CN115707268A

CN115707268A - Light emitting device and method of manufacturing the same

Info

Publication number: CN115707268A
Application number: CN202110888664.6A
Authority: CN
Inventors: 刘铭全
Original assignee: TCL Technology Group Co Ltd
Current assignee: TCL Technology Group Co Ltd
Priority date: 2021-08-02
Filing date: 2021-08-02
Publication date: 2023-02-17

Abstract

The application discloses light-emitting device and a preparation method thereof, the light-emitting device comprises an anode, a hole transport layer, a light-emitting layer and a cathode which are sequentially arranged, the hole transport layer comprises a first sub-hole transport body layer, a hole transport doping layer and a second sub-hole transport body layer, the hole transport doping layer and the second sub-hole transport body layer are arranged on one side, close to the light-emitting layer, of the first sub-hole transport body layer on the same layer, the hole transport doping layer is doped with phosphorescent molecules, and the doping quality percentage of the phosphorescent molecules is 15% -80%. The application improves the overall luminous efficiency of the light-emitting device.

Description

Light emitting device and method of manufacturing the same

Technical Field

The application relates to the technical field of display, in particular to a light-emitting device and a preparation method thereof.

Background

In recent years, the emergence of Quantum Dot Light Emitting Diodes (QLEDs) brings a new breakthrough to the field of intelligent display and illumination, and a Light Emitting layer in the QLED is composed of inorganic Quantum dots, and the Light Emitting wavelength can be adjusted by changing the size of the Quantum dots, so the QLED is widely considered as a powerful competitor for future illumination and display.

In the prior art, two light emitting modes, namely, charge injection type light emission and Fluorescence Resonance Energy Transfer (FRET) light emission, are generally realized by using a hole transport layer uniformly doped with phosphorescent molecules, however, the FRET light emitting mode has a low probability of FRET energy transfer, and direct recombination of carriers in a light emitting layer is also influenced, so that the overall light emitting efficiency of the QLED is low.

Disclosure of Invention

The embodiment of the application provides a light-emitting device and a preparation method thereof, which aim to solve the technical problem that the overall light-emitting efficiency of the light-emitting device in the prior art is low.

The embodiment of the application provides a light-emitting device, the light-emitting device comprises an anode, a hole transport layer, a light-emitting layer and a cathode which are sequentially arranged, the hole transport layer comprises a first sub-hole transport body layer, a hole transport doping layer and a second sub-hole transport body layer, the hole transport doping layer and the second sub-hole transport body layer are arranged on the same layer of one side, close to the light-emitting layer, of the first sub-hole transport body layer, the hole transport doping layer is doped with phosphorescent molecules, and the doped mass percentage of the phosphorescent molecules is 15% -80%.

Optionally, in some embodiments of the present application, the doping percentage of the phosphorescent molecule is 50% to 60%.

Optionally, in some embodiments of the present application, the hole-transporting doped layer further comprises a hole-transporting material selected from one or more of poly (9, 9-dioctylfluorene-CO-N- (4-butylphenyl) diphenylamine), polyvinylcarbazole, poly (N, N 'bis (4-butylphenyl) -N, N' -bis (phenyl) benzidine), poly (9, 9-dioctylfluorene-CO-bis-N, N-phenyl-1, 4-phenylenediamine), 4',4 ″ -tris (carbazol-9-yl) triphenylamine, 4' -bis (9-carbazolyl) biphenyl, N '-diphenyl-N, N' -bis (3-methylphenyl) -1,1 '-biphenyl-4, 4' -diamine, and N, N '-diphenyl-N, N' - (1-naphthyl) -1,1 '-biphenyl-4, 4' -diamine.

Optionally, in some embodiments of the present application, the thickness of the hole transporting doped layer is 3nm to 5nm; and/or

The thickness of the first sub hole transmission body layer is 20nm-60nm, and the thickness of the second sub hole transmission body layer is 3nm-5nm.

Optionally, in some embodiments of the present application, a top surface of the hole transport doping layer and a top surface of the second sub hole transport body layer are flush; and/or

The ratio of the top surface area of the hole-transporting doped layer to the top surface area of the second sub-hole-transporting body layer is 0.8-1.2.

Optionally, in some embodiments of the present application, the hole-transporting doping layer includes a plurality of hole-transporting doping portions, and the plurality of hole-transporting doping portions are arranged in an array; and/or

The hole-transporting doped layer comprises a plurality of hole-transporting doped parts, the top surfaces of the hole-transporting doped parts are quadrilateral, and the side length of the quadrilateral is 50-300 nm.

