1. An iridium (III) complex is a complex using 3, 5-dimethylphenyl-6-isopropylisoquinoline as a ring metal ligand and 3, 7-dimethyl-4, 6-nonanedione as an auxiliary ligand, wherein alkyl substituents at the same alpha position in a beta-diketone auxiliary ligand are different, and the iridium (III) complex has the chemical structure:

2. a process for preparing an iridium (III) complex as claimed in claim 1, wherein the iridium (III) complex is obtained by reacting iridium trichloride hydrate with 3, 5-dimethylphenyl-6-isopropylisoquinoline to give an iridium chloro-bridged dimer, and then reacting with 3, 7-dimethyl-4, 6-nonanedione under basic conditions.

3. The method for preparing an iridium (iii) complex according to claim 2, characterized by comprising the specific steps of:

step S1, weighing 5g of tetrakis (3, 5-dimethylphenyl-6-isopropylisoquinoline) iridium dichloride dimer, 1.97g of anhydrous sodium carbonate and 3.52g of 3, 7-dimethyl-4, 6-nonanedione in a 500mL three-necked round bottom flask;

step S2, adding 150mL of ethylene glycol monoethyl ether, and heating and refluxing at 125 ℃ for reaction for 8 h;

step S3, cooling, filtering, washing with water and absolute ethyl alcohol in sequence, and drying to obtain a sample;

step S4, dissolving the sample in dichloromethane, and passing through a silica gel column;

and step S5, adding absolute ethyl alcohol, removing dichloromethane by rotary evaporation, filtering and drying to obtain the iridium (III) complex.

4. A deep red OLED device comprising a light-emitting layer, wherein the light-emitting layer comprises the iridium (iii) complex of claim 1 doped with tris (4-carbazolyl-9-ylphenyl) amine (TCTA), wherein the iridium (iii) complex has a doping concentration of 8-22%.

5. The deep red OLED device of claim 4, wherein the OLED device includes a composite of the following layers:

(a) an anode;

(b) a hole injection layer;

(c) a hole transport layer;

(d) a light emitting layer;

(e) a hole blocking layer;

(f) an electron transport layer;

(g) an electron injection layer;

(h) a cathode layer.

6. The deep red OLED device of claim 5 wherein:

(1) the anode is an Indium Tin Oxide (ITO) conductive glass layer;

(2) the hole injection layer is HAT-CN;

(3) the hole transport layer is TAPC;

(4) the electron transport layer is TmpyPb;

(5) the electron injection layer is Liq;

(6) the cathode is a metal aluminum layer.

7. The deep red OLED device of claim 6 wherein:

(1) the thickness of the hole injection layer is 5 nm;

(2) the thickness of the hole transport layer is 30 nm;

(3) the thickness of the luminescent layer is 30 nm;

(4) the thickness of the electron transport layer is 30 nm;

(5) the thickness of the electron injection layer is 2 nm.

8. The deep red OLED device of claim 7 wherein:

the color coordinates of the deep red OLED device are (0.68, 0.32).

9. Use of a deep red OLED device according to any one of claims 4 to 8 in the manufacture of OLED flat panel displays and solid state lighting.

Background

Organic Light Emitting Diodes (OLEDs) are an efficient electro-optic conversion technology with important applications in the field of flat panel displays and solid state lighting. In OLED devices, a new family of organic materials is involved, where organic light emitting materials are one of the most central key materials. The iridium complex phosphorescent material is an organic luminescent molecular material with the most excellent performance so far, and small molecular red and green iridium phosphorescent materials are successfully applied to the OLED display industry, but the wide application of the iridium complex phosphorescent material is still influenced by the defects of efficiency and luminescent purity.

