Carrier transport layer structure and thin film light emitting diode containing the carrier transport layer structure

Abstract

The present invention discloses a carrier transport layer structure, comprising a metal oxide transport layer, an organic transport layer and a self-assembled monolayer located between the metal oxide transport layer and the organic transport layer, wherein the structural formula of the self-assembled monolayer is R1-R-R2, wherein the R1 end is used to connect the metal oxide transport layer, the R2 end is used to connect the organic transport layer, R1 contains a carboxyl group or a phosphate group, R is selected from a carbon-based skeleton, and R2 has the same or similar functional groups in the organic transport layer. The carrier transport layer structure of the present invention can improve the contact performance (adhesion performance) between the metal oxide transport layer and the organic transport layer and enhance carrier injection. The present invention also provides a thin film light emitting diode containing the carrier transport layer structure.

Description

Technical Field

[0001] The present invention relates to the technical field of light emitting diodes, and more specifically to a carrier transport layer structure and a thin film light emitting diode containing the carrier transport layer structure. Background Art

[0002] With the continuous innovation and development of light-emitting semiconductor materials and the maturity of device optical structure design technology, thin-film light-emitting diodes have emerged in the field of light emission and display in recent years. Among them, organic light-emitting diodes have long been out of the laboratory and have been commercially applied in the display field. Compared with traditional light-emitting diodes, they have a wider range of applications due to their convenient processing, thinness, flexibility and rollability, and fast response speed, thus creating a huge market share. Quantum dot light-emitting diodes, as a wide color gamut display device, are considered to be a strong competitor to replace liquid crystal displays. In recent years, they have also made amazing progress in device performance and gradually embarked on the process of commercialization. The rapidly developing perovskite light-emitting diodes in the laboratory have also demonstrated their strong potential. The external quantum efficiency in the green, red and near-infrared regions has exceeded the 20% mark, and in the blue and white light fields, it has also exceeded 12%.

[0003] Among them, the modification and selection of the luminescent material itself is indispensable, but the selection and design of the interface layer also plays a vital role in the performance of the device. The research on the interface layer now mainly focuses on the contact between the interface layer and the luminescent layer, and more importantly, the influence of the interface layer on the luminescent layer itself, while little attention is paid to the interaction between the interface layers.

[0004] At present, there are several main schemes for the design and application of carrier transport layers of thin-film light-emitting diodes, such as Figure 1 As shown: First (Scheme A), the organic transport layer is located between the transparent substrate and the light-emitting layer, that is, the organic transport layer (such as PVK, PTAA, TCTA, TAPC, PCBM, etc.) is used as the carrier transport layer structure. Figure 2 As shown: Second (Scheme B), the metal oxide transport layer is located between the transparent substrate and the light-emitting layer, and the metal oxide layer (SnO2, ZnO, CuO, NiOx, etc.) is used as the carrier transport layer structure. Figure 3As shown: The third (Scheme C), the transparent substrate is sequentially provided with a metal oxide layer, an organic transport layer and a light-emitting layer, and a double-layer structure of a metal oxide layer and an organic transport layer is used as a carrier transport layer structure. Among them, for Scheme A, although the organic transport layer has been successfully and widely used in the field of thin-film light-emitting diodes as a commonly used hole transport layer material, its lower carrier transport efficiency compared to the inorganic metal oxide layer usually makes the thin-film light-emitting diode based on the single-layer structure of the organic transport layer inefficient. For Scheme B, Scheme B uses metal oxide as a transport layer, which has the advantages of high carrier mobility, high transparency and high stability. However, there is usually a serious exciton quenching effect at the interface of the oxide-light-emitting layer, which affects the carrier recombination and device efficiency. For Scheme C, Scheme C is an improved structure based on Scheme B. The organic transport layer can effectively improve the contact problem between the oxide and the light-emitting layer, and can also improve the film quality of the light-emitting layer while optimizing the carrier transport. The organic transport layer, as an intermediate layer between the oxide and the light-emitting layer, also plays a role in relaxing the energy level barrier, which is more conducive to the injection of carriers. Although the introduction of the organic transport layer improves the contact problem between the carrier transport layer and the light-emitting layer, the double-layer transport layer structure creates another problem, namely the contact problem between the transport layers (metal oxide layer and organic transport layer): for example, there is only a weak van der Waals force between nickel oxide and PVK. This weak interaction causes poor adhesion and stability between the nickel oxide-PVK interface and makes carrier injection difficult.

