Patent ID: 12232344

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following clearly and completely describes technical solutions in embodiments of the present disclosure with reference to the accompanying drawings in the embodiments of the present disclosure. Apparently, the described embodiments are only some embodiments rather than all the embodiments of the present disclosure. All other embodiments obtained by a person skilled in the art based on the embodiments of the present disclosure without creative efforts shall fall within the protection scope of the present disclosure.

In the description of the present disclosure, it is to be understood that terms “first” and “second” are used merely for the purpose of description, and shall not be construed as indicating or implying relative importance or implying a quantity of indicated technical features. To simplify the disclosure of the present disclosure, components and settings in particular examples are described below. Certainly, they are merely examples and are not intended to limit the present disclosure. The present disclosure provides examples of various particular processes and materials, but a person of ordinary skill in the art may be aware of application of another process and/or use of another material.

For a conventional electroluminescent device in the present invention, since there is a technical problem that carriers accumulate at an interface between an electron function layer and a quantum dot emission layer and at an interface between a hole function layer and the quantum dot emission layer, resulting in quenching and reducing the luminous efficiency of the electroluminescent device, the present embodiment is provided to overcome the defect.

Referring toFIG.1, an embodiment of the present invention provides an electroluminescent device100. The electroluminescent device100includes an anode20, a hole function layer30, a quantum dot emission layer40, an electron function layer50, and a cathode that are stacked on a side. The electroluminescent device100may be a top-emitting device, or may be a bottom-emitting device. The anode20is disposed on a substrate10. The hole function layer30is disposed on the anode20. The quantum dot emission layer40is disposed on the hole function layer30. The electron function layer50is disposed on the quantum dot emission layer40. The cathode60is disposed on the electron function layer50.

In the embodiment of the present invention, the substrate10may be a glass substrate, the anode20may be a transparent indium tin oxide (ITO) electrode, and the cathode60may be an aluminum electrode.

In the prior art, the insulating properties of the organic long-chain ligands on the surface of the quantum dot emission layer40may cause carriers (holes, electrons) to accumulate at the interface between the quantum dot emission layer40and the hole function layer30and at the interface between the quantum dot emission layer40and the electron function layer50, resulting in quenching. In the embodiment of the present invention, the quantum dot emission layer40is doped with a carrier transport material, which can change the electrical conductivity of the quantum dot emission layer40, but does not change the light emitting characteristics of the quantum dot emission layer40. In this way, a quantity of diffusion channels of the carriers can be increased, the diffusion of the carriers in the quantum dot emission layer40can be facilitated, and the quenching caused by the accumulation of the carriers at the above interfaces can be effectively reduced. The “doping” mentioned in the embodiment of the present invention refers to mixing another material into a certain film material, and the mixed material does not change the crystal structure of the original film material. Therefore, the carrier transport material that is doped in the embodiment of the present invention will not enter the crystal structure of the quantum dot light emitting material of the quantum dot emission layer40.

The carrier transport material includes at least one of a hole transport material or an electron transport material. In the embodiment of the present invention, the carrier transport material includes both the hole transport material and the electron transport material. The hole transport material may be a P-type organic transport material, and the electron transport material may be an N-type organic transport material. The P-type organic transport material is good for transporting holes, and the N-type organic transport material is good for transporting electrons. The holes are transported to the quantum dot light emitting material or the hole transport material in the quantum dot emission layer40through the hole function layer30. The electrons are transported to the quantum dot light emitting material or the electron transport material in the quantum dot emission layer40through the electron function layer50. In this way, the quantity of diffusion channels of the carriers in the quantum dot emission layer40can be increased.

In the quantum dot emission layer40, since a contact area between the carrier transport material and the quantum dot light emitting material is increased, a pin heterojunction is formed between the quantum dot light emitting material and the hole transport material and the electron transport material. In this way, countless tiny pin heterojunctions can effectively increase the recombination probability of the holes and electrons in the quantum dot emission layer40, thereby improving the quantum dot efficiency of the electroluminescent device.

In detail, a mass ratio of the carrier transport material to the quantum dot light emitting material is in a range of 0.1% to 2%. Within this range, the luminous efficiency of quantum dots can be effectively improved. The doped carrier transport material should not be too much, otherwise the quantum dot emission layer40that is a semiconductor itself may be changed to a conductive film layer. This may cause the electroluminescent device to be incapable of emitting light.

Further, when the carrier transport material includes both the hole transport material and the electron transport material, and a doping mass ratio of the hole transport material to the electron transport material is in a range of 0.1-10. In this way, the injection and the transport of the holes and electrons in the quantum dot emission layer40can be effectively improved.

On the one hand, the selection of the carrier transport material is mainly to meet the transport capacity of the carriers to effectively transport the carriers. On the other hand, the carrier transport material can be selected according to a band offset formed by a conduction band/valence band of the carrier transport material and a conduction band/valence band of the quantum dot light emitting material. The band offset formed by the conduction band/valence band of the carrier transport material and the conduction band/valence band of the quantum dot light emitting material is in a range of 0.1-0.5 eV. This facilitates the recombination of the holes and electrons in the quantum dot emission layer40.

