A method for improving light-emitting efficiency of an organic light-emitting diode by using defects

Abstract

The application discloses a method for improving the light-emitting efficiency of an organic light-emitting diode by defects, which comprises the following steps: 1) depositing an electron donor material in an electrically induced exciplex on the surface of an ITO conductive glass substrate to form a hole transport layer; 2) depositing an electron acceptor material in the electrically induced exciplex on the surface of the hole transport layer to form an electron transport layer; 3) depositing an electron injection material on the surface of the electron transport layer to form an electron injection layer; 4) depositing an electrode material on the surface of the electron injection layer to form a cathode layer; and 5) irradiating the device obtained in the step 4) from the ITO conductive glass substrate end by using a femtosecond pulse laser until obvious color change appears on the surface of the device. The application improves the light-emitting efficiency of the device by irradiating the organic light-emitting diode by using the femtosecond pulse laser, and the operation is simple and convenient, the structure and preparation process of the organic light-emitting diode do not need to be changed, and the electron donor material is rich in types.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic semiconductor, in particular to a method for improving the light-emitting efficiency of an organic light-emitting diode by using defects. BACKGROUND

[0002] An organic light-emitting diode (OLED) has excellent imaging performance, flexibility, wearable, low energy consumption and other advantages, and has been widely commercialized and applied in the display industry. In order to improve the light-emitting efficiency of the device as much as possible, researchers have tried various light-emitting channels to improve the light-emitting efficiency of the device. Among them, using exciplex and electroplex as light-emitting species to improve the light-emitting efficiency of the device and improve the light color is a common technical means. Research has found that increasing the number of the above species in the organic light-emitting diode as much as possible is beneficial to improving the light-emitting efficiency of the device, thereby improving the overall performance of the device.

[0003] 4,4'-cyclohexylbis[N,N-bis(4-methylphenyl)aniline] (TAPC) has good hole transport performance, so it is often used in the hole transport layer of an organic light-emitting diode. The organic light-emitting diode in which TAPC participates in the work will additionally generate an electroluminescent signal under current injection. The unique light-emitting mechanism makes it often used with wide-bandgap electron transport materials to prepare white organic light-emitting diodes. Therefore, improving the ability of TAPC molecules to emit electroluminescent signals is beneficial to further improving the light-emitting efficiency of the device. However, at present, the light-emitting efficiency of the organic light-emitting diode device is mainly improved by increasing the modulation layer, which makes the device structure more complex and increases the difficulty of the preparation process. Or, physically and chemically modifying the functional layer in the device to increase the coupling output, which also increases the difficulty of the preparation process of the device.

[0004] Therefore, it is of great significance to develop a simple and convenient method for improving the light-emitting efficiency of an organic light-emitting diode. SUMMARY

[0005] The purpose of the present application is to provide a method for improving the light-emitting efficiency of an organic light-emitting diode by using defects.

[0006] The technical scheme adopted by the present application is:

[0007] A method for improving the light-emitting efficiency of an organic light-emitting diode by using defects comprises the following steps:

[0008] 1) Depositing an electron donor material in an electroplex on the surface of an ITO conductive glass substrate to form a hole transport layer;

[0009] 2) depositing an electron acceptor material in the electrically excited exciplex on the surface of the hole transport layer to form an electron transport layer;

[0010] 3) depositing an electron injection material on the surface of the electron transport layer to form an electron injection layer;

[0011] 4) depositing an electrode material on the surface of the electron injection layer to form a cathode layer;

[0012] 5) irradiating the device obtained in step 4) from the ITO conductive glass substrate end with a femtosecond pulsed laser until a significant color change appears on the surface of the device to obtain an organic light-emitting diode.

[0013] Preferably, the ITO conductive glass substrate in step 1) is pretreated before use. The specific operation of the pretreatment is as follows: the ITO conductive glass substrate is sequentially cleaned with isopropanol, acetone, aqueous detergent, and water, dried, and then placed in a plasma cleaning machine for plasma treatment.

[0014] Preferably, the electron donor material in step 1) is at least one of 4,4'-cyclohexylbis[N,N-bis(4-methylphenyl)aniline] (TAPC), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD), 9,9-bis[4-(di-p-tolyl)aminophenyl]-2,7-bis(9-carbazolyl)fluorene (TAKF), poly(9,9-dioctylfluorenyl-2,7-diyl)-co-(N,N'-diphenyl)-N,N'-bis(p-butyloxyphenyl)-1,4-diaminobenzene (PFB), and 4,4-bis(9-carbazol) biphenyl (CBP).

[0015] Preferably, the thickness of the hole transport layer in step 1) is 70-100 nm.

[0016] Preferably, the electron acceptor material in step 2) is at least one of 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi), 3,3'-(5'-(3-(pyridin-3-yl)phenyl)-[1,1':3',1''-terphenyl]-3,3''-diyl)dipyridine (TmPyPB), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), and 2,6-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (26DCzPPy).

