CN109935663B - Preparation method of composite material film and QLED device - Google Patents
Preparation method of composite material film and QLED device Download PDFInfo
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Abstract
The invention discloses a preparation method of a composite material film and a QLED device, wherein the method comprises the following steps: PSS (patterned sapphire substrate) is dissolved in an organic solvent to obtain a composite material solution; and preparing the composite material solution into a film to obtain the composite material film. The composite material formed by the amino acid modified graphene oxide and PEDOT and PSS has good electrical property and low work function, and forms good ohmic contact with LUMO of a quantum dot luminescent material, so that the hole transport property is improved. Meanwhile, electrons can be effectively prevented from being transmitted from the light-emitting layer to the cathode, so that the electron and hole recombination efficiency of the light-emitting layer is reduced, and the overall light-emitting and display performance of the device is improved.
Description
Technical Field
The invention relates to the field of QLED devices, in particular to a composite material film, a preparation method thereof and a QLED device.
Background
Over the past years, conducting polymers (PEDOT: PSS (poly 3, 4-ethylenedioxythiophene/polystyrene sulfonate)), self-assembling organic molecules and wide band gap vacuum deposition of inorganic metal oxides (e.g., MoO)3，V2O5NiO, etc.) are widely used in the hole transport and injection materials of QLEDs. In addition, specific metal fluorides, n-type semiconductors (TiO)2ZnO), n-type organic semiconductors (BCP), etc. may be used in electron transport and injection materials of quantum dot LEDs. Recently, compatible solution phase processable metal oxide nanoparticle materials (MoO)3，V2O5NiO) has become a hotspot in research on hole transport layers of QLEDs. Because the processing of these materials is free of expensive thermal evaporation techniques and is compatible with continuous roll-to-roll processing techniques that can be mass produced. In the context of QLED functional layers, several new liquid-phase processable materials and concepts have been developed. Such as water-soluble graphene oxide materials, carbon nanodot materials, and the like. These materials may be loaded with other nanoparticles by themselves or by chemical modificationThe rice particles are used as a charge injection or transport material.
Graphene oxide is a common derivative of graphene. Because the edge has a large number of oxygen-containing functional groups, such as carboxyl, hydroxyl, epoxy, and the like, the graphene oxide has good dispersibility in solvents such as water, ethanol, and the like. Graphene or graphene oxide is a promising next-generation transparent conductive film on a photoelectric device. For good device performance, the electrodes and active layer should have good energy level matching, which can increase the electron or hole transport rate. However, graphene oxide has a work function of about 5.3eV and graphene has a work function of about 4.7eV, which cannot be matched with the molecular energy level of most active materials. Therefore, the adjustment and control of the work function of the graphene or the graphene oxide are of great significance for the application of the graphene or the graphene oxide in photoelectric devices.
Disclosure of Invention
In view of the defects of the prior art, the present invention aims to provide a composite material thin film, a preparation method thereof and a QLED device, and aims to solve the problem that the existing graphene oxide cannot be matched with the molecular energy levels of most active materials.
The technical scheme of the invention is as follows:
a preparation method of a composite material film comprises the following steps:
PSS (patterned sapphire substrate) is dissolved in an organic solvent to obtain a composite material solution;
and preparing the composite material solution into a film to obtain the composite material film.
The preparation method of the composite material film comprises the following steps: and dissolving graphene oxide and amino acid in an organic solvent, and combining the amino acid and the graphene oxide to obtain the amino acid modified graphene oxide.
The preparation method of the composite material film comprises the following steps:
dissolving graphene oxide and sodium chloroacetate in an alkaline aqueous solution, and carrying out oxidation reaction on the graphene oxide and the sodium chloroacetate to obtain carboxylated graphene oxide;
mixing the carboxylated graphene oxide with an acyl chlorination reagent, and carrying out substitution reaction on the carboxylated graphene oxide and the acyl chlorination reagent to obtain acyl chlorinated graphene oxide;
and dissolving the acyl-chlorinated graphene oxide and amino acid in an organic solvent, and combining the amino acid and the acyl-chlorinated graphene oxide to prepare the amino acid-modified graphene oxide.
The preparation method of the composite material film comprises the following steps of (1) selecting amino acid from alanine, lysine, serine, glutamic acid, cysteine, phenylalanine, aspartic acid, asparagine, arginine or tyrosine;
and/or the organic solvent is selected from one or more of methanol, acetonitrile, dimethylformamide, dimethyl sulfoxide and N-methylpyrrolidone.
The preparation method of the composite material film comprises the step of dissolving graphene oxide and amino acid in an organic solvent, wherein the graphene oxide and the amino acid are dissolved in the organic solvent according to the molar ratio of 1: 0.02-0.05.
The preparation method of the composite material film comprises the following steps of dissolving alkali in an aqueous solution to prepare the alkaline aqueous solution, wherein the alkali is selected from sodium hydroxide, potassium hydroxide, lithium hydroxide or ammonia water;
and/or the acid chlorination reagent is selected from thionyl chloride, oxalyl chloride, sulfuryl chloride or thionyl chloride.
