CN107026242B - A kind of organic iridium of dark blue light (III) complex OLED device - Google Patents

Abstract

The invention discloses a deep blue organic iridium (III) complex OLED device, the light-emitting layer is a light-emitting layer formed by doping DPEPO with an organic iridium (III) complex having a structure of formula A, Traditional iridium(Ⅲ) blue light materials and devices have problems such as low quantum efficiency, non-standard luminous color, and high excitation energy. The novel iridium (Ⅲ) complex phosphorescent material synthesized by the invention and the OLED device made thereof have good photoluminescence performance, high quantum yield, short excited state lifetime, and can realize standard deep blue light emission. The device has good electroluminescent performance, has the advantages of high external quantum efficiency, high luminous brightness, high current density, and low lighting voltage, and is close to the standard blue light color coordinates (0.14, 0.08). The prepared OLED device can be used in commercial OLEDs display and lighting fields.

Description

A Deep Blue Organic Iridium(Ⅲ) Complex OLED Device

technical field

The invention relates to the field of preparation of organic electroluminescence devices, in particular to an OLED device of deep blue light organic iridium (III) complexes.

Background technique

Iridium(III)-based organic light-emitting diode (OLED) technology has been widely concerned since it came out in 1999. A complete OLED device is like a sandwich burger. On the transparent conductive anode, the hole transport layer/luminescent layer/electron transport layer/metal cathode are deposited on the transparent conductive anode by thermal vacuum evaporation or spin coating. After the voltage is applied, the phenomenon of electroluminescence can appear. When the OLED device is working, electrons and holes are injected through the cathode and anode respectively, and they capture and recombine with each other in the light-emitting layer to form excitons, which convert the luminescence center from the ground state to the excited state, and the singlet excited state radiation moves back to the ground state, emitting Visible light is emitted, which is fluorescence in the traditional sense. Since the molecules in the singlet excited state only account for 25%, the remaining 75% of the triplet excitons cannot return to the ground state by radiation due to the transition barrier, and can only dissipate the energy in a non-radiative transition. This is tantamount to a huge loss in luminous efficiency. The iridium(III) complex can greatly enhance the gyration coupling by using the heavy atom effect, promote the intersystem leap, utilize the excitons in the triplet state, and emit phosphorescence, which can theoretically achieve 100% internal quantum conversion efficiency ( IQE). This makes the phosphorescent OLEDs of iridium(Ⅲ) complexes have the best luminous properties, reaching or even exceeding that of inorganic light-emitting diodes (LEDs).

Iridium complexes generally have a +3 valence, which is a typical MLCT transition. The iridium ion in the excited state transitions the electrons on the d orbital to the π* orbital of the ligand, and then returns to the excited state to emit photons. In this process, the energy gap between the LUMO and HOMO of the ligand determines the energy of the photon emitted when returning to the excited state, thereby changing the color of the emitted light. When the electronic effect is used to decrease the HOMO and increase the LUMO, the emission peak of the complex will shift to blue; otherwise, the emission peak will shift to red. Therefore, by changing the type of iridium complex, the OLED thus prepared can be made into various colors. So far, the green device of the iridium (III) complex has achieved the highest external quantum efficiency of 26.8% and the red 18.4% without adding light. Blue phosphorescent materials, especially deep blue light materials, develop relatively slowly. In the case of the closest standard blue light, the maximum external quantum efficiency of the device with the color coordinates of (0.15,0.12) can only reach 8.4%, and the device brightness is only a few hundred cd/ m ² , low current density and power efficiency. Mechanism studies have found that when the energy level of the triplet state increases, the increase in the non-radiative transition rate often exceeds the radiative transition rate, resulting in a decrease in luminous efficiency; moreover, the short-wavelength emission of blue light requires higher energy excitation, and the stability of the material itself is also critical. Tested. Therefore, in the research of blue light materials, the blue shift of emission wavelength and the improvement of efficiency often cannot be realized at the same time. In addition, the relatively high HOMO and LUMO energy levels also put forward higher requirements on the transport layer materials.

Contents of the invention

In view of the above analysis, the present invention aims to provide a deep blue organic iridium (III) complex OLED device preparation method to solve the problems of low quantum efficiency and red shift of luminous color of traditional iridium (III) blue light materials and devices.

