WO2024078562A1

WO2024078562A1 - Film and preparation method therefor, and photoelectric device

Info

Publication number: WO2024078562A1
Application number: PCT/CN2023/124182
Authority: WO
Inventors: 吴劲衡
Original assignee: Tcl科技集团股份有限公司
Priority date: 2022-10-14
Filing date: 2023-10-12
Publication date: 2024-04-18

Abstract

A film and a preparation method therefor, and a photoelectric device (100). The preparation method comprises: providing a substrate, and disposing a mixed solution of a metal oxide material, a polycyanamide compound and an aldehyde compound onto the substrate (S11, S12); performing a first annealing treatment at a first temperature (S13); and performing a second annealing treatment at a second temperature to obtain a film, wherein the second temperature is higher than the first temperature (S14). The preparation method improves the electron mobility, durability and structural stability of a film.

Description

Thin film and preparation method thereof, photoelectric device

This application claims priority to the Chinese patent application filed with the China Patent Office on October 14, 2022, with application number 202211261968.0 and application name “Thin film and preparation method thereof, optoelectronic device and display device”, the entire contents of which are incorporated by reference in this application.

Technical Field

The present application relates to the field of display technology, and in particular to a thin film and a preparation method thereof, and an optoelectronic device.

Background technique

QLED (Quantum Dots Light-Emitting Diode) is an emerging display device with a structure similar to OLED (Organic Light-Emitting Diode), that is, a sandwich structure consisting of a hole transport layer, a light-emitting layer and an electron transport layer. Compared with OLED, the characteristic of QLED is that its luminescent material uses inorganic quantum dots with more stable performance. The unique quantum size effect, macroscopic quantum tunneling effect, quantum size effect and surface effect of quantum dots make them show excellent physical properties, especially their optical properties. Compared with organic fluorescent dyes, quantum dots prepared by colloid method have the advantages of adjustable spectrum, high luminous intensity, high color purity, long fluorescence life, and single light source can excite multi-color fluorescence. In addition, QLED has a long life, simple packaging process or no packaging, and is expected to become the next generation of flat panel displays with broad development prospects. QLED is based on the electroluminescence of inorganic semiconductor quantum dots. In theory, the stability of inorganic semiconductor quantum dots is higher than that of organic small molecules and polymers; on the other hand, due to the quantum confinement effect, the luminescent line width of quantum dot materials is smaller, so that it has better color purity. At present, the luminous efficiency of QLED has basically reached the commercialization requirements.

However, there are still many application problems with QLED, among which device stability and lifespan are the more difficult problems to solve. Nowadays, the electron transport layer materials commonly used in QLED are generally films made of metal oxide particles. Such materials may cause problems such as increased gaps and cracks between particles due to heat and material stress changes during the continuous operation of the device, resulting in leakage, short circuit and other problems in the device, and even causing device performance degradation or direct damage or destruction of the device.

Technical Solutions

The present application provides a thin film and a preparation method thereof, and a photoelectric device.

The present application provides a method for preparing a thin film, comprising:

Providing a mixed solution of a metal oxide material, a melamine compound and an aldehyde compound;

Providing a substrate, and placing the mixed solution on the substrate;

performing a first annealing process at a first temperature; and

Performing a second annealing treatment at a second temperature to obtain the film;

Wherein, the second temperature is higher than the first temperature.

Optionally, in some embodiments of the present application, the first temperature is 120-150° C.; and/or

The first annealing treatment lasts for 10-30 minutes; and/or

The second temperature is 350-550° C.; and/or

The second annealing treatment lasts for 5-10 minutes.

Optionally, in some embodiments of the present application, the first temperature is 130-140° C.; and/or

The first annealing treatment lasts for 15-20 minutes; and/or

The second temperature is 400-500° C.; and/or

The second annealing treatment lasts for 6-8 minutes.

Optionally, in some embodiments of the present application, the first annealing treatment generates poly(melamine-based compound-aldehyde compound); and/or

The second annealing treatment generates graphite-like carbon nitride.

Optionally, in some embodiments of the present application, the bandgap width of the metal oxide material is 2.0 eV to 6.0 eV; and/or

The metal oxide material is selected from metal oxides or doped metal oxides, the metal oxide is selected from one or more of zinc oxide, titanium dioxide, tin dioxide, aluminum oxide, calcium oxide, silicon dioxide, gallium oxide, zirconium oxide, and nickel oxide, the doped metal oxide comprises the metal oxide and a doping element, the doping element is selected from one or more of Mg, Ca, Li, Ga, Al, Co, and Mn; and/or

The average particle size of the metal oxide material is 2 to 10 nm; and/or

The melamine compound is selected from one or more of melamine and dicyandiamide; and/or

The boiling point of the aldehyde compound is (-20) to 80°C; and/or

The aldehyde compound is selected from aliphatic aldehydes having 1 to 4 carbon atoms.

Optionally, in some embodiments of the present application, the aldehyde compound is selected from one or more of carbon formaldehyde, acetaldehyde, propionaldehyde, and butyraldehyde.

Optionally, in some embodiments of the present application, in the mixed solution, the concentration of the metal oxide material is 20-40 mg/mL; and/or

In the mixed solution, the concentration of the melamine compound is 0.5 to 2 mmol/mL; and/or

The molar ratio of the aldehyde compound to the melamine compound in the mixed solution is (2-3):1.

Optionally, in some embodiments of the present application, the mixed solution is prepared by the following method:

Dispersing the metal oxide material in a solvent to obtain a first solution;

adding the melamine compound to the first solution and mixing them, so that the melamine compound and the metal oxide material undergo a coordination reaction to obtain a second solution;

The aldehyde compound is added to the second solution and mixed to obtain the mixed solution.

Optionally, in some embodiments of the present application, the solvent is selected from one or more of ethanol, methanol, and propanol.

In addition, the present application also provides a thin film, the material of which includes a metal oxide material, poly (melamine-based compound aldehyde compound) and graphite-like carbon nitride.

Optionally, in some embodiments of the present application, the poly(melamine-based compound-aldehyde compound) is coordinated and connected with the metal oxide material, the graphite-like carbon nitride has a network carbon-nitrogen chain structure, and the metal oxide material is embedded in the network carbon-nitrogen chain structure.

Optionally, in some embodiments of the present application, the content of the metal oxide material in the film is in the range of 93.5% to 98.5%; and/or

In the film, the content of poly(melamine compound aldehyde compound) is in the range of 1.0% to 1.5%; and/or

In the film, the content of the graphite-like carbon nitride is in the range of 1.0% to 1.5%.

Optionally, in some embodiments of the present application, the poly(melamine compound aldehyde compound) is selected from one or more of poly(melamine aldehyde compound) and poly(melamine aldehyde compound); and/or

The metal oxide material is selected from metal oxides or doped metal oxides, and the metal oxide is selected from zinc oxide, titanium dioxide, tin dioxide, aluminum oxide, calcium oxide, silicon dioxide, gallium oxide, One or more of zirconium oxide and nickel oxide, the doped metal oxide comprises the metal oxide and a doping element, and the doping element is selected from one or more of Mg, Ca, Li, Ga, Al, Co, and Mn; and/or

The average particle size of the metal oxide material is 2 to 10 nm.

In addition, the present application also provides a photoelectric device, comprising a stacked cathode, an electron transport layer, a light-emitting layer and an anode, wherein the electron transport layer comprises a thin film, and the material of the thin film comprises a metal oxide material, poly (melamine-type compound aldehyde compound) and graphite-like carbon nitride.

The average particle size of the metal oxide material is 2 to 10 nm.

