CN106328823B - A kind of organic film, preparation method and its application in organic electroluminescence device is prepared - Google Patents

Abstract

The invention discloses an organic thin film, a preparation method and its application in the preparation of an organic electroluminescence device, belonging to the technical field of organic electroluminescence, and the preparation method of an organic thin film. The specific steps include: a solution atomization process; a liquid film formation process; solvent volatilization process; surface tension control process; solid film formation process; finally form a film with a thickness of 10-100nm. The organic thin film prepared by the preparation method can be used as a hole injection layer, a light emitting layer, an electron injection layer or a transport layer in an organic electroluminescent device. The invention proposes to dilute the solution and control the edge of the liquid film by using a low surface tension solvent. The balance of surface tension keeps the liquid film evenly distributed during the solvent volatilization process, overcomes the influence of surface tension, and realizes an organic electroluminescent device with excellent performance on this basis.

Description

A kind of organic thin film, preparation method and its application in the preparation of organic electroluminescence device application

technical field

The invention belongs to the technical field of organic electroluminescence, and in particular relates to an organic thin film, a preparation method and its application in the preparation of organic electroluminescence devices.

Background technique

In the past 30 years, organic electroluminescent technology has continuously made major breakthroughs under the unremitting efforts of scientific researchers in various countries, and has already reached the practical level in various performance indicators (H. Sasabe, J. Kido, J. Mater. Chem. C2013, 1, 1699). The continuous emergence of mobile phones, TVs, VR and other smart devices using organic electroluminescent display panels, as well as lamps such as table lamps and bedroom lamps using organic electroluminescent lighting panels, have announced the beginning of the practical use of organic electroluminescent technology.

However, the higher manufacturing cost still restricts the further development of the practical application of organic electroluminescence technology. The vacuum thermal evaporation process (S.Reineke, F.Lindner, F. , G.Schwartz, N.Seidler, K.Walzer, B.Lussem, K.Leo, Nature 2009, 459, 234) is an important factor leading to high costs. Therefore, there is a wet preparation process with the characteristics of simple process, simple equipment, easy large-scale production and no need for vacuum conditions, especially the spin-coating coating method (J.H.Burroughes, D.D.C. Bradley, A.R.Brown, R.N.Marks, K.Mackay, R.H.Friend , P.L.Burns, A.B.Holmes, Nature 1990, 347, 539), was proposed for the preparation of organic electroluminescent devices, thereby reducing its manufacturing cost. For the spin coating method, although it has been proved to be an effective experimental method in the laboratory, when it is applied to mass production, it still faces certain problems (F.C.Krebs, Sol.Energ. Mater.Sol.C 2009,93,394), first of all, this process cannot achieve high material utilization rate, and it is difficult to further reduce the cost; secondly, this process needs to be processed separately, which is difficult to be compatible with the assembly line process, which affects the improvement of production efficiency; finally, This process has high requirements on the viscosity of the solution, and it is difficult to use the solution with low viscosity, especially the solution of small organic molecules with limited solubility.

A new process ultrasonic spraying method with a material utilization rate of more than 90%, that is, the ultrasonic nozzle is used to atomize the solution of organic materials into micron-sized droplets, which are driven by the airflow to reach the surface of the substrate and repolymerize into a liquid film layer. The solvent volatilizes and the solute solidifies to form an organic film, which has attracted the attention of researchers in the field of optoelectronics and applied it to the preparation of organic solar cells (S.Na, B.Yu, S.Kim, D.Vak, T.Kim, J. .Yeo, D.Kim, Sol.Energ.Mater.Sol.C2010,94,1333), perovskite solar cells and other fields (Zhou Hang, Xia Zhonggao, Chai Gaoda, Wang Yan, Preparation of a perovskite solar cell method, publication number: 105098082A, 2015-11-25). In addition to having a very high material utilization rate, the process is also compatible with assembly line production, and can utilize low-viscosity organic solutions to prepare organic films. However, the film quality of organic films prepared by ultrasonic spraying method still has certain problems, because the optoelectronic devices in these fields have relatively low requirements on film quality, and the optoelectronic devices prepared by ultrasonic spraying technology are currently mainly concentrated in solar cells (S.F.Tedde , J.Kern, T.Sterzl, J.Furst, P.Lugli, O.Hayden, NanoLett.2009, 9, 980), organic transistors (N.A.Azarova, J.W.Owen, C.A.McLellan, M.A.Grimminger, E.K.Chapman, J.E.Anthony, O.D. Jurchescu,Org.Electron.2010,11,1960) and polymer light-emitting devices (K.Gilissen, J.Stryckers, P.Verstappen, J.Drijkoningen, G.Heintges, L.Lutsen, J.Manca, W.Maes, W. Deferme, Org. Electron. 2010, 20, 31) field. For organic electroluminescent devices, this type of device has high requirements for carrier balance, exciton generation area and distribution, so the quality of organic thin films must reach a certain level to meet the needs of this type of device.