The green light iridium complex is an organic iridium phosphorescent material which is the earliest and the most mature in research and development, and compared with the green light iridium complex, the green light iridium complex is limited by an energy band law and a narrow energy gap, and the development of a red light iridium phosphorescent molecular material is delayed, so that the color purity, the efficiency and the service life of the red light iridium phosphorescent molecular material need to be further improved. Compared with a green light iridium complex, the red light iridium complex has larger conjugation degree, and pi-pi interaction among molecules is enhanced along with the increase of the conjugation degree of a ring metal ligand, so that the aggregation of the molecules is easily caused, and the phenomena of agglomeration and concentration quenching are generated, thereby causing the dual reduction of the efficiency and the service life of a device.

Another problem hindering the commercialization of the red iridium phosphorescent molecular material is that it is difficult to achieve high efficiency and high color purity simultaneously, and a deep red iridium phosphorescent material having high efficiency, stability, brightness, and CIE coordinates (0.68,0.32) is rarely reported. With the rapid development of the OLED industry and the pursuit of high-definition display, technologists in science and technology and industry are still searching for novel iridium complex phosphorescent materials with higher efficiency and purer color, and there is still an urgent need for novel deep red iridium complex phosphorescent materials with higher efficiency and purer chromaticity in the OLED industry.

Disclosure of Invention

In view of the above analysis, the technical problem to be solved by the present invention is to overcome the problem that it is difficult to simultaneously achieve high efficiency and high color purity of the red light iridium complex phosphorescent material in the prior art, and provide a deep red light iridium complex, a preparation method thereof, and a deep red light OLED device, which can be applied to the fields of commercial OLED flat panel display and solid state lighting.

The purpose of the invention is mainly realized by the following technical scheme:

(1) an iridium (III) complex (namely an iridium (III) complex phosphorescent material) is a complex which takes 3, 5-dimethylphenyl-6-isopropylisoquinoline as a ring metal ligand and 3, 7-dimethyl-4, 6-nonanedione as an auxiliary ligand, wherein alkyl substituents at alpha positions in beta-diketone auxiliary ligands are different, and the iridium (III) complex has the chemical structure:

(2) the preparation method comprises the steps of reacting hydrated iridium trichloride with 3, 5-dimethylphenyl-6-isopropyl isoquinoline to obtain an iridium-chlorine bridge dimer, and then reacting with 3, 7-dimethyl-4, 6-nonanedione under an alkaline condition to obtain an iridium complex.

(3) The iridium (III) complex is used for preparing a deep red light emitting OLED device, wherein the light emitting layer is prepared by doping tris (4-carbazolyl-9-yl phenyl) amine (TCTA) with the iridium (III) complex. .

(4) The deep red light emitting OLED device is applied to the preparation of OLED flat panel display and solid state lighting.

Further, the light emitting layer of the deep red light emitting OLED device is formed by doping tris (4-carbazolyl-9-ylphenyl) amine (TCTA) with the iridium (III) complex phosphorescent material, the doping concentration of the iridium (III) complex is 8-22%, and the OLED device comprises a composite material formed by the following layers:

(a) an anode;

(b) a hole injection layer;

(c) a hole transport layer;

(d) a light emitting layer;

(e) a hole blocking layer;

(f) an electron transport layer;

(g) an electron injection layer;

(h) a cathode layer.

Further:

(a) the anode is an Indium Tin Oxide (ITO) conductive glass layer;

(b) the hole injection layer is HAT-CN;

(c) the hole transport layer is TAPC;

(d) the electron transport layer is TmpyPb;

(e) the electron injection layer is Liq;

(f) the cathode is a metal aluminum layer.

Further:

(a) the thickness of the hole injection layer is 5 nm;

(b) the thickness of the hole transport layer is 30 nm;

(c) the thickness of the luminescent layer is 30 nm;

(d) the thickness of the electron transport layer is 30 nm;

(e) the thickness of the electron injection layer is 2 nm.

Compared with the prior art, the invention has the following beneficial effects:

(1) beta-diketone iridium complex phosphorescent materials are the most common iridium complex phosphorescent materials, and alkyl groups on the same alpha position of a beta-diketone ligand are the same in the beta-diketone iridium complex phosphorescent materials reported in the literature, wherein the beta-diketone iridium complex phosphorescent materials comprise the latest generation of commercialized deep red material iridium complex phosphorescent materials which are successfully applied to the OLED display industry. The invention belongs to iridium complex phosphorescent materials with different alkyl groups on the same alpha position of a beta-diketone ligand.