In the preparation method of the composite material film, in the step of dissolving graphene oxide and sodium chloroacetate in an alkaline aqueous solution, the graphene oxide and the sodium chloroacetate are dissolved in the alkaline aqueous solution according to the molar ratio of 1: 0.04-0.06;
and/or in the step of carrying out oxidation reaction on the graphene oxide and sodium chloroacetate to obtain carboxylated graphene oxide, wherein the temperature of the oxidation reaction is 20-30 ℃, and the time of the oxidation reaction is 3-5 h.
In the preparation method of the composite material film, in the step of mixing the carboxylated graphene oxide and the acyl chlorination reagent, the concentration of the carboxylated graphene oxide in the acyl chlorination reagent is 2-3 mg/mL;
and/or in the step of carrying out substitution reaction on the carboxylated graphene oxide and an acyl chlorination reagent to obtain acyl chlorinated graphene oxide, wherein the temperature of the substitution reaction is 50-70 ℃, and the time of the substitution reaction is 20-25 h;
and/or in the step of dissolving the acyl-chlorinated graphene oxide and the amino acid in the organic solvent, dissolving the acyl-chlorinated graphene oxide and the amino acid in the organic solvent according to the mole ratio of the acyl-chlorinated graphene oxide to the amino acid of 1: 0.02-0.05;
and/or in the step of combining the amino acid with the acyl-chlorinated graphene oxide, the temperature of the combination is 80-100 ℃, and the time of the combination is 20-25 h.
The preparation method of the composite material film comprises the step of dissolving the amino acid modified graphene oxide and PEDOT: PSS in an organic solvent, wherein the amino acid modified graphene oxide and the PEDOT: PSS are dissolved in the organic solvent according to the mass ratio of 0.01-0.1: 1.
A QLED device comprises a hole transport layer, wherein the hole transport layer is a composite material film prepared by the method.
Has the advantages that: the composite material formed by the amino acid modified graphene oxide and PEDOT and PSS has good electrical property and low work function, and forms good ohmic contact with LUMO of a quantum dot luminescent material, so that the hole transport property is improved. Meanwhile, electrons can be effectively prevented from being transmitted from the light-emitting layer to the cathode, so that the electron and hole recombination efficiency of the light-emitting layer is reduced, and the overall light-emitting and display performance of the device is improved.
Drawings
Fig. 1 is a schematic structural diagram of a QLED device including an electron transport layer in a front-loading structure according to the present invention.
Fig. 2 is a schematic structural diagram of a QLED device with an electron transport layer in a flip-chip structure according to the present invention.
Detailed Description
The invention provides a composite material film, a preparation method thereof and a QLED device, and the invention is further described in detail below in order to make the purpose, technical scheme and effect of the invention clearer and more clear. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The invention provides a preparation method of a composite material film, which comprises the following steps:
PSS (patterned sapphire substrate) is dissolved in an organic solvent to obtain a composite material solution;
and preparing the composite material solution into a film to obtain the composite material film.
The composite material formed by the amino acid modified graphene oxide and PEDOT and PSS has good electrical property and low work function, and forms good ohmic contact with LUMO of a quantum dot luminescent material, so that the hole transport property is improved. Meanwhile, electrons can be effectively prevented from being transmitted from the light-emitting layer to the cathode, so that the electron and hole recombination efficiency of the light-emitting layer is reduced, and the overall light-emitting and display performance of the device is improved. Wherein, the PEDOT/PSS is a high molecular polymer aqueous solution composed of PEDOT (3, 4-ethylene dioxythiophene monomer) and PSS (polystyrene sulfonate).
In one embodiment, the method for preparing the amino acid-modified graphene oxide comprises the following steps: and dissolving graphene oxide and amino acid in an organic solvent, and combining the amino acid and the graphene oxide to obtain the amino acid modified graphene oxide. The amino acid contains amino and carboxyl, the graphene oxide contains carboxyl, epoxy and hydroxyl, the two substances can directly perform chemical reaction under certain conditions, and the amino acid is grafted to a graphene oxide lamella through a covalent bond, so that the amino acid modified graphene oxide is obtained.
In one preferred embodiment, the preparation method of the amino acid-modified graphene oxide comprises the following steps:
dissolving graphene oxide and sodium chloroacetate in an alkaline aqueous solution, and carrying out oxidation reaction on the graphene oxide and the sodium chloroacetate to obtain carboxylated graphene oxide;
mixing the carboxylated graphene oxide with an acyl chlorination reagent, and carrying out substitution reaction on the carboxylated graphene oxide and the acyl chlorination reagent to obtain acyl chlorinated graphene oxide;
and dissolving the acyl-chlorinated graphene oxide and amino acid in an organic solvent, and combining the amino acid and the acyl-chlorinated graphene oxide to prepare the amino acid-modified graphene oxide.
