Green light emitting diode device and preparation method thereof

Abstract

The invention discloses a green light-emitting diode device and a preparation method thereof. FAPbBr3 perovskite nanocrystals are synthesized by a ligand-assisted reprecipitation method, wherein FABr and PbBr2 serve as FA sources, Pb sources, and Br sources, chloroform serves as an antisolvent, and acetonitrile serves as a reaction quencher. The green light-emitting diode device comprises a substrate printed with an anode, a hole transport layer, a hole injection layer, a light-emitting layer, a first electron transport layer, a second electron transport layer, and a cathode, which are arranged in sequence from bottom to top. By adding thiophenol as a new organic ligand to acetonitrile to replace part of the traditional ligand, the surface defects of the material are significantly passivated, thereby improving the photoluminescence quantum yield of the material and the photoelectric performance of the LED prepared from the material. Unlike traditional ligands, thiophenol does not contain a long alkyl chain but has a benzene ring with better conductivity, so the electrical performance of the LED prepared using the thiophenol is also improved. In addition, it can be proved that the introduction of thiophenol does not affect the emission wavelength of the LED.

Description

Technical Field

[0001] The present invention relates to the field of perovskite luminescence or perovskite display technology, and in particular to a green light-emitting diode device and a preparation method thereof. Background Art

[0002] Light-emitting diodes (LEDs) have surpassed traditional lighting sources and are profoundly changing the lighting and display industries. Currently, a variety of materials are available for commercialized LEDs, such as III-V semiconductor LEDs, organic LEDs (OLEDs), and colloidal quantum dot LEDs (QLEDs). However, the further development of III-V semiconductor LEDs is limited by harsh growth conditions and expensive equipment, as well as the limited luminescence spectra of the materials. Compared to III-V semiconductor LEDs, OLEDs have become an alternative in the LED field due to their solution and vacuum deposition capabilities, large-area light emission, and flexibility. However, they suffer from low thermal stability and chemical specificity and high efficiency under high brightness and high current density conditions, while core-shell quantum dots are difficult to manufacture on a macroscale due to the cumbersome manufacturing process and expensive raw materials. All of these shortcomings hinder the progress of cost-effective multi-scenario electroluminescent applications. Finding promising electroluminescent materials is important for promoting the development of the lighting and display industries.

[0003] Perovskite nanocrystals (PeNCs) are a promising new semiconductor material with the characteristics of low cost, spectral tunability and high photoluminescence quantum yield, which has broadened optoelectronic application scenarios. At present, one of the important factors affecting the commercialization of perovskite light-emitting diodes (PeLEDs) is their low external quantum efficiency (EQE). In addition, low color purity and poor device life are also serious obstacles to the commercialization of PeLEDs. Therefore, when promoting the commercial development of PeLEDs, issues such as how to improve EQE, reduce the full width at half maximum (FWHM), reduce efficiency roll-off and extend the service life of the device should be considered.

[0004] It has been shown that adding appropriate amounts of novel ligands to perovskite materials can effectively improve the device efficiency and service life of PeLEDs. Therefore, finding a suitable ligand additive to improve the optoelectronic performance of PeLEDs is one of the effective ways to address the existing difficulties in the field of perovskite displays.

[0005] Therefore, a green light emitting diode device and a preparation method thereof are developed to solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to design a green light emitting diode device and a preparation method thereof in order to solve the above problems.

[0007] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0008] A green light-emitting diode device includes a substrate with an anode printed thereon, a hole transport layer, a hole injection layer, a perovskite light-emitting layer, a first electron transport layer, a second electron transport layer, and a cathode, which are arranged in sequence from bottom to top.

[0009] Preferably, the hole transport layer is made of PEDOT:PSS; and the hole injection layer is made of PVK.

[0010] Furthermore, the first electron transport layer is a TPBi electron transport layer, and the second transport layer is a LiF electron transport layer.

[0011] Preferably, the cathode is made of Al.