(2) The invention takes beta-diketone ligands with different alkyl groups on the same alpha position as auxiliary ligands to synthesize a novel iridium (III) complex, and through photoelectric property test, the maximum emission wavelength of the novel iridium (III) complex in dichloromethane is 519nm, and the quantum yield of the novel iridium (III) complex in solution reaches 72%.

(3) Then 8-22% of iridium (III) complex is taken as a guest material, TCTA host material is doped, and the iridium (III) complex phosphorescent material OLED device is prepared, wherein under the condition of not considering light emission, under the condition of high doping concentration of 20%, the maximum current efficiency is 15.23cd/A, the maximum lumen efficiency is 15.95cd/A, the maximum external quantum efficiency is 18.30%, and the deep red light color coordinate is (0.68, 0.32).

(4) In order to compare the light emitting performance of beta-diketone iridium complex phosphorescent materials with the same alkyl group at the alpha position, iridium complexes B and C are designed, wherein C is a latest generation commercial deep red material and is used as a doping material to prepare an OLED device. The research shows that under the condition of not considering the light extraction, the optimal doping concentration of B is 10 percent, and the maximum brightness of the corresponding device is 8355cd/m²The maximum current efficiency and the lumen efficiency are respectively 7.71cd/A and 4.03lm/W, the maximum External Quantum Efficiency (EQE) reaches 13.31 percent, the maximum emission light wavelength is 624nm, the deep red light is emitted, and the CIE color coordinate is (0.68, 0.32); the optimum doping concentration of C is 10%, and the maximum brightness of the corresponding device is 5024cd/m²Maximum current efficiency and lumen efficiency of 11.77cd/A and 9.48lm/W respectively, maximum External Quantum Efficiency (EQE) of 13.49%, maximum emission light wavelength of 624nm, deep red light emission, CIE color coordinates of (0.68, 0.32).

Therefore, although the iridium complex phosphorescent material formed by taking the beta-diketone ligands with different alkyl groups on the same alpha position as the auxiliary ligands and the beta-diketone iridium complex phosphorescent material with the same alkyl groups on the same alpha position have the color coordinates of (0.68,0.32) and are all deep red light, the deep red iridium complex material and the device provided by the invention have better luminous performance, such as current efficiency, lumen efficiency and maximum external quantum efficiency, are remarkably improved, are superior to the recent generation of commercial deep red iridium complex phosphorescent material (C), and are expected to be used in the fields of OLED panel display and solid-state lighting.

Drawings

FIG. 1: the voltage-current density-luminance (in the figures (a) and (e)), the current efficiency-luminance (in the figures (c) and (g)), the lumen efficiency-luminance (in the figures (d) and (h)), and the external quantum efficiency-luminance (in the figures (b) and (f)) characteristics of the OLED device (a-OLED) of the present invention.

FIG. 2: voltage-current density-luminance ((a) in the figure), current efficiency-luminance ((c) in the figure), lumen efficiency-luminance ((d) in the figure), and external quantum efficiency-luminance ((B) in the figure) of an OLED device of a prior art beta-diketoiridium complex phosphorescent material (B-OLED).

FIG. 3: voltage-current density-luminance ((a) in the figure), current efficiency-luminance ((C) in the figure), lumen efficiency-luminance ((d) in the figure), and external quantum efficiency-luminance ((b) in the figure) characteristics of an OLED device of another β -diketone iridium complex phosphorescent material (C-OLED) of the prior art.

FIG. 4: the photoluminescence spectrum of the iridium (III) complex phosphorescent material of the invention is compared with that of the prior art, wherein a curve A represents the iridium (III) complex phosphorescent material of the invention, and a curve B and a curve C represent two beta-diketone iridium complex phosphorescent materials of the prior art respectively.