The carrier transport material includes at least one of 4,4′-(bis(9-carbazolyl))biphenyl (CBP), Poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine) (TFB), Poly (N,N′-bis-4-butylphenyl-N,N′-bisphenyl)benzidine (Poly-TBD), Poly (9,9-di-n-octylfluorenyl-2,7-diyl) (PFO), 1,3,5-Tris (1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi), 4,7-Diphenyl-1,10-phenanthroline (Bphen), or 4,6-Bis(3,5-di(pyridin-3-yl)phenyl)-2-methylpyrimidine (B3PYMPM). The CBP, the TFB, the Poly-TBD, and the PFO may be used as hole transport materials, and the TPBi, the Bphen, and the B3PYMPM may be used as electron transport materials. In the embodiment of the present invention, the quantum dot emission layer40is doped with both the hole transport material and the electron transport material. The doped hole transport material may be the CBP, and the doped electron transport material may be the TPBi.

In the embodiment of the present invention, the hole function layer30includes a hole injection layer, the electron function layer50includes an electron injection layer, the hole injection layer is in direct contact with one side surface of the quantum dot emission layer40, and the electron injection layer is in direct contact with another side surface of the quantum dot emission layer40.

In the embodiment of the present invention, the hole injection layer may be a PEDOT:PSS material, and the electron injection layer may be a ZnO material.

In other embodiments, the hole function layer30further includes a hole transport layer, and the electron function layer50further includes an electron transport layer, to improve the transport ability of the carriers before reaching the quantum dot emission layer40. In detail, the hole function layer30includes a hole injection layer and a hole transport layer that are stacked. The electron function layer50includes an electron transport layer and an electron injection layer that are stacked. The hole transport layer is in direct contact with one side surface of the quantum dot emission layer40. The electron transport layer is in direct contact with another side surface of the quantum dot emission layer40.

Referring toFIG.2, an embodiment of the present invention further provides a method for manufacturing the electroluminescent device100in the above embodiment. The method includes steps as follows. S10: Dispersing a carrier transport material in a first organic solvent, and uniformly mixing the first organic solvent to form a first solution. S20: Dissolving a quantum dot light emitting material in a second organic solvent, and uniformly mixing the second organic solvent to form a second solution. S30: Mixing the first solution with the second solution to form a mixed solution. S40: Coating the mixed solution on a substrate10provided with an anode20and a hole function layer30to form a quantum dot emission layer40.

In detail, the CBP and the TPBi materials may be selected as the carrier transport materials, and the CBP and the TPBi are simultaneously dispersed in the first organic solvent. In this way, the carrier transport materials can be fully dissolved and uniformly mixed by means of ultrasonic vibration.

The first organic solvent may be a non-polar solvent, and includes at least one of hexane, heptane, octane, nonane, decane, or cyclohexane. A mass fraction of the carrier transport material in the first solution is in a range of 0.1% to 5%, and within this range, the carrier transport material has desirable solubility.

In the embodiment of the present invention, a same material is selected as the materials of the second organic solvent and the first organic solvent, so as to increase the uniformity of mixing the first solution with the second solution.

When the first solution and the second solution are mixed, ultrasonic vibration is also performed to fully diffuse the solute in the solution, and then the mixed solution is filtered using a 0.45 um PET filter to remove large particles. The first solution and the second solution are mixed in different proportions. During the mixing, it is necessary to ensure that the mass ratio of the carrier transport material to the quantum dot light emitting material in the two solutions is in a range of 0.1%-2%.

On the substrate10provided with the anode20and the hole injection layer (and the hole transport layer), the mixed solution is sequentially spin-coated or vapor-deposited, and then a process, such as baking is performed to form the quantum dot emission layer40. The first solvent and the second solvent will volatilize during the formation of the quantum dot emission layer40, not affecting the luminous efficiency of the quantum dot emission layer40.

Then the electron function layer50and the cathode60are successively provided on the quantum dot emission layer40. The electron function layer50includes an electron injection layer. In other embodiments, the electron function layer50may further include the electron transport layer formed on the electron injection layer.

Based on the above, the embodiments of the present invention provide an electroluminescent device and a manufacturing method therefor. The electroluminescent device includes an anode20, a hole function layer30, a quantum dot emission layer40, an electron function layer50, and a cathode60that are sequentially stacked. The quantum dot emission layer40is doped with a carrier transport material. On the one hand, the carrier transport material can improve the conductivity of quantum dot light emitting material and facilitate the injection and the transport of carriers. On the other hand, p-type and n-type transport materials are mixed with the quantum dot light emitting material to form tiny pin-type heterojunctions. Therefore, the recombination probability of the carriers can be increased, and the luminous quantum efficiency of the electroluminescent device can be improved.

In the foregoing embodiments, the descriptions of the embodiments have different focuses. For a part that is not detailed in an embodiment, reference may be made to the relevant description of other embodiments.

The electroluminescent device and the manufacturing method therefor in the embodiments of the present invention are described in detail above. The principle and implementations of the present invention are described herein through specific examples. The description about the embodiments of the present invention is merely provided to help understand the technical solutions and core ideas of the present invention. It should be appreciated by a person skilled in the art that, modifications may still be made to the technical solutions described in the foregoing embodiments, or equivalent replacements may be made to the part of the technical features; and these modifications or replacements will not cause the essence of corresponding technical solutions to depart from the scope of the technical solutions in the embodiments of the present invention.