Optionally, in some embodiments of the present application, the hole-transporting doped layer includes a plurality of hole-transporting doped portions, and a distance between two adjacent hole-transporting doped portions in a row direction and/or a column direction is 100nm to 300nm.

Optionally, in some embodiments of the present application, the first hole transporting sub-body layer and the second hole transporting sub-body layer are integrally formed, at least one opening is formed on the second hole transporting sub-body layer, and the hole transporting doping layer is disposed in the opening.

Optionally, in some embodiments of the present application, the material of the first sub-hole transporting body layer and the material of the second sub-hole transporting body layer are each independently selected from one or more of poly (9, 9-dioctylfluorene-CO-N- (4-butylphenyl) diphenylamine), polyvinylcarbazole, poly (N, N '-bis (4-butylphenyl) -N, N' -bis (phenyl) benzidine), poly (9, 9-dioctylfluorene-CO-bis-N, N-phenyl-1, 4-phenylenediamine), 4',4 ″ -tris (carbazol-9-yl) triphenylamine, 4' -bis (9-carbazolyl) biphenyl, N '-diphenyl-N, N' -bis (3-methylphenyl) -1,1 '-biphenyl-4, 4' -diamine, and N, N '-diphenyl-N, N' - (1-naphthyl) -1,1 '-biphenyl-4, 4' -diamine; and/or

The phosphorescent molecule is selected from one or more of bis (4, 6-difluorophenylpyridine-N, C2) picolinoyl iridium, bis [2- (4, 6-difluorophenyl) -4- (2, 4, 6-trimethylphenyl) pyridine-C2, N ] picolinoyl, bis [2- (5-cyano-4, 6-difluorophenyl) pyridine-C2, N) ] picolinoyl iridium, tris (2-phenylpyridine) iridium (III), tris [2- (p-tolyl) pyridine ] iridium (III), and bis (2-phenylpyridine-C2, N) iridium (III) acetylacetonate.

The embodiment of the application also provides a preparation method of the light-emitting device, which comprises the following steps:

providing an anode;

sequentially forming a hole transport layer, a light emitting layer and a cathode on the anode; the hole transport layer comprises a first sub-hole transport body layer, a hole transport doping layer and a second sub-hole transport body layer, the hole transport doping layer and the second sub-hole transport body layer are arranged on the same layer of the first sub-hole transport body layer close to one side of the light emitting layer, the hole transport doping layer is doped with phosphorescent molecules, and the doping quality percentage of the phosphorescent molecules is 15% -80%.

Compared with the light emitting device in the prior art, in the light emitting device provided by the present application, the hole transport layer includes a first sub-hole transport body layer and a second sub-hole transport body layer that are not doped with phosphorescent molecules, and a hole transport doping layer that is doped with phosphorescent molecules, and the doping quality percentage of the phosphorescent molecules is 15% to 80%. Therefore, in the application, the arrangement of the second sub-hole transporting body layer and the first sub-hole transporting body layer, which are not doped with phosphorescent molecules, enables the hole transporting material not to be affected by the phosphorescent molecules, so that direct recombination of holes and electrons in the light emitting layer can be guaranteed not to be affected, and in addition, the mass percentage of the phosphorescent molecules is increased due to the fact that the hole transporting doped layer contains 15% -80% of the phosphorescent molecules, and further the probability of FRET energy transfer can be increased, and on the premise that direct recombination of holes and electrons in the light emitting layer is not affected, the overall luminous efficiency of the light emitting device is improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a schematic view of a first structure of a light emitting device provided in the present application.

Fig. 2 is a schematic top view of the light emitting device shown in fig. 1.

Fig. 3A to 3G are flow chart structural views of a method of manufacturing the light emitting device shown in fig. 1.

Fig. 4 is a schematic diagram of a second structure of the light emitting device provided in the present application.

Fig. 5 is a schematic top view of the light emitting device shown in fig. 4.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application. Furthermore, it should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the invention, are given by way of illustration and explanation only, and are not intended to limit the scope of the invention. In the present application, unless indicated to the contrary, the use of the directional terms "upper" and "lower" generally refer to the upper and lower positions of the device in actual use or operation, and more particularly to the orientation of the figures of the drawings; while "inner" and "outer" are with respect to the outline of the device.

The present application provides a light emitting device and a method of manufacturing the same, which are described in detail below. It should be noted that the following description of the embodiments is not intended to limit the preferred order of the embodiments.

In the QLED, since the hole mobility of the hole transport layer is usually much lower than the electron mobility of the electron transport layer, too many electrons will pass through the light emitting layer and enter the hole transport layer, which not only reduces the carrier utilization of the device, but also causes some damage to the hole transport layer.