The purpose of the present invention is mainly achieved through the following technical solutions:

Two organic iridium(III) complexes are used to optimize the structure of OLED devices, realize deep blue light emission, and significantly improve device efficiency and performance.

The invention provides a kind of organic electroluminescence device that can be used for organic iridium (III) complex, and described device comprises:

1) anode;

2) hole injection layer;

3) hole transport layer;

4) Light-emitting layer

5) Hole blocking layer;

6) Electron transport layer;

7) Electron injection layer;

8) cathode;

Wherein: the light-emitting layer is a light-emitting layer formed by doping DPEPO with an organic iridium (III) complex having a structure of formula A.

A structure is:

further:

1) The anode is an indium tin oxide (ITO) conductive glass layer;

2) the hole injection layer is MoO ₃ layer;

3) the hole transport layer has a double-layer structure, and the double-layer structure is successively MoO ₃ doped mCP:MoO ₃ layer and a pure mCP layer;

4) The hole blocking layer is a pure DPEPO layer;

5) The electron transport layer is a TPBi layer;

6) The electron injection layer is a LiF layer;

7) The cathode is a metal aluminum layer.

go a step further:

1) The thickness of the hole injection layer is 0.8-1.2nm;

2) In the hole transport layer with a double-layer structure: the doping concentration of mCP:MoO ₃ layer MoO ₃ is 15-25%, the thickness is 5-15nm, and the thickness of the pure mCP layer is 25-35nm;

3) The doping concentration of the organic iridium (III) complex in the light-emitting layer is 10-15%, and the thickness is 5-15nm;

4) The thickness of the hole blocking layer is 5-15nm;

5) The thickness of the electron transport layer is 25-35nm;

6) The thickness of the electron injection layer is 0.5-1.5nm;

7) The thickness of the cathode layer is 80-120nm.

The beneficial effects of the present invention are as follows:

The OLED device designed by the invention for the iridium (Ⅲ) complex has good electroluminescent performance, has the advantages of high external quantum efficiency, high luminous brightness, high current density, and low lighting voltage, and is close to the standard blue light color coordinates (0.14,0.08), the prepared OLED device can be used in the field of commercial OLED display and lighting, as a good blue light pixel point, which can improve the luminous efficiency and brightness of the OLED device.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Description of drawings

Fig. 1 is organic electroluminescence device structure of the present invention; Fig. 2 is electroluminescence spectrum figure and color coordinate diagram of the present invention; Fig. 3 is current density-voltage-brightness (I-V-L) curve of the present invention; Fig. 4 is power efficiency of the present invention - Current density-external quantum efficiency (P-I-E) curve. Figure 5 shows the structure of the organic electroluminescent device of the present invention.

The drawings are for the purpose of illustrating specific embodiments only and are not to be considered as limitations of the invention, and like reference numerals refer to like parts throughout the drawings.

The structure of organic electroluminescent device of the present invention is as follows (in conjunction with Fig. 5):

ITO/MoO ₃ (1nm)/mCP:MoO ₃ (20wt.%,10nm)/mCP(30nm)/Ir(fdpt) ₃ :DPEPO(12wt.%,20nm)/DPEPO(10nm)/TPBi(30nm)/ LiF(1nm)/Al(100nm).

Detailed ways

Preferred embodiments of the present invention will be specifically described below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the application and are used together with the embodiments of the present invention to explain the principles of the present invention.

Manufacturing and testing of OLED devices: The device preparation in this part is completed in the composite evaporation system manufactured by Shenyang Huiyu Vacuum Technology Co., Ltd. In the organic chamber, the organic materials are placed in different evaporation sources whose temperature can be controlled separately. During the evaporation process, the vacuum degree of the chamber is higher than 9×10 ^-5 Pa. On anodized indium tin oxide (ITO) glass The hole injection layer, the hole transport layer, the light emitting layer, the hole blocking layer, and the electron transport layer are successively evaporated, and finally the substrate is transferred to the metal evaporation chamber for the electron injection layer and the cathode metal aluminum evaporation. During the evaporation process of organic materials, a film thickness controller is used to accurately monitor the film thickness, and the evaporation rate of the material is The evaporation rate of aluminum metal is The evaporation rate is detected in real time by a crystal oscillator. The electroluminescence spectrum, luminance, current-voltage-luminance (IVL) curve and color coordinates were measured by a computer-controlled Keithley 2400 source meter, and the external quantum yield of the device was measured by Hamamatsu C9920-12.