Optionally, in some embodiments of the present application, the material of the light-emitting layer is selected from one or more of quantum dot materials, doped or undoped inorganic perovskite semiconductors, or organic-inorganic hybrid perovskite semiconductors; the quantum dot material is selected from one or more of single-structure quantum dots and core-shell structure quantum dots, and the single-structure quantum dots are selected from II-VI compounds, III-V compounds, II-V compounds, III-VI compounds, IV-VI compounds, I-III-VI compounds, II-IV-VI compounds and one or more of group IV elements, the group II-VI compounds are selected from one or more of CdSe, CdS, CdTe, ZnSe, ZnS, CdTe, ZnTe, CdZnS, CdZnSe, CdZnTe, ZnSeS, ZnSeTe, ZnTeS, CdSeS, CdSeTe, CdTeS, CdZnSeS, CdZnSeTe and CdZnSTe, the group III-V compounds are selected from one or more of InP, InAs, GaP, GaAs, GaSb, AlN, AlP, InAsP, InNP, InNSb, GaAlNP and InAlNP, the group I-III-VI compounds are selected from CuInS ₂ , CuInSe ₂ and AgInS ₂ ; the core of the quantum dot of the core-shell structure is selected from any one of the single structure quantum dots, and the shell material of the quantum dot of the core-shell structure is selected from one or more of CdS, CdTe, CdSeTe, CdZnSe, CdZnS, CdSeS, ZnSe, ZnSeS and ZnS; the general structural formula of the inorganic perovskite semiconductor is AMX ₃ , wherein A is a Cs ⁺ ion, M is a divalent metal cation selected from one or more of Pb ²⁺ , Sn ²⁺ , Cu ²⁺ , Ni ²⁺ , Cd ²⁺ , Cr ²⁺ , Mn ²⁺ , Co ²⁺ , Fe ²⁺ , Ge ²⁺ , Yb ²⁺ , Eu ²⁺ , and X is a halogen anion selected from one or more of Cl ^- , Br ^- , and I ^- ; the general structural formula of the organic-inorganic hybrid perovskite semiconductor is BMX ₃ , wherein B is an organic amine cation selected from CH ₃ (CH ₂ ) _n-2 NH ³⁺ or NH ₃ (CH ₂ ) _n NH ₃ ²⁺ , wherein n ≥ 2, M is a divalent metal cation selected from one or more of Pb ²⁺ , Sn ²⁺ , Cu ²⁺ , Ni ²⁺ , Cd ²⁺ , Cr ²⁺ , Mn ²⁺ , Co ²⁺ , Fe ²⁺ , Ge ²⁺ , Yb ²⁺ , Eu ²⁺ , and X is a halogen anion selected from one or more of Cl ^- , Br ^- , and I ^- ; and/or

The cathode and the anode are independently selected from a metal electrode, a carbon electrode and a composite electrode formed by one or more of doped or undoped metal oxide electrodes; wherein the material of the metal electrode is selected from one or more of Al, Ag, Cu, Mo, Au, Ba, Ca and Mg; the material of the carbon electrode is selected from one or more of graphite, carbon nanotubes, graphene and carbon fiber; the material of the doped or undoped metal oxide electrode is selected from one or more of ITO, FTO, ATO, AZO, GZO, IZO, MZO and AMO; the material of the composite electrode is selected from AZO/Ag/AZO, AZO/Al/AZO, ITO/Ag/ITO, ITO/Al/ITO, ZnO/Ag/ZnO, ZnO/Al/ZnO, _TiO2 /Ag/TiO2, TiO2/Al/ _TiO2 , ZnS/Ag/ZnS, _ZnS /Al/ZnS _, _TiO2 /Ag/ _TiO2 and _TiO2 /Al/TiO One or more of ₂ .

Optionally, in some embodiments of the present application, the optoelectronic device further includes a hole functional layer, and the hole functional layer is arranged between the anode and the light-emitting layer; the hole functional layer includes a hole injection layer and/or a hole transport layer.

Optionally, in some embodiments of the present application, the material of the hole injection layer includes poly(3,4- One or more of ethylenedioxythiophene)-polystyrene sulfonic acid, 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanoquinone-dimethane, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene, copper phthalocyanine, transition metal oxides, and transition metal sulfide compounds; wherein the transition metal oxides include one or more of _NiOx , _MoOx , _WOx , _CrOx , and CuO; the metal sulfide compounds include one or more of _MoSx , _MoSex , _WSx , _WSex , and CuS; wherein the value of x in each compound can be determined according to the valence of the atoms in the compound; and/or

The hole transport layer includes materials of poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine), polyvinylcarbazole, poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine), poly(9,9-dioctylfluorene-co-bis-N,N-phenyl-1,4-phenylenediamine), 4,4',4"-tri(carbazole-9-yl)triphenylamine, 4,4'-bis(9-carbazole)biphenylamine, One or more of benzene, N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine, N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid), Spiro-NPB, Spiro-TPD, doped or undoped graphene, C60, _NiO , _MoO3 , _WO3 , _V2O5 , _CrO3 , _MoSx , _MoSex , _WSx , _WSex , _CuOx , CuSCN and CuS; wherein the value of x in each compound can be determined according to the valence of the atoms in the compound.

The preparation method of the film of the present application includes providing a substrate, placing a mixed solution of a metal oxide material, a melamine compound and an aldehyde compound on the substrate; performing a first annealing treatment at a first temperature; and performing a second annealing treatment at a second temperature to obtain the film; wherein the second temperature is higher than the first temperature. By performing the first annealing treatment at a lower first temperature, the melamine compound and the aldehyde compound can react to form a poly (melamine compound aldehyde compound), and the poly (melamine compound aldehyde compound) polymerizes and bridges between the metal oxide materials to form a dense film layer; and by performing the second annealing treatment at a relatively high second temperature, the melamine compound can be self-sintered to generate a graphite-like phase carbon nitride with a network carbon-nitrogen chain structure, and the graphite-like phase carbon nitride is constructed between the metal oxide materials to form a network carbon-nitrogen chain bridge. In this way, on the one hand, a channel can be provided for the migration of electrons to improve the electron mobility of the film, and on the other hand, the two annealing treatments can effectively improve the firmness of the connection between the materials in the film, improve the durability and structural stability of the film, and make the film not easy to crack even at high temperatures.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will describe the embodiments. The drawings that need to be used are briefly introduced. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

FIG1 is a schematic flow chart of an embodiment of a method for preparing a thin film provided by the present application;

FIG2 is a schematic diagram of a flow chart of a specific embodiment of step S11 in FIG1 ;

FIG3 is a schematic flow chart of a specific embodiment of a method for preparing a thin film provided by the present application;

FIG. 4 is a schematic structural diagram of an optoelectronic device according to an embodiment of the present application.

The reference numerals are summarized as follows:
Optoelectronic device 100; cathode 10; electron transport layer 20; light emitting layer 30; anode 40; hole functional layer 50.

Embodiments of the present application

The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

The embodiments of the present application provide thin films and methods for preparing the same, and optoelectronic devices. The following are detailed descriptions. It should be noted that the order of description of the following embodiments does not limit the preferred order of the embodiments. In addition, in the description of the present application, the term "including" means "including but not limited to". The terms first, second, third, etc. are used only as labels and do not impose numerical requirements or establish an order.

In this application, "and/or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and/or B may represent: A exists alone, A and B exist at the same time, and B exists alone. A and B may be singular or plural.

In this application, expressions such as "one or more" refer to one or more of the listed items, and "more than one" refers to any combination of two or more of these items, including any combination of single items or plural items. For example, "at least one of a, b or c" or "at least one of a, b and c" can all mean: a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, where a, b and c can be single or plural, respectively.