Currently, the emission mechanism of QLED generally adopts a composite emission mechanism mainly based on charge injection emission and assisted by FRET energy transfer emission. In the former, carriers are injected into a light-emitting layer, and the carriers are recombined to form excitons and generate radiation transition; the latter is the formation of excitons near the light-emitting layer (e.g., in a hole-transporting layer or an electron-transporting layer) that generate radiative transitions by energy transfer to the light-emitting layer via FRET. At present, research has been conducted on adding a phosphorescent small molecule material into a light emitting layer or a hole transport layer, using the phosphorescent small molecule as a donor for FRET energy transfer to capture excessive electrons, and enhancing the FRET energy transfer mechanism in the QLED, thereby improving the light emitting efficiency of the QLED while preventing the excessive electrons from damaging the hole transport layer.

However, in experimental research, the inventors of the present application found that adding a phosphorescent small molecule material into a light emitting layer causes a change in the light emitting property of the light emitting layer itself, and when a hole transport layer doped with phosphorescent molecules is used to implement two light emitting modes of charge injection type light emitting and FRET energy transfer light emitting, not only the probability of FRET energy transfer is low, but also direct recombination of carriers in the light emitting layer is affected, so that the overall light emitting efficiency of the QLED is low.

Referring to fig. 1 and fig. 2, a light emitting device 10 is provided according to a first embodiment of the present application to solve the above technical problem. The light-emitting device 10 includes an anode 1, a hole transport layer 3, a light-emitting layer 4, and a cathode 6, which are sequentially disposed.

The light-emitting device 10 in this embodiment may be a light-emitting device having a positive structure or a light-emitting device having an inverted structure. The light-emitting device 10 may further include a substrate (not shown in the figure), in the light-emitting device of the positive type structure, the substrate is located on the side of the anode 1 away from the cathode 6, and the substrate is a base of the anode 1; in the light emitting device of the inversion structure, the substrate is located on the side of the cathode 6 away from the anode 1, and the substrate is a base of the cathode 6, and the following embodiments of the present application will be described by taking the light emitting device 10 as a light emitting device of the positive type structure as an example, but the present invention is not limited thereto. The material of the anode 1 may be a transparent metal oxide such as Indium Gallium Zinc Oxide (IGZO), indium Zinc Tin Oxide (IZTO), indium Gallium Zinc Tin Oxide (IGZTO), indium Tin Oxide (ITO), indium Zinc Oxide (IZO), indium Aluminum Zinc Oxide (IAZO), indium Gallium Tin Oxide (IGTO), or Antimony Tin Oxide (ATO), or Zinc Tin Oxide (ZTO), etc.

The hole transport layer 3 includes a first sub-hole transport body layer 31, a hole transport doping layer 32, and a second sub-hole transport body layer 33. The hole-transporting doping layer 32 and the second hole-transporting sub-body layer 33 are disposed on the same layer on the side of the first hole-transporting sub-body layer 31 close to the light-emitting layer 4. The first sub-hole transporting body layer 31 and the second sub-hole transporting body layer 33 both function to ensure that holes are directly recombined with electrons in the light-emitting layer 4 to form excitons and emit light.

Specifically, the material of the first sub-hole transporting bulk layer 31 may be an organic material, such as may include one or more of poly (9, 9-dioctylfluorene-CO-N- (4-butylphenyl) diphenylamine) (TFB), polyvinylcarbazole (PVK), poly (N, N 'bis (4-butylphenyl) -N, N' -bis (phenyl) benzidine) (poly-TPD), poly (9, 9-dioctylfluorene-CO-bis-N, N-phenyl-1, 4-Phenylenediamine) (PFB), 4',4 ″ -tris (carbazol-9-yl) triphenylamine (TCTA), 4' -bis (9-Carbazole) Biphenyl (CBP), N '-diphenyl-N, N' -bis (3-methylphenyl) -1,1 '-biphenyl-4, 4' -diamine (TPD), and N, N '-diphenyl-N, N' - (1-naphthyl) -1,1 '-biphenyl-4, 4' -diamine (NPB); the material of the first sub hole transport body layer 31 may also be an inorganic material, such as may include copper oxide (Cu) ₂ O) or copper gallium oxide nanoparticles (Cu) _x Ga _1-x O), and so forth. Wherein, the thickness of the first sub hole transporting body layer 31 is 20nm to 60nm, such as 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm or 60nm.

In this embodiment, the material of the second sub hole transporting body layer 33 is the same as the material of the first sub hole transporting body layer 31, and is not described herein again.