The amino acid contains amino and carboxyl, the graphene oxide contains carboxyl, epoxy and hydroxyl, the two substances can directly perform chemical reaction under certain conditions, and the amino acid is grafted to the graphene oxide lamella through a covalent bond. However, in the embodiment of the present invention, a carboxylated graphene oxide is prepared first, and the purpose is to oxidize hydroxyl groups present at the edges of the graphene oxide into carboxyl groups, because the carboxyl groups are more reactive than the hydroxyl groups and are more easily complexed with amino acids, thereby increasing the amount of amino acids bound to the surface of the graphene oxide.
Then, activating carboxyl in the carboxylated graphene oxide, specifically, performing substitution reaction on the carboxylated graphene oxide by using an acyl chlorination reagent to substitute-OH on the carboxyl at the edge of the carboxylated graphene oxide by using the acyl chlorination reagent to generate the acyl chlorinated graphene oxide, wherein the obtained acyl chlorinated graphene oxide has stronger chemical activity and is easier to react with-NH of amino acid2Amide is generated by the reaction, so that the binding capacity of the amino acid and the graphene oxide is further improved.
The grafting of amino acids to graphene oxide is a reduction process. When the amino acid is grafted to the graphene oxide, the content of O in the amino acid is reduced, and the value of C to O is increased, so that the amino acid has certain reduction performance. The graphene oxide contains a large amount of oxygen-containing groups, so that the original perfect sp2 structure of the graphene is destroyed, the conductivity of the graphene oxide is poor, the reduction effect of the amino acid contributes to the recovery of the sp2 structure to a certain extent, and the recovery of the conductivity is facilitated to a certain extent, so that the conductivity of the amino acid modified graphene oxide is better than that of the original graphene oxide after the amino acid is grafted to the graphene oxide.
The graphene oxide has a high work function (5.3 eV), the problem of energy level matching needs to be considered when the graphene oxide is applied to a photoelectric device, and the high work function is not easily matched with the molecular energy level of the active layer and is difficult to form ohmic contact. The amino acids being amphoteric dipoles, -COOH negatively charged, -NH2Positively charged, the dipole passing through the positively charged-NH2The modified graphene oxide is modified on the surface of graphene oxide, and negatively charged-COOH deviates from the surface of graphene oxide, so that an interface dipole layer is formed on the surface of graphene oxide, the direction of the interface dipole layer points to positive charges from negative charges, namely points to graphene oxide, and equivalently, an electric field pointing to graphene oxide is added, so that the interface work function of graphene oxide is reduced. After the amino acid modifies the graphene oxide, the work function of the graphene oxide is obviously reduced to be close to 4.0eV at the lowest, the reduction amplitude reaches 1.3eV, and the maximum work function of the graphene oxide is 4.5eV which is lower than the work function of the graphene by 4.7 eV. Therefore, the work function of the amino acid modified graphene oxide is between 4.0 and 4.5eV, good ohmic contact can be formed between the amino acid modified graphene oxide and the LUMO of the quantum dot luminescent material in the QLED, electrons can be easily transferred to an electrode, the recombination of the electrons and holes is reduced, the hole transmission efficiency is improved, and the efficiency and other properties of the device are also improved.
The amino acid modified graphene oxide can not be used independently on the transparent conductive film electrode, on one hand, in the process of grafting amino acid, the reduction degree of the graphene oxide is not enough, the sp2 structure is not recovered enough, and the conductivity of the graphene oxide still cannot meet the requirements of the film electrode; on the other hand, the amino acid-modified graphene oxide is in a sheet form with a size of hundreds of nanometers, and a continuous film cannot be formed by suspension coating on a substrate in a solution mode, so that the amino acid-modified graphene oxide cannot be effectively overlapped. Therefore, the amino acid modified graphene oxide is doped to a certain extentPSS, namely PEDOT, which has high conductivity and can improve the conductivity of the amino acid modified graphene oxide on one hand, and PSS, on the other hand, the PEDOT, PSS and the amino acid modified graphene oxide are mechanically mixed and are made into a film through spin coating, the amino acid modified graphene oxide and the PEDOT are bonded through pi-pi, and the PSS contains a negatively charged group SO3-The composite material formed by PEDOT, PSS and the amino acid modified graphene oxide can form stable suspension in water through electrostatic repulsion.
The device performance of the composite material film formed by the amino acid modified graphene oxide and PEDOT: PSS as the hole transport layer is better than that of a device formed by singly using the PEDOT: PSS as the hole transport layer. Since the energy band gap of the graphene oxide is wide, electrons can be effectively prevented from being transmitted from the light emitting layer to the anode, and the electron and hole recombination efficiency of the light emitting layer is reduced. Meanwhile, the prepared film has good electrical property and low work function, forms good ohmic contact with LUMO of the quantum dot luminescent material, improves the hole transmission performance, and improves the overall luminescence and display performance of the device.
In one embodiment, the amino acid is selected from alanine (Ala), lysine (Lys), serine (Ser), glutamic acid (Glu), cysteine (Cys), phenylalanine (Phe), aspartic acid (Asp), asparagine (Asn), arginine (Arg), tyrosine (Leu), and the like, but is not limited thereto.