[0005] Therefore, it is necessary to provide a carrier transport layer structure to solve the above-mentioned deficiencies in the prior art. Summary of the invention

[0006] In order to overcome the defects of the prior art, the object of the present invention is to provide a carrier transport layer structure which improves the contact performance (adhesion performance) between the metal oxide transport layer and the organic transport layer and enhances the carrier injection.

[0007] In order to achieve the above-mentioned purpose, the present invention discloses a carrier transport layer structure, comprising a metal oxide transport layer, an organic transport layer and a self-assembled monolayer located between the metal oxide transport layer and the organic transport layer, wherein the structural formula of the self-assembled monolayer is R1-R-R2, wherein the R1 end is used to connect the metal oxide transport layer, the R2 end is used to connect the organic transport layer, R1 contains a carboxyl group or a phosphate group, R is selected from a carbon-based skeleton, and R2 has the same or similar functional groups in the organic transport layer.

[0008] Compared with the prior art, the carrier transport layer structure of the present invention introduces a self-assembled monolayer between the metal oxide transport layer and the organic transport layer to ensure smooth flow of carriers between the metal oxide transport layer and the organic transport layer. The R1 end of the self-assembled monolayer is connected to the metal oxide transport layer and R1 contains a carboxyl group or a phosphate group. Since the surface of the metal oxide often contains a large number of hydroxyl groups, the carboxyl group or the phosphate group at the R1 end can be combined with the suspended hydroxyl group on the surface of the metal oxide through a dehydration condensation reaction, thereby firmly anchoring on the surface of the metal oxide transport layer; wherein the carbon-based skeleton of R is orderly and closely arranged through the van der Waals force between molecules; the R2 end is connected to the organic transport layer and R2 has the same or similar functional group in the organic transport layer, because the interaction force of organic groups with the same or similar structure is the strongest, which improves the adhesion.

[0009] Correspondingly, the present invention also provides a thin film light emitting diode, comprising the above-mentioned carrier transport layer structure.

[0010] The beneficial effects of the present invention are:

[0011] (1) The self-assembled monolayer not only improves the adhesion between the self-assembled monolayer and the metal oxide transport layer, but also adjusts the hydrophilic and hydrophobic properties of the metal oxide surface. In the preparation process of thin-film light-emitting diodes, many dangling hydroxyl groups will inevitably appear on the surface of the metal oxide, which usually makes the surface potential of the metal oxide higher. When the self-assembled monolayer with the structural formula R1-R-R2 is introduced, the phosphate group or carboxyl group at the R1 end will undergo a dehydration condensation reaction with the excess hydroxyl group during the spin coating annealing process to form a covalent bond and anchor it on the metal oxide surface, thereby greatly improving the adhesion between the self-assembled monolayer and the metal oxide transport layer. In addition, the hydrophilic and hydrophobic properties of the surface can be effectively changed by selecting the hydrophilic and hydrophobic functional groups at the R1 end.