[0012] A method for preparing a green light emitting diode device comprises the following steps:

[0013] S1. Dissolve PbBr2 and FABr in dimethylformamide respectively to prepare PbBr2 and FABr solutions with certain concentrations;

[0014] S2. Mix the fully dissolved PbBr2 and FABr solution, oleic acid, and oleylamine in a certain proportion in a clean glass bottle and stir evenly.

[0015] S3. Rapidly drop the prepared mixed solution into chloroform and stir vigorously;

[0016] S4, adding an acetonitrile solution containing a certain amount of thiophenol to the solution obtained in step S3 according to a certain volume ratio;

[0017] S5, centrifuging the solution obtained in step S4, removing the supernatant to collect the FAPbBr3 perovskite nanocrystal precipitate and redispersing it in octane;

[0018] S6. Centrifuge the solution obtained in step S5 again, collect the supernatant, filter it, and store it for subsequent experiments;

[0019] S7, ultrasonically cleaning the glass substrate printed with ITO and treating it with ultraviolet ozone;

[0020] S8, filtering the PEDOT:PSS suspension, spin-coating it on an ITO substrate, and annealing it;

[0021] S9, PVK was dissolved in chlorobenzene and spin-coated on the PEDOT:PSS film, followed by annealing for 30 mins;

[0022] S10, spin-coating the prepared perovskite nanocrystal material on the treated substrate and annealing;

[0023] S11. Transfer the spin-coated substrate to an evaporator and sequentially evaporate TPBi, LiF and Al thin films.

[0024] Furthermore, the perovskite nanocrystal material was synthesized by a ligand-assisted reprecipitation (LARP) method, wherein the reaction quencher added during the synthesis was acetonitrile, and a certain amount of a new ligand thiophenol was added to the acetonitrile.

[0025] Furthermore, acetonitrile is used as the solvent, and the concentration of thiophenol added is in the range of 5 to 20 mg / ml.

[0026] Preferably, the molecular structure of thiophenol is:

[0027]

[0028] Preferably, in step S1, the concentration range of PbBr2 in the PbBr2 and FABr solutions is 0.3-0.6 mol / L; the concentration range of FABr is 0.6-1.2 mol / L.

[0029] Preferably, in step S2, the amount of oleylamine added is in the range of 20 to 30 μl; the amount of oleic acid added is in the range of 200 to 300 μl.

[0030] The beneficial effects of the present invention are:

[0031] 1. FAPbBr3 perovskite nanocrystals were synthesized by ligand-assisted reprecipitation. Unlike the hot injection method, this synthesis method is convenient and easy to operate. It does not require heating or inert gas protection. The precursor solution can be crystallized into perovskite nanocrystals in air, thus greatly saving the cost and time of material synthesis.

[0032] 2. By introducing a new ligand, thiophenol, into the perovskite luminescent material during the ligand-assisted reprecipitation method, the surface defects of FAPbBr3 perovskite nanocrystals were effectively passivated, significantly improving their PLQY and significantly enhancing the optoelectronic performance of the PeLED prepared with this material without affecting the luminescent wavelength of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic structural diagram of a green light emitting diode device involved in the present invention;

[0034] Figure 2 is an electroluminescence (EL) spectrum diagram of an example involved in the present invention;

[0035] Figure 3 is the external quantum efficiency-luminance curve of the example involved in the present invention;

[0036] Figure 4 is the current density-voltage-brightness curve of the example LED involved in the present invention;

[0037] Figure 5This is a comparison chart of the photoluminescence quantum yields of the FAPbBr3 perovskite nanocrystal materials in Examples 1 and 3 of the present invention;

[0038] The reference numerals in the figure are: 1. substrate with printed anode, 2. hole transport layer, 3. hole injection layer, 4. perovskite light-emitting layer, 5. first electron transport layer, 6. first electron transport layer, 7. cathode. DETAILED DESCRIPTION

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the embodiments of the present invention. It should be understood that the described embodiments are only a portion of the embodiments of the present invention, not all of them. Generally, the components of the embodiments of the present invention described and illustrated in the drawings herein may be arranged and designed in a variety of different configurations.