Various embodiments of the present application may be presented in the form of a range; it should be understood that The description of the formula is only for convenience and brevity and should not be understood as a hard limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single values within the range. For example, the range description from 0.04 to 0.1 should be considered to have specifically disclosed sub-ranges, such as from 0.04 to 0.05, from 0.05 to 0.06, from 0.06 to 0.07, from 0.07 to 0.09, etc., as well as single numbers within the range, such as 0.04, 0.05 and 0.06, regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

The present application provides a method for preparing a thin film. Referring to FIG. 1 , FIG. 1 is a schematic flow chart of an embodiment of a method for preparing a thin film provided by the present application, which specifically includes the following steps:

Step S11: providing a mixed solution of a metal oxide material, a melamine compound and an aldehyde compound;

Step S12: providing a substrate, and placing the mixed solution on the substrate;

Step S13: performing a first annealing treatment at a first temperature;

Step S14: performing a second annealing treatment at a second temperature to obtain the thin film; wherein the second temperature is higher than the first temperature.

In this embodiment, by performing the first annealing treatment at the lower first temperature, the melamine compound and the aldehyde compound can react to generate poly (melamine compound aldehyde compound), and the poly (melamine compound aldehyde compound) can polymerize and bridge between the metal oxide materials to form a dense film layer; and by performing the second annealing treatment at the relatively high second temperature, the melamine compound can be self-sintered to generate a graphite-like carbon nitride with a network carbon-nitrogen chain structure, and the graphite-like carbon nitride can form a network carbon-nitrogen chain bridge between the metal oxide materials. In this way, on the one hand, a channel can be provided for the migration of electrons to improve the electron mobility of the film, and on the other hand, the two annealing treatments can effectively improve the firmness of the connection between the materials in the film, improve the durability and structural stability of the film, and make the film not easy to crack even at high temperatures.

In step S11:

In one embodiment, the metal oxide material can be a metal oxide with a bandgap of 2.0 eV to 6.0 eV and electron migration capability. The metal oxide material is selected from metal oxides or doped metal oxides, and the metal oxide is selected from one or more of zinc oxide, titanium dioxide, tin dioxide, aluminum oxide, calcium oxide, silicon dioxide, gallium oxide, zirconium oxide, and nickel oxide. The material includes the metal oxide and a doping element, wherein the doping element is selected from one or more of Mg, Ca, Li, Ga, Al, Co, and Mn, and the doping ratio of the doping element in the doped metal oxide can be 0 to 50%.

In one embodiment, the average particle size of the metal oxide material is in the range of 2 to 10 nm, such as 2 to 5 nm, 3 to 5 nm, 3 to 8 nm, 8 to 10 nm, etc.

In one embodiment, in step S11, in the mixed solution, the concentration of the metal oxide material is 20-40 mg/mL, such as 20-25 mg/mL, 25-30 mg/mL, 30-35 mg/mL, 35-40 mg/mL, etc. This concentration range can make the metal oxide material dispersed evenly, reduce the aggregation of nanoparticles so that it can form a good film, and reduce the defects and roughness of the film after film formation. The concentration of the melamine compound is 0.5-2 mmol/mL, such as 0.5-1 mg/mL, 1-1.5 mg/mL, 1.5-2 mg/mL, etc. This concentration range can improve the firmness, durability and structural stability of the film, and avoid excessive concentration that may affect the electronic transmission performance of the film.

In one embodiment, the melamine compound is selected from one or more of melamine and dicyandiamide.

In one embodiment, the boiling point of the aldehyde compound is (-20) to 80°C, specifically, (-10) to 80°C, (-10) to 70°C, 0 to 70°C, 0 to 60°C, 10 to 60°C, 20 to 50°C, 30 to 40°C, etc. The aldehyde compound having the boiling point is relatively low, and can be boiled and vaporized by heating at a relatively low temperature, so that the aldehyde compound remaining after the two annealing treatments can be removed by heating, thereby reducing the residual aldehyde compound in the film.

Furthermore, the aldehyde compound is selected from aliphatic aldehydes having 1 to 4 carbon atoms, such as one or more of formaldehyde, acetaldehyde, propionaldehyde, and butyraldehyde.

In one embodiment, in the mixed solution, the molar ratio of the aldehyde compound to the melamine compound is (2-3):1, such as 2:1, 2.5:1, 3:1, etc. The molar ratio of the aldehyde compound to the melamine compound in this range can support more complete polymerization of the aldehyde compound and the melamine compound, while also avoiding the addition of too much aldehyde compound, which may cause the metal oxide material in the mixed solution to agglomerate due to the relatively small polarity of the aldehyde compound, and the excessive aldehyde compound not being polymerized, which may have a negative impact on the performance of the film.

In one embodiment, the mixed solution further includes a solvent, and the solvent is a polar solvent. Specifically, the solvent can be selected from one or more of ethanol, methanol, propanol, etc. It can be understood that Ethanol, methanol, and propanol are only some examples of the solvents, and the solvent is not limited to one of ethanol, methanol, propanol, etc.

In one embodiment, referring to FIG. 2 , FIG. 2 is a schematic flow chart of a specific embodiment of step S11 in FIG. 1 , wherein the mixed solution in step S11 is prepared by the following method:

Step S111: dispersing the metal oxide material into a solvent to obtain a first solution;

Step S112: adding the melamine compound to the first solution and mixing them, so that the melamine compound and the metal oxide material undergo coordination reaction to obtain a second solution;

Step S113: adding the aldehyde compound to the second solution and mixing the mixture to obtain the mixed solution.

In this embodiment, in the method for preparing the mixed solution of the metal oxide material, the melamine compound and the aldehyde compound, the melamine compound is first added to make it fully and evenly mixed with the metal oxide material. The melamine compound has an amino group and is easy to form a ligand so as to be adsorbed on the metal oxide material and connect with the metal atoms in the metal oxide material by a coordination bond. After coordination with the metal oxide material, the melamine compound can affect the metal oxide material in the form of a ligand, improve the dispersibility of the melamine compound, and avoid agglomeration of the metal oxide material.

It can be understood that the mixing can be a known mixing method such as stirring mixing or ultrasonic mixing, and the present application does not limit the mixing method.

In step S12:

The type of the substrate is not limited, and it can be a commonly used substrate, such as a rigid substrate made of glass; or a flexible substrate made of polyimide. The substrate can also be a substrate including an anode and a light-emitting layer, and the mixed solution in step S12 can be disposed on the surface of the light-emitting layer. The substrate can also include a cathode, and accordingly, the mixed solution in step S12 can be disposed on the surface of the cathode.

The mixed solution may be disposed on the substrate by a method known in the art, such as a solution method. Specifically, the solution method includes but is not limited to one or more of spin coating, coating, inkjet printing, scraping, dip pulling, soaking, spraying, rolling or casting.

In step S13:

In one embodiment, the first temperature may be 120-150°C, that is, the temperature range of the first annealing treatment is 120-150°C. Specifically, the first temperature may be 120-130°C, 130-140°C, 140-150°C, etc. The temperature range of 120-150°C can make the aldehyde compound and the melamine compound have It has good polymerization reaction activity, can support the polymerization reaction of aldehyde compounds and melamine compounds to generate poly (melamine compounds aldehyde compounds), and polymerize and bridge between metal oxide materials to form a dense film layer.

In one embodiment, the first annealing treatment lasts for 10-30 minutes, such as 10-15 minutes, 15-20 minutes, 20-25 minutes, 25-30 minutes, etc. The first annealing treatment within this time range can fully support the first annealing treatment and support the polymerization reaction of the aldehyde compound and the melamine compound.

