Ink and laminated light emitting device and display device comprising the same

Abstract

This invention relates to an ink comprising a solvent and n-type non-stoichiometric metal oxides and metal nanoparticles dispersed in the solvent, wherein the mass ratio of the n-type non-stoichiometric metal oxides to the metal nanoparticles is (3:1) to (1:2). The ink can be used to fabricate an electron collecting layer via a solution method. This electron collecting layer and hole transport layer together form a charge generation layer. The charge generation layer not only possesses excellent charge generation capabilities but also excellent capabilities for injecting electrons into the electron transport layer, which is beneficial for improving the current efficiency of multilayer light-emitting devices, reducing driving voltage, and extending device lifespan.

Description

Technical Field

[0001] This invention relates to the field of light-emitting device technology, and in particular to ink and multilayer light-emitting devices and display devices containing the same. Background Technology

[0002] Organic light-emitting diode (OLED) devices and quantum dot light-emitting diode (QLED) devices are widely used in the display field due to their advantages such as high color gamut and flexibility. However, conventional OLED and QLED devices have a relatively short lifespan. To overcome this technical limitation, stacked light-emitting devices have become a research hotspot.

[0003] Vapor deposition and solution deposition are both commonly used manufacturing processes for light-emitting devices. Compared with vapor deposition, solution deposition has higher material utilization and cost-effectiveness, making it more suitable for large-scale production. However, solution deposition is technically challenging, and it is still difficult to easily produce functional layers of devices with excellent performance using solution deposition.

[0004] Furthermore, in the fabrication process of multilayer light-emitting devices, the charge generation layer (CGL) is the key to the fabrication of multilayer light-emitting devices. The charge generation layer produced by the current technology is difficult to guarantee that it has both good charge generation and collection capabilities, as well as good ability to inject electrons into the electron transport layer. The voltage division of the charge generation layer is often high, which makes it difficult for the final multilayer light-emitting device to work at a low driving voltage, resulting in a short device life. Summary of the Invention

[0005] Therefore, it is necessary to provide an ink in which an electron collecting layer can be formed by solution processing. This electron collecting layer, together with the hole transport layer, constitutes a charge generating layer with strong charge generation capability. Furthermore, it has a strong ability to inject electrons into the electron transport layer and can also reduce the partial voltage of the charge generating layer.

[0006] Furthermore, a stacked light-emitting device and display device that can reduce driving voltage and extend device lifespan are also provided.

[0007] One embodiment of the present invention provides an ink comprising a solvent and an n-type nonstoichiometric metal oxide and metal nanoparticles dispersed in the solvent, wherein the mass ratio of the n-type nonstoichiometric metal oxide to the metal nanoparticles is (3:1) to (1:2).

[0008] In one embodiment, the n-type nonstoichiometric metal oxide has at least one of the following properties:

[0009] (1) Annealing temperature <150℃;

[0010] (2) Conductivity > 1×10 -6S / m;

[0011] (3) The LUMO energy level after film formation is < -4.8 eV, and the Efemi energy level is < -5.1 eV;

[0012] (4) It does not precipitate when dispersed in the solvent for at least 24 hours.

[0013] In one embodiment, the n-type nonstoichiometric metal oxide includes MoO. 3-x V2O 5-x And WO 3-x At least one of them, and 0 < x < 0.5.

[0014] In one embodiment, the metal nanoparticles have at least one of the following properties:

[0015] (1) Particle size < 10 nm;

[0016] (2) It does not precipitate when dispersed in the solvent for at least 24 hours;

[0017] (3) It can be stored stably in fatty amine compounds for at least 3 days without aggregation.

[0018] In one embodiment, the aliphatic amine compound includes at least one of ethylenediamine, diethylenetriamine, tetraethylenepentamine, and polyethyleneimine.

[0019] In one embodiment, the n-type non-stoichiometric metal oxide comprises at least one of partially hydrogen-reduced MoO3, V2O5, and WO3; and / or

[0020] The metal nanoparticles include at least one of Ag, Al, Cu, and Au.