[0040] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0041] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not require further definition or explanation in subsequent drawings.

[0042] In the description of the present invention, it should be understood that the terms "upper", "lower", "inside", "outside", "left", "right", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the inventive product is conventionally placed when in use, or are the orientations or positional relationships conventionally understood by those skilled in the art. These are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0043] Furthermore, the terms “first”, “second”, etc. are merely used for distinguishing descriptions and should not be understood as indicating or implying relative importance.

[0044] In the description of the present invention, it should also be noted that, unless otherwise expressly specified or limited, terms such as "disposed" and "connected" should be understood in a broad sense. For example, "connected" can mean a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can also mean internal communication between two components. Those skilled in the art will be able to understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0045] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0046] like Figure 1 As shown, the green light-emitting diode device includes, from bottom to top, a substrate printed with a transparent indium tin oxide (ITO) anode, a hole transport layer, a hole injection layer, a light-emitting layer, a first electron transport layer, a second electron transport layer, and a cathode. The hole transport layer is made of PEDOT:PSS; the hole injection layer is made of PVK. The first electron transport layer is TPBi, and the second electron transport layer is LiF. The cathode is made of Al.

[0047] A method for preparing a green light emitting diode device comprises the following steps:

[0048] S1. Dissolve PbBr2 and FABr in dimethylformamide respectively to prepare PbBr2 and FABr solutions with certain concentrations;

[0049] S2. Mix the fully dissolved PbBr2 and FABr solution, oleic acid, and oleylamine in a certain proportion in a clean glass bottle and stir evenly; the amount of oleylamine added is in the range of 20-30 μl; the amount of oleic acid added is in the range of 200-300 μl;

[0050] S3. Rapidly drop the prepared mixed solution into chloroform and stir vigorously;

[0051] S4, adding an acetonitrile solution containing a certain amount of thiophenol to the solution obtained in step S3 according to a certain volume ratio;

[0052] S5, centrifuging the solution obtained in step S4, removing the supernatant to collect the FAPbBr3 perovskite nanocrystal precipitate and redispersing it in octane;

[0053] S6. Centrifuge the solution obtained in step S5 again, collect the supernatant, filter it, and store it for subsequent experiments;

[0054] S7, ultrasonically cleaning the glass substrate printed with ITO and treating it with ultraviolet ozone;

[0055] S8, filtering the PEDOT:PSS suspension, spin-coating it on an ITO substrate, and annealing it;

[0056] S9, PVK was dissolved in chlorobenzene and spin-coated on the PEDOT:PSS film, followed by annealing for 30 mins;

[0057] S10, spin-coating the prepared perovskite nanocrystal material on the treated substrate and annealing;

[0058] S11. Transfer the spin-coated substrate to an evaporator and sequentially evaporate TPBi, LiF and Al thin films.

[0059] The perovskite nanocrystals were synthesized using the LARP method. Acetonitrile was used as a reaction quencher, and a certain amount of a novel ligand, thiophenol, was added to the acetonitrile. Acetonitrile was used as the solvent, and the concentration of thiophenol was in the range of 5 to 20 mg / ml. The molecular structure of thiophenol is:

[0060]

[0061] In step S1, the concentration of PbBr2 in the PbBr2 and FABr solutions is in the range of 0.3 to 0.6 mol / L; the concentration of FABr is in the range of 0.6 to 1.2 mol / L.

[0062] Example 1 (control group):

[0063] Synthesis of FAPbBr3 perovskite nanocrystals: Dissolve a certain amount of PbBr2 and FABr in a certain amount of dimethylformamide (DMF) to prepare solutions with concentrations of 0.4 mol / L and 0.8 mol / L, respectively. Combine the fully dissolved PbBr2 and FABr solutions with 250 μl of oleic acid and 25 μl of oleylamine in a clean glass bottle and stir thoroughly. Rapidly add the resulting mixture dropwise to 8 ml of the antisolvent chloroform and stir vigorously for 35 seconds to produce FAPbBr3 nanocrystals. After 35 seconds, quickly add acetonitrile to the solution in a volume ratio (perovskite solution volume: acetonitrile solution volume = 3:1) and stop stirring. The resulting solution is centrifuged at 5500 rpm for 5 minutes. The supernatant is then removed to collect the FAPbBr3 nanocrystal precipitate and redisperse it in 2.5 ml of octane. The resulting solution was centrifuged again at 5500 rpm for 5 mins, and the supernatant was collected and filtered with a 0.22 μm filter and stored in a dark room at 4°C for subsequent experiments.

