organic layer between described first electrode (102) that is connected with substrate (101) and second electrode (108) is: hole injection layer (103), emission layer (104), hole blocking layer (105), electron transfer layer (106), electron injecting layer (107), they connect successively, described substrate (102) is connected with hole injection layer (103), and electron injecting layer (107) is connected with second electrode (108).

12. the organic electroluminescence device of the complex of iridium of dendroid green light as claimed in claim 11 preparation is characterized in that, it is characterized in that, the material of described substrate (101) is the plastics of glass or transparent flexibility; First electrode (102) is for being easy to nickel, platinum or the gold that the hole is injected; Perhaps, indium tin oxide or indium-zinc oxide; The material of hole injection layer (103) is water miscible poly-(3, the 4-Ethylenedioxy Thiophene) or poly styrene sulfonate; Emission layer (104) is made by the complex of iridium of the dendroid green light of above-mentioned chemical formula (1) separately; The material of hole blocking layer (105) is phenanthroline derivative, triazole derivative, oxadiazole derivative or aluminium complex; Material Wei oxazole, oxadiazole, isoxazole, triazole, thiadiazoles, imidazoles or the aluminium complex of electron transfer layer (106); Electron injecting layer (107), material be LiF, NaCl, NaOH, CsF, Cs ₂CO ₃Or Ca (acac) ₃Second electrode (108), material be low work function metal Ca, Ba, Al, Mg or Ag.

13. the organic electroluminescence device of the complex of iridium of described dendroid green light as claimed in claim 12 preparation is characterized in that the material of described hole blocking layer (105) is 2,9-dimethyl-4,7-phenylbenzene-1,10-phenanthroline.

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