In one embodiment, the organic solvent is selected from one or more of methanol, acetonitrile, Dimethylformamide (DMF), Dimethylsulfoxide (DMSO), and N-methylpyrrolidone (NMP), and the like.
In one embodiment, the alkaline aqueous solution is prepared by dissolving a base in an aqueous solution, wherein the base is selected from sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonia water, or the like, but is not limited thereto.
In one embodiment, the acid chloride reagent is selected from thionyl chloride, oxalyl chloride, sulfuryl chloride, thionyl chloride, or the like, but is not limited thereto.
In one embodiment, in the step of dissolving graphene oxide and sodium chloroacetate in an alkaline aqueous solution, the graphene oxide and the sodium chloroacetate are dissolved in the alkaline aqueous solution at a molar ratio of the graphene oxide to the sodium chloroacetate of 1: 0.04-0.06. The reaction of graphene oxide and sodium chloroacetate needs to be carried out under an alkaline condition, when the amount of sodium chloroacetate is small, the carboxylation reaction is insufficient, and when the amount of sodium chloroacetate is large, the subsequent washing operation is difficult to remove. When the color of the solution gradually changes from the earthy yellow of the graphene oxide to black, the fact that the hydroxyl of the graphene oxide is converted into carboxyl is shown.
In one embodiment, in the step of performing an oxidation reaction on graphene oxide and sodium chloroacetate to obtain carboxylated graphene oxide, the temperature of the oxidation reaction is 20-30 ℃, the time of the oxidation reaction is 3-5h, and the carboxylation reaction is sufficient under the condition.
In one embodiment, in the step of mixing the carboxylated graphene oxide and the acyl chlorination reagent, the concentration of the carboxylated graphene oxide in the acyl chlorination reagent is 2-3mg/mL, the substitution reaction is insufficient when the acyl chlorination reagent is small, and the acyl chlorination reagent is difficult to remove by evaporation when the acyl chlorination reagent is large.
In one embodiment, in the step of subjecting the carboxylated graphene oxide and the acyl chlorination reagent to a substitution reaction to obtain the acyl chlorinated graphene oxide, the temperature of the substitution reaction is 50-70 ℃, the time of the substitution reaction is 20-25h, and the substitution reaction is performed under such conditions.
In one embodiment, in the step of dissolving graphene oxide or acylchlorinated graphene oxide and an amino acid in an organic solvent, the graphene oxide or acylchlorinated graphene oxide and the amino acid are dissolved in the organic solvent at a molar ratio of the graphene oxide or acylchlorinated graphene oxide to the amino acid of 1:0.02 to 0.05. When the amino acid is less, the work function reduction effect of the graphene oxide is not obvious, and when the amino acid is modified more, the surface modification layer of the graphene oxide is too thick, so that the hole transmission efficiency is influenced.
In one embodiment, in the step of binding the amino acid to the acylchlorinated graphene oxide, the binding temperature is 80-100 ℃ and the binding time is 20-25h, under which condition the amino acid is sufficiently bound to the acylchlorinated graphene oxide.
In one embodiment, in the step of dissolving the amino acid-modified graphene oxide and the PEDOT: PSS in the organic solvent, the amino acid-modified graphene oxide and the PEDOT: PSS are dissolved in the organic solvent according to the mass ratio of the amino acid-modified graphene oxide to the PEDOT: PSS of 0.01-0.1: 1. When the amount of the amino acid modified graphene oxide is large, the dispersion effect of the amino acid modified graphene oxide in a PEDOT (Poly ethylene styrene) PSS (Poly ethylene styrene) matrix is poor, the roughness of a film is high, and the performance of a device is influenced.
The following examples illustrate the preparation of the composite film in detail.
The first embodiment is as follows: the following description will be made in detail by taking an example of preparing a composite material film using graphene oxide, sodium hydroxide, sodium chloroacetate, thionyl chloride, alanine, and Dimethylformamide (DMF).
(1) Preparing graphene oxide: sequentially adding 1g of graphite powder, 0.5 g of sodium nitrate and 3g of potassium permanganate into 23mL of concentrated sulfuric acid, and stirring for 2 hours in an ice-water bath (the temperature is kept below 10 ℃); then, the temperature is raised to 35 ℃, stirring is continued for 30min, and 150mL of deionized water is slowly added; heating to 95 deg.C, stirring for 30min, adding 30% hydrogen peroxide (15 mL), and filtering while hot; washing with 5% HCl solution and deionized water until no sulfate radical is detected in the filtrate, and finally drying the filter cake;
(2) preparation of carboxylated graphene oxide: dissolving 200mg of graphene oxide, 10mg of sodium hydroxide and 10mg of sodium chloroacetate in 400mL of deionized water, performing ultrasonic treatment at room temperature for 4h, then washing and centrifuging with deionized water for 5 times, then washing with hydrochloric acid for 2 times, adjusting the solution to be neutral, then washing with deionized water for 3 times, and finally performing vacuum drying on a sample at 50 ℃ for 24h to obtain carboxylated graphene oxide;
(3) preparation of acyl-chlorinated graphene oxide: 50mg of carboxylated graphene oxide and 20mL of thionyl chloride were mixed and subjected to heat-preserving reflux treatment at 60 ℃ for 24 hours. Then evaporating thionyl chloride at 100 ℃, and washing the solid mixture with ethanol to obtain acylchlorinated graphene oxide;
(4) preparation of amino acid modified graphene oxide: dissolving the obtained 30mg of acyl-chlorinated graphene oxide and 10mmol of alanine in 30mLDMF, keeping the temperature and stirring for 24h at 90 ℃, then sequentially washing with 5 wt% of sodium hydroxide solution, deionized water and ethanol, and vacuum-drying a sample for 24h at 50 ℃ to obtain amino acid modified graphene oxide;
(5) mixing 30mg of amino acid modified graphene oxide and a proper amount of PEDOT: PSS to prepare a solution (the mass ratio of the amino acid modified graphene oxide to the PEDOT: PSS is 1: 0.05), and forming a composite material solution;
(6) and dripping the composite material solution onto a substrate, and carrying out spin coating at 120 ℃ to anneal to form a film.