FIG. 5: the OLED device of the invention is schematically structured.

FIG. 6: the iridium (III) complex has a chemical structural formula.

FIG. 7: chemical structures of β -diketone iridium complexes of comparative example 1 (fig. (B)) and comparative example 2 (fig. (C)) compared with those of the iridium (iii) complex of the present invention.

Detailed Description

Example 1: synthesis, purification and structural characterization of iridium (III) complex phosphorescent material (A) of the invention

(1) Preparation of

Weighing tetrakis (3, 5-dimethylphenyl-6-isopropylisoquinoline) iridium dichloride dimer (5g, 3.67mmol), anhydrous sodium carbonate (1.97g, 18.58mmol) and 3, 7-dimethyl-4, 6-nonanedione (3.52g, 19.10mmol), placing in a 500mL three-neck round-bottom flask, adding 150mL ethylene glycol monoethyl ether, heating and refluxing at 125 ℃ for reaction for 8h, cooling, filtering, washing with water and anhydrous ethanol successively, and drying. The sample was dissolved in dichloromethane, passed through a silica gel column rapidly, a small amount of anhydrous ethanol was added, dichloromethane was removed by rotary evaporation, and filtration and drying were carried out to obtain 5.48g of (a) with a yield of 80.78%.

(2) Characterization of

Anal.Calcd for C₅₁H₅₉N₂O₂Ir:C,66.28；H,6.43；N,3.03.Found:C,66.30；H,6.44；N,3.04.¹H-NMR(500MHz,CDCl₃)δ(ppm):8.90-8.89(dd,J＝8.3,5.4Hz,2H),8.15-8.11(m,2H),7.95(s,2H),7.59-7.54(m,3H),7.14-7.12(dd,J＝6.5,1.5Hz,2H),6.57(s,2H),4.79-4.76(t,J＝6.1Hz,1H),3.13-3.10(hept,J＝6.9Hz,2H),2.35(s,6H),1.82-1.71(m,2H),1.63-1.48(m,1H),1.46-1.45(d,J＝2.6Hz,6H),1.39-1.37(dd,J＝6.9，3.6Hz，12H)，1.26-1.14(m，2H)，1.02-0.95(m，2H)，0.78-0.76(m，6H)，0.36-0.28(ddd，J＝14.9，11.0，6.4Hz，6H)，-0.20--0.24(td，J＝7.4，3.1Hz，4H).¹³C-NMR(125MHz,CDCl₃)δ(ppm):191.34，191.30，190.79，169.06，169.00，150.95，150.92，148.82,148.78,146.84,146.80，145.91，145.82，145.77，140.90，140.87，137.49,137.34，137.32，130.60,130.49，129.46，129.44，129.34，127.95，127.05，126.65，126.63，125.23，123.02，117.05,117.02，116.99，98.26，97.23，95.88，46.95，46.88，46.81,46.77,34.27,34.25,27.70,27.66，27.21，27.18,23.99，23.83，23.80,23.58,23.52，21.27,18.69,18.67,17.49。

Comparative example 1: synthesis, purification and structure characterization of beta-diketone iridium complex phosphorescent material (B) in prior art

(1) Preparation of

Weighing tetrakis (3, 5-dimethylphenyl-6-isopropylisoquinoline) iridium dichloride dimer (5g, 3.67mmol), anhydrous sodium carbonate (1.97g, 18.58mmol) and 2, 6-dimethylheptanedione (2.98g, 19.1mmol), placing in a 500mL three-necked round bottom flask, adding 150mL ethylene glycol monoethyl ether, heating and refluxing at 125 ℃ for 8h, cooling, filtering, washing with water and anhydrous ethanol successively, and drying. The sample was dissolved in dichloromethane, flash-passed through a silica gel column, a small amount of absolute ethanol was added, dichloromethane was removed by rotary evaporation, and filtration and drying were carried out to give (B)5.4g with a yield of 82.09%.