[0012] (2) Improve the adhesion between the metal oxide transport layer and the organic transport layer. In the preparation process of thin-film light-emitting diodes, solution processing of a multilayer structure is often involved. This process requires the selection of a suitable solvent to avoid scouring or corroding the lower structure when the upper structure is formed into a film. The erosion between the layers is always inevitable, which requires strong adhesion between the lower thin films. The R1 end of the present invention undergoes a dehydration condensation reaction with the hydroxyl group of the metal oxide transport layer through the phosphate group or carboxyl group at the R1 end to form a covalent bond, which is anchored on the surface of the metal oxide to greatly improve the adhesion between the self-assembled monolayer and the metal oxide transport layer. The R2 end is connected to the organic transport layer and R2 has the same or similar functional groups in the organic transport layer. There is a strong interaction between the self-assembled monolayer and the organic transport layer, which greatly improves the adhesion between the metal oxide transport layer and the organic transport layer, and enhances the ability of the carrier transport layer structure to resist solution erosion.

[0013] (3) The metal oxide transport layer of the present invention is not in direct contact with the light-emitting layer, and the self-assembled monolayer has the function of passivating the surface defects of the metal oxide, reducing the luminescence quenching of the metal oxide surface, and improving the luminescence efficiency of the light-emitting layer.

[0014] (4) It can enhance the injection of carriers. For thin-film light-emitting diodes, the transport process of carriers in the transport layer is one of the key factors that determine the efficiency. Carrier mobility determines the speed of carrier transmission inside the material, while the energy level structure determines the speed of carrier injection between layers. In the present invention, the R2 end is used to connect the organic transport layer and R2 has the same or similar functional groups in the organic transport layer, so that an energy band coupling based on this structure can be formed, so that the energy levels of the upper and lower transport layer structures tend to be consistent, reducing the carrier transmission barrier, and is more conducive to carrier injection and transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic diagram showing the structure of the prior art using an organic transport layer as a carrier transport layer.

[0016] Figure 2 A schematic diagram showing a structure in which a metal oxide layer is used as a carrier transport layer in the prior art.

[0017] Figure 3 A schematic diagram showing the prior art using a double-layer structure of a metal oxide layer and an organic transport layer as a carrier transport layer structure.

[0018] Figure 4 A schematic diagram showing the structure of the carrier transport layer of the present invention.

[0019] Figure 5 A schematic diagram showing the molecular structure of compound 1 and its position and connection relationship with the metal oxide transport layer and the organic transport layer.

[0020] Figure 6 Schematic diagram showing the reaction route of compound 1 (2PACz) anchored on the surface of the metal oxide layer via a dehydration condensation reaction.

[0021] Figure 7 Schematic diagram showing the binding of compound 1 (2PACz) to PVK.

[0022] Figure 8 A schematic diagram showing Example 1 of a thin film light emitting diode of the present invention.

[0023] Fig. 9 The device performance curve of the LED prepared in Example 1 is shown.

[0024] Fig.10A schematic diagram showing Example 2 of a thin film light emitting diode of the present invention.

[0025] Fig.11 The device performance curve of the LED prepared in Example 2 is shown. DETAILED DESCRIPTION

[0026] In order to explain the technical content, structural features, achieved objectives and effects of the present invention in detail, the following is a detailed description in conjunction with the implementation methods and the accompanying drawings.

[0027] Please refer to Figure 4 The present invention discloses a carrier transport layer structure, including a metal oxide transport layer, an organic transport layer and a self-assembled monolayer (SAM) between the metal oxide transport layer and the organic transport layer. The structural formula of the self-assembled monolayer is R1-R-R2, wherein the R1 end is used to connect the metal oxide transport layer, the R2 end is used to connect the organic transport layer, R1 contains a carboxyl group or a phosphate group, R is selected from a carbon-based skeleton, and R2 has the same or similar functional group in the organic transport layer. Furthermore, the carrier transport layer structure is located between a transparent substrate and a light-emitting layer, the organic transport layer is arranged close to the light-emitting layer, and the metal oxide transport layer is arranged close to the transparent substrate. Of course, the substrate can also be opaque and can be arranged according to the requirements of single-sided or double-sided light emission.