[0064] Perovskite LED fabrication: A glass substrate printed with ITO was ultrasonically cleaned at 80°C for 30 minutes using a mixture of detergent and deionized water, ammonia (25%), and hydrogen peroxide (28%) (volume ratio: 5:1:1). The solution was then treated with UV-ozone for 20 minutes. Filtered PEDOT:PSS was then spin-coated on the ITO substrate at 4000 rpm for 40 seconds as a hole transport layer and annealed at 140°C for 15 minutes. PVK (4 mg / ml) dissolved in chlorobenzene was then spin-coated at 1000 rpm for 40 seconds on the PEDOT:PSS substrate as a hole injection layer and annealed at 170°C for 30 minutes. Perovskite nanocrystals were spin-coated at 1000 rpm for 40 seconds on the treated substrate as the light-emitting layer and annealed at 70°C for 10 minutes. Finally, the spin-coated substrate was transferred to an evaporator, and TPBi, LiF, and Al were sequentially evaporated as the electron transport layer and metal electrode, with thicknesses of 40 nm, 1 nm, and 100 nm, respectively.

[0065] Example 2:

[0066] Synthesis of FAPbBr3 perovskite nanocrystals: A certain amount of PbBr2 and FABr were dissolved in a certain amount of dimethylformamide (DMF) to prepare solutions with concentrations of 0.4 mol / L and 0.8 mol / L, respectively. The fully dissolved PbBr2 and FABr solutions were mixed with 250 μl of oleic acid and 25 μl of oleylamine in a clean glass bottle and stirred thoroughly. The mixed solution was quickly added dropwise to 8 ml of the antisolvent chloroform and stirred vigorously for 35 seconds to produce FAPbBr3 nanocrystals. At 35 seconds, a thiophenol-doped acetonitrile solution was quickly added to the solution at a volume ratio (perovskite solution volume: doped acetonitrile solution volume = 3:1). The thiophenol concentration in the acetonitrile solution was 5 mg / ml. The resulting solution was centrifuged at 5500 rpm for 5 minutes. The supernatant was then removed to collect the FAPbBr3 nanocrystal precipitate and redispersed in 2.5 ml of octane. The resulting solution was centrifuged again at 5500 rpm for 5 mins, and the supernatant was collected and filtered with a 0.22 μm filter and stored in a dark room at 4°C for subsequent experiments.

[0067] Perovskite LED fabrication: A glass substrate printed with ITO was ultrasonically cleaned at 80°C for 30 minutes using a mixture of detergent and deionized water, ammonia (25%), and hydrogen peroxide (28%) (volume ratio: 5:1:1). The solution was then treated with UV-ozone for 20 minutes. Filtered PEDOT:PSS was then spin-coated on the ITO substrate at 4000 rpm for 40 seconds as a hole transport layer and annealed at 140°C for 15 minutes. PVK (4 mg / ml) dissolved in chlorobenzene was then spin-coated at 1000 rpm for 40 seconds on the PEDOT:PSS substrate as a hole injection layer and annealed at 170°C for 30 minutes. Perovskite nanocrystals were spin-coated at 1000 rpm for 40 seconds on the treated substrate as the light-emitting layer and annealed at 70°C for 10 minutes. Finally, the spin-coated substrate was transferred to an evaporator, and TPBi, LiF, and Al were sequentially evaporated as the electron transport layer and metal electrode, with thicknesses of 40 nm, 1 nm, and 100 nm, respectively.