Contents of the invention

In order to solve the above shortcomings in the prior art, the present invention adopts the introduction of a low surface tension solvent to dilute the solution and the introduction of an auxiliary solvent to rebuild the tension balance at the edge of the liquid film, so as to realize an organic thin film with a smooth surface that can be applied to organic electroluminescent devices.

Technical scheme of the present invention realizes by following way:

A kind of preparation method of organic thin film, concrete steps are as follows:

First, the indium tin oxide electrode (ITO) substrate is ultrasonically cleaned with toluene, acetone, ethanol, and deionized water in sequence, and then dried for later use;

(1) During the solution atomization process (process 1), place the treated ITO substrate on a heating platform, control the temperature at 30-80°C, place the ultrasonic nozzle 5-20cm above the ITO substrate, and The liquid port feeds the organic material solution to the ultrasonic nozzle at a rate of 0.5-5ml/min, and at the same time feeds a diversion gas with a pressure of 0.01-0.05MPa from the air inlet, and forms 20-100 micron droplets through ultrasonic atomization;

(2) The liquid film formation process (process 2), under the action of the diversion gas, the atomized droplets will reach the ITO substrate, and as the number of atomized droplets reaching the substrate increases, the atomized droplets will repolymerize to form 20-100 micron liquid film layer.

(3) Solvent volatilization process (process 3): keep the substrate temperature at 50-100°C by controlling the heating platform, when the solution forming the liquid film layer has a low surface tension, that is, the wetting angle of the organic material solution is less than 3 °, no need to take measures, go to step (5); when the wetting angle is greater than 3°, you need to go to step (4) to avoid the shrinkage of the liquid film due to the influence of surface tension, and make the liquid film layer The middle solvent gradually volatilizes within 1-10min;

(4), surface tension control process (process 4): around the substrate where the liquid film obtained in step (3), introduce an auxiliary organic solvent and make its liquid level equal to the liquid film liquid level obtained in step (3), The tension balance formed by the liquid-gas, solid-liquid and gas-solid surface tension at the edge of the liquid film before the introduction of the auxiliary solvent becomes the liquid-gas surface tension of the liquid film and the liquid-gas surface tension of the auxiliary solvent The more stable tension balance formed (as shown in Figure 2) enables the liquid film to maintain a uniform distribution during the solvent volatilization process;

(5) Solid film formation process (process 5): After the solvent in the liquid film layer solution formed in step 2 evaporates, the remaining organic material will be deposited on the substrate and solidified to form a film with a thickness of 10-100nm.

Further, during the solution atomization process, the guiding gas introduced is argon, nitrogen or helium.

Further, during the solution atomization process, the mass fraction of the organic material solution introduced is 0.01 mg/mL-10 mg/mL, wherein the organic material is 9,9'-(2,6-pyridinediyldi -3,1-phenylene)bis-9H-carbazole (26DCzPPy), 4,4'-N,N-dicarbazole-biphenyl (CBP), 4,4',4'-tri(carbazole- 9-yl)triphenylamine (TCTA), 9,9-spirobifluorene-diphenylphosphine oxide (SPPO1), 4,4'-cyclohexylbis[N,N-bis(4-methylphenyl)aniline ](TAPC), 1,3,5-tris(2-N-benzene-benzimidazole)benzene (TPBi), 2,2'-(1,3-phenyl)bis[5-(4-tert-butyl phenyl)-1,3,4-oxadiazole] (OXD-7), poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (PEDOT:PSS), tri( 2-phenylpyridine) iridium [Ir(ppy) ₃ ], tris(pinenyl-2-phenylpyridine) iridium [Ir(mppy) ₃ ], bis(4,6-difluorophenylpyridine-N , C2) iridium picolinate (Firpic), tris(1-phenylisoquinoline) iridium [Ir(piq) ₃ ] or (acetylacetonate) bis(2-methyldibenzo[f,h]quinone Oxaline) iridium [Ir(MDQ) ₂ (acac)]; the solvent in the solution is toluene, chloroform, tetrahydrofuran, ethanol, methanol, butanol or water; in order to ensure that the solution mass fraction is 0.01-10mg/mL, the surface tension Dilute the solution with very low solvent methanol, tetrahydrofuran or toluene.

Further, in the surface tension control process, the auxiliary solvent is the same solvent as the liquid film composition or other solvents with relatively high surface tension, such as toluene, butanol or water.