[0021] In one embodiment, the solvent includes at least one of alcohols, ketones, and esters.

[0022] An embodiment of the present invention also provides the application of ink as described in any of the above embodiments in the fabrication of an electron collection layer.

[0023] An embodiment of the present invention also provides a stacked light-emitting device, comprising a plurality of light-emitting layers, wherein an electron transport layer, an electron collection layer and a hole transport layer are disposed between at least two adjacent light-emitting layers, the electron collection layer being located between the electron transport layer and the hole transport layer, and the electron collection layer being prepared by solution method using ink as described in any of the above embodiments.

[0024] An embodiment of the present invention also provides a display device, including the stacked light-emitting device as described in the above embodiment.

[0025] The aforementioned ink is formed by mixing and dispersing n-type non-stoichiometric metal oxides and metal nanoparticles in a solvent at a specific mass ratio. After the electron collection layer is fabricated using the ink via a solution method and further processed into a stacked light-emitting device, the electron collection layer and the hole transport layer together form a charge generation layer. The charge generation layer not only has good charge generation capability but also good ability to inject electrons into the electron transport layer. It can also effectively reduce the partial voltage of the charge generation layer, which is beneficial to improving the current efficiency of the stacked light-emitting device, reducing the driving voltage during operation, and extending the device lifespan. Moreover, each functional layer of the stacked light-emitting device, including the electron collection layer, can be prepared using a solution method as the main method. During film formation, it will not affect the film structure of other functional layers, which is beneficial to improving the performance stability of the stacked light-emitting device. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the stacked light-emitting device in Example 1.

[0027] Figure label:

[0028] 100: Stacked light-emitting device; 101: Anode substrate; 102: Hole injection layer; 103: First hole transport layer; 104: First light-emitting layer; 105: Electron transport layer; 106: Electron collection layer; 107: Second hole transport layer; 108: Second light-emitting layer; 109: Electron injection layer; 110: Cathode. Detailed Implementation

[0029] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0031] In this invention, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions that include the listed features.

[0032] One embodiment of the present invention provides a stacked light-emitting device, which includes multiple light-emitting layers. At least two adjacent light-emitting layers are provided with an electron transport layer, an electron collection layer and a hole transport layer. The electron collection layer is located between the electron transport layer and the hole transport layer. The electron collection layer is prepared by solution method using ink.

[0033] The inventors discovered that the n-type doped / electron collector / hole transport layer is one of the most common structural forms of charge generation layers. When preparing this type of charge generation layer using a solution method, the electron collector layer needs to form charge separation units with the hole transport layer and also transport electrons to the electron transport layer. This requires the electron collector layer to have a high carrier concentration to reduce the voltage division of the charge generation layer, enabling the multilayer light-emitting device to operate at a lower driving voltage and to extend its lifetime. However, the materials used for the functional layers of commonly fabricated multilayer light-emitting devices using solution methods often lack suitable energy levels and conductivity. Using these materials as electron collector layers makes it difficult to achieve the goals of enabling the multilayer light-emitting device to operate at a lower driving voltage and extending its lifetime.

[0034] To address this, the inventors improved the aforementioned charge generation layer structure. Specifically, they provided an ink that can be used to fabricate an electron collection layer via a solution method. The electron collection layer and hole transport layer together constitute the charge generation layer of the stacked light-emitting device. This charge generation layer not only possesses strong charge generation capabilities but also excellent ability to inject electrons into the electron transport layer. The stacked light-emitting device has a simple structure and can be prepared using a solution method, which is simpler and has lower production costs compared to other preparation methods such as vapor deposition. Understandably, the solution method can include, for example, spin coating, inkjet printing, etc., and is not limited to these.

[0035] In one specific example, the ink comprises a solvent and n-type nonstoichiometric metal oxides and metal nanoparticles dispersed in the solvent.