Furthermore, the first annealing treatment may be performed in an inert atmosphere, such as nitrogen, argon, or the like.

It is understandable that in step S13, the melamine compounds will not completely participate in the polymerization reaction with the aldehyde compounds, and some of the melamine compounds will not participate in the polymerization. After the first annealing treatment, melamine compounds still exist. In a specific embodiment, only about 50% of the melamine compounds in the mixed solution polymerize with the aldehyde compounds, and the melamine compounds that do not participate in the reaction can at least partially participate in the reaction in step S14.

In step S14:

In one embodiment, the second temperature may be 350-550°C, that is, the temperature range of the second annealing treatment is 350-550°C. Specifically, the second temperature may be 350-500°C, 400-500°C, 450-550°C, 350-450°C, etc. The temperature range of 350-550°C can support the melamine compound existing between the metal oxide materials to undergo a self-sintering reaction to sinter and form carbon nitride, wherein most of the carbon nitride material obtained by sintering is a graphite-like carbon nitride (gC ₃ N ₄ ), and the graphite-like carbon nitride has a network carbon-nitrogen chain structure, and the metal oxide material is embedded in the network carbon-nitrogen chain structure, thereby constructing a network carbon-nitrogen chain bridge between the metal oxide materials, and the network carbon-nitrogen chain bridge can provide a channel for the migration of electrons to improve the electron mobility of the film. In addition, it can also avoid damage and destruction to the substrate and other materials on the substrate caused by excessive temperature.

In one embodiment, the second annealing treatment is performed for 5-10 minutes, such as 5-6 minutes, 6-8 minutes, 8-10 minutes, etc. Performing the second annealing within this time range can support the formation of graphite-like carbon nitride while also avoiding damage to the substrate and metal oxide materials.

Furthermore, the second annealing treatment can also be performed in an inert atmosphere, such as nitrogen or argon atmosphere. middle.

It is understandable that in the second annealing treatment, the melamine compound undergoes a self-sintering reaction to generate graphite-like carbon nitride and may also generate other non-graphite carbon nitride.

Refer to FIG. 3 , which is a schematic flow chart of a specific embodiment of a method for preparing a thin film provided by the present application, which specifically includes the following steps:

Step S21: providing a mixed solution of a metal oxide material, a melamine compound and formaldehyde;

Step S22: providing a substrate, and placing the mixed solution on the substrate;

Step S23: performing a first annealing treatment at 120-150° C. to polymerize the melamine compound and formaldehyde to generate poly(melamine compound formaldehyde);

Step S24: performing a second annealing treatment at 350-550° C. to cause the melamine compound to undergo a self-sintering reaction to generate graphite-like carbon nitride (g-C 3 N 4 ) to form the film.

In this embodiment, by performing a first annealing treatment at 120-150°C, the melamine compound can react with formaldehyde to generate poly(melamine compound formaldehyde), and the poly(melamine compound formaldehyde) can polymerize and bridge between metal oxide materials to form a dense film layer; and by performing a second annealing treatment at 350-550°C, the melamine compound can be self-sintered to generate a graphite-like carbon nitride with a network carbon-nitrogen chain structure, and the graphite-like carbon nitride can form a network carbon-nitrogen chain bridge between metal oxide materials. In this way, on the one hand, a channel can be provided for the migration of electrons to improve the electron mobility of the film, and on the other hand, the two annealing treatments can effectively improve the firmness of the connection between the materials in the film, improve the durability and structural stability of the film, and make the film not easy to crack even at high temperatures.

The preparation method described in the present application can effectively improve the firmness of the connection between the materials in the film through two annealing treatments, enhance the durability and structural stability of the film, and make the film less likely to crack even at high temperatures.

In this embodiment, in the mixed solution of the metal oxide material, melamine compound and aldehyde compound, the melamine compound has multiple amino groups, which are easily adsorbed on the metal oxide material and connected with the metal atom by coordination bonds. Moreover, after the melamine compound coordinates with the metal oxide material, it can affect the metal oxide material in the form of a ligand, such as forming a repulsive force of the same charge between the particles of the metal oxide material, which improves the dispersibility of the metal oxide material to a certain extent. At the same time, the polyamine compound has the characteristic of multiple amino groups, which makes the mixed solution weakly alkaline. The weakly alkaline environment can greatly improve the metal The dispersibility of metal oxide materials can turn the originally light white colloidal solution into a completely transparent clear solution. In addition, when the metal oxide material forms a film, the product of the polymerization of melamine compounds and aldehyde compounds has an umbrella-shaped or fan-shaped structure, which enables the nano-metal oxide particles to obtain better particle spacing during film formation, improves film formation, and improves the electronic transmission performance of the film.

In this embodiment, the thin film formed by the first annealing treatment and the second annealing treatment includes both graphite-like carbon nitride and poly(melamine-like compound aldehyde compound), wherein the poly(melamine-like compound aldehyde compound) is connected to the metal oxide material, the graphite-like carbon nitride has a network carbon-nitrogen chain structure, and the metal oxide material is embedded in the network carbon-nitrogen chain structure.

The present application provides a thin film, the material of which includes a metal oxide material, poly(melamine-based compound, aldehyde-based compound) and graphite-like carbon nitride.

In one embodiment, the film may include other materials, such as non-graphite carbon nitride, aldehyde compounds, etc., in addition to the metal oxide material, poly (melamine-based compounds, aldehyde compounds) and graphite-like carbon nitride.

In the film, the poly(melamine compound aldehyde compound) is coordinated and connected with the metal oxide material, the graphite-like carbon nitride has a network carbon-nitrogen chain structure, and the metal oxide material is embedded in the network carbon-nitrogen chain structure.

Among them, the metal oxide material can refer to the relevant description above, which will not be repeated here.

In the film, the content of the metal oxide material ranges from 93.5% to 98.5%, such as 93.5% to 95.0%, 95.0% to 96.0%, 96.0% to 97.0%, 97.0% to 98.0%, 98.0% to 98.5%, etc. The metal oxide material in this content range enables the film to have better electron transport performance.

In one embodiment, in the film, the content range of poly(melamine-like compound aldehyde compound) is 1.0% to 1.5%, for example, 1.0% to 1.1%, 1.1% to 1.2%, 1.2% to 1.3%, 1.3% to 1.4%, 1.4% to 1.5%, etc.; the poly(melamine-like compound aldehyde compound) in this content range can make the metal oxide material in the film have better particle spacing, better film forming properties and electron transmission properties.

The poly(melamine compound aldehyde compound) is selected from one or more of poly(melamine aldehyde compound) and poly(melamine aldehyde compound). In one specific embodiment, the poly(melamine compound aldehyde compound) is polymerized from a melamine compound and an aldehyde compound. In other specific embodiments, the poly(melamine compound aldehyde compound) is commercially available.

In one embodiment, the content of the graphite-like carbon nitride in the film is in the range of 1.0% to 1.5%, such as 1.0% to 1.1%, 1.1% to 1.2%, 1.2% to 1.3%, 1.3% to 1.4%, 1.4% to 1.5%, etc. Graphite-like carbon nitride in this content range can provide the film with better structural stability and electron mobility.

In one embodiment, the film provided in the present application is prepared by the above-mentioned film preparation method.

The present application also provides a photoelectric device, see Figure 4, which is a schematic diagram of the structure of an embodiment of a photoelectric device provided by the present application. The photoelectric device 100 includes a cathode 10, an electron transport layer 20, a light-emitting layer 30 and an anode 40 arranged in a stacked manner. The electron transport layer 20 is prepared by the method for preparing the thin film described above, or is the thin film described above.