[0028] It can be understood that the R1 end of the self-assembled monolayer is an anchoring group, which contains a carboxyl group or a phosphate group at the head end of the molecule; R is a carbon-based skeleton, which serves as the main part of the single molecule. The carbon-based skeleton refers to a skeleton based on a carbon group, which can be a long chain or a ring, saturated or unsaturated, or a benzene ring, preferably an alkyl chain; R2 is at the end of the molecule, and it has the same or similar functional groups in the organic transport layer connected to it.

[0029] In a preferred technical solution, the material of the metal oxide transport layer is selected from at least one of tin oxide, copper oxide, nickel oxide, zinc oxide, and tungsten trioxide. The metal oxide material can be formed on a transparent or opaque substrate by spin coating, blade coating, evaporation, inkjet printing, drop coating, roll-to-roll printing, screen printing, spray coating, mechanical embossing, etc. to form a metal oxide transport layer.

[0030] In a preferred technical solution, the material of the organic transport layer is selected from at least one of aromatic amines, carbazoles, imidazoles, pyridines, and fullerenes. The organic material can be formed on a transparent or opaque substrate by spin coating, scraper coating, evaporation, inkjet printing, drop coating, roll-to-roll printing, screen printing, spray coating, mechanical embossing, etc. to form an organic transport layer. Further, the material of the organic transport layer may be, but is not limited to, at least one of PVK (poly(9-vinylcarbazole)), TCTA (tri(4-carbazolyl-9-ylphenyl)amine), TAPC (4,4'-cyclohexylbis[N,N-di(4-methylphenyl)aniline]), PTAA (poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine]), PCBM (fullerene derivative), Poly(3,5-pyridine)), Poly-TPD (N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine), and TFB (poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(4,4'-(N-(4-n-butyl)phenyl)-diphenylamine)]). Furthermore, since R2 has the same or similar functional group as that in the organic transport layer, R2 is selected from at least one of carbazole, triarylamine, pyridine, fullerene, and diphenylquinone.

[0031] In a preferred technical solution, the material of the self-assembled monolayer is selected from at least one of Compound 1 to Compound 4, but is not limited thereto.

[0032]

[0033]

[0034] The synthesis of compound 2 can be found in DOI: 10.1039 / c8ee01831f.

[0035] In a preferred technical solution, the material of the self-assembled monolayer is selected from compound 1, and the material of the organic transport layer is selected from PVK or TCTA; or, the material of the self-assembled monolayer is selected from compound 2, and the material of the organic transport layer is selected from TAPC or PTAA; or, the material of the self-assembled monolayer is selected from compound 3, and the material of the organic transport layer is selected from PCBM; or, the material of the self-assembled monolayer is selected from compound 4, and the material of the organic transport layer is selected from Poly (3,5-pyridine). Further, please refer to Table 1, which also gives the material of the organic transport layer and the corresponding self-assembled monolayer material, and indicates the same or similar functional groups, as follows:

[0036] Table 1 Materials of organic transport layer and corresponding self-assembled monolayer materials

[0037]

[0038]

[0039]

[0040] It can also be seen from Table 1 that for organic molecules with carrier transport capabilities (materials of organic transport layers), they are usually molecular structures containing large delocalized π bonds or large conjugated systems (such as benzene rings and their derivative structures). When the materials of the self-assembled monolayer contain the same or similar large π bonds or conjugated systems as those of the organic transport layer, they can be tightly combined with each other through π-π interactions, effectively improving the binding force.

[0041] The working principle of the carrier transport layer structure of the present invention is described in detail below using compound 1 (2PACz) as an example, but this certainly does not limit the protection scope of the present invention.

[0042] Please refer to Figure 5 , one side shows the molecular structure of compound 1, and the other side shows the position and connection relationship between the molecular structure and the metal oxide transport layer and the organic transport layer in the form of a schematic diagram. Figure 1 It can be known that R1, R and R2 in compound 1 correspond to the anchor group, alkyl chain and functional group respectively, and the anchor group is used to connect the metal oxide transport layer, and the functional group is used to connect the organic transport layer. The remaining compounds can refer to the display of compound 1 and will not be elaborated here.