[0036] n-type non-stoichiometric metal oxides refer to a class of metal oxides that conduct charge using electrons as charge carriers. The ratio of metal to oxygen atoms in these oxides is not strictly stoichiometric, making them difficult to represent with precise molecular formulas. Conventional n-type metal oxides, due to their high metal valence, significant organic residues from synthesis, and the adsorption of impurity gases, often result in low work functions when used in solution-based fabrication of multilayer light-emitting devices. This makes it difficult for these devices to achieve the performance levels of those formed by vapor deposition. Furthermore, additional treatments such as UV or oxygen plasma treatment are often required to remove impurities before the deposition of other functional layers.

[0037] The use of n-type non-stoichiometric metal oxides, compared to conventional n-type metal oxides, significantly reduces the metal valence state. Due to the formation of defect states, more oxygen vacancies are provided. The increased oxygen vacancy concentration enhances the n-type characteristics of the metal oxide, which is more conducive to improving the work function of the metal oxide and narrowing the distance between the Efemi level and the LUMO level. In particular, after the electron collection layer is formed, the resulting electron collection layer has a stronger electron collection capability. The electron collection layer and the hole transport layer can work together to form a charge generation layer with high charge generation capability.

[0038] Furthermore, metal nanoparticles are added to the ink. On the one hand, metal nanoparticles can further enhance the charge generation capability. On the other hand, due to their high surface states, metal nanoparticles can reduce the energy level barrier between the electron collection layer and the electron transport layer, thereby reducing the driving voltage and improving the current efficiency. This is beneficial for the smooth injection of collected electrons into the electron transport layer. It also helps to avoid the accumulation of charge at the interface between the electron collection layer and the electron transport layer due to the energy level barrier, which could lead to electrochemical reactions and damage to the film structure. This effectively inhibits the degradation of the charge generation layer and significantly improves the lifetime of the stacked light-emitting device.

[0039] In a specific example, the above-mentioned n-type non-stoichiometric metal oxide has at least one of the following properties (1) to (4).

[0040] (1) Annealing temperature <150℃.

[0041] If the annealing temperature is too high, it may damage other functional layers that have already been prepared. An annealing temperature of <150℃ can ensure that other functional layers that have already been prepared are not damaged or affected.

[0042] (2) Conductivity > 1×10 -6 S / m.

[0043] Materials with higher electrical conductivity form electron-collecting layers that are more conducive to charge transport.

[0044] (3) The LUMO energy level after film formation is < -4.8 eV, and the Efemi energy level is < -5.1 eV.

[0045] After the n-type non-stoichiometric metal oxide material is deposited, it has a deep work function and LUMO energy level, and the energy difference between Efemi and LUMO is small. This ensures that the charge generation layer formed by the electron collection layer and hole transport layer has good charge generation capability. No additional treatment such as UV or oxygen plasma treatment is required before the subsequent other functional layers are deposited. The performance level of the stacked light-emitting device prepared by the solution method is close to that of the device prepared by the vapor deposition method.

[0046] (4) It does not precipitate when dispersed in a solvent for at least 24 hours.

[0047] The n-type non-stoichiometric metal oxide with this characteristic has good dispersibility in ink, which further facilitates the preparation of an electron collecting layer with more stable and superior performance and quality.

[0048] Specifically, n-type non-stoichiometric metal oxides may include, but are not limited to, MoO. 3-x V2O 5-x And WO 3-x At least one of them, and 0 < x < 0.5. Understandably, they are metal oxides that enhance n-type properties after the trace amount of metal valence state in conventional n-type metal oxides such as MoO3, V2O5 and WO3 is reduced and the oxygen vacancy concentration is increased.

[0049] More specifically, the valence state of metal oxides can be reduced by trace amounts through partial reduction, thereby forming n-type non-stoichiometric metal oxides. For example, partial hydrogenation reduction can be used to form partially hydrogen-reduced n-type non-stoichiometric metal oxides such as MoO3, V2O5, and WO3. Understandably, partial hydrogen reduction refers to the partial reduction of metal atoms in n-type metal oxides such as MoO3, V2O5, and WO3, resulting in a decrease in the valence state of some of these metal atoms. For instance, partial hydrogen reduction of MoO3 reduces the valence state of some Mo atoms from +6 to +5.