In this embodiment, the hole transporting doped layer 32 is doped with phosphorescent molecules. Specifically, the material of the hole transporting doped layer 32 includes a hole transporting material and a phosphorescent molecular material. The hole transport material is the same as that of the first sub hole transport body layer 31. The phosphorescent molecule may be any material that satisfies FRET energy transfer conditions, such as bis (4, 6-difluorophenylpyridine-N, C2) picolinoyiridium (FIrPic), bis [2- (4, 6-difluorophenyl) -4- (2, 4, 6-trimethylphenyl) pyridine-C2, N]Picolinoyl (PhFIrPic), bis [2- (5-cyano-4, 6-difluorophenyl) pyridine-C2, N)]Iridium picolinate (FCNIrPic), iridium (III) tris (2-phenylpyridine) (Ir (ppy) ₃ ) Tris [2- (p-tolyl) pyridine]Iridium (III) (Ir (mppy) ₃ ) And bis (2-phenylpyridine-C2, N) iridium (III) acetylacetonate (Ir (ppy) ₂ (acac)). The hole-transporting doped layer 32 may include a phenanthrene derivative or the like. In some embodiments, the material of the hole-transporting doped layer 32 may also be composed of a hole-transporting material and a phosphorescent molecular material, which are not described herein again.

Among them, the following conditions are required for FRET energy transfer to occur: (1) The emission spectrum of the energy donor must overlap partially with the absorption spectrum of the energy acceptor; (2) The exciton lifetime of the energy donor must be longer than that of the energy acceptor; (3) The distance between the energy donor and the energy acceptor must be within the FRET energy transfer radius; wherein the size within the FRET energy transfer radius is related to the molar extinction coefficients of the energy donor and the energy acceptor and the degree of spectral overlap. In this embodiment, the phosphorescent molecule serves as an energy donor for FRET energy transfer, and can transfer exciton energy of the phosphorescent molecule in the hole-transporting doped layer 32 toward the light-emitting layer 4, thereby improving light-emitting efficiency of the light-emitting device 10.

Wherein, the doping percentage of the phosphorescent molecule is 15-80%, such as 15%, 30%, 40%, 50%, 55%, 60%, 70% or 80%.

The hole transport layer in a light emitting device typically includes a hole transport material and phosphorescent molecules. On one hand, the hole transport material in the hole transport layer can realize direct recombination of holes and electrons in the light emitting layer, and further generate excitons to emit light; on the other hand, the phosphorescent molecule in the hole transport layer serves as an energy donor in FRET energy transfer, and can transfer exciton energy of the phosphorescent molecule in a direction close to the light-emitting layer, thereby improving the light-emitting efficiency of the light-emitting device. However, in the research work of the inventors of the present application, it is found that the phosphorescent molecules in the prior art are generally uniformly doped into the hole transport layer, and the uniform doping of the phosphorescent molecules in the hole transport layer not only results in a low utilization rate of the phosphorescent molecules, but also affects the performance of the hole transport material in the hole transport layer, thereby not only resulting in a low probability of FRET energy transfer, but also affecting the direct recombination luminescence of holes and electrons in the light emitting layer.

In this embodiment, the hole transport layer 3 is formed by arranging the first and second

hole transporting sub-layers

31 and 33 including undoped phosphorescent molecules and the hole transporting doped layer 32 doped with phosphorescent molecules, and the doping amount percentage of the phosphorescent molecules is 15% to 80%. On one hand, the arrangement of the second hole transporting sub-body layer 33 and the first hole transporting sub-body layer 31, which are not doped with phosphorescent molecules, enables the hole transporting material to be free from the influence of the phosphorescent molecules, thereby ensuring that direct recombination of holes and electrons in the light emitting layer 4 is not affected; on the other hand, in the embodiment, the doping concentration of the phosphorous molecules in the hole transporting doping layer 32 is set to be 15% to 80%, so that the mass percentage of the phosphorous molecules in the hole transporting doping layer 32 is increased, the probability of FRET energy transfer can be increased, and the overall light emitting efficiency of the light emitting device 10 is improved on the premise that direct recombination of holes and electrons in the light emitting layer 4 is not influenced.

In the present embodiment, the doping percentage of the phosphorescent molecule is 50% to 60%, for example, 50%, 52%, 55%, 57% or 60%. When the doping weight percentage of the phosphorescent molecule is too low, e.g., less than 50%, the probability of FRET energy transfer is not greatly increased, and when the doping weight percentage of the phosphorescent molecule is too high, e.g., more than 60%, the recombination luminous efficiency of holes and electrons may be affected. Therefore, through a large number of experimental studies, the inventors of the present application find that, in the range of 50% to 60% of doping quality of phosphorescent molecules, while ensuring high light emission efficiency of the combination of holes and electrons, the probability of FRET energy transfer in the hole transporting doped layer 32 can be significantly increased, thereby further improving the light emission efficiency of the device.