[0017] Preferably, the thickness of the electron transport layer in step 2) is 70-100 nm.

[0018] Preferably, the electron injection material in step 3) is at least one of LiF, C S F, Li2O.

[0019] Preferably, the thickness of the electron injection layer in step 3) is 0.5-5 nm.

[0020] Preferably, the electrode material in step 4) is at least one of Al, Ba, Ca and Cs.

[0021] Preferably, the thickness of the cathode layer in step 4) is 100-150 nm.

[0022] Preferably, the frequency of the femtosecond pulsed laser in step 5) is 500-1000 Hz, the pulse width is 90-130 fs, and the irradiation time is 30-60 s.

[0023] An organic light-emitting diode prepared by the above method.

[0024] Use of the above organic light-emitting diode in the preparation of a display device or an illumination device.

[0025] Principle of the present application: the present application uses a femtosecond pulsed laser to irradiate an organic light-emitting diode, which changes the molecular structure of the electron donor material in the electrically excited complex, thereby increasing the number of defects, enhancing the light-emitting intensity of the device, and ultimately significantly improving the overall light-emitting efficiency of the device.

[0026] The present application has the beneficial effect of improving the light-emitting efficiency of the device by using a femtosecond pulsed laser to irradiate an organic light-emitting diode, which is simple and convenient to operate, does not require changes to the structure and preparation process of the organic light-emitting diode, and is suitable for a wide variety of electron donor materials, making it suitable for large-scale popularization and application. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Schematic diagram of the device irradiated by the femtosecond pulsed laser in the examples.

[0028] Figure 2 Electroluminescence spectrum of the organic light-emitting diode in the examples under different voltages.

[0029] Figure 3 Electroluminescence spectrum of the organic light-emitting diode in the comparative examples under different voltages.

[0030] Figure 4 External quantum efficiency-luminance characteristic curve of the organic light-emitting diodes in the examples and comparative examples. DETAILED DESCRIPTION

[0031] The present application will be further explained and described below with reference to specific examples.

[0032] Examples:

[0033] A method for improving the light-emitting efficiency of an organic light-emitting diode by using defects, comprising the following steps:

[0034] 1) The ITO conductive glass substrate (a conventional product available on the market; with an ITO film deposited on one side) is ultrasonically cleaned with isopropanol for 15 minutes, then with acetone for 15 minutes, then with a detergent aqueous solution for 5 minutes, then with deionized water for 20 minutes, then placed in a vacuum drying oven and dried at 75°C, then placed in a vacuum plasma cleaning machine and the surface of the ITO film is subjected to O2 plasma treatment for 90 seconds (to remove organic impurities on the surface of the ITO film and improve the hydrophilicity of the surface of the ITO film), then TAPC is deposited on the surface of the pretreated ITO conductive glass substrate (the side with the ITO film) by vacuum evaporation to form a hole transport layer with a thickness of 85 nm;

[0035] 2) TPBi is deposited on the surface of the hole transport layer by vacuum evaporation to form an electron transport layer with a thickness of 85 nm;

[0036] 3) LiF is deposited on the surface of the electron transport layer by vacuum evaporation to form an electron injection layer with a thickness of 1 nm;

[0037] 4) Al is deposited on the surface of the electron injection layer by vacuum evaporation to form a cathode layer with a thickness of 120 nm;

[0038] 5) The device obtained in step 4) is irradiated from the ITO conductive glass substrate end by femtosecond pulsed laser (a schematic diagram of the device irradiated by femtosecond pulsed laser is shown in Figure 1 ) until the surface of the device becomes obviously orange, the frequency of the femtosecond pulsed laser is 500 Hz, the pulse width is 110 fs, the irradiation time is 60 seconds, and an organic light-emitting diode is obtained.

[0039] Comparative Example:

[0040] An organic light-emitting diode, prepared by the following method:

[0041] 1) The ITO conductive glass substrate (same as in Example 1) is ultrasonically cleaned with isopropanol for 15 minutes, then with acetone for 15 minutes, then with a detergent aqueous solution for 5 minutes, then with deionized water for 20 minutes, then placed in a vacuum drying oven and dried at 75°C, then placed in a vacuum plasma cleaning machine and the surface of the ITO film is subjected to O2 plasma treatment for 90 seconds, then TAPC is deposited on the surface of the pretreated ITO conductive glass substrate (the side with the ITO film) by vacuum evaporation to form a hole transport layer with a thickness of 85 nm;

[0042] 2) TPBi was deposited on the surface of the hole transport layer by vacuum evaporation to form an electron transport layer with a thickness of 85 nm;

[0043] 3) LiF was deposited on the surface of the electron transport layer by vacuum evaporation to form an electron injection layer with a thickness of 1 nm;

[0044] 4) Al was deposited on the surface of the electron injection layer by vacuum evaporation to form a cathode layer with a thickness of 120 nm, thereby obtaining an organic light-emitting diode.