[0050] Furthermore, partially hydrogen-reduced n-type non-stoichiometric metal oxides such as MoO3, V2O5, and WO3 can be obtained by, but not limited to, dispersing the metal powder used to form the n-type non-stoichiometric metal oxides in an alcohol solvent and reacting it with H2O2. Understandably, n-type non-stoichiometric metal oxides can be obtained not only by the methods described above, but also by reduction with reducing agents such as organophosphates, vitamin C, and ethylene glycol.

[0051] In a specific example, the above-mentioned metal nanoparticles have at least one of the following properties (1) to (3).

[0052] (1) Particle size < 10 nm.

[0053] Smaller particle size makes it easier to disperse evenly in solvents, resulting in inks with better dispersibility.

[0054] (2) It does not precipitate when dispersed in a solvent for at least 24 hours.

[0055] Metal nanoparticles with this property can be stably dispersed in ink.

[0056] (3) It can be stored stably in aliphatic amine compounds for at least 3 days without aggregation.

[0057] Aliphatic amine-stabilized metal nanoparticles, which are metal nanoparticles with the addition of aliphatic amine compounds as stabilizers, can ensure that the metal nanoparticles do not aggregate in the solvent for at least 3 days, which is beneficial to improving dispersibility. In addition, it is beneficial to reduce the energy level barrier between the electron collection layer and the electron transport layer, making it easier for the collected electrons to be injected into the electron transport layer.

[0058] More specifically, the metal nanoparticles may include, for example, at least one of Ag, Al, Cu and Au, but are not limited thereto.

[0059] More specifically, the aliphatic amine compound may be, for example, at least one of ethylenediamine, diethylenetriamine, tetraethylenepentamine, and polyethyleneimine, but is not limited thereto.

[0060] The aforementioned metal nanoparticles can be obtained by, but not limited to, mixing an alcohol solution containing phenylhydrazine with metal ions and aliphatic amine compound stabilizers and reacting under heating conditions until the color becomes constant.

[0061] Furthermore, in a specific example, the mass ratio of n-type non-stoichiometric metal oxide to metal nanoparticles in the ink is (3:1) to (1:2). Studies have found that controlling the mass ratio of n-type non-stoichiometric metal oxide to metal nanoparticles within this range effectively combines the performance advantages of both. This allows the charge generation layer, formed by the ink and the hole transport layer after the electron collection layer is formed via a solution method, to not only have good charge generation capabilities but also facilitate the smooth injection of collected electrons into the electron transport layer, thus improving device lifespan. If there is too little n-type non-stoichiometric metal oxide and too much metal nanoparticle, the charge separation efficiency will decrease due to the reduced contact area between the n-type non-stoichiometric metal oxide and the hole transport layer; conversely, if there is too much n-type non-stoichiometric metal oxide and too few metal nanoparticles, the electron injection efficiency into the electron transport layer will decrease, both leading to an increase in the device's driving voltage. Understandably, the mass ratio of n-type non-stoichiometric metal oxide to metal nanoparticles can be, for example, 3:1, 3:2, 2:1, 2:2, 1:1, 1:2, etc., and is not limited to these. Preferably, the mass ratio of n-type non-stoichiometric metal oxide to metal nanoparticles is 1:1.

[0062] Furthermore, the solvent mentioned above is a non-aqueous solvent, which may include, for example, alcohols, ketones, and esters, and is not limited thereto. Using non-aqueous solvents such as alcohols, ketones, and esters provides moderate volatility, facilitates film formation, and does not adversely affect other fabricated functional layers in the multilayer light-emitting device. Preferably, the solvent is an alcohol with a boiling point between 100°C and 200°C, such as n-hexanol or n-pentanol.

[0063] The above ink can be prepared by, but is not limited to, the following steps:

[0064] n-type nonstoichiometric metal oxides and metal nanoparticles are mixed in a solvent.