In this embodiment, the electron transport layer 20 in the optoelectronic device 100 is formed by a mixed solution of the metal oxide material, a melamine compound and an aldehyde compound, after the first annealing treatment and the second annealing treatment. The melamine compound has multiple amino groups, which are easily adsorbed on the metal oxide material and connected to the metal atom by a coordination bond. After coordination with the metal oxide material, the melamine compound can affect the metal oxide material in the form of a ligand, such as forming a repulsive force of the same charge between the particles of the metal oxide material, which improves the dispersibility of the metal oxide material to a certain extent. At the same time, the polymelamine compound has the characteristic of multiple amino groups, which makes the mixed solution weakly alkaline. The weakly alkaline environment can greatly improve the dispersibility of the metal oxide material, and can make the originally light white colloidal solution become a completely transparent clear solution. After the first annealing treatment, the aldehyde compound and the melamine compound undergo a polymerization reaction, and the metal oxide materials are polymerized and bridged into a dense film layer. After the second annealing treatment, part of the melamine between the metal oxide materials will undergo a self-sintering reaction to form carbon nitride, wherein most of the sintered carbon nitride materials are graphite-like carbon nitride (g-C3N4), thereby constructing a network of carbon-nitrogen chain bridges between the metal oxide materials. On the one hand, it can provide a channel for the migration of electrons to improve the electron mobility of the electron transport layer 20. On the other hand, the two annealing treatments can further improve the firmness of the connection between the materials in the electron transport layer 20, thereby improving the durability and structural stability of the electron transport layer 20, and making it less prone to cracking even at high temperatures.

The photoelectric device 100 may be a positive structure or an inverted structure. In one embodiment, the photoelectric device 100 is a positive light emitting diode, and the substrate is connected to one side of the anode 40. In another embodiment, the photoelectric device 100 is an inverted light emitting diode, and the substrate is connected to one side of the cathode 10. In one embodiment, the photoelectric device 100 is a top-emitting light emitting diode. In another embodiment, the photoelectric device 100 is a top-emitting light emitting diode. It can be a bottom-emitting light emitting diode. The type of the substrate is not limited, and it can be a conventionally used substrate, for example, a rigid substrate made of glass; or a flexible substrate made of polyimide.

In one embodiment, the material of the light-emitting layer 30 is selected from one or more of quantum dot materials, or doped or undoped inorganic perovskite semiconductors, or organic-inorganic hybrid perovskite semiconductors; the quantum dot material is selected from one or more of single-structure quantum dots and core-shell structure quantum dots, the single-structure quantum dots are selected from one or more of II-VI group compounds, III-V group compounds, II-V group compounds, III-VI group compounds, IV-VI group compounds, I-III-VI group compounds, II-IV-VI group compounds and IV group single substances, the II-VI group compounds are selected from one or more of CdSe, CdS , CdTe, ZnSe, ZnS, CdTe, ZnTe, CdZnS, CdZnSe, CdZnTe, ZnSeS, ZnSeTe, ZnTeS, CdSeS, CdSeTe, CdTeS, CdZnSeS, CdZnSeTe and CdZnSTe, the III-V group compound is selected from one or more of InP, InAs, GaP, GaAs, GaSb, AlN, AlP, InAsP, InNP, InNSb, GaAlNP and InAlNP, the I-III-VI group compound is selected from CuInS ₂ , CuInSe ₂ and AgInS ₂ ; the core of the quantum dot with core-shell structure is selected from any one of the single structure quantum dots, and the shell material of the quantum dot with core-shell structure is selected from one or more of CdS, CdTe, CdSeTe, CdZnSe, CdZnS, CdSeS, ZnSe, ZnSeS and ZnS; the general structural formula of the inorganic perovskite semiconductor is AMX ₃ , wherein A is a Cs ⁺ ion, M is a divalent metal cation selected from one or more of Pb ²⁺ , Sn ²⁺ , Cu ²⁺ , Ni ²⁺ , Cd ²⁺ , Cr ²⁺ , Mn ²⁺ , Co ^{2+, Fe 2+, Ge 2+} ^, ^Yb ²⁺ , Eu ²⁺ , and X is a halogen anion selected from one or more of Cl ^- , Br ^- , and I ^- ; the general structural formula of the organic-inorganic hybrid perovskite semiconductor is BMX ₃ , wherein B is an organic amine cation selected from CH ₃ (CH ₂ ) _n-2 NH ³⁺ or NH ₃ (CH ₂ ) _n NH ₃ ²⁺ , wherein n ≥ 2, M is a divalent metal cation selected from one or more of Pb ²⁺ , Sn ²⁺ , Cu ²⁺ , Ni ²⁺ , Cd ²⁺ , Cr ²⁺ , Mn ²⁺ , Co ²⁺ , Fe ²⁺ , Ge ²⁺ , Yb ²⁺ , Eu ²⁺ , and X is a halogen anion selected from one or more of Cl ^- , Br ^- , and I ^- .

In a specific embodiment, the material of the light-emitting layer 30 is oil-soluble quantum dots, including binary phase quantum dots, ternary phase quantum dots, and quaternary phase quantum dots; wherein the binary phase quantum dots include CdS, CdSe, CdTe, InP, _AgS , PbS, PbSe, HgS, etc., the ternary phase quantum dots include _ZnXCd1 _- XS, _CuXIn1 _- _XS , ZnXCd1 _- _XSe , ZnXSe1 _- XS, ZnXCd1 _-XTe _, _PbSeXS1 _-X , etc., and the quaternary phase quantum dots include _ZnXCd1 _- XS/ZnSe, CuXIn1 _- XS/ZnS, ZnXCd1 _- _XSe /ZnS, CuInSeS, _ZnXCd1-XTe /ZnS, _PbSeXS1 _-X _/ ZnS, etc. The oil-soluble quantum dots are connected to the surface with ligands that are easily soluble in solvents with low polarity, and the ligands are selected from acid ligands, thiol ligands, amine ligands, (oxygen) phosphine ligands, phosphorus One or more of lipids, phospholipids, polyvinyl pyridine, etc. Among them, the acid ligand is one or more of decadecanoic acid, undecylenic acid, tetradecanoic acid, oleic acid, and stearic acid; the thiol ligand is one or more of octadecyl mercaptan, dodecyl mercaptan, and octadecyl mercaptan; the amine ligand includes one or more of oleylamine, octadecylamine, and octaamine; the (oxygen) phosphine ligand is one or more of trioctylphosphine and trioctylphosphine oxide. In quantum dot ink, the concentration of quantum dots is 10 to 100 mg/mL, such as 10 to 20 mg/mL, 20 to 50 mg/mL, 50 to 100 mg/mL, etc. Within this concentration range, the solution processing performance of quantum dots is good and the dispersibility is good.

In one embodiment, the cathode 10 and the anode 40 are independently selected from one or more of a metal electrode, a carbon electrode, a doped or undoped metal oxide electrode and a composite electrode; wherein the material of the metal electrode is selected from one or more of Al, Ag, Cu, Mo, Au, Ba, Ca and Mg; the material of the carbon electrode is selected from one or more of graphite, carbon nanotubes, graphene and carbon fiber; the material of the doped or undoped metal oxide electrode is selected from one or more of ITO, FTO, ATO, AZO, GZO, IZO, MZO and AMO; the material of the composite electrode is selected from AZO/Ag/AZO, AZO/Al/AZO, ITO/Ag/ITO, ITO/Al/ITO, ZnO/Ag/ZnO, ZnO/Al/ZnO, TiO ₂ /Ag/TiO ₂ , TiO ₂ /Al/TiO ₂ , ZnS/Ag/ZnS, ZnS/Al/ZnS, TiO ₂ /Ag/TiO ₂ and one or more of TiO ₂ /Al/TiO _2. Wherein, "/" represents a stacked structure, for example, the composite electrode AZO/Ag/AZO represents an electrode of a composite structure of three layers stacked together consisting of an AZO layer, an Ag layer and an AZO layer. The thickness of the cathode 10 is 30-100 nm. In a specific embodiment, the material of the cathode 10 is Ag or Cu, so that the cathode 10 has a small resistance so that carriers can be smoothly injected.