The thickness of the hole-transporting doped layer 32 is 3nm to 5nm, such as 3nm, 3.5nm, 4nm, 4.5nm or 5nm. Since the distance between the energy donor and the energy acceptor in the FRET energy transfer must be within the FRET energy transfer radius, the FRET energy transfer radius is usually 3nm to 5nm. Therefore, the present embodiment can improve the utilization rate of the phosphorous molecules in the hole transporting doped layer 32 by setting the thickness of the hole transporting doped layer 32 to 3nm to 5nm.

In this embodiment, the thickness of the hole-transporting doped layer 32 is 5nm. The probability of FRET energy transfer is positively correlated to the thickness of the hole-transporting doped layer 32 in the FRET energy transfer radius range of 3nm to 5nm. Therefore, the above arrangement can maximize the utilization rate of phosphorescent molecules by setting the thickness of the hole transporting doped layer 32 to 5nm, thereby maximizing the probability of FRET energy transfer.

In this embodiment, the thickness of the second sub hole transporting body layer 33 is the same as that of the hole transporting doped layer 32. The top surface 32A of the hole transporting doped layer 32 and the top surface 33A of the second sub hole transporting body layer 33 are flush. The arrangement improves the surface flatness of the hole-transport doping layer 32 and the second sub-hole-transport body layer 33, so that the film flatness of the light-emitting layer 4 can be improved in the subsequent film-forming process of the light-emitting layer 4, and the influence on the light-emitting efficiency of the device due to the unevenness of the film is avoided.

In the present application, the "top surface" is referred to a bottom surface, the top surface 32A of the hole-transporting doped layer 32 refers to a surface of the hole-transporting doped layer 32 away from the anode 1, and the top surface 33A of the second hole transporting sub-body layer 33 refers to a surface of the second hole transporting sub-body layer 33 away from the anode 1.

Referring to fig. 2, in the present embodiment, the ratio of the top surface area a of the hole transporting doped layer 32 to the top surface area B of the second hole transporting bulk layer 33 is 0.8-1.2, such as 0.8, 0.9, 1.0, 1.1 or 1.2. The specific size of the above ratio can be set according to the actual application requirement, which is not limited in the present application.

It should be noted that the light emitting device in the present application is a single light emitting pixel, and the "top surface area" corresponds to the top surface area of the hole transporting doping layer/the second sub-hole transporting body layer in the single light emitting pixel.

In the present embodiment, the hole transporting doped layer 32 includes a plurality of hole transporting dopants 321. The plurality of hole-transporting doped portions 321 are arranged in an array. The arrangement can simplify the process operation difficulty and is beneficial to saving the process cost.

Wherein the top surface of the hole transporting doping portion 321 is quadrilateral. The side length of the quadrangle is 50nm-300nm, such as 50nm, 80nm, 100nm, 120nm, 150nm, 180nm, 200nm, 230nm, 250nm, 280nm or 300nm. In this embodiment, the quadrilateral is a parallelogram, such as may be rectangular or square. The side lengths m and n of two adjacent sides of the quadrangle are both 50nm-300nm.

The distance between two adjacent hole-transporting doped portions 321 in the row direction and/or the column direction is 100nm to 300nm, such as 100nm, 120nm, 150nm, 180nm, 200nm, 230nm, 250nm, 280nm or 300nm. In this embodiment, a distance p between two adjacent hole-transporting doped portions 321 in the row direction and a distance q between two adjacent hole-transporting doped portions 321 in the column direction are both 100nm to 300nm, where p and q may be the same or different, and the specific values of p and q may be set according to actual situations, which is not limited in this application.

In this embodiment, the material of the light emitting layer 4 may be core-shell quantum dot materials such as CdZnSe/CdZnS, cdZnSe/ZnSe/ZnCdS, and CdZnSe/ZnSe/ZnS. The thickness of the light-emitting layer 4 may be 10nm to 60nm, such as 10nm, 20nm, 25nm, 30nm, 40nm, 45nm, 50nm or 60nm.

The material of the cathode 6 may comprise one or more of Ag, al or Mg/Ag. The thickness of the cathode 6 may be 20nm-120nm, such as 20nm, 25nm, 30nm, 40nm, 50nm, 60nm, 80nm, 90nm, 100nm, 110nm or 120nm.

In the present embodiment, the light-emitting device 10 further includes a hole injection layer 2 and an electron transport layer 5. The hole injection layer 2 is located between the anode 1 and the hole transport layer 3. An electron transport layer 5 is located between the light-emitting layer 4 and the cathode 6.