In the specific examples described below, in addition to the iridium(III) complexes (Ir(dpt) ₃ and Ir(fdpt) ₃ ), in the existing organic light-emitting diode (OLED) technology, its structure and origin All known to those skilled in the art, its structural formula is respectively as follows:

The OLED prepared by the present invention has a very high current density. Compared with other materials with the same light-emitting wavelength, the maximum EQE can reach a level close to 20%, and the maximum brightness is 3195 and 20070cd/m ² respectively, both of which exceed State-of-the-art device performance in this research area. Under the experimental condition of luminance of 1000cd/m ² , the EQE of the device still maintains a high level. The device performance results of the present invention are shown in the following table. At a current density of 9mA/cm ^-2 , the electroluminescence spectra (EL) of Ir(dpt) ₃ and Ir(fdpt) ₃ are obtained. For Ir(fdpt) ₃ , the maximum emission peaks are located at 431 and 458nm, achieving a good The deep blue light is emitted, the color coordinates are (0.15, 0.11) and there is no emission peak of other functional materials in the spectrum, which shows that the device structure design is reasonable, and the effective energy transfer between the host material and the luminescent center is realized. From its current-voltage-luminance (JVL) curve, it can be concluded that the turn-on voltage (V) of the device is 3.7V, the maximum brightness (L _max ) is 3195cd/m ² , and the maximum external quantum efficiency (EQE) is 19.4%. However, as the brightness increases, the efficiency of the device rolls off more seriously. For Ir(dpt) ₃ , its maximum emission peaks are located at 458 and 483nm, realizing sky blue light emission with color coordinates of (0.15, 0.21). Compared with Ir(fdpt) ₃ , the turn-on voltage (V) is reduced to 3.5V , the maximum brightness (L _max ) increased to 20070cd/m ² , and the maximum external quantum efficiency (EQE) was 21.9%.

In summary, the embodiments of the present invention provide a highly efficient deep blue Ir(III) phosphorescent OLED device.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of changes or modifications within the technical scope disclosed in the present invention. Replacement should be covered within the protection scope of the present invention.

Claims (4)

1. An organic iridium (Ⅲ) complex phosphorescent material, characterized in that: the organic iridium (Ⅲ) complex phosphorescent material is an iridium (III) complex with phenyltriazole derivatives as a ligand, and the structural formula is as follows As shown in A: A: Wherein: R is hydrogen or fluorine; When R is hydrogen, the iridium (III) complex is Ir(dpt) ₃ ; When R is fluorine, the iridium(III) complex is Ir(fdpt) ₃ . 2. An organic electroluminescence device, utilizing the organic iridium (Ⅲ) complex phosphorescent material described in claim 1, is characterized in that said device comprises: 1) anode; 2) hole injection layer; 3) hole transport layer; 4) Light-emitting layer; 5) Hole blocking layer; 6) Electron transport layer; 7) Electron injection layer; 8) cathode; Wherein: the light-emitting layer is a light-emitting layer formed by doping DPEPO with an organic iridium (III) complex having a structure of formula A, A: 3. An organic electroluminescent device as claimed in claim 2, characterized in that: 1) The anode is an indium tin oxide (ITO) conductive glass layer; 2) the hole injection layer is MoO ₃ layer; 3) the hole transport layer has a double-layer structure, and the double-layer structure is successively MoO ₃ doped mCP:MoO ₃ layer and a pure mCP layer; 4) The hole blocking layer is a pure DPEPO layer; 5) The electron transport layer is a TPBi layer; 6) The electron injection layer is a LiF layer; 7) The cathode is a metal aluminum layer. 4. An organic electroluminescent device as claimed in claim 3, characterized in that: 1) The thickness of the hole injection layer is 0.8-1.3nm; 2) In the hole transport layer: the doping concentration of mCP:MoO ₃ layer MoO ₃ is 15-25%, the thickness is 5-15nm, and the thickness of the pure mCP layer is 25-35nm; 3) The doping concentration of the organic iridium (III) complex in the light-emitting layer is 10-15%, and the thickness is 20nm; 4) The thickness of the hole blocking layer is 5-15nm; 5) The thickness of the electron transport layer is 25-35nm; 6) The thickness of the electron injection layer is 0.5-1.5nm; 7) The thickness of the cathode is 80-120nm.