Example two: the following description will be made in detail by taking an example of preparing a composite material thin film using graphene oxide, sodium hydroxide, sodium chloroacetate, oxalyl chloride, lysine, and dimethyl sulfoxide (DMSO).
(1) Preparing graphene oxide: the same as the first embodiment;
(2) preparation of carboxylated graphene oxide: dissolving 200mg of graphene oxide, 10mg of sodium hydroxide and 10mg of sodium chloroacetate in 400mL of deionized water, performing ultrasonic treatment at room temperature for 4h, then washing and centrifuging with deionized water for 5 times, then washing with hydrochloric acid for 2 times, adjusting the solution to be neutral, then washing with deionized water for 3 times, and finally performing vacuum drying on a sample at 50 ℃ for 24h to obtain carboxylated graphene oxide;
(3) preparation of acyl-chlorinated graphene oxide: 50mg of carboxylated graphene oxide and 20mL of oxalyl chloride were mixed and refluxed for 24 hours at 60 ℃. Then oxalyl chloride is evaporated and removed at 100 ℃, and the solid mixture is washed by ethanol to prepare acylchlorinated graphene oxide;
(4) preparation of amino acid modified graphene oxide: dissolving the obtained 30mg of acyl-chlorinated graphene oxide and 10mmol of lysine in 30mL of DMSO, keeping the temperature and stirring for 24h at 90 ℃, then sequentially washing with 5 wt% of sodium hydroxide solution, deionized water and ethanol, and drying the sample for 24h at 50 ℃ in vacuum to obtain amino acid modified graphene oxide;
(5) mixing 30mg of amino acid modified graphene oxide and a proper amount of PEDOT: PSS to prepare a solution (the mass ratio of the amino acid modified graphene oxide to the PEDOT: PSS is 1: 0.01) to form a composite material solution;
(6) and dripping the composite material solution onto a substrate, and carrying out spin coating at 120 ℃ to anneal to form a film.
Example three: the following description will be made in detail by taking an example of preparing a composite thin film using graphene oxide, sodium hydroxide, sodium chloroacetate, sulfonyl chloride, glutamic acid, and N-methylpyrrolidone (NMP).
(1) Preparing graphene oxide: the same as the first embodiment;
(2) preparation of carboxylated graphene oxide: dissolving 200mg of graphene oxide, 10mg of sodium hydroxide and 10mg of sodium chloroacetate in 400mL of deionized water, performing ultrasonic treatment at room temperature for 4h, then washing and centrifuging with deionized water for 5 times, then washing with hydrochloric acid for 2 times, adjusting the solution to be neutral, then washing with deionized water for 3 times, and finally performing vacuum drying on a sample at 50 ℃ for 24h to obtain carboxylated graphene oxide;
(3) preparation of acyl-chlorinated graphene oxide: 50mg of carboxylated graphene oxide and 20mL of sulfonyl chloride were mixed and refluxed for 24 hours at 60 ℃. Then evaporating and removing sulfonyl chloride at 100 ℃, and washing a solid mixture with ethanol to obtain acyl-chlorinated graphene oxide;
(4) preparation of amino acid modified graphene oxide: adding the obtained 30mg of acylchlorinated graphene oxide and 10mmol of glutamic acid into 30mLNMP, keeping the temperature and stirring for 24h at 90 ℃, then sequentially washing with 5 wt% of sodium hydroxide solution, deionized water and ethanol, and vacuum-drying the sample for 24h at 50 ℃ to obtain amino acid modified graphene oxide;
(5) mixing 30mg of amino acid modified graphene oxide and a proper amount of PEDOT: PSS to prepare a solution (the mass ratio of PEDOT: PSS to amino acid modified graphene oxide is 1: 0.1), and forming a composite material solution;
(6) and dripping the composite material solution onto a substrate, and carrying out spin coating at 120 ℃ to anneal to form a film.
The invention also provides a composite material film, wherein the composite material film is prepared by the preparation method.