[0043] Please refer to Figure 6 Schematic diagram of the reaction route of compound 1 (2PACz) anchored on the surface of the metal oxide layer through dehydration condensation reaction. Figure 6 It can be seen that the phosphate group of the anchoring group in compound 1 (2PACz) combines with the suspended hydroxyl group on the surface of the metal oxide through a dehydration condensation reaction, thereby firmly anchoring on the surface of the metal oxide transport layer.

[0044] Please refer to Figure 7 , Schematic diagram of compound 1 (2PACz) binding to PVK. Figure 7 It can be seen that the carbazole group of compound 1 (2PACz) is combined with the carbazole group of PVK on it through π-π interaction (strong van der Waals force), making the arrangement of PVK more orderly and compact. Therefore, the introduced self-assembled monolayer can tightly combine the originally weakly bound double-layer transport layer structure.

[0045] The present invention also provides a thin film light emitting diode, comprising the above-mentioned carrier transport layer structure. In a preferred embodiment, the carrier transport layer structure is used to transport holes. Specifically, please refer to Figure 8 , an anode is provided on one side of the carrier transport layer structure, and a light-emitting portion, an electron transport layer and a cathode are provided in sequence on the other side of the carrier transport layer structure. In another embodiment, the carrier transport layer structure is used to transport electrons, specifically, a cathode is provided on one side of the carrier transport layer structure, and a light-emitting portion, a hole transport layer and an anode are provided in sequence on the other side of the carrier transport layer structure.

[0046] In order to further illustrate the effect of the thin film light emitting diode, a specific embodiment is described below, but the invention is not limited thereto.

[0047] Example 1

[0048] Please refer to Figure 8 , using compound 1 (2PACz) as the material for the self-assembled monolayer to form a blue perovskite LED. From the direction in the figure, the thin film light-emitting diode includes an anode, a carrier transport layer structure, a light-emitting part, an electron transport layer and a cathode from bottom to top. Figure 8 In the example, ITO is a transparent electrode (anode), NiO x is a metal hole transport layer, 2PACz is a self-assembled monolayer, PVK is an organic hole transport layer, (PEA / IPA)2Cs n-1 PbB 3n+1 It is the perovskite light-emitting layer, TPBi is the electron transport layer, and LiF / Al is the metal electrode (cathode). In this blue perovskite LED, 2PACz and PVK are both organic molecules with the same functional group (carbazole) that conduct holes.

[0049] The method for preparing the thin film light emitting diode of this embodiment is as follows:

[0050] 1. Clean the ITO conductive glass with isopropyl alcohol, detergent, deionized water, and isopropyl alcohol ultrasonic cleaning in sequence, and then place it in an oven to dry. Before use, clean the ITO glass sheet in a plasma surface cleaner for 5 minutes.

[0051] 2. Deposition of NiO on the cleaned ITO glass sheet x Transport layer, NiO x Precursor solution: Ni(CH3COO)2·4H2O and NH2CH2CH2OH were dissolved in ethanol at a molar ratio of 1:1, stirred at 70 °C for 12 h, and Ni 2+ The molar concentration of NiO is 0.1M. x The precursor solution was then filtered using a 0.45 μm PTFE filter. xThe thin film was obtained by spin coating at 3000 rpm for 50 seconds and thermal annealing at 270° C. for 45 minutes in the atmosphere.

[0052] 3. The self-assembled monolayer was obtained by spin coating the substrate with 2PACz solution (dissolved in ethanol, 0.25 mg / mL) at 2000 rpm for 1 minute, followed by thermal annealing at 100° C. for 10 minutes in a nitrogen-protected glove box.

[0053] 4.PVK layer passes through ITO / NiO x The PVK solution (dissolved in chlorobenzene, 8 mg / mL) was further spin-coated on the 2PACz film at 2000 rpm for 30 seconds, and then the film was thermally annealed at 150° C. for 30 minutes.