An application of an organic thin film in the preparation of an organic electroluminescent device. The organic thin film prepared by the above ultrasonic spraying method can be used as a hole injection layer, a light emitting layer, an electron injection layer or a transport layer in the organic electroluminescent device. details as follows:

The organic thin film prepared by the above-mentioned ultrasonic spraying method can be applied to organic electroluminescent devices as a hole injection layer or transport layer to improve the hole injection capability of the anode, wherein the hole injection layer that can be prepared by the ultrasonic spraying method has PEDOT: PSS, TAPC, TCTA, CBP, etc.;

The organic thin film prepared by the above ultrasonic spraying method can be applied to organic electroluminescent devices as a light-emitting layer, and the light-emitting layer can be a non-doped single light-emitting layer or multiple light-emitting layers, or a host-guest doped single light-emitting layer or multiple light-emitting layers layer, the present invention is preferably a single light-emitting layer doped with host and guest. The host materials of the luminescent layer that can be prepared by spraying ultrasonic method include: CBP, 26DCzPPy, TCTA, SPPO1, TAPC, TPBi and their mixed hosts in any proportion, and the guest luminescent materials include Ir(ppy) ₃ , Ir(mppy) ₃ , Firpic, Ir(piq) ₃ , Ir(MDQ) ₂ (acac) and any guest mixed among them, the host-guest doping ratio can be 0.1%-50% (mass ratio).

The organic thin film prepared by the above ultrasonic spraying method can be applied to organic electroluminescent devices as an electron injection layer or transport layer to improve the electron injection ability of the cathode. Among them, the electron injection or transport layer that can be prepared by the ultrasonic spraying method includes QXD-7, TPBi , SPPO1, etc.

Compared with prior art, the present invention has following advantage:

By introducing a low surface tension solvent to dilute the solution and introducing an auxiliary solvent to rebuild the tension balance at the edge of the liquid film, the influence of the surface tension of the solution can be effectively overcome, so that the liquid film is always uniformly distributed during the solvent volatilization process. An organic thin film with a flat surface for an organic electroluminescent device, especially an organic small molecule thin film. The organic thin film prepared based on the method proposed in the present invention can be used as a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer and an electron injection layer in an organic electroluminescent device, so that the organic light emitting device can obtain excellent performance .

Description of drawings

Fig. 1: The present invention adopts the schematic diagram of the process of ultrasonic spraying to prepare organic thin film;

Figure 2: A schematic diagram of the present invention introducing an auxiliary solvent to rebuild the edge tension balance of the liquid film;

Fig. 3: the atomic force microscope picture of the PEDOT:PSS thin film prepared by Example 1 and Example 2 of the present invention; Wherein, a is the ultrasonic spraying method, b is the spin coating method;

Fig. 4: the luminance-voltage characteristic curve of the organic electroluminescent device of the PEDOT:PSS thin film preparation based on ultrasonic spraying method and spin coating coating method of the present invention;

Fig. 5: the efficiency-brightness characteristic curve of the green light organic electroluminescent device of the PEDOT:PSS thin film preparation based on ultrasonic spraying method and spin coating coating method of the present invention;

Fig. 6: the prepared SPPO1 of the present invention is doped with 10wt% Ir (mppy) _The fluorescent micrograph of thin film;

Among them, a is the fluorescence microscope picture of the film prepared without introducing auxiliary solvent during the solvent volatilization process, and b is the fluorescence micrograph of the film prepared by introducing auxiliary solvent during the solvent volatilization process;

Fig. 7: the SPPO1 prepared by ultrasonic spraying method of the present invention doped 10wt%Ir (mppy) _The atomic force microscope picture of the thin film;

Among them, a is the topography diagram of the film, and b is the phase diagram of the film;

Fig. 8: Efficiency-brightness characteristic curves of organic electroluminescent devices in Example 3 and Example 5 of the present invention using thin films prepared by ultrasonic spraying method and thermal evaporation method as the light-emitting layer.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings.

Example 1

The PEDOT:PSS film was prepared by ultrasonic spraying technology, and the green light with the structure of ITO/PEDOT:PSS/TAPC/TcTa/CBP:Ir(ppy) ₃ /TmPyPhB/LiF/Mg:Ag was prepared based on it as a hole injection layer For organic electroluminescent devices, the hole injection layer is prepared by ultrasonic spraying technology, and the preparation of the remaining layers of the device is carried out in a multi-source organic molecule vapor deposition system. The detailed preparation process is as follows:

(1) The ITO substrate is ultrasonically cleaned with toluene, acetone, ethanol, and deionized water in sequence, and then dried.