The material of the hole injection layer 2 may be 3, 4-ethylenedioxythiophene: organic materials such as sodium polystyrene sulfonate (PEDOT: PSS), nickel oxide (NiO) _x ) Tungsten trioxide (WO) ₃ ) Or molybdenum trioxide (MoO) ₃ ) And the like. The thickness of the hole injection layer 2 is 10nm to 60nm, and may be 10nm, 20nm, 25nm, 30nm, 40nm, 50nm, or 60nm, for example.

The material of the electron transport layer 5 may include zinc oxide (ZnO), zinc magnesium oxide (ZnMgO), zinc aluminum oxide (ZnAlO), zinc magnesium lithium oxide (ZnMgLiO), titanium oxide (TiO) ₂ ) Tin oxide (SnO) ₂ ) Or zirconium oxide (ZrO) ₃ ) One or more of (a). The thickness of the electron transport layer 5 may be 20nm to 80nm, such as 20nm, 25nm, 30nm, 40nm, 50nm, 60nm or 80nm.

Referring to fig. 3A to fig. 3G, a method for manufacturing the light emitting device 10 in the first embodiment of the present application includes the following steps:

step 101: an anode 1 (hereinafter referred to as an anode substrate) with a substrate (not shown) as a base is provided, and a hole injection layer 2 is formed on the anode 1, as shown in fig. 3A.

Specifically, step 101 specifically includes the following steps:

step 1011: and pretreating the anode substrate. Firstly, ultrasonically cleaning the anode substrate for 15min by using deionized water, acetone and absolute ethyl alcohol in sequence; then, carrying out ultraviolet-ozone treatment on the cleaned anode substrate for about 15min to further clean the anode substrate and improve the surface activity and the surface work function of the anode substrate;

step 1012: a PEDOT: PSS solution was spin-coated on the anode 1 of the anode substrate and placed in an air atmosphere, and annealed at 150 ℃ for 15min to form a hole injection layer 2. The thickness of the hole injection layer 2 was 30nm.

Step 102: a first sub hole transporting body layer 31 is formed on the hole injecting layer 2 as shown in fig. 3B.

Wherein, step 102 specifically comprises the following steps:

step 1021: preparing a PVK solution with the concentration of 6mg/mL by using chlorobenzene as a solvent and PVK as a solute;

step 1022: after the sample annealed in step 101 is cooled, it is placed in a nitrogen atmosphere, and a PVK solution is spin-coated on the hole injection layer 2, and annealed at 150 ℃ for 30min to form a first sub-hole transporting body layer 31. Wherein the thickness of the first sub hole transport body layer 31 is 35nm.

Step 103: a hole-transporting doping base layer 32a is formed on the first sub hole-transporting body layer 31, as shown in fig. 3C.

Wherein, step 103 specifically comprises the following steps:

step 1031: preparing a PVK solution with the concentration of 6mg/mL by using chlorobenzene as a solvent and PVK as a solute; using chlorobenzene as a solvent and a blue phosphorescent small molecular material (Firpic) as a solute to prepare a Firpic solution with the concentration of 6 mg/mL; and mixing the Firpic solution with the PVK solution to form a mixed solution, and carrying out ultrasonic cleaning for 10min to ensure that the Firpic is uniformly dispersed in the mixed solution.

Wherein, in the mixed solution, the volume ratio of the PVK solution to the Firpic solution is 1.

Step 1032: after the sample annealed in step 102 is cooled, the mixed solution in step 1031 is spin-coated onto the first sub hole transporting body layer 31 to form the hole transporting doping base layer 32a. Wherein, in the hole-transporting doped base layer 32a, the weight percentage of Firpic is 55%. The thickness of the hole-transporting doped base layer 32a was 5nm.

Step 104: the hole-transporting doped base layer 32a is etched to form a hole-transporting doped layer 32, as shown in fig. 3D.

Specifically, the hole-transporting doped base layer 32a is etched by a photolithography process, so that the hole-transporting doped base layer 32a is formed as a plurality of hole-transporting doped portions 321 arranged in an array. A plurality of hole transporting doping portions 321 form a receiving space 322 therebetween.

Step 105: a second sub-hole transporting body layer 33 is formed in the accommodating space 322, and the first sub-hole transporting body layer 31, the hole transporting doping layer 32 and the second sub-hole transporting body layer 33 form a hole transporting layer 3, as shown in fig. 3E.

Specifically, PVK is used as a hole transport material, and a mask plate and a vacuum thermal evaporation method are used to form the second sub-hole transport body layer 33 in the accommodating space 322 by evaporation. Wherein the thickness of the second sub hole transporting body layer 33 is the same as that of the hole transporting doped layer 32, and the top surface 33A of the second sub hole transporting body layer 33 is flush with the top surface 32A of the hole transporting doped layer 32. The arrangement can ensure that the quantum dot solution can be uniformly coated on the surfaces of the hole transport doping layer 32 and the second sub-hole transport body layer 33 in the subsequent preparation process of the luminescent layer 4, and the influence on the luminous efficiency of the device due to uneven coating is avoided.