[0045] Performance test:

[0046] 1) The electroluminescence spectra of the organic light-emitting diodes in the examples and the comparative examples under different voltages are shown in Figure 2 and Figure 3 .

[0047] As can be seen from Figure 2 and Figure 3 , the luminous intensity of the organic light-emitting diode in the example (which was irradiated by a femtosecond pulsed laser) is significantly increased compared with the organic light-emitting diode in the comparative example (which was not irradiated by a femtosecond pulsed laser), which indicates that irradiating the organic light-emitting diode by a femtosecond pulsed laser indeed significantly improves the luminous intensity of the device, thereby significantly improving the overall luminous efficiency of the device.

[0048] 2) The external quantum efficiency (EQE)-luminance characteristic curves of the organic light-emitting diodes in the examples and the comparative examples are shown in Figure 4 .

[0049] As can be seen from Figure 4 , the external quantum efficiency of the organic light-emitting diode in the example (which was irradiated by a femtosecond pulsed laser) is significantly increased compared with the organic light-emitting diode in the comparative example (which was not irradiated by a femtosecond pulsed laser), which indicates that irradiating the organic light-emitting diode by a femtosecond pulsed laser indeed significantly improves the luminous efficiency of the device.

[0050] In addition, it was found (by the same test method as above) that when TAPC in the example was replaced by TPD, TAKF, PFB, CBP, or a combination of at least two of TAPC, TPD, TAKF, PFB and CBP, and / or TPBi in the example was replaced by TmPyPB, BCP, 26DCzPPy, or a combination of at least two of TPBi, TmPyPB, BCP and 26DCzPPy, the luminous intensity and luminous efficiency of the obtained organic light-emitting diode were also significantly improved compared with the corresponding organic light-emitting diode which was not irradiated by a femtosecond pulsed laser.

[0051] The above embodiments are the preferred embodiments of the present application, but the embodiments of the present application are not limited to the above embodiments, and any changes, modifications, substitutions, combinations, simplifications, etc. made without departing from the spirit and principles of the present application should be equivalent replacement manners and should be included in the protection scope of the present application.

Claims

1. A method for improving the luminous efficiency of organic light-emitting diodes using defect-assisted methods, characterized in that, Includes the following steps: 1) Electron donor material from the electrostimulated complex is deposited on the surface of an ITO conductive glass substrate to form a hole transport layer; 2) Electron acceptor material from the electrostimulated complex is deposited on the surface of the hole transport layer to form an electron transport layer; 3) Electron injection material is deposited on the surface of the electron transport layer to form an electron injection layer; 4) Electrode material is deposited on the surface of the electron injection layer to form a cathode layer; 5) Irradiate the device obtained in step 4) with a femtosecond pulsed laser from the ITO conductive glass substrate until a color change appears on the device surface, thus obtaining an organic light-emitting diode; Step 1) The electron donor material is at least one of 4,4'-cyclohexylbis[N,N-di(4-methylphenyl)aniline], N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine, 9,9-bis[4-(di-p-tolyl)aminophenyl]-2,7-bis(9-carbazole)fluorene, poly(9,9-dioctylfluorenyl-2,7-diyl)-co-(N,NO-diphenyl)-N,N'-di(p-butyloxyphenyl)-1,4-diaminobenzene, and 4,4'-bis(9-carbazole)biphenyl. Step 5) The frequency of the femtosecond pulsed laser is 500Hz to 1000Hz, the pulse width is 90fs to 130fs, and the irradiation time is 30s to 60s.

2. The method according to claim 1, characterized in that: Step 1) The thickness of the hole transport layer is 70nm to 100nm.

3. The method according to claim 1, characterized in that: Step 2) The electron acceptor material is at least one of 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene, 3,3'-(5'-(3-(pyridin-3-yl)phenyl)-[1,1':3',1''-terphenyl]-3,3''-diyl)pyridine, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, and 2,6-bis[3-(9H-carbazole-9-yl)phenyl]pyridine.

4. The method according to claim 1 or 3, characterized in that: Step 2) The thickness of the electron transport layer is 70nm to 100nm.

5. The method according to claim 1, characterized in that: Step 3) The electron injection material is LiF or C. S At least one of F and Li₂O.

6. The method according to claim 1 or 5, characterized in that: Step 3) The thickness of the electron injection layer is 0.5 nm to 5 nm.

7. An organic light-emitting diode, characterized in that, Made by the method described in any one of claims 1 to 6.

8. The application of an organic light-emitting diode as described in claim 7 in the manufacture of a display device or a lighting device.

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