(2) Put the treated ITO substrate on the heating platform, control the substrate temperature at 30°C, place the ultrasonic nozzle at 10cm above the ITO substrate, and feed PEDOT into the nozzle at a rate of 3ml/min: PSS solution (a 3wt% aqueous solution obtained by diluting 19 times the volume of methanol, the 3wt% aqueous solution is from Xi'an Baolaite Optoelectronics Technology Co., Ltd.), atomized by an ultrasonic nozzle to form 20 micron droplets, under the action of 0.5MPa nitrogen gas When the droplets reach the ITO substrate and repolymerize to form a 100-micron liquid film layer, due to the extremely low surface tension of methanol (the wetting angle of the PEDOT:PSS solution after dilution with methanol is 2°), the liquid film will It is always evenly distributed on the ITO substrate, so it is only necessary to ensure that the substrate temperature is stable at 30°C, and the solvent in the liquid film is slowly volatilized within 5 minutes, that is, a 40nm thick sprayed PEDOT:PSS film is obtained, and finally the sample is placed in the oven Heat and anneal at 120°C for 10 minutes in a dry box.

(3) Place the annealed substrate in a multi-source organic molecular vapor deposition system. The same vacuum chamber of the system includes an organic evaporation area (10 evaporation sources) and a metal evaporation area (2 evaporation sources). , the two areas and each evaporation source are isolated from each other to avoid mutual pollution. The substrate can be rotated to the upper part of the organic evaporation area or the metal evaporation area to facilitate the growth of materials. The substrate is 25cm away from the evaporation source and can rotate and revolve. To ensure the uniformity of the metal film and the organic film, the materials used are placed in different evaporation sources in different evaporation areas. The temperature of each evaporation source can be controlled independently, and then vacuumed to 6×10 ^-4 Pa.

(4), replace the mask plate with an organic mask plate, keep the above vacuum conditions unchanged, continue to vapor-deposit TAPC, TcTa, CBP:Ir(ppy) ₃ , TmPyPhB, and LiF on the above substrate as holes respectively The transport layer, the hole transport buffer layer, the green light emitting layer, the electron transport layer, and the electron injection layer have thicknesses of 20, 5, 30, 50, and 0.5 nm, respectively. The growth rate of TAPC, TcTa, CBP:Ir(ppy) ₃ , TmPyPhB is 0.1-0.2nm/s, the growth rate of LiF is 0.01-0.02nm/s, and the doping ratio of CBP:Ir(ppy) ₃ is 8% .

(5), replace the mask plate with a cathode mask plate, keep the above vacuum conditions unchanged, continue to evaporate Mg:Ag as the cathode on LiF, the thickness of the Mg:Ag layer is 100nm, and the doping ratio is 10: 1. The evaporation rate is 0.2nm/s.

Example 2

For comparison, the PEDOT:PSS film prepared by the common spin coating method was used as the hole injection layer, and the same structure was prepared as ITO/PEDOT:PSS/TAPC/TcTa/CBP:Ir(ppy) ₃ /TmPyPhB/LiF/Mg :Ag green light organic electroluminescent device, except for the hole injection layer, the preparation process of other functional layers of the device is the same as that of the above device.

(1) The ITO substrate is ultrasonically cleaned with toluene, acetone, ethanol, and deionized water in sequence, and then dried.

(2), put the treated ITO substrate on the spin coater, drop 40 microliters of PEDOT:PSS undiluted 3wt% aqueous solution (Xi'an Baolaite Optoelectronics Technology Co., Ltd.), at a speed of 5000 rpm, Rotate for 60 seconds to obtain a PEDOT:PSS film with a thickness of 30nm, and put the sample into a drying oven at 120°C for heating and annealing for 10min.

(3) Place the annealed substrate in a multi-source organic molecular vapor deposition system. The same vacuum chamber of the system includes an organic evaporation area (10 evaporation sources) and a metal evaporation area (2 evaporation sources). , the two areas and each evaporation source are isolated from each other to avoid mutual pollution. The substrate can be rotated to the upper part of the organic evaporation area or the metal evaporation area to facilitate the growth of materials. The substrate is 25cm away from the evaporation source and can rotate and revolve. To ensure the uniformity of the metal film and the organic film, the materials used are placed in different evaporation sources in different evaporation areas. The temperature of each evaporation source can be controlled independently, and then vacuumed to 6×10 ^-4 Pa.