The invention also provides a QLED device, which comprises a hole transport layer, wherein the hole transport layer is the composite material film.
In one embodiment, the QLED device includes an anode, a hole transport layer, a quantum dot light emitting layer, and a cathode, which are stacked, wherein the hole transport layer is the composite thin film of the present invention.
In a preferred embodiment, the QLED device comprises an anode, a hole transport layer, a quantum dot light emitting layer, an electron transport layer and a cathode, which are stacked, wherein the hole transport layer is the composite material thin film of the present invention.
It should be noted that the invention is not limited to the QLED device with the above structure, and may further include an interface functional layer or an interface modification layer, including but not limited to one or more of an electron blocking layer, a hole blocking layer, an electrode modification layer, and an isolation protection layer. The QLED devices described herein may be partially encapsulated, fully encapsulated, or unpackaged.
The structure of the QLED device with the electron transport layer and the preparation method thereof are explained in detail as follows:
the QLED device may be classified into a forward-mounted structure and a flip-chip structure according to the light emitting type of the QLED device.
As one embodiment, when the QLED device is a QLED device with a front-mount structure, as shown in fig. 1, the QLED device includes an anode 2 (the anode 2 is stacked on a substrate 1), a hole transport layer 3, a quantum dot light-emitting layer 4, an electron transport layer 5, and a cathode 6, which are stacked from bottom to top, where the hole transport layer 3 is a composite material film according to the present invention.
As another embodiment, when the QLED device is a flip-chip QLED device, as shown in fig. 2, the QLED device includes a cathode 6 (the cathode 6 is stacked on a substrate 1), an electron transport layer 5, a quantum dot light-emitting layer 4, a hole transport layer 3, and an anode 2, wherein the hole transport layer 3 is a composite material film according to the present invention.
Preferably, the material of the anode is selected from doped metal oxides; wherein the doped metal oxide includes, but is not limited to, one or more of indium-doped tin oxide (ITO), fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), indium-doped zinc oxide (IZO), magnesium-doped zinc oxide (MZO), and aluminum-doped magnesium oxide (AMO).
Preferably, the material of the quantum dot light-emitting layer is selected from one or more of red quantum dots, green quantum dots and blue quantum dots, and can also be selected from yellow quantum dots. Specifically, the material of the quantum dot light emitting layer is selected from one or more of CdS, CdSe, CdTe, ZnO, ZnS, ZnSe, ZnTe, GaAs, GaP, GaSb, HgS, HgSe, HgTe, InAs, InP, InSb, AlAs, AlP, CuInS, CuInSe and various core-shell structure quantum dots or alloy structure quantum dots. The quantum dots of the present invention can be selected from cadmium-containing or cadmium-free quantum dots. The quantum dot light emitting layer of the material has the characteristics of wide and continuous excitation spectrum distribution, high emission spectrum stability and the like.
Preferably, the material of the electron transport layer is selected from materials with good electron transport capability, such as but not limited to ZnO, Ca, Ba, CsF, LiF, CsCO3And Alq3One or more of (a).
Preferably, the material of the cathode is selected from one or more of a conductive carbon material, a conductive metal oxide material and a metal material; wherein the conductive carbon material includes, but is not limited to, one or more of doped or undoped carbon nanotubes, doped or undoped graphene oxide, C60, graphite, carbon fibers, and porous carbon; the conductive metal oxide material includes, but is not limited to, one or more of ITO, FTO, ATO, and AZO; metallic materials include, but are not limited to, Al, Ag, Cu, Mo, Au, or alloys thereof; wherein, the metal material has a form including but not limited to one or more of a compact film, a nanowire, a nanosphere, a nanorod, a nanocone and a hollow nanosphere.
The invention also provides a preparation method of the QLED device with the formal structure and the electron transmission layer, which comprises the following steps:
providing a substrate containing an anode, and preparing a hole transport layer on the anode, wherein the hole transport layer is the composite material film;
preparing a quantum dot light emitting layer on the hole transport layer;
preparing an electron transport layer on the quantum dot light emitting layer;
and preparing a cathode on the electron transport layer to obtain the QLED device.
The preparation method of each layer can be a chemical method or a physical method, wherein the chemical method comprises one or more of but not limited to a chemical vapor deposition method, a continuous ion layer adsorption and reaction method, an anodic oxidation method, an electrolytic deposition method and a coprecipitation method; physical methods include, but are not limited to, physical coating methods or solution methods, wherein solution methods include, but are not limited to, spin coating, printing, knife coating, dip-coating, dipping, spraying, roll coating, casting, slot coating, bar coating; physical coating methods include, but are not limited to, one or more of thermal evaporation coating, electron beam evaporation coating, magnetron sputtering, multi-arc ion coating, physical vapor deposition, atomic layer deposition, pulsed laser deposition.