[0065] The multilayer light-emitting device provided in one embodiment of the present invention includes multiple light-emitting layers. It is understood that the number of light-emitting layers can be two, three, four, or more. An electron transport layer, an electron collection layer, and a hole transport layer are disposed between at least two adjacent light-emitting layers. It is understood that if the number of light-emitting layers exceeds two, an electron transport layer, an electron collection layer, and a hole transport layer can be disposed between each adjacent light-emitting layer, or only between some of the adjacent light-emitting layers.

[0066] In a specific example, the thickness of the electron collection layer is 10 nm to 30 nm. Within this range, the thickness of the electron collection layer ensures good charge generation capability without affecting the conductivity of the device.

[0067] Another embodiment of the present invention also provides the application of the above-mentioned ink in the fabrication of an electron collection layer.

[0068] Another embodiment of the present invention provides a display device including the above-described stacked light-emitting devices. It is understood that the display device may include, for example, a display screen for a mobile phone, computer, television, etc.

[0069] The ink of the present invention and its applications are further described in detail below through specific embodiments and comparative examples. The structure of the multilayer light-emitting device prepared in each embodiment is relatively specific. It can be understood that in other embodiments, it is not limited to this. For example, the injection layer and the transport layer between the light-emitting layer and the corresponding electrode layer may be absent, or only one of them may be present; the number of light-emitting layers is not limited to two layers, but may also be three or more layers; the material selection and thickness setting of each layer may also be determined according to the specific product; the multilayer light-emitting device can be an upright device or an inverted device, and the corresponding anode may be disposed close to the substrate, or the cathode may be disposed close to the substrate.

[0070] Example 1

[0071] This embodiment describes the process of fabricating an electron collecting layer using ink and further fabricating a stacked light-emitting device, mainly including the following steps:

[0072] S11: Preparation of n-type nonstoichiometric metal oxides

[0073] 0.1 g of Mo powder was dispersed in 10 ml of ethanol and stirred evenly. Then, 0.35 ml of H2O2 (30%) solution was added to the above mixed solution. After reacting for 18 hours, the mixed solution was placed in a vacuum chamber to dry, and the dried solid was obtained. The main component was partially hydrogenated MoO3.

[0074] S12: Preparation of metal nanoparticle dispersion

[0075] 10 mL of 0.011 g / mL phenylhydrazine isopropanol solution was slowly added dropwise to 40 mL of isopropanol solution containing 1 mmol silver acetate and 3 mmol tetraethylenepentamine (TEPA), and stirred at 60 °C until the color was constant. The solution was then centrifuged and vacuum dried to obtain Ag NPs. 10 mg of the dried Ag NPs was weighed and then uniformly dispersed in 10 mL of n-hexanol.

[0076] S13: Ink Preparation

[0077] 10 mg of the n-type non-stoichiometric metal oxide containing partially hydrogenated MoO3 prepared in step S11 was added to the dispersion containing Ag NPs metal nanoparticles prepared in step S12. The mixture was stirred thoroughly at room temperature, and centrifuged to remove insoluble matter before use. The mass ratio of the n-type non-stoichiometric metal oxide to the metal nanoparticles was 1:1.

[0078] S14: Fabrication of multilayer light-emitting devices

[0079] Figure 1 A schematic diagram of the structure of the stacked light-emitting device 100 is shown. The specific fabrication steps include:

[0080] S141: Clean the ITO anode substrate 101 and then treat it under UV conditions for 15 min;

[0081] S142: On the ITO anode substrate 101 after step (1) treatment, spin-coat a 30nm thick PEDOT:PSS and bake at 150°C for 20min in air atmosphere to form a hole injection layer 102.

[0082] Step (3): Spin coat a 20nm thick TFB onto the hole injection layer 102 formed in step (2), and bake at 180°C for 60min in a nitrogen atmosphere to form the first hole transport layer 103.