(2) Characterization of

Anal.Calcd for C₄₉H₅₅N₂O₂Ir:C,65.67；H,6.19；N,3.13.Found:C,65.65；H,6.19；N,3.12.¹H-NMR(500MHz,CDCl₃)δ(ppm):8.90(d,J＝8.8Hz,2H),8.11(t,J＝5.0Hz,2H),7.94(s,2H),7.61-7.47(m,4H),7.14(d,J＝6.4Hz,2H),6.56(s,2H),4.80(s,1H),3.12(hept,J＝6.9Hz,2H),2.34(s,6H),1.99(hept,J＝6.8Hz,2H),1.60-1.49(m,1H),1.45-1.28(m,18H),0.67(d,J＝6.9Hz,6H),0.33(d,J＝6.8Hz,6H).¹³C-NMR(125MHz,CDCl₃)δ(ppm):192.33,168.95,150.90,148.82,146.76,145.61,140.86,137.20,130.58,129.39,127.93,127.01,126.71,125.16,123.04,117.12,94.10，39.36,34.22，23.98，23.82，23.48，21.25，20.20,19.19。

Comparative example 2: synthesis, purification and structural characterization of another beta-diketone iridium complex phosphorescent material (C) in the prior art

(1) Preparation of

Weighing tetrakis (3, 5-dimethylphenyl-6-isopropylisoquinoline) iridium dichloride dimer (5g, 3.67mmol), anhydrous sodium carbonate (1.97g, 18.58mmol) and 3, 7-diethyl-4, 6-nonanedione (4.06g, 19.1mmol) into a 500mL three-neck round-bottom flask, adding 150mL ethylene glycol monoethyl ether, heating and refluxing at 125 ℃ for reaction for 8h, cooling, filtering, washing with water and anhydrous ethanol successively, and drying. The sample was dissolved in dichloromethane, flash-passed through a silica gel column, a small amount of absolute ethanol was added, dichloromethane was removed by rotary evaporation, and filtration and drying were carried out to give 5.78g of (C) with a yield of 82.87%.

(2) Characterization of

Anal.Calcd for C₅₃H₆₁N₂O₂Ir:C,66.99；H,6.47；N,2.95.Found:C,66.97；H,6.45；N,2.94.¹H-NMR(500MHz,CDCl₃)δ(ppm):8.91-8.88(d,J＝8.8Hz,2H)，8.17-8.15(d,J＝6.4Hz,2H)，7.95(s,2H)，7.58-7.54(m,4H)，7.12-7.10(d，J＝6.4Hz,2H),6.56(s,2H),4.80(s,1H),3.12-3.08(hept,J＝6.9Hz,2H),2.34(s,6H),1.56-1.52(m,2H),1.44(s,6H),1.39-1.37(dd,J＝6.49,3.5Hz,12H),1.32-1.23(m,2H),1.12-1.04(m,2H),0.92-0.78(m,2H),0.43-0.40(t,J＝7.4Hz,6H),-0.17--0.19(t,J＝7.4Hz,6H)；¹³C-NMR(125MHz,CDCl₃)δ(ppm):189.54,169.03,150.94,148.81，146.87,145.94，141.16，137.63，130.54，129.41，127.98，127.05，126.60,125.26，123.02，116.90，100.44,54.89,34.27,26.53,26.16,23.99,23.78,23.59,21.26，11.68，11.17。

Example 2: preparation and performance comparison test of OLED device

As shown in fig. 5, the OLED device has a classical structure comprising (1) an ITO anode; (2) HAT-CN hole injection layer 5 nm; (3) 30nm of a TAPC hole transport layer; (4) target complex A, B or C-doped TCTA (light emitting layer) 30 nm; (5) TmPyPb electron transport layer 30 nm; (6) the Liq electron injection layer is 2 nm; (7) and an Al cathode.