[0068] Example 3:

[0069] Synthesis of FAPbBr3 perovskite nanocrystals: A certain amount of PbBr2 and FABr were dissolved in a certain amount of dimethylformamide (DMF) to prepare solutions with concentrations of 0.4 mol / L and 0.8 mol / L, respectively. The fully dissolved PbBr2 and FABr solutions were mixed with 250 μl of oleic acid and 25 μl of oleylamine in a clean glass bottle and stirred thoroughly. The prepared solution was quickly added dropwise to 8 ml of the antisolvent chloroform and stirred vigorously for 35 seconds to produce FAPbBr3 nanocrystals. At 35 seconds, a solution of acetonitrile doped with thiophenol was quickly added to the solution at a volume ratio (perovskite solution volume: doped acetonitrile solution volume = 3:1). The acetonitrile solution was doped with thiophenol at a concentration of 10 mg / ml. The resulting solution was centrifuged at 5500 rpm for 5 minutes. The supernatant was then removed to collect the FAPbBr3 nanocrystal precipitate and redispersed in 2.5 ml of octane. The resulting solution was centrifuged again at 5500 rpm for 5 minutes, and the supernatant was collected, filtered through a 0.22 μm filter, and stored in a darkroom at 4°C for subsequent experiments. Perovskite LED fabrication: Glass substrates printed with ITO were ultrasonically cleaned at 80°C for 30 minutes using a mixture of detergent and deionized water, ammonia (25%), and hydrogen peroxide (28%) (5:1:1 volume ratio) and then treated with UV-ozone for 20 minutes. The filtered PEDOT:PSS was then spin-coated on the ITO substrate (at 4000 rpm for 40 seconds) as a hole transport layer and annealed at 140°C for 15 minutes. PVK was then dissolved in chlorobenzene at a concentration of 4 mg / ml and spin-coated at 1000 rpm for 40 seconds on the PEDOT:PSS substrate as a hole injection layer. The layer was then annealed at 170°C for 30 minutes. Perovskite nanocrystals were spin-coated at 1000 rpm for 40 seconds onto the treated substrate to form the light-emitting layer, followed by annealing at 70°C for 10 minutes. Finally, the spin-coated substrate was transferred to an evaporator, where TPBi, LiF, and Al were sequentially deposited to thicknesses of 40 nm, 1 nm, and 100 nm as the electron transport layer and metal electrode, respectively.

[0070] Example 4:

[0071] Synthesis of FAPbBr3 perovskite nanocrystals: A certain amount of PbBr2 and FABr were dissolved in a certain amount of dimethylformamide (DMF) to prepare solutions with concentrations of 0.4 mol / L and 0.8 mol / L, respectively. The fully dissolved PbBr2 and FABr solutions were mixed with 250 μl of oleic acid and 25 μl of oleylamine in a clean glass bottle and stirred thoroughly. The prepared solution was quickly added dropwise to 8 ml of the antisolvent chloroform and stirred vigorously for 35 seconds to produce FAPbBr3 nanocrystals. At 35 seconds, a solution of acetonitrile doped with thiophenol was quickly added to the solution at a volume ratio (perovskite solution volume: doped acetonitrile solution volume = 3:1). The acetonitrile solution was doped with thiophenol at a concentration of 20 mg / ml. The resulting solution was centrifuged at 5500 rpm for 5 minutes. The supernatant was then removed to collect the FAPbBr3 nanocrystal precipitate and redispersed in 2.5 ml of octane. The resulting solution was centrifuged again at 5500 rpm for 5 minutes, and the supernatant was collected, filtered through a 0.22 μm filter, and stored in a darkroom at 4°C for subsequent experiments. Perovskite LED fabrication: Glass substrates printed with ITO were ultrasonically cleaned at 80°C for 30 minutes using a mixture of detergent and deionized water, ammonia (25%), and hydrogen peroxide (28%) (5:1:1 volume ratio) and then treated with UV-ozone for 20 minutes. The filtered PEDOT:PSS was then spin-coated on the ITO substrate (at 4000 rpm for 40 seconds) as a hole transport layer and annealed at 140°C for 15 minutes. PVK was then dissolved in chlorobenzene at a concentration of 4 mg / ml and spin-coated at 1000 rpm for 40 seconds on the PEDOT:PSS substrate as a hole injection layer. The layer was then annealed at 170°C for 30 minutes. Perovskite nanocrystals were spin-coated at 1000 rpm for 40 seconds onto the treated substrate to form the light-emitting layer, followed by annealing at 70°C for 10 minutes. Finally, the spin-coated substrate was transferred to an evaporator, where TPBi, LiF, and Al were sequentially deposited to thicknesses of 40 nm, 1 nm, and 100 nm as the electron transport layer and metal electrode, respectively.