(4), replace the mask plate with an organic mask plate, keep the above vacuum conditions unchanged, continue to vapor-deposit TAPC, TcTa, CBP:Ir(ppy) ₃ , TmPyPhB, and LiF on the above substrate as holes respectively The transport layer, the hole transport buffer layer, the green light emitting layer, the electron transport layer, and the electron injection layer have thicknesses of 20, 5, 30, 50, and 0.5 nm, respectively. The growth rate of TAPC, TcTa, CBP:Ir(ppy) ₃ , TmPyPhB is 0.1-0.2nm/s, the growth rate of LiF is 0.01-0.02nm/s, and the doping ratio of CBP:Ir(ppy) ₃ is 8% .

(5), replace the mask plate with a cathode mask plate, keep the above vacuum conditions unchanged, continue to evaporate Mg:Ag as the cathode on LiF, the thickness of the Mg:Ag layer is 100nm, and the doping ratio is 10: 1. The evaporation rate is 0.2nm/s.

The thickness and the growth rate of the vacuum thermal evaporation process growth film described in embodiment 1 and embodiment 2 are controlled by the L-400 film thickness controller made in the United States, and the evaluation of film quality is completed by Bruker's atomic force microscope. The photoelectric test system of Keithley 2400 current and voltage source and Otsuka Electronics MCPD-9800 spectrometer was tested in the air at room temperature. The atomic force microscope images of the PEDOT:PSS films prepared by the two processes are shown in Figure 3, and the brightness-voltage and efficiency-brightness characteristics of the device are shown in Figure 4 and Figure 5.

It can be seen from Figure 3 that, the same as the PEDOT:PSS film prepared by the spin coating method, the ultrasonic sprayed PEDOT:PSS film also has a relatively flat surface morphology, and its surface roughness is about 2.75 nm. When the PEDOT:PSS film prepared by ultrasonic spraying is applied to an organic electroluminescent device as a hole injection layer, the performance of the device is even better than that of the spin-coated PEDOT:PSS film in terms of brightness and efficiency roll-off. See Figure 4 and Figure 5. Spin-coated PEDOT:PSS film as the hole injection layer has the highest brightness of 45380cd/m ² , while the device of PEDOT:PSS film prepared by ultrasonic spraying can reach 70340cd/m ² . Although the highest efficiency of the spray-coated PEDOT:PSS device is 61.0cd/A, which is lower than that of the spin-coated PEDOT:PSS device at 67.8cd/A, when the brightness reaches 10000cd/ ^m2 , the efficiency of the former can still be maintained at 56.4cd/A while that of the latter dropped to 50.5cd/A. In summary, it can be seen that the PEDOT:PSS film prepared by ultrasonic spraying can be used as a hole injection layer to effectively realize high-performance organic electroluminescent devices.

Embodiment 3:

On the basis of the PEDOT:PSS hole injection layer prepared by ultrasonic spraying technology, we used ultrasonic spraying and introduced the surface tension control process to prepare the light-emitting layer with SPPO1 as the host and Ir(mppy) ₃ as the guest, thus realizing the structure of ITO /PEDOT:PSS/SPPO1:Ir(mppy) ₃ /BmPyPhB/LiF/Mg:Ag green light organic electroluminescent device, the electron transport layer and electrode of the device are prepared in a multi-source organic molecule vapor deposition system, detailed The preparation process is as follows:

(1) The ITO substrate was ultrasonically cleaned with toluene, acetone, ethanol, and deionized water in sequence, and then dried.

(2) Put the treated ITO substrate on the heating platform, control the substrate temperature at 30°C, place the ultrasonic nozzle at 10cm above the ITO substrate, and feed PEDOT into the nozzle at a rate of 3ml/min: PSS solution (a 3wt% aqueous solution obtained by diluting 19 times the volume of methanol, the 3% aqueous solution is from Xi'an Baolaite Optoelectronics Technology Co., Ltd.), atomized by an ultrasonic nozzle to form 20 micron droplets, under the action of 0.5MPa nitrogen gas Under the condition, the droplets reach the ITO substrate and repolymerize to form a 100 micron liquid film layer. Since methanol has an extremely low surface tension (the wetting angle is 2°), the liquid film is always evenly distributed on the ITO substrate during the solvent volatilization process. Therefore, it is only necessary to ensure that the substrate temperature is stable at 30°C, and the solvent in the liquid film is slowly volatilized within 5 minutes, that is, a 40nm-thick sprayed PEDOT:PSS film is obtained, and finally the sample is placed in a drying oven at 120°C and heated and annealed for 10 minutes .