Wherein:

(1) the chemical formula of TmPyPb is:

(2) TCTA has the formula:

(3) the chemical formula of Liq is:

(4) HAT-CN has the formula:

(5) TAPC has the formula:

(1) photoelectric property test of iridium (III) complex phosphorescent material (A)

When a is a guest material and the host material TCTA is doped at concentrations of 8%, 10%, 12%, 14%, 16%, 18%, 20% and 22%, respectively, voltage-current density-luminance, current efficiency-luminance, lumen efficiency-luminance, and external quantum efficiency-luminance characteristic curves of the OLED device are shown in fig. 1, and the corresponding main performance parameters are listed in table 1.

As can be seen from FIG. 1 and Table 1, the optimum doping concentration for A is 20%, corresponding to a maximum luminance of 6822cd/m for the device²The maximum current efficiency and the lumen efficiency are respectively 15.23cd/A and 15.95lm/W, the maximum External Quantum Efficiency (EQE) reaches 18.30 percent, the maximum emission light wavelength is 625nm, deep red light is emitted, and the CIE color coordinate is (0.68, 0.32).

TABLE 1 Main Performance parameters for different doping concentrations A

(2) Photoelectric property test of beta-diketone iridium complex phosphorescent material (B) in prior art

When B is a guest material and the host material TCTA is doped at concentrations of 8%, 10%, 12% and 14%, respectively, the voltage-current density-luminance, current efficiency-luminance, lumen efficiency-luminance and external quantum efficiency-luminance characteristic curves of the OLED device are measured, as shown in fig. 2, corresponding main performance parametersAre listed in table 2. The optimum doping concentration of B is 10%, and the maximum brightness of the corresponding device is 8355cd/m²The maximum current efficiency and the lumen efficiency are respectively 7.71cd/A and 4.03lm/W, the maximum External Quantum Efficiency (EQE) reaches 13.31 percent, the maximum emission light wavelength is 624nm, the deep red light is emitted, and the CIE color coordinate is (0.68, 0.32).

TABLE 2 Main Performance parameters for different doping concentrations B

③ photoelectric property test of beta-diketone iridium complex phosphorescent material (C) in the prior art

When C is a guest material and the host material TCTA is doped at concentrations of 8%, 10%, 12% and 14%, respectively, the voltage-current density-luminance, current efficiency-luminance, lumen efficiency-luminance and external quantum efficiency-luminance characteristic curves of the OLED device were measured, as shown in fig. 3, and the corresponding main performance parameters are listed in table 3. The optimum doping concentration of C is 10%, and the maximum brightness of the corresponding device is 5024cd/m²Maximum current efficiency and lumen efficiency of 11.77cd/A and 9.48lm/W respectively, maximum External Quantum Efficiency (EQE) of 13.49%, maximum emission light wavelength of 624nm, deep red light emission, CIE color coordinates of (0.68, 0.32).

TABLE 3 Main Performance parameters for different doping concentrations C

As can be seen from the examples and comparative examples, the photoluminescence spectra (FIG. 4) and the photophysical property parameters of the iridium (III) complex phosphorescent material (A) of the present invention and two beta-diketone iridium complex phosphorescent materials (represented by (B) and (C), respectively) of the prior art are shown in Table 4.

Photophysical performance parameters of tables 4A, B and C

compound	λabs[nm]	λex(nm)	λem[nm]	FWHM(nm)	ФPL
						A	293,348,429,479	287	619	51	0.72
B	292,349,427,478	273	621	51	0.68
						C	292,349,430,480	277	618	51	0.66

The photoelectric property data of the OLED device (A-OLED) prepared by the iridium (III) complex phosphorescent material of the invention and the OLED devices (respectively represented by (B-OLED) and (C-OLED)) prepared by two beta-diketone iridium complex phosphorescent materials in the prior art are shown in Table 5.

TABLE 5 optoelectronic Performance data of OLED devices tested prepared with different iridium phosphorescent complex phosphorescent materials at optimal doping concentrations

In summary, the embodiments of the present invention provide a high-efficiency deep red light iridium complex phosphorescent material and a phosphorescent OLED device.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are also included in the scope of the present invention.