In one embodiment, the optoelectronic device 100 may further include a hole functional layer 50, and the hole functional layer 50 is disposed between the anode 40 and the light-emitting layer 30. The hole functional layer 50 may include a hole injection layer and/or a hole transport layer. That is, the hole functional layer 50 may include only one layer of the hole injection layer and the hole transport layer, or the hole functional layer 50 may also include a two-layer structure of the hole injection layer and the hole transport layer, wherein the hole injection layer is disposed near the anode 40 side, and the hole transport layer is disposed near the light-emitting layer 30 side.

The material of the hole injection layer can be selected from materials with hole injection ability, including but not limited to poly (3,4-ethylenedioxythiophene) - polystyrene sulfonic acid (PEDOT:PSS), 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanoquinone-dimethane (F4-TCNQ), 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (HATCN), copper phthalocyanine (CuPc), transition metal oxides, transition metal sulfide compounds. One or more kinds. Wherein, the transition metal oxide includes one or more of _NiOx , _MoOx , _WOx , _CrOx , and CuO. The metal sulfide compound includes one or more of _MoSx , _MoSex , _WSx , _WSex , and CuS. Wherein, the value of x in each compound can be determined according to the valence of the atoms in the compound.

The material of the hole transport layer is selected from poly (9,9-dioctylfluorene-co-N-(4-butylphenyl) diphenylamine), polyvinyl carbazole, poly (N,N'-bis (4-butylphenyl) -N,N'-bis (phenyl) benzidine), poly (9,9-dioctylfluorene-co-bis-N,N-phenyl-1,4-phenylenediamine), 4,4',4"-tri (carbazole-9-yl) triphenylamine, 4,4'-bis (9-carbazole) biphenyl , N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine, N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid), Spiro-NPB, Spiro-TPD, doped or undoped graphene, C60, NiO, MoO ₃ , WO ₃ , V ₂ O ₅ , CrO ₃ , MoS _x , MoSe _x , WS _x , WSe _x , CuO _x , CuSCN and CuS; wherein the value of x in each compound can be determined according to the valence of the atoms in the compound.

It should be noted that the light emitting device 100 may also include other layer structures, such as an electron injection layer.

It should be noted that the preparation methods of the various film layers including the cathode 10, the light-emitting layer 30 and the anode 40 in the optoelectronic device 100 include but are not limited to solution method and deposition method. The solution method includes but is not limited to spin coating, coating, inkjet printing, scraping, dip pulling, soaking, spraying, rolling or casting; the deposition method includes chemical method and physical method. The chemical method includes but is not limited to chemical vapor deposition, continuous ion layer adsorption and reaction method, anodic oxidation method, electrolytic deposition method or coprecipitation method. The physical method includes but is not limited to thermal evaporation coating method, electron beam evaporation coating method, magnetron sputtering method, multi-arc ion plating method, physical vapor deposition method, atomic layer deposition method or pulsed laser deposition method. When the film layer is prepared by the solution method, a drying process needs to be added to convert the wet film into a dry film.

It should be noted that the optoelectronic device 100 is obtained by packaging. The packaging process can be performed by a common machine packaging or by manual packaging. Preferably, in the packaging process environment, the oxygen content and the water content are both lower than 0.1 ppm to ensure the stability of the device.

The present application also relates to a display device, which includes the optoelectronic device provided by the present application. The display device can be any electronic product with a display function, including but not limited to smart phones, tablet computers, laptop computers, digital cameras, digital video cameras, smart wearable devices, smart weighing electronic scales, car displays, televisions or e-book readers, wherein smart wearable devices For example, it can be a smart bracelet, a smart watch, a virtual reality (VR) helmet, etc.

The present application is described in detail below through specific embodiments. The following embodiments are only partial embodiments of the present application and are not limitations of the present application.

Example 1

This embodiment provides a method for preparing a photoelectric device, the method comprising the following steps:

Step 1: Clean the ITO conductive glass substrate (the thickness of the ITO layer is 120 nm) with a detergent to preliminarily remove stains on the surface, then ultrasonically clean it in deionized water, acetone, anhydrous ethanol, and deionized water for 20 minutes respectively to remove impurities on the surface, and blow dry it with high-purity nitrogen.

Step 2: Disperse nano ZnO with a particle size of 2 to 5 nm in ethanol, add melamine to the ZnO-ethanol solution, and stir for 30 minutes. It can be clearly observed that the ZnO-ethanol solution becomes clear, and then add an aldehyde compound to obtain a mixed solution. In the mixed solution, the concentration of nano ZnO is 30 mg/mL, the concentration of melamine is 1 mmol/mL, and the concentration of the aldehyde compound is 3 mmol/mL. The mixed solution is spin-coated on the dot ITO layer at a spin coating speed of 3000 r/min for 10 seconds, and then placed at 130° C. for 30 minutes to react melamine with the aldehyde compound to generate poly (melamine aldehyde compound), and then heated to 550° C. and placed for 5 minutes to allow part of the melamine to undergo self-sintering reaction to generate graphite-like carbon nitride, thereby obtaining an electron transport layer with a thickness of 50 nm.

Step 3: Spin-coat a CdSeS/ZnS green quantum dot material with a concentration of 30 mg/mL on the electron transport layer, wherein the surface of the CdSeS/ZnS green quantum dot in the CdSeS/ZnS green quantum dot material is connected with an octanthiol ligand, and each 1 mg of CdSeS/ZnS green quantum dot corresponds to 0.2 mmol of the octanthiol ligand. The spin-coating speed is 2000 rpm, the spin-coating time is 30 s, and then heated on a hot plate at 80°C for 10 minutes to obtain a light-emitting layer with a thickness of 70 nm.

Step 4: Spin-coat the TFB material with a concentration of 8 mg/mL on the light-emitting layer at a spin-coating speed of 3000 r/min for 30 seconds, and then heat at 120°C for 10 minutes to obtain a hole transport layer with a thickness of 80 nm; and spin-coat the PEDOT:PSS material (wherein the molar ratio of PEDOT to PSS is 1:1) on the hole transport layer at a spin-coating speed of 5000 r/min for 30 seconds, and then heat at 150°C for 15 minutes to obtain a hole injection layer with a thickness of 80 nm.

Step 5: Depositing Ag on the hole injection layer by thermal evaporation at a vacuum degree not higher than 3×10 ^-4 Pa, wherein the evaporation rate is 1 angstrom/second for 200 seconds to obtain an anode with a thickness of 60 nm;

Step 6: encapsulating with epoxy resin to obtain a photoelectric device;

Example 2

This embodiment is basically the same as the embodiment 1, and the only difference is that in step 2, nano-TiO ₂ is used to replace the nano-ZnO in the embodiment 1.

Example 3

This embodiment is basically the same as the embodiment 1, and the only difference is that in step 2, nano ZrO ₂ is used to replace the nano ZnO in the embodiment 1.