(3) Put the annealed substrate into the petri dish on the heating platform, control the temperature of the substrate at 50°C, place the ultrasonic nozzle at 10cm above the substrate, and pass through the nozzle at a rate of 2ml/min. Into the toluene solution containing SPPO1 and Ir(mppy) ₃ (mass fraction is 1mg/mL, the mass ratio of SPP01 and Ir(mppy) ₃ is 10:1), atomized by an ultrasonic nozzle to form droplets with a size of 20 microns, in Under the action of 0.5MPa nitrogen gas, the droplets reach the ITO substrate PEDOT:PSS film and re-polymerize to form a 100 micron liquid film layer. Add the toluene solution to the petri dish to make the solution height in the petri dish flush with the liquid film , the substrate temperature is controlled at 50°C. During the solvent volatilization process, the liquid film will always be evenly distributed by the tension of the solution in the petri dish during the solvent volatilization process. After the solvent volatilizes slowly within 5 minutes, a uniform spray SPPO1:Ir(mppy ) ₃ film, and finally put the sample into a drying oven at 80°C and anneal for 10 minutes to remove the solvent.

(4) Place the annealed substrate in a multi-source organic molecular vapor deposition system. The same vacuum chamber of the system includes an organic evaporation area (10 evaporation sources) and a metal evaporation area (2 evaporation sources). , the two areas and each evaporation source are isolated from each other to avoid mutual pollution. The substrate can be rotated to the upper part of the organic evaporation area or the metal evaporation area to facilitate the growth of materials. The substrate is 25cm away from the evaporation source and can rotate and revolve. To ensure the uniformity of the metal film and the organic film, the materials used are placed in different evaporation sources in different evaporation areas. The temperature of each evaporation source can be controlled independently, and then vacuumed to 6×10 ^-4 Pa.

(5), replace the mask plate with an organic mask plate, keep the above-mentioned vacuum conditions unchanged, and sequentially vapor-deposit BmPyPhB and LiF on the above-mentioned SPPO1:Ir(mppy) ₃ as the electron transport layer and the electron modification layer respectively, with the thicknesses being respectively 40, 0.5nm. The growth rate of BmPyPhB is 0.2nm/s, and that of LiF is 0.02nm/s.

(6), replace the mask plate with a cathode mask plate, keep the above vacuum conditions constant, continue to evaporate Mg:Ag as the cathode on LiF, the thickness of the Mg:Ag layer is 100nm, and the doping ratio is 10: 1. The evaporation rate is 0.2nm/s.

Example 4

For comparison, on the basis of the PEDOT:PSS hole injection layer prepared by ultrasonic spraying technology, we used ultrasonic spraying and did not introduce surface tension control process to prepare the light-emitting layer with SPPO1 as the host and Ir(mppy) ₃ as the guest. The details The preparation process is as follows:

(1) The ITO substrate was ultrasonically cleaned with toluene, acetone, ethanol, and deionized water in sequence, and then dried.

(2) Put the treated ITO substrate on the heating platform, control the substrate temperature at 30°C, place the ultrasonic nozzle at 10cm above the ITO substrate, and feed PEDOT into the nozzle at a rate of 3ml/min: PSS solution (a 3wt% aqueous solution obtained by diluting 19 times the volume of methanol, the 3% aqueous solution is from Xi'an Baolaite Optoelectronics Technology Co., Ltd.), atomized by an ultrasonic nozzle to form 20 micron droplets, under the action of 0.5MPa nitrogen gas Under the condition, the droplets reach the ITO substrate and repolymerize to form a 100 micron liquid film layer. Since methanol has an extremely low surface tension (the wetting angle is 2°), the liquid film is always evenly distributed on the ITO substrate during the solvent volatilization process. Therefore, it is only necessary to ensure that the substrate temperature is stable at 30°C, and the solvent in the liquid film is slowly volatilized within 5 minutes, that is, a 40nm-thick sprayed PEDOT:PSS film is obtained, and finally the sample is placed in a drying oven at 120°C and heated and annealed for 10 minutes .

(3) Put the annealed substrate on the heating platform, control the temperature of the substrate at 50°C, place the ultrasonic nozzle at 10 cm above the substrate, and spray the nozzle with SPPO1 and The toluene solution of Ir(mppy) ₃ (the mass fraction is 1 mg/mL, the mass ratio of SPP01 and Ir(mppy) ₃ is 10:1), is atomized by an ultrasonic nozzle to form droplets with a size of 20 microns, and the 0.5 Under the action of MPa nitrogen, the droplets reach the ITO substrate PEDOT:PSS film and repolymerize to form a 100 micron liquid film layer. The substrate temperature is controlled at 50°C, and the SPPO1:Ir( mppy) ₃ film, and finally put the sample into a drying oven at 80°C for 10 minutes to heat and anneal to remove the solvent.