[0054] 5. Continue to spin-coat the perovskite light-emitting layer on the above-prepared substrate. The blue light perovskite layer solution (emission peak at 493nm) was prepared by dissolving CsBr (19.2mg), PbBr2 (55.1mg), PEABr (24.2mg) and IP ABr (8.4mg) in 1L DMSO at a molar ratio of 3:5:4:2, and stirring was continued at room temperature for 12 hours while keeping PbBr2 at 493nm. 2+ The molar concentration of is 0.15 M. The spin coating condition is 4000 rpm for 2 minutes, and 100 μL of ethyl acetate is dropped as an anti-solvent from the start of spin coating to the 26th second. The film is then annealed at 70° C. for 10 minutes.

[0055] 6. Finally, TPBi (35nm) and LiF / Al (1nm / 100nm) were deposited by thermal evaporation in sequence, with a vacuum degree of <1×10 -6 Torr. The active area of ​​the device is 8mm 2 , determined by the overlapping area of ​​ITO and Al electrodes.

[0056] The device performance curve of the LED prepared in Example 1 is as follows: Fig. 9 As shown. Fig. 9 (a) It can be seen that the startup voltage of the device with self-assembled monolayer (with SAM) is reduced from 3.8V to 2.1V compared with the device without self-assembled monolayer (without SAM), which indicates that the addition of SAM makes hole injection smoother. As the hole injection is smoother, the overall current density of the device is improved, achieving a very high brightness of 10392cd / m 2 .from Fig. 9 (b) It can be seen that after modification with the self-assembled monolayer, the maximum external quantum efficiency of the device has also been significantly improved, from 8.9% to 14.5%. Fig. 9(c) This indicates that the modification of the self-assembled monolayer can stabilize the device. The devices with the self-assembled monolayer have an overall improved efficiency compared to the devices without the self-assembled monolayer. Fig. 9 (d) The maximum current efficiency of the blue light device with self-assembled molecular layer is improved from 14.2cd / A to 23.2cd / A compared with the device without self-assembled molecular layer.

[0057] Example 2

[0058] Please refer to Fig.10 , using compound 1 (2PACz) as the material for the self-assembled monolayer to form a green light perovskite LED. The thin film light-emitting diode, as shown in the figure, includes an anode, a carrier transport layer structure, a light-emitting part, an electron transport layer and a cathode from bottom to top. Fig.10 In the example, ITO is a transparent electrode (anode), NiO x is a metal hole transport layer, 2PACz is a self-assembled monolayer, PVK is an organic hole transport layer, PEA2(Cs 0.933 FA 0.067 ) n-1 Pb n Br 3n+1 It is the perovskite light-emitting layer, TPBi is the electron transport layer, and LiF / Al is the metal electrode (cathode). As mentioned above, 2PACz and PVK are organic molecules with the same functional group (carbazole) and conduct holes.

[0059] The preparation method thereof is referred to Example 1 and will not be described in detail here.

[0060] The device performance curve of the LED prepared in Example 2 is as follows: Fig.11 As shown. Fig.11 (a) It can be seen that the starting voltage of the device with SAM is reduced from 2.7V to 2.1V compared with the device without SAM, which indicates that SAM makes hole injection smoother. This smoother hole injection can improve the overall current density of the device and the brightness is also increased from the original 45100cd / m 2 Increased to 83561cd / m 2 .from Fig.11 (b) It can also be seen that after modification with the self-assembled monolayer, the maximum external quantum efficiency of the green light device is significantly improved from 21.6% to 26%. Fig.11 (c) This indicates that the modification of the self-assembled monolayer can stabilize the device. The devices with the self-assembled monolayer have an overall improved efficiency compared to the devices without the self-assembled monolayer. Fig.11(d) The maximum current efficiency of the blue light device with self-assembled molecular layer is also improved from 69.6 cd / A to 91.0 cd / A compared with the device without self-assembled molecular layer.