Example 4

This embodiment is basically the same as the embodiment 1, and the only difference is that melamine is used in step 2 to replace the melamine in the embodiment 1.

Example 5

This embodiment is substantially the same as embodiment 1, except that in step 2, the concentration of melamine in the mixed solution is 0.5 mmol/mL.

Example 6

This embodiment is substantially the same as embodiment 1, except that in step 2, the concentration of melamine in the mixed solution is 2 mmol/mL.

Example 7

This embodiment is substantially the same as embodiment 1, except that in step 2, the concentration of melamine in the mixed solution is 0.3 mmol/mL.

Example 8

This embodiment is substantially the same as embodiment 1, except that in step 2, the concentration of melamine in the mixed solution is 2.5 mmol/mL.

Example 9

This embodiment is substantially the same as embodiment 1, except that in step 2, the concentration of the aldehyde compound in the mixed solution is 2 mmol/mL.

Example 10

This embodiment is substantially the same as embodiment 1, except that in step 2, the concentration of the aldehyde compound in the mixed solution is 1.5 mmol/mL.

Embodiment 11

This embodiment is basically the same as embodiment 1, except that: in step 2, the aldehyde in the mixed solution The concentration of the compound was 3.5 mmol/mL.

Example 12

This embodiment is basically the same as embodiment 1, except that in step 2, the temperature is kept at 130° C. for 30 minutes, and then the temperature is raised to 350° C. and kept at 350° C. for 5 minutes.

Example 13

This embodiment is basically the same as embodiment 1, except that in step 2, the temperature is placed at 130° C. for 30 minutes, and then the temperature is raised to 450° C. and placed for 5 minutes.

Comparative Example 1:

This comparative example is basically the same as Example 1, except that in step 2, nano ZnO with a particle size of 2 to 5 nm is dispersed in ethanol at a concentration of 30 mg/mL and spin-coated on the ITO layer, wherein the spin coating speed is 3000 r/min for 10 seconds, and then heated at 130° C. for 30 minutes to obtain an electron transport layer with a thickness of 50 nm.

Comparative Example 2

This comparative example is substantially the same as Example 1, except that in step 2, the temperature is only placed at 130° C. for 30 minutes.

The QLED light-emitting diodes in Examples 1-13 and Comparative Examples 1-2 were subjected to performance tests, and the test indicators and test methods were as follows:

Device T95_1knit life (h): refers to the time required for the brightness of the device to decay from 100% to 95% at a starting brightness of 1000 nits;

Electron mobility: Test the current density (J)-voltage (V) of each optoelectronic device, draw a curve relationship diagram, fit the space charge limited current (SCLC) region in the relationship diagram, and then calculate the electron mobility according to the famous Child's law formula:
J＝(9/8)ε _r ε ₀ μ _e V ² /d ³ ;

Among them, J is the current density (unit: mA/ ^mm2 ); _εr is the relative dielectric constant; _ε0 is the vacuum dielectric constant; _μe is the electron mobility; V is the voltage applied to the anode and cathode (unit: V); d is the distance between the cathode and the anode (unit: mm).

External quantum efficiency (EQE): measured using an EQE optical test instrument.

Table 1 Performance test results of the light emitting devices of Examples 1-13 and Comparative Examples 1-2

From Table 1 we can see that:

Compared with Comparative Examples 1 and 2, the T95-1k nit life of the optoelectronic devices of Examples 1-4 at 25°C and 80°C showed a significant increase, especially at a high temperature of 80°C, the life was increased by 4-8 times, and the electron mobility and external quantum efficiency EQE were significantly improved. The electron transport layer prepared by the method for preparing the thin film provided by the present application improves the performance of the electron transport layer, including the electron mobility, and improves the material firmness, durability and structural stability of the electron transport layer.

Examples 1 and 5-8 illustrate that too little or too much melamine used in the preparation of the electron transport layer will affect the electron transport performance and structural stability of the electron transport layer. Among them, the amount of melamine used in Example 7 is too little, the amount of poly (melamine formaldehyde) generated is small, and the amount of graphite-like carbon nitride generated by melamine is also small, resulting in an unstable structure of the electron transport layer. In Example 8, a higher concentration of melamine may cause too much melamine to not be polymerized and the self-sintering reaction to exist in the electron transport layer, thereby affecting the electron transport performance.

Examples 1 and 9-11 illustrate that too little or too much aldehyde compound used in the preparation of the electron transport layer will affect the electron transport performance and structural stability of the electron transport layer.

The thin film and its preparation method, and the optoelectronic device provided in the embodiments of the present application are introduced in detail above. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea; at the same time, for technical personnel in this field, according to the idea of the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

A method for preparing a thin film, comprising:

Providing a mixed solution of a metal oxide material, a melamine compound and an aldehyde compound;

Providing a substrate, and placing the mixed solution on the substrate;

performing a first annealing process at a first temperature; and

Performing a second annealing treatment at a second temperature to obtain the film;

Wherein, the second temperature is higher than the first temperature.
The preparation method according to claim 1, wherein

The first temperature is 120-150° C.; and/or

The first annealing treatment lasts for 10-30 minutes; and/or

The second temperature is 350-550° C.; and/or

The second annealing treatment lasts for 5-10 minutes.
The preparation method according to claim 2, wherein

The first temperature is 130-140° C.; and/or

The first annealing treatment lasts for 15-20 minutes; and/or

The second temperature is 400-500° C.; and/or

The second annealing treatment lasts for 6-8 minutes.
The preparation method according to claim 1, wherein

The first annealing treatment generates poly(melamine-based compound-based aldehyde compound); and/or

The second annealing treatment generates graphite-like carbon nitride.
The preparation method according to claim 1, wherein

The bandgap width of the metal oxide material is 2.0 eV to 6.0 eV; and/or

The metal oxide material is selected from metal oxides or doped metal oxides, the metal oxide is selected from one or more of zinc oxide, titanium dioxide, tin dioxide, aluminum oxide, calcium oxide, silicon dioxide, gallium oxide, zirconium oxide, and nickel oxide, the doped metal oxide comprises the metal oxide and a doping element, the doping element is selected from one or more of Mg, Ca, Li, Ga, Al, Co, and Mn; and/or

The average particle size of the metal oxide material is 2 to 10 nm; and/or

The melamine compound is selected from one or more of melamine and dicyandiamide; and/or

The boiling point of the aldehyde compound is (-20) to 80°C; and/or

The aldehyde compound is selected from aliphatic aldehydes having 1 to 4 carbon atoms.
The preparation method according to claim 5, wherein the aldehyde compound is selected from one or more of carbon formaldehyde, acetaldehyde, propionaldehyde, and butyraldehyde.
The preparation method according to claim 1, wherein

In the mixed solution, the concentration of the metal oxide material is 20 to 40 mg/mL; and/or

In the mixed solution, the concentration of the melamine compound is 0.5 to 2 mmol/mL; and/or

The molar ratio of the aldehyde compound to the melamine compound in the mixed solution is (2-3):1.
The preparation method according to claim 1, wherein the mixed solution is prepared by the following method:

Dispersing the metal oxide material in a solvent to obtain a first solution;

adding the melamine compound to the first solution and mixing them, so that the melamine compound and the metal oxide material undergo coordination reaction to obtain a second solution;

The aldehyde compound is added to the second solution and mixed to obtain the mixed solution.
The preparation method according to claim 8, wherein the solvent is selected from one or more of ethanol, methanol and propanol.
A film, wherein the material of the film comprises metal oxide material, poly (melamine compound aldehyde compound) and graphite-like carbon nitride.
The film according to claim 10, wherein the poly (polymelamine compound aldehyde compound) is coordinated and connected with the metal oxide material, the graphite-like carbon nitride has a network carbon-nitrogen chain structure, and the metal oxide material is embedded in the network carbon-nitrogen chain structure.
The film according to claim 10, wherein