[0083] Step (4): Spin-coat a 60nm thick light-emitting polymer F8BT onto the hole transport layer 103 formed in step (3), and bake at 130°C for 10min to form the first light-emitting layer 104;

[0084] Step (5): Spin-coat a 10nm thick ZnO layer on the first light-emitting layer 104 formed in step (4), and anneal at 100°C for 10min to form an electron transport layer 105;

[0085] Step (6): Spin-coat a 20 nm thick layer of ink obtained in step S13 onto the electron transport layer 105 formed in step (5), and bake at 120°C for 15 min to form an electron collection layer 106.

[0086] Step (7): Spin-coat a 20nm thick TFB layer on the electron collection layer 106 formed in step (6) and bake at 150°C for 30min to form the second hole transport layer 107;

[0087] Step (8): Spin-coat an 80nm thick light-emitting polymer F8BT onto the second hole transport layer 107 formed in step (7), and bake at 130°C for 15min to form the second light-emitting layer 108;

[0088] Step (9): Vacuum evaporation of 1 nm LiF and 100 nm thick Al on the second light-emitting layer 108 formed in step (8), and finally encapsulation and annealing at 80°C for 30 min to form an electron injection layer 109 and a cathode 110.

[0089] Example 2

[0090] Steps S21-S22 and S24 are the same as steps S11-S12 and S14 in Example 1. The difference is that step S23 is different from step S13 in Example 1.

[0091] S23: Ink Preparation

[0092] 30 mg of the n-type non-stoichiometric metal oxide containing partially hydrogenated MoO3 prepared in step S21 was added to the dispersion containing Ag NPs metal nanoparticles prepared in step S22. The mixture was stirred thoroughly at room temperature, and centrifuged to remove insoluble matter before use. The mass ratio of the n-type non-stoichiometric metal oxide to the metal nanoparticles was 3:1.

[0093] Example 3

[0094] Steps S31-S32 and S34 are the same as steps S11-S12 and S14 in Example 1. The difference is that step S33 is different from step S13 in Example 1.

[0095] S33: Ink Preparation

[0096] 5 mg of the n-type non-stoichiometric metal oxide containing partially hydrogenated MoO3 prepared in step S31 was added to the dispersion containing Ag NPs metal nanoparticles prepared in step S32. The mixture was stirred thoroughly at room temperature, and centrifuged to remove insoluble matter before use. The mass ratio of the n-type non-stoichiometric metal oxide to the metal nanoparticles was 1:2.

[0097] Example 4

[0098] Steps S42 to S44 are the same as steps S12 to S14 in Example 1. The difference is that step S41 is different from step S11 in Example 1.

[0099] S41: Preparation of n-type nonstoichiometric metal oxides

[0100] 0.1 g of vanadium powder was dispersed in 10 ml of ethanol and stirred evenly. Then, 0.5 ml of H2O2 (30%) solution was added to the above mixed solution. After reacting for 3 hours, the mixed solution was placed in a vacuum chamber to dry, and the dried solid was obtained. The main component of the dried solid was partially hydrogenated V2O5.

[0101] Example 5

[0102] Steps S51 to S53 are the same as steps S11 to S13 in Example 1. The difference is that step S54 is different from step S14 in Example 1.

[0103] S54: Fabrication of multilayer light-emitting devices

[0104] Step (1): Clean the ITO anode substrate and then treat it under UV conditions for 15 min;

[0105] Step (2): On the ITO substrate processed in step (1), spin-coat a 50nm thick PEDOT:PSS layer and bake it at 150°C for 20 minutes in an air atmosphere to form a hole injection layer;

[0106] Step (3): Spin coat a 30nm thick TFB layer onto the hole injection layer formed in step (2), and bake it at 160℃ for 30min in a nitrogen atmosphere to form the first hole transport layer.