[0061] Of course, in addition to the combination of compound 1 (2PACz) and PVK listed in Examples 1-2, compound 1 (2PACz) can also be combined with TCTA, compound 2 can be combined with TAPC or PTAA, compound 3 can be combined with PCBM, and compound 4 can be combined with Poly (3,5-pyridine). Please refer to Examples 1-2 and will not be elaborated here.

[0062] In summary, the carrier transport layer structure of the present invention introduces a self-assembled monolayer between the metal oxide transport layer and the organic transport layer to ensure smooth flow of carriers between the metal oxide transport layer and the organic transport layer. The R1 end of the self-assembled monolayer is connected to the metal oxide transport layer and R1 contains a carboxyl group or a phosphate group. Since the surface of the metal oxide often contains a large number of hydroxyl groups, the carboxyl group or phosphate group at the R1 end can be combined with the dangling hydroxyl groups on the surface of the metal oxide through a dehydration condensation reaction (such as Figure 6 As shown), it is firmly anchored on the surface of the metal oxide transport layer; wherein the carbon-based skeleton of R is arranged in an orderly and dense manner through the van der Waals force between molecules; the R2 end is connected to the organic transport layer and R2 has the same or similar functional groups in the organic transport layer, because the organic groups with the same or similar structures have the strongest interaction force, thereby improving the adhesion.

[0063] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. Therefore, equivalent changes made according to the scope of the patent application of the present invention are still within the scope covered by the present invention.

Claims

1. A thin film light emitting diode, characterized in that: The invention comprises a carrier transport layer structure, wherein the carrier transport layer structure is used to transport holes, an anode is arranged on one side of the carrier transport layer structure, and a light-emitting portion, an electron transport layer and a cathode are arranged in sequence on the other side of the carrier transport layer structure, or the carrier transport layer structure is used to transport electrons, a cathode is arranged on one side of the carrier transport layer structure, and a light-emitting portion, a hole transport layer and an anode are arranged in sequence on the other side of the carrier transport layer structure, and the carrier transport layer structure comprises a metal oxide transport layer, an organic transport layer and a layer located between the metal oxide transport layer and the organic A self-assembled monolayer between the organic transport layers, the structural formula of the self-assembled monolayer is R1-R-R2, wherein the R1 end is used to connect the metal oxide transport layer, the R2 end is used to connect the organic transport layer, R1 contains a carboxyl group or a phosphate group, R is selected from a carbon-based skeleton, R2 has the same functional group as the organic transport layer, the material of the metal oxide transport layer is selected from at least one of tin oxide, copper oxide, nickel oxide, zinc oxide, and tungsten trioxide, and the material of the organic transport layer is selected from at least one of aromatic amines, carbazoles, imidazoles, pyridines, and fullerenes.

2. The thin film light emitting diode according to claim 1, characterized in that: The material of the organic transport layer is selected from at least one of PVK, TCTA, TAPC, PTAA, PCBM, Poly (3,5-pyridine), and Poly-TPD.

3. The thin film light emitting diode according to claim 2, characterized in that: The R2 is selected from at least one of carbazole, triarylamine, pyridine and fullerene.

4. The thin film light emitting diode according to claim 2, characterized in that: The material of the self-assembled monolayer is selected from at least one of the following compounds:

5. The thin film light emitting diode according to claim 4, characterized in that: The material of the self-assembled monolayer is selected from compound 1, and the material of the organic transport layer is selected from PVK or TCTA; or, The material of the self-assembled monolayer is selected from compound 2, and the material of the organic transport layer is selected from TAPC or PTAA; or, The material of the self-assembled monolayer is selected from compound 3, and the material of the organic transport layer is selected from PCBM; or, The material of the self-assembled monolayer is selected from Compound 4, and the material of the organic transport layer is selected from Poly (3,5-pyridine).

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