Example 5

For comparison, a layer of SPPO1 doped with 10wt% Ir(mppy) was vapor _- deposited on the sprayed PEDOT:PSS film by vacuum thermal evaporation method as the light-emitting layer, and the same structure was prepared as ITO/PEDOT:PSS/SPPO1:Ir( mppy) ₃ /BmPyPhB/LiF/Mg:Ag green organic electroluminescent device. The preparation of the light-emitting layer, electron transport layer and electrodes of the device is carried out in a multi-source organic molecule vapor deposition system. The detailed preparation process is as follows:

(1) The ITO substrate was ultrasonically cleaned with toluene, acetone, ethanol, and deionized water in sequence, and then dried.

(2) Put the treated ITO substrate on the heating platform, control the substrate temperature at 30°C, place the ultrasonic nozzle at 10cm above the ITO substrate, and feed PEDOT into the nozzle at a rate of 3ml/min: PSS solution (a 3wt% aqueous solution obtained by diluting 19 times the volume of methanol, the 3% aqueous solution is from Xi'an Baolaite Optoelectronics Technology Co., Ltd.), atomized by an ultrasonic nozzle to form 20 micron droplets, under the action of 0.5MPa nitrogen gas Under the condition, the droplets reach the ITO substrate and repolymerize to form a 100 micron liquid film layer. Since methanol has an extremely low surface tension (the wetting angle is 2°), the liquid film is always evenly distributed on the ITO substrate during the solvent volatilization process. Therefore, it is only necessary to ensure that the substrate temperature is stable at 30°C, and the solvent in the liquid film is slowly volatilized within 5 minutes, that is, a 40nm-thick sprayed PEDOT:PSS film is obtained, and finally the sample is placed in a drying oven at 120°C and heated and annealed for 10 minutes .

(3) Place the annealed substrate in a multi-source organic molecular vapor deposition system. The same vacuum chamber of the system includes an organic evaporation area (10 evaporation sources) and a metal evaporation area (2 evaporation sources). , the two areas and each evaporation source are isolated from each other to avoid mutual pollution. The substrate can be rotated to the upper part of the organic evaporation area or the metal evaporation area to facilitate the growth of materials. The substrate is 25cm away from the evaporation source and can rotate and revolve. To ensure the uniformity of the metal film and the organic film, the materials used are placed in different evaporation sources in different evaporation areas. The temperature of each evaporation source can be controlled independently, and then vacuumed to 6×10 _-4 Pa.

(4), replace the mask plate with an organic mask plate, keep the above vacuum conditions unchanged, sequentially vapor-deposit SPPO1:Ir(mppy) ₃ , BmPyPhB, and LiF on the above-mentioned PEDOT:PSS film as the light-emitting layer and electron transport layer respectively. layer, electronic modification layer, the thickness is 30, 40, 0.5nm respectively. The doping ratio of SPPO1:Ir(mppy) ₃ in the light-emitting layer is that the mass ratio of SPP01 and Ir(mppy) ₃ is 10:1, the growth rate of the light-emitting layer and BmPyPhB is 0.2nm/s, and the growth rate of LiF is 0.02nm/s .

(6), replace the mask plate with a cathode mask plate, keep the above vacuum conditions constant, continue to evaporate Mg:Ag as the cathode on LiF, the thickness of the Mg:Ag layer is 100nm, and the doping ratio is 10: 1. The evaporation rate is 0.2nm/s.

The thickness and the growth rate of the vacuum thermal evaporation process growth film described in embodiment 3 and embodiment 5 are controlled by the L-400 film thickness controller made in the United States, and the evaluation of film quality is completed by Mingmei fluorescence microscope and Bruker company atomic force microscope, and the obtained The performance of the device was tested in air at room temperature using a photoelectric test system based on Keithley 2400 current and voltage source and Otsuka Electronics MCPD-9800 spectrometer. The fluorescence microscopy and atomic force microscopy images of the SPPO1:Ir(mppy) ₃ thin film prepared by the spraying method are shown in Figures 6 and 7, respectively, and the efficiency-brightness characteristics of the device are shown in Figure 8.

According to Examples 3 and 4, it can be seen from Figure 6 that there are many wrinkles in the film prepared without the tension control process in the spraying process, which seriously affects the application of the film in organic electroluminescent devices, while in the spraying process the tension control process The film formed after control has higher uniformity. As for the microscopic morphology of the sprayed organic small molecule luminescent film, it can be seen from its atomic force microscope, that is, it can be seen from Figure 7 that the surface roughness of the film is only 0.529 nanometers, and the phase difference is only 10°. The method can realize the organic small molecule thin film with smooth surface and uniform doping of host and guest.