[0107] Step (4): Spin-coat a 20nm thick green QDs ink onto the hole transport layer formed in step (3), and bake at 100℃ for 10min to form the first light-emitting layer;

[0108] Step (5): Spin-coat a 30nm thick ZnO layer on the first light-emitting layer formed in step (4), and anneal at 100℃ for 10min to form the first electron transport layer;

[0109] Step (6): Spin-coat a 20 nm thick layer of ink obtained in step S53 onto the electron transport layer formed in step (5), and bake at 120°C for 15 min to form an electron collection layer;

[0110] Step (7): Spin-coat a 30nm thick TFB layer on the electron collection layer formed in step (6) and bake at 120℃ for 30min to form a second hole transport layer;

[0111] Step (8): Spin-coat a 20nm thick green QDs ink onto the second hole transport layer formed in step (7), and bake at 100°C for 15min to form the second light-emitting layer;

[0112] Step (9): Spin-coat a 30nm thick ZnO layer on the second light-emitting layer formed in step (8), and anneal at 100℃ for 10min to form the second electron transport layer;

[0113] Step (10): Vacuum deposit a 100 nm thick Al layer on top of the second electron transport layer formed in step (9), and finally encapsulate and anneal at 10 °C for 30 min to form a cathode.

[0114] Comparative Example 1

[0115] Steps CS11-CS12 and CS14 are the same as steps S11-S12 and S14 in Example 1. The difference is that step CS13 is different from step S13 in Example 1.

[0116] CS13: Ink Preparation

[0117] 40 mg of the n-type non-stoichiometric metal oxide containing partially hydrogenated MoO3 prepared in step CS11 was added to the dispersion containing Ag NPs metal nanoparticles prepared in step CS12. The mixture was stirred thoroughly at room temperature, and centrifuged to remove insoluble matter before use. The mass ratio of the n-type non-stoichiometric metal oxide to the metal nanoparticles was 4:1.

[0118] Comparative Example 2

[0119] Steps CS21-CS22 and CS24 are the same as steps S11-S12 and S14 in Example 1. The difference is that step CS23 is different from step S13 in Example 1.

[0120] CS53: Ink Preparation

[0121] 3.33 mg of the n-type non-stoichiometric metal oxide containing partially hydrogenated MoO3 prepared in step CS21 was added to the dispersion containing Ag NPs metal nanoparticles prepared in step CS22. The mixture was stirred thoroughly at room temperature, and centrifuged to remove insoluble matter before use. The mass ratio of the n-type non-stoichiometric metal oxide to the metal nanoparticles was 1:3.

[0122] Comparative Example 3

[0123] Steps CS31 and CS34 are the same as steps S11 and S14 in Example 1. The difference is that steps CS32 and CS33 are different from steps S12 and S13 in Example 1.

[0124] CS32: This step is omitted; no metal nanoparticles are added.

[0125] CS33: Ink Preparation

[0126] Disperse 10 mg of the n-type non-stoichiometric metal oxide containing partially hydrogenated MoO3 prepared in step CS31 into 10 ml of n-hexanol, stir thoroughly at room temperature, centrifuge to remove insoluble matter, and set aside for later use.

[0127] Comparative Example 4

[0128] Steps CS42 to CS44 are the same as steps S12 to S14 in Example 1. The difference is that step CS41 is different from step S11 in Example 1.

[0129] CS41: Uses MoO3, which is not partially hydrogenated.

[0130] Comparative Example 5

[0131] Steps CS51 and CS54 are the same as steps S51 and S54 in Example 5. The difference is that steps CS52 and CS53 are different from steps S52 and S53 in Example 5.

[0132] CS52: This step is omitted; no metal nanoparticles are added.

[0133] CS53: Ink Preparation

[0134] Disperse 10 mg of the n-type non-stoichiometric metal oxide containing partially hydrogenated MoO3 prepared in step CS51 into 10 ml of n-hexanol, stir thoroughly at room temperature, centrifuge to remove insoluble matter, and set aside for later use.

[0135] The driving voltage, current efficiency, and LT95 lifetime of the stacked light-emitting devices prepared in Examples 1 to 5 and Comparative Examples 1 to 5 were tested. The driving voltage and current efficiency were tested using an IVL device, and the LT95 lifetime was tested using a lifetime aging device. The test results are shown in Table 1 below.