Step 106: a light-emitting layer 4 is formed on the hole-transporting doped layer 32 and the second sub hole-transporting body layer 33, as shown in fig. 3F.

Firstly, preparing a quantum dot solution with the concentration of 10mg/mL by taking n-octane as a solvent and CdSe/ZnS as a solute;

next, a quantum dot solution was spin-coated on the hole transporting doping layer 32 and the second sub hole transporting bulk layer 33, and annealed at 80 ℃ for 30min to form the light emitting layer 4. Wherein the thickness of the light-emitting layer 4 is 20nm.

Step 107: an electron transport layer 5 and a cathode 6 are sequentially formed on the light emitting layer 4, as shown in fig. 3G.

Specifically, step 107 specifically includes the following steps:

step 1071: and preparing a ZnO solution with the concentration of 30mg/mL by using ethanol as a solvent and ZnO as a solute, spin-coating the ZnO solution on the light-emitting layer 4, and annealing at 80 ℃ for 30min to form the electron transport layer 5. Wherein the thickness of the electron transport layer 5 is 40nm.

Step 1072: an Ag electrode layer having a thickness of 100nm was formed on the electron transport layer 5 by a vacuum thermal evaporation method to form a cathode 6.

Thus, the method for manufacturing the light-emitting device 10 according to the first embodiment of the present application is completed.

The present application provides light-emitting devices prepared in examples 2 to 5 in addition to the light-emitting device prepared in the above-described first example (hereinafter, referred to as example 1), and the light-emitting properties of the light-emitting devices prepared in examples 1 to 5 were measured.

Among them, examples 2 to 5 are different from example 1 in that: the mass percentages of the phosphorus molecules in the hole transport doping layers are different. In addition, the present application also determined that the light emitting devices prepared in examples 1-5 were at the same luminance (1000 cd/m) ² ) Current density and maximum external quantum efficiency at, as shown in table 1:

TABLE 1

It can be known from comparative analysis that when the doping mass percentage of the phosphorescent molecule is 50%, 55% or 60%, the current density and the maximum external quantum efficiency of the corresponding light-emitting device are better, that is, the light-emitting efficiency of the device is better, which indicates that the increase of the FRET energy transfer probability in the hole transport doping layer 32 plays an obvious auxiliary role in improving the overall light-emitting efficiency of the device, and when the doping mass percentage of the phosphorescent molecule is 55%, the current density can reach 23.5cd/a, and the maximum external quantum efficiency can reach 20.2%.

Referring to fig. 4 and 5, a light emitting device 20 according to a second embodiment of the present application is different from the first embodiment in that: the first sub-hole transporting body layer 31 is integrally formed with the second sub-hole transporting body layer 33. The second hole transporting sub-body layer 33 has at least one opening 331. The hole-transporting doped layer 32 is disposed in the opening 331.

The preparation method of the hole transport layer 3 in this embodiment may include the following steps:

(1) A hole transporting body base layer is formed on the hole injection layer 2. The material of the hole-transporting body base layer is the same as that of the first sub hole-transporting body layer 31 in the first embodiment, and is not described herein again. Specifically, the hole transport bulk base layer may be formed by evaporation, spin coating, or coating.

(2) The hole transporting body base layer is etched to form an opening 331 in the hole transporting body base layer. The un-etched portions of the hole transport body base layer are the first sub hole transport body layer 31 and the second sub hole transport body layer 33. That is, the first sub hole transporting body layer 31 and the second sub hole transporting body layer 33 are integrally formed.

(3) A hole-transporting doped layer 32 is formed within the opening. Wherein the hole-transporting doped layer 32 may be formed using an inkjet printing process.

Thus, the present embodiment provides the first sub-hole transporting body layer 31 and the second sub-hole transporting body layer 33 as an integrated structure, so that the hole transporting body layer can be formed in one process in the manufacturing process of the light emitting device 20. Therefore, when the hole transporting doping layer 32 is subsequently prepared, the hole transporting body layer (including the first hole transporting sub-body layer 31 and the second hole transporting sub-body layer 33) may be formed on the hole injection layer 2 at one time, then the opening 331 may be formed on the hole transporting body layer, and the hole transporting doping layer 32 may be formed in the opening 331 through an inkjet printing process, so that the light emitting efficiency of the light emitting device may be improved, the process may be simplified, and the process cost may be saved.