As one embodiment, in order to obtain a high quality hole transport layer, the substrate (e.g., ITO conductive glass) containing the anode needs to be subjected to a pretreatment step. The specific pretreatment steps comprise: cleaning the whole piece of ITO conductive glass with a cleaning agent to primarily remove stains on the surface, then sequentially carrying out ultrasonic cleaning in deionized water, acetone, absolute ethyl alcohol and deionized water for 20 min respectively to remove impurities on the surface, and finally blowing the ITO conductive glass with high-purity nitrogen to obtain the ITO conductive glass.
As one embodiment, the step of preparing the hole transport layer on the anode specifically includes: the prepared composite material solution is spin-coated on the anode and then annealed at the temperature of 100-120 ℃ to form a film. Wherein the film thickness can be controlled by adjusting the concentration of the composite material solution, the spin-coating speed and the spin-coating time, and preferably, the thickness of the hole transport layer is 20-60 nm.
As one embodiment, the step of preparing the quantum dot light emitting layer on the hole transport layer specifically includes: and (3) placing the prepared substrate with the hole transport layer on a spin coater, spin-coating the prepared quantum dot luminescent substance solution with a certain concentration to form a film, and drying at a proper temperature. The thickness of the quantum dot light-emitting layer is controlled by adjusting the concentration of the solution, the spin-coating speed and the spin-coating time, and preferably, the thickness of the quantum dot light-emitting layer is 20-60 nm.
As one embodiment, the step of preparing the electron transport layer on the quantum dot light emitting layer specifically includes: and (3) placing the substrate with the prepared quantum dot light emitting layer in an evaporation chamber, and thermally evaporating an electron transmission layer with the thickness of about 70-90nm through a mask plate at the evaporation speed of about 0.01-0.5 nm/s.
As one embodiment, the step of preparing the cathode on the electron transport layer specifically includes: the substrate deposited with the functional layers is placed in an evaporation bin, a layer of 15-30nm metal silver or aluminum and the like is thermally evaporated through a mask plate to be used as a cathode, or a nano Ag wire or a Cu wire and the like are used, and the materials have low resistance so that carriers can be smoothly injected.
The invention also provides a preparation method of the QLED device with the inverted structure and the electron transmission layer, which comprises the following steps:
providing a substrate containing a cathode, and preparing an electron transport layer on the cathode;
preparing a quantum dot light-emitting layer on the electron transport layer;
preparing a hole transport layer on the quantum dot light-emitting layer, wherein the hole transport layer is the composite material film;
and preparing an anode on the hole transport layer to obtain the QLED device.
The preparation method of each layer can be a chemical method or a physical method, wherein the chemical method comprises one or more of but not limited to a chemical vapor deposition method, a continuous ion layer adsorption and reaction method, an anodic oxidation method, an electrolytic deposition method and a coprecipitation method; physical methods include, but are not limited to, physical coating methods or solution methods, wherein solution methods include, but are not limited to, spin coating, printing, knife coating, dip-coating, dipping, spraying, roll coating, casting, slot coating, bar coating; physical coating methods include, but are not limited to, one or more of thermal evaporation coating, electron beam evaporation coating, magnetron sputtering, multi-arc ion coating, physical vapor deposition, atomic layer deposition, pulsed laser deposition.
As one embodiment, the step of preparing the electron transport layer on the substrate including the cathode specifically includes: and (3) placing the substrate containing the cathode in an evaporation bin, and thermally evaporating an electron transmission layer with the thickness of about 70-90nm through a mask plate at the evaporation speed of about 0.01-0.5 nm/s.
As one embodiment, the step of preparing the quantum dot light-emitting layer on the electron transport layer specifically includes: and (3) placing the substrate with the prepared electron transmission layer on a spin coater, spin-coating the prepared quantum dot luminescent substance solution with a certain concentration to form a film, and drying at a proper temperature. The thickness of the quantum dot light-emitting layer is controlled by adjusting the concentration of the solution, the spin-coating speed and the spin-coating time, and preferably, the thickness of the quantum dot light-emitting layer is 20-60 nm.
As one embodiment, the step of preparing the hole transport layer on the quantum dot light emitting layer specifically includes: the prepared composite material solution is spin-coated on the quantum dot light-emitting layer and then annealed at the temperature of 100-120 ℃ to form a film. Wherein the film thickness can be controlled by adjusting the concentration of the composite material solution, the spin-coating speed and the spin-coating time, and preferably, the thickness of the hole transport layer is 20-60 nm.
As one embodiment, the step of preparing the anode on the hole transport layer specifically includes: and (3) placing the substrate on which the functional layers are deposited in an evaporation bin, and thermally evaporating a layer of 15-30nm metal silver or aluminum and the like as an anode through a mask plate, or using a nano Ag wire or a Cu wire and the like.
The invention also comprises the following steps: and carrying out packaging treatment on the obtained QLED device, wherein the packaging treatment can adopt a common machine for packaging and can also adopt manual packaging. Preferably, the packaging treatment environment has an oxygen content and a water content lower than 0.1 ppm, so as to ensure the stability of the QLED device.