According to Examples 3 and 5, when the organic electroluminescent device adopts the spray-coated organic small molecule film as the light-emitting layer, the device shows excellent performance, although compared with the device using the thermal evaporation light-emitting layer, the device is slightly inferior in brightness , the highest brightness is only 8130cd/m ₂ , but its efficiency is comparable to that of thermal evaporation devices. The highest efficiency of sprayed devices reaches 24.7cd/A, while the highest efficiency of thermal evaporation devices is 24.0cd/A. The above results show that the organic small molecule thin film prepared by ultrasonic spraying method can be applied in organic electroluminescent devices and achieve excellent device performance.

Claims (7)

1. a preparation method of organic film, is characterized in that, concrete steps are as follows: First, the indium tin oxide electrode (ITO) substrate is ultrasonically cleaned with toluene, acetone, ethanol, and deionized water in sequence, and then dried for later use; (1) Solution atomization process: place the treated ITO substrate on the heating platform, control the temperature at 30-80°C, place the ultrasonic nozzle 5-20cm above the ITO substrate, Inject organic material solution into the ultrasonic nozzle at a rate of -5ml/min, and at the same time inject diversion gas with a pressure of 0.01-0.05MPa from the air inlet, and form liquid droplets of 20-100 microns through ultrasonic atomization; (2) Liquid film formation process: Under the action of diversion gas, the atomized droplets will reach the ITO substrate, and the atomized droplets will repolymerize to form a liquid film layer of 20-100 microns; (3) Solvent volatilization process: keep the substrate temperature at 50-100°C by controlling the heating platform. When the solution forming the liquid film layer has a low surface tension, that is, the wetting angle of the organic material solution is less than 3°, enter the step (5); when the infiltration angle is greater than 3 °, then enter step (4); (4), surface tension control process: around the substrate where the liquid film obtained in step (3) is located, an auxiliary organic solvent is introduced and its liquid level is equal to that of the liquid film obtained in step (3), so that no auxiliary organic solvent is introduced The tension balance formed by the liquid-gas, solid-liquid and gas-solid surface tension at the edge of the liquid film before the solvent becomes the tension balance formed by the liquid-gas surface tension of the liquid film and the liquid-gas surface tension of the auxiliary solvent ; (5) Solid thin film formation process: After the solvent in the liquid film layer solution formed in step 2 volatilizes, the remaining organic material will be deposited on the substrate and solidified to form a thin film with a thickness of 10-100 nm. 2 . The method for preparing an organic thin film according to claim 1 , wherein, during the atomization of the solution, the diversion gas introduced is argon, nitrogen or helium. 3 . 3. The preparation method of a kind of organic thin film as claimed in claim 1, is characterized in that: in described solution atomization process, the mass fraction of the organic material solution that feeds is 0.01mg/mL-10mg/mL, wherein , the organic materials are 9,9'-(2,6-pyridyldi-3,1-phenylene)bis-9H-carbazole (26DCzPPy), 4,4'-N,N-dicarbazole-linked Benzene (CBP), 4,4',4'-tris(carbazol-9-yl)triphenylamine (TCTA), 9,9-spirobifluorene-diphenylphosphine oxide (SPPO1), 4,4'- Cyclohexylbis[N,N-bis(4-methylphenyl)aniline](TAPC), 1,3,5-tris(2-N-benzene-benzimidazole)benzene(TPBi), 2,2' -(1,3-phenyl)bis[5-(4-tert-butylphenyl)-1,3,4-oxadiazole](OXD-7), poly(3,4-ethylenedioxy Thiophene)-poly(styrenesulfonic acid) (PEDOT:PSS), tris(2-phenylpyridine)iridium [Ir(ppy) ₃ ], tris(pinenyl-2-phenylpyridine)iridium [Ir( mppy) ₃ ], bis(4,6-difluorophenylpyridine-N,C2)pyridinecarboyl iridium (Firpic), tris(1-phenylisoquinoline) iridium [Ir(piq) ₃ ] or ( acetylacetonate) bis(2-methyldibenzo[f,h]quinoxaline) iridium [Ir(MDQ) ₂ (acac)]; the solvent in the organic material solution is toluene, chloroform, tetrahydrofuran, ethanol, methanol , butanol or water. 4. The preparation method of an organic thin film as claimed in claim 1, characterized in that: the auxiliary solvent is the same solvent as the composition of the liquid film layer. 5. The preparation method of a kind of organic thin film as claimed in claim 1, is characterized in that: described auxiliary solvent is toluene, butanol or water. 6. An organic thin film, characterized in that it is prepared by the method according to any one of claims 1-5. 7. The application of a kind of organic thin film prepared by any one of claims 1-5 in the preparation of organic electroluminescent devices.