The light emitting device and the method for manufacturing the same provided by the embodiments of the present application are described in detail above, and the principles and embodiments of the present application are explained herein by applying specific examples, and the above description of the embodiments is only used to help understanding the method and the core ideas of the present application; meanwhile, for those skilled in the art, according to the idea of the present application, the specific implementation manner and the application scope may be changed, and in summary, the content of the present specification should not be construed as a limitation to the present application.

Claims

1. A light-emitting device is characterized by comprising an anode, a hole transport layer, a light-emitting layer and a cathode which are sequentially arranged, wherein the hole transport layer comprises a first sub-hole transport body layer, a hole transport doping layer and a second sub-hole transport body layer, the hole transport doping layer and the second sub-hole transport body layer are arranged on one side, close to the light-emitting layer, of the first sub-hole transport body layer in the same layer, the hole transport doping layer is doped with phosphorescent molecules, and the doping quality percentage of the phosphorescent molecules is 15% -80%.

2. The light-emitting device according to claim 1, wherein the doping percentage of the phosphorescent molecule is 50% to 60%.

3. The light-emitting device of claim 1, wherein the hole-transporting doped layer further comprises a hole-transporting material selected from one or more of poly (9, 9-dioctylfluorene-CO-N- (4-butylphenyl) diphenylamine), polyvinylcarbazole, poly (N, N 'bis (4-butylphenyl) -N, N' -bis (phenyl) benzidine), poly (9, 9-dioctylfluorene-CO-bis-N, N-phenyl-1, 4-phenylenediamine), 4',4 "-tris (carbazol-9-yl) triphenylamine, 4' -bis (9-carbazolyl) biphenyl, N '-diphenyl-N, N' -bis (3-methylphenyl) -1,1 '-biphenyl-4, 4' -diamine, and N, N '-diphenyl-N, N' - (1-naphthyl) -1,1 '-biphenyl-4, 4' -diamine.

4. The light-emitting device according to claim 1, wherein the hole-transporting doped layer has a thickness of 3nm to 5nm; and/or

5. The light-emitting device according to claim 1, wherein a top surface of the hole-transporting doped layer and a top surface of the second sub-hole-transporting body layer are flush; and/or

The ratio of the top surface area of the hole transport doping layer to the top surface area of the second sub hole transport body layer is 0.8-1.2.

6. The light-emitting device according to claim 1, wherein the hole-transporting doped layer comprises a plurality of hole-transporting doped portions arranged in an array; and/or the hole transport doping layer comprises a plurality of hole transport doping parts, the top surfaces of the hole transport doping parts are quadrilateral, and the side length of the quadrilateral is 50-300 nm.

7. The light-emitting device according to claim 1, wherein the hole-transporting doped layer comprises a plurality of hole-transporting doped portions, and a distance between two adjacent hole-transporting doped portions in a row direction and/or a column direction is 100nm to 300nm.

8. The light-emitting device according to claim 1, wherein the first hole transporting sub-body layer is integrally formed with the second hole transporting sub-body layer, at least one opening is formed in the second hole transporting sub-body layer, and the hole transporting doping layer is disposed in the opening.

9. A light-emitting device according to claim 1, wherein the material of the first sub-hole-transporting bulk layer and the material of the second sub-hole-transporting bulk layer are each independently selected from one or more of poly (9, 9-dioctylfluorene-CO-N- (4-butylphenyl) diphenylamine), polyvinylcarbazole, poly (N, N 'bis (4-butylphenyl) -N, N' -bis (phenyl) benzidine), poly (9, 9-dioctylfluorene-CO-bis-N, N-phenyl-1, 4-phenylenediamine), 4',4 ″ -tris (carbazol-9-yl) triphenylamine, 4' -bis (9-carbazole) biphenyl, N '-diphenyl-N, N' -bis (3-methylphenyl) -1,1 '-biphenyl-4, 4' -diamine and N, N '-diphenyl-N, N' - (1-naphthyl) -1,1 '-biphenyl-4, 4' -diamine; and/or

10. A method for manufacturing a light emitting device, comprising:

providing an anode;

sequentially forming a hole transport layer, a light emitting layer and a cathode on the anode; the hole transport layer comprises a first sub-hole transport body layer, a hole transport doping layer and a second sub-hole transport body layer, the hole transport doping layer and the second sub-hole transport body layer are arranged on one side, close to the light emitting layer, of the first sub-hole transport body layer in the same layer, the hole transport doping layer is doped with phosphorescent molecules, and the doping quality percentage of the phosphorescent molecules is 15% -80%.

11. The method of claim 10, wherein the phosphorescent molecule has a doping content of 50% to 60%.