In the film, the content of the metal oxide material is in the range of 93.5% to 98.5%; and/or

In the film, the content of poly(melamine compound aldehyde compound) is in the range of 1.0% to 1.5%; and/or

In the film, the content of the graphite-like carbon nitride is in the range of 1.0% to 1.5%.
The film according to claim 10, wherein

The poly(melamine compound aldehyde compound) is selected from poly(melamine aldehyde compound) and poly(melamine aldehyde compound). (melamine-aldehyde compounds); and/or

The metal oxide material is selected from metal oxides or doped metal oxides, the metal oxide is selected from one or more of zinc oxide, titanium dioxide, tin dioxide, aluminum oxide, calcium oxide, silicon dioxide, gallium oxide, zirconium oxide, and nickel oxide, the doped metal oxide comprises the metal oxide and a doping element, the doping element is selected from one or more of Mg, Ca, Li, Ga, Al, Co, and Mn; and/or

The average particle size of the metal oxide material is 2 to 10 nm.
A photoelectric device comprises a cathode, an electron transport layer, a light-emitting layer and an anode which are stacked, wherein the electron transport layer comprises a thin film, and the material of the thin film comprises a metal oxide material, poly (melamine-based compound aldehyde compound) and graphite-like carbon nitride.
The optoelectronic device according to claim 14, wherein the poly(melamine-based compound-aldehyde compound) is coordinated and connected with the metal oxide material, the graphite-like carbon nitride has a network carbon-nitrogen chain structure, and the metal oxide material is embedded in the network carbon-nitrogen chain structure.
The optoelectronic device according to claim 14, wherein

In the film, the content of the metal oxide material is in the range of 93.5% to 98.5%; and/or

In the film, the content of poly(melamine compound aldehyde compound) is in the range of 1.0% to 1.5%; and/or

In the film, the content of the graphite-like carbon nitride is in the range of 1.0% to 1.5%.
The optoelectronic device according to claim 14, wherein

The poly(melamine compound aldehyde compound) is selected from one or more of poly(melamine aldehyde compound) and poly(melamine aldehyde compound); and/or

The metal oxide material is selected from metal oxides or doped metal oxides, the metal oxide is selected from one or more of zinc oxide, titanium dioxide, tin dioxide, aluminum oxide, calcium oxide, silicon dioxide, gallium oxide, zirconium oxide, and nickel oxide, the doped metal oxide comprises the metal oxide and a doping element, the doping element is selected from one or more of Mg, Ca, Li, Ga, Al, Co, and Mn; and/or

The average particle size of the metal oxide material is 2 to 10 nm.
The optoelectronic device according to claim 14, wherein

The material of the light-emitting layer is selected from quantum dot materials, doped or non-doped inorganic perovskite semiconductors The quantum dot material is selected from one or more of a single structure quantum dot and a core-shell structure quantum dot, the single structure quantum dot is selected from one or more of a II-VI group compound, a III-V group compound, a II-V group compound, a III-VI group compound, a IV-VI group compound, a I-III-VI group compound, a II-IV-VI group compound and a IV group element, the II-VI group compound is selected from one or more of CdSe, CdS, CdTe, ZnSe, ZnS, CdTe, One or more of the group consisting of ZnTe, CdZnS, CdZnSe, CdZnTe, ZnSeS, ZnSeTe, ZnTeS, CdSeS, CdSeTe, CdTeS, CdZnSeS, CdZnSeTe and CdZnSTe; the III-V group compound is one or more of the group consisting of InP, InAs, GaP, GaAs, GaSb, AlN, AlP, InAsP, InNP, InNSb, GaAlNP and InAlNP; the I-III-VI group compound is one or more of the group consisting of CuInS 2 , CuInSe 2 and AgInS 2 ; the core of the quantum dot with core-shell structure is selected from any one of the single structure quantum dots, and the shell material of the quantum dot with core-shell structure is selected from one or more of CdS, CdTe, CdSeTe, CdZnSe, CdZnS, CdSeS, ZnSe, ZnSeS and ZnS; the general structural formula of the inorganic perovskite semiconductor is AMX 3 , wherein A is a Cs + ion, M is a divalent metal cation selected from one or more of Pb 2+ , Sn 2+ , Cu 2+ , Ni 2+ , Cd 2+ , Cr 2+ , Mn 2+ , Co 2+, Fe 2+, Ge 2+ , Yb 2+ , Eu 2+ , and X is a halogen anion selected from one or more of Cl - , Br - , and I - ; the general structural formula of the organic-inorganic hybrid perovskite semiconductor is BMX 3 , wherein B is an organic amine cation selected from CH3 ( CH2 ) n- 2NH3+ or NH3 ( CH2 )nNH32+ , wherein n≥2, M is a divalent metal cation selected from one or more of Pb2 + , Sn2 + , Cu2 + , Ni2 + , Cd2 + , Cr2 + , Mn2 + , Co2 + , Fe2 + , Ge2 + , Yb2 + , Eu2 + , and X is a halogen anion selected from one or more of Cl- , Br- , and I- ; and/or

The cathode and the anode are independently selected from a metal electrode, a carbon electrode and a composite electrode formed by one or more of doped or undoped metal oxide electrodes; wherein the material of the metal electrode is selected from one or more of Al, Ag, Cu, Mo, Au, Ba, Ca and Mg; the material of the carbon electrode is selected from one or more of graphite, carbon nanotubes, graphene and carbon fiber; the material of the doped or undoped metal oxide electrode is selected from one or more of ITO, FTO, ATO, AZO, GZO, IZO, MZO and AMO; the material of the composite electrode is selected from AZO/Ag/AZO, AZO/Al/AZO, ITO/Ag/ITO, ITO/Al/ITO, ZnO/Ag/ZnO, ZnO/Al/ZnO, TiO2 /Ag/TiO2, TiO2/Al/ TiO2 , ZnS/Ag/ZnS, ZnS /Al/ZnS , TiO2 /Ag/ TiO2 and TiO2 /Al/TiO One or more of 2 .
The optoelectronic device according to claim 14, wherein the optoelectronic device further comprises a hole functional layer, wherein the hole functional layer is arranged between the anode and the light-emitting layer; the hole functional layer comprises a hole injection layer and/or a hole transport layer.
The optoelectronic device according to claim 19, wherein

The material of the hole injection layer includes one or more of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid, 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanoquinone-dimethane, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene, copper phthalocyanine, transition metal oxides, and transition metal sulfur compounds; wherein the transition metal oxides include one or more of NiOx , MoOx , WOx , CrOx , and CuO; the metal sulfur compounds include one or more of MoSx , MoSex , WSx , WSex , and CuS; wherein the value of x in each compound can be determined according to the valence of the atoms in the compound; and/or

The hole transport layer includes materials of poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine), polyvinylcarbazole, poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine), poly(9,9-dioctylfluorene-co-bis-N,N-phenyl-1,4-phenylenediamine), 4,4',4"-tri(carbazole-9-yl)triphenylamine, 4,4'-bis(9-carbazole)biphenylamine, One or more of benzene, N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine, N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid), Spiro-NPB, Spiro-TPD, doped or undoped graphene, C60, NiO , MoO3 , WO3 , V2O5 , CrO3 , MoSx , MoSex , WSx , WSex , CuOx , CuSCN and CuS; wherein the value of x in each compound can be determined according to the valence of the atoms in the compound.