[0072] Maximum EQE(%) Example 1 13.17 Example 2 14.59 Example 3 16.15 Example 4 14.61

[0073] Table 1 Maximum external quantum efficiency of FAPbBr3 perovskite nanocrystal LED devices

[0074] From Table 1 and Figure 2 、 Figure 3It can be seen that the addition of thiophenol has little effect on the wavelength of the LED, so it can be concluded that it does not affect the band gap of the material. However, its maximum external quantum efficiency has been significantly improved, reaching a maximum of 16.15%. This is because the introduction of thiophenol effectively passivates the defects on the surface of the FAPbBr3 perovskite nanocrystals, which can also be explained by Figure 5 The improvement of PLQY can be seen. Figure 4 It can be seen that the introduction of thiophenol affects the current density of the device. This is because the benzene ring on thiophenol has better conductivity than traditional long alkyl chain ligands such as oleic acid and oleylamine.

[0075] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a green light emitting diode device, characterized in that: The following steps are involved: S1. Dissolve PbBr2 and FABr in two bottles of dimethylformamide respectively to prepare PbBr2 and FABr solutions with certain concentrations; S2. Mix the fully dissolved PbBr2 and FABr solution, oleic acid, and oleylamine in a certain proportion in a clean glass bottle and stir evenly. S3, quickly adding the solution obtained in step S2 dropwise into chloroform and stirring vigorously; S4, adding an acetonitrile solution containing a certain amount of thiophenol to the solution obtained in step S3 according to a certain volume ratio; S5, centrifuging the solution obtained in step S4, removing the supernatant to collect the FAPbBr3 perovskite nanocrystal precipitate and redispersing it in octane; S6. Centrifuge the solution obtained in step S5 again, collect the supernatant, filter it, and store it for subsequent experiments; S7, ultrasonically cleaning the glass substrate printed with ITO and treating it with ultraviolet ozone; S8, filtering the PEDOT:PSS suspension, spin-coating it on an ITO substrate, and annealing it; S9, PVK was dissolved in chlorobenzene and spin-coated on the PEDOT:PSS film, followed by annealing for 30 mins; S10, spin-coating the prepared perovskite nanocrystal material on the substrate obtained in step S9 and annealing; S11. Transfer the spin-coated substrate to an evaporator and sequentially evaporate TPBi, LiF and Al thin films.

2. The method for preparing a green light emitting diode device according to claim 1, wherein: The perovskite nanocrystal material is synthesized by a ligand-assisted reprecipitation (LARP) method. Acetonitrile is used as a reaction quencher during the synthesis, and a certain amount of ligand thiophenol is added to the acetonitrile.

3. The method for preparing a green light emitting diode device according to claim 2, wherein: Acetonitrile was used as the solvent, and the concentration of thiophenol added ranged from 5 to 20 mg / ml.

4. The method for preparing a green light emitting diode device according to claim 3, wherein: The molecular structure of thiophenol is: 。 5. The method for preparing a green light emitting diode device according to claim 1, wherein: In step S1, the concentration of PbBr2 in the PbBr2 and FABr solutions ranges from 0.3 to 0.6 mol / L; the concentration of FABr ranges from 0.6 to 1.2 mol / L.

6. The method for preparing a green light emitting diode device according to claim 1, wherein: In step S2, the amount of oleylamine added is in the range of 20-30 μl; the amount of oleic acid added is in the range of 200-300 μl.

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