[0136] Table 1 Performance test results of stacked light-emitting devices

[0137]

[0138] As shown in Table 1, compared with Comparative Examples 1 to 3, and with Comparative Example 5, Examples 1 to 4, and Example 5, can demonstrate that when ink prepared by mixing n-type non-stoichiometric metal oxides and metal nanoparticles is further fabricated into a multilayer light-emitting device, within a specific mass ratio range of (3:1) to (1:2), the multilayer light-emitting device exhibits a lower driving voltage, higher current efficiency, and longer lifespan. However, if there is too much n-type non-stoichiometric metal oxide and too little metal nanoparticles, the generated charge is more difficult to inject smoothly into the electron transport layer, reducing electron injection efficiency and easily causing charge accumulation at the charge generation layer interface, leading to increased driving voltage, decreased current efficiency, and shorter device lifespan. Conversely, if there is too little n-type non-stoichiometric metal oxide and too much metal nanoparticles, the reduced contact area between the n-type non-stoichiometric metal oxide and the hole transport layer decreases the ability of the electron collection layer to separate charge from the hole transport layer, also resulting in increased driving voltage, decreased current efficiency, and shorter device lifespan.

[0139] Compared with Comparative Example 4, Examples 1 to 4 show that when conventional MoO3 is used without partial hydrogenation reduction, the low conductivity of MoO3 weakens the n-type characteristics, resulting in increased driving voltage, reduced current efficiency, and shorter device lifespan in the fabricated multilayer light-emitting device.

[0140] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0141] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A multilayer light-emitting device, characterized in that, It includes multiple light-emitting layers, and at least two adjacent light-emitting layers are provided with an electron transport layer, an electron collection layer and a hole transport layer. The electron collection layer is located between the electron transport layer and the hole transport layer. The electron collection layer is prepared by solution method using ink. The ink comprises a solvent and n-type nonstoichiometric metal oxides and metal nanoparticles dispersed in the solvent, wherein the mass ratio of the n-type nonstoichiometric metal oxides to the metal nanoparticles is (3:1) to (1:2); The n-type nonstoichiometric metal oxides include MoO. 3-x V2O 5-x And WO 3-x At least one of the following, and 0 < x < 0.5; the conductivity of the n-type non-stoichiometric metal oxide is > 1 × 10⁻⁶. -6 S / m; The LUMO energy level of the n-type non-stoichiometric metal oxide film is <-4.8eV, and the Efemi energy level is <-5.1eV; The thickness of the electron collection layer is 10 nm to 30 nm.

2. The stacked light-emitting device according to claim 1, characterized in that, The n-type nonstoichiometric metal oxide has at least one of the following properties: (1) Annealing temperature <150℃; (2) It does not precipitate when dispersed in the solvent for at least 24 hours.

3. The stacked light-emitting device according to claim 1, characterized in that, The metal nanoparticles have at least one of the following properties: (1) Particle size < 10 nm; (2) It does not precipitate when dispersed in the solvent for at least 24 hours.

4. The stacked light-emitting device according to claim 1, characterized in that, The metal nanoparticles are stable in aliphatic amine compounds for at least 3 days without aggregation.

5. The stacked light-emitting device according to claim 4, characterized in that, The aliphatic amine compounds include at least one of ethylenediamine, diethylenetriamine, tetraethylenepentamine, and polyethyleneimine.

6. The stacked light-emitting device according to any one of claims 1 to 4, characterized in that, The n-type non-stoichiometric metal oxide includes at least one of partially hydrogen-reduced MoO3, V2O5, and WO3.

7. The stacked light-emitting device according to any one of claims 1 to 4, characterized in that, The mass ratio of the n-type non-stoichiometric metal oxide to the metal nanoparticles is 1:

1.

8. The stacked light-emitting device according to any one of claims 1 to 4, characterized in that, The solvent includes at least one of alcohols, ketones, and esters.

9. The stacked light-emitting device according to claim 8, characterized in that, The solvent is an alcohol compound with a boiling point of 100℃ to 200℃.

10. A display device, characterized in that, Including the stacked light-emitting device as described in any one of claims 1 to 9.

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