In summary, according to the composite material film, the preparation method thereof and the QLED device provided by the invention, the composite material formed by the amino acid modified graphene oxide and PEDOT: PSS has good electrical properties and a low work function, and forms good ohmic contact with LUMO of a quantum dot luminescent material, so that the hole transport performance is improved. In addition, the composite material formed by the amino acid modified graphene oxide and PEDOT and PSS can effectively prevent electrons from being transmitted from the quantum dot light-emitting layer to the anode, so that the electron and hole recombination efficiency of the quantum dot light-emitting layer is reduced, and the overall light-emitting and display performance of the device is improved.
It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.
Claims (10)
1. A preparation method of a composite material film is characterized by comprising the following steps:
PSS (patterned sapphire substrate) is dissolved in an organic solvent to obtain a composite material solution;
preparing the composite material solution into a film to obtain the composite material film;
wherein the amino acid is an amphoteric dipole and has an amino group and a carboxyl group, the amino group is modified on the graphene oxide surface, and the carboxyl group is away from the graphene oxide surface, so that an interface dipole layer is formed on the graphene oxide surface.
2. The method for preparing the composite material thin film according to claim 1, wherein the method for preparing the amino acid-modified graphene oxide comprises the steps of: and dissolving graphene oxide and amino acid in an organic solvent, and combining the amino acid and the graphene oxide to obtain the amino acid modified graphene oxide.
3. The method for preparing the composite material thin film according to claim 1, wherein the method for preparing the amino acid-modified graphene oxide comprises the steps of:
dissolving graphene oxide and sodium chloroacetate in an alkaline aqueous solution, and carrying out oxidation reaction on the graphene oxide and the sodium chloroacetate to obtain carboxylated graphene oxide;
mixing the carboxylated graphene oxide with an acyl chlorination reagent, and carrying out substitution reaction on the carboxylated graphene oxide and the acyl chlorination reagent to obtain acyl chlorinated graphene oxide;
and dissolving the acyl-chlorinated graphene oxide and amino acid in an organic solvent, and combining the amino acid and the acyl-chlorinated graphene oxide to prepare the amino acid-modified graphene oxide.
4. The method for preparing a composite film according to any one of claims 1 to 3, wherein the amino acid is selected from alanine, lysine, serine, glutamic acid, cysteine, phenylalanine, aspartic acid, asparagine, arginine or tyrosine;
and/or the organic solvent is selected from one or more of methanol, acetonitrile, dimethylformamide, dimethyl sulfoxide and N-methylpyrrolidone.
5. The method for preparing a composite material film according to claim 2, wherein in the step of dissolving graphene oxide and an amino acid in an organic solvent, the graphene oxide and the amino acid are dissolved in the organic solvent at a molar ratio of the graphene oxide to the amino acid of 1:0.02 to 0.05.
6. The method for preparing the composite material film according to claim 3, wherein the alkaline aqueous solution is prepared by dissolving an alkali in an aqueous solution, wherein the alkali is selected from sodium hydroxide, potassium hydroxide, lithium hydroxide or ammonia water;
and/or the acid chlorination reagent is selected from thionyl chloride, oxalyl chloride, sulfuryl chloride or thionyl chloride.
7. The method for preparing the composite material film according to claim 3, wherein in the step of dissolving graphene oxide and sodium chloroacetate in the aqueous alkaline solution, the graphene oxide and the sodium chloroacetate are dissolved in the aqueous alkaline solution in a molar ratio of 1: 0.04-0.06;
and/or in the step of carrying out oxidation reaction on the graphene oxide and sodium chloroacetate to obtain carboxylated graphene oxide, wherein the temperature of the oxidation reaction is 20-30 ℃, and the time of the oxidation reaction is 3-5 h.
8. The method for preparing a composite material thin film according to claim 3, wherein in the step of mixing the carboxylated graphene oxide and the acyl chlorination reagent, the concentration of the carboxylated graphene oxide in the acyl chlorination reagent is 2 to 3 mg/mL;
and/or in the step of carrying out substitution reaction on the carboxylated graphene oxide and an acyl chlorination reagent to obtain acyl chlorinated graphene oxide, wherein the temperature of the substitution reaction is 50-70 ℃, and the time of the substitution reaction is 20-25 h;
and/or in the step of dissolving the acyl-chlorinated graphene oxide and the amino acid in the organic solvent, dissolving the acyl-chlorinated graphene oxide and the amino acid in the organic solvent according to the mole ratio of the acyl-chlorinated graphene oxide to the amino acid of 1: 0.02-0.05;
and/or in the step of combining the amino acid with the acyl-chlorinated graphene oxide, the temperature of the combination is 80-100 ℃, and the time of the combination is 20-25 h.
9. The method for preparing a composite material film according to any one of claims 1 to 3, wherein in the step of dissolving the amino acid-modified graphene oxide and PEDOT: PSS in the organic solvent, the amino acid-modified graphene oxide and the PEDOT: PSS are dissolved in the organic solvent in a mass ratio of the amino acid-modified graphene oxide to the PEDOT: PSS of 0.01 to 0.1: 1.
10. A QLED device comprising a hole transport layer, wherein the hole transport layer is a composite film prepared by the method of any one of